Tue, 19 Dec 2023 07:01:51 +0000 http://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15898 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15898 Wed, 17 Oct 2018 14:36:40 +0100 austingeorge
I am a novice renovator, and have been doing as much reading as possible on the considerations to some major renovation work I am doing to my early edwardian mid-terrace house. To fill in the gaps and satisfy my anxiety, it would be great to hear some advice on my questions below. This forum seems the best place to ask such questions as i've learned significantly more from this forum than any other.

To describe the house a bit:
I have a ground floor suspended timber floor void that is only accessible from above There's a subfloor supporting wall in the centre, and 4-5 vents placed around the base of the external walls.

My ultimate aim is to install electric UFH as the solitary means of heating this room (a new kitchen). All in an effort to save space by not having a rad(s). I'll be lifting the old floorboards, to make required changes and inspect, but wanted to check that my plans won't cause me any issues with condensation/rot

There's two aspects to this:

1. I wanted to install UFH. There is already a nice full set of original 20mm thick pine floorboards which i want to leave intact under the new floor. I planned to gently pull them up, install UFI, a vapour barrier over top of joists, put the boards back, put 9mm ply on top, and then UFH wiring and tiles. Are there any glaring issues with this? I don't want to cause rot of my floor above the vapour barrier, but then surely the UFH will keep the boards and ply dry? Am I missing something, and worrying over nothing?

2. Joists are 100mm deep, and I wanted to use PIR as thick as possible between these (400mm centres). Should i be considering a specific thickness of PIR to reduce risk of interstitial condensation in the joists? Or is it that there will be no vapour from inside the room to condense because of the aforementioned vapour barrier under the floorboards?

Any advice on hanging 100mm PIR between 100mm deep joists?

I've got a few more questions, but they're interrelated to this to a lesser extent, so i'll open another thread.

Thanks for any help/responses provided!
Austin]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15897 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15897 Mon, 15 Oct 2018 17:30:13 +0100 Nick Parsons
All the RSJs I have had anything to do with have been wholly internal and have been fire-protected but have not required insulation. I cannot see any reason why there should be a problem with insulation behind the fire-'slabbing', but having not come across this exact situation before, can anyone see any problems?

Also, on the internal RSJs I have 'slabbed' I was asked once to use 2 x layers of 'pink' fire-board, and other times only one.

What do you think?

Thanks!]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15878 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15878 Thu, 27 Sep 2018 01:31:06 +0100 peaks_ccb
I'd like to construct something cheaper if possible - I can buy the 2400x1000 triple glazed unit itself for £400. Can I get the roofer to mount that on a curb together with some aluminium profile and silicon? Is there a cheap DIY solution that is tried and tested?

Thanks!]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15871 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15871 Sun, 23 Sep 2018 08:44:18 +0100 Dominic Cooney There is no mains gas.
Main farmhouse has oil, but would prefer not to use oil if possible.

We would like Underfloor heating (had it in last 2 places we did), and intending to fit MVHR (paying even more time and attention to air-tightness this time).

Building is oriented almost exactly north-south so roof slopes are facing east-west.


Any ideas?


...Don't say "have you worked out the heat demand of the building?"!]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15874 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15874 Mon, 24 Sep 2018 22:34:33 +0100 cczmark
My builder has installed steel beams over 2 patio doors. This is 2x I shaped beams bolted together rather than one single beam. Plus a beam that connects into it. I don't have the option of insulating between the beams.

These will have some sort of fire protection board (?Fire-rated plasterbd) applied to them.

Q: Seems to me I am looking at lots of cold-bridging here. What insulation options do I have? Without falling foul of fire regs...

Builder says I can apply some insulation to the beam web with no problem (probably just stick some EPS to it...)

Thanks,
Mark.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15867 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15867 Thu, 20 Sep 2018 19:30:56 +0100 cczmark
I'm in the middle of a building project (extension plus existing house reconfig & EWI), really wanted to do something properly eco but frankly it's been a fight against the whole industry - architects, builders, suppliers. I'll post the lessons learned here at some point...!

My contractor had originally proposed 80mm EWI using some type of fibreboard which he (or more accurately his subbie) has used on a similar project locally. I'd seen this being installed and the quality looks OK. Our existing walls are 9in solid brick and pretty sound.

I proposed 100mm Grey EPS and that's what is in the spec. My contractor is of the "I've been doing this 30yrs and we do it this way" variety. He says 1) we don't need 100mm and 2) is proposing 80mm all round (i.e. including the reveals). This sounds not right to me. See image - his proposal is Option A but mine is Option B.

Any advice or links to authoritative sources of window detailing would be appreciated!

Thanks in advance,
Mark.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15869 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15869 Thu, 20 Sep 2018 19:37:14 +0100 cczmark
Final one for today - we have curved bay windows which we will need to apply EWI. Any flexible materials / other options or best practices please?

Thanks all,
Mark.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15861 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15861 Fri, 14 Sep 2018 16:11:27 +0100 baffled http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15857 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15857 Thu, 13 Sep 2018 14:25:08 +0100 krishna
1. Can't insulate internally (so no insulation under the rafters).
2. The rafters are only 70mm or 75mm deep (varies depending on which part of the roof - there are three pitches.
3. We are not allowed to alter the ridge height.

If we put insulation between the rafters with breathable felt on top, I understand from building control we will need to leave a 10mm gap above the insulation, thus limiting us to 60mm of insulation.

In checking with Kingspan about their Nilvent breathable membrane, they said the alternative is to lay the Nilvent taught and counterbatten above. As far as I can see, this will raise the height of the roof by about 25mm?

Another possibility I can see from looking at the product brochure for Nilvent, is to lay sarking boards over the rafters, membrane on top of this, and nail the slates directly down, without the need for battens. This would actually be 5mm less than the current set up. This, it seems to me will allow us to fully fill between the rafters with 70mm insulation and, if say we used 20mm Pavatex Isolair sarking boards, this would provide a (small?) contribution to the insulation itself.

Is it worth doing the latter (or is that even feasible?) or should we stick with 60mm insulation with a gap to allow the breather membrane to drape between the rafters? Anything else I haven't thought of?

Also, what insulation between the rafters? Building control say I have to use PIR or something else of equivalent thermal efficiency. Would phenolic board make a significant difference?

Thank you.

Krishna]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15826 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15826 Thu, 02 Aug 2018 15:51:38 +0100 andylebalcon Would appreciate input from all.
We are renovating an old farmhouse that predominantly has no insulation or heating.
So far we have insulated between ceiling joists in various rooms where we can take up loft boards and stuff sheepswool between.
Over our dining room however it is difficult to do this.
i attach a detail cross section of ceiling construction.
Above is a very large windy, unventilated loft, which we would like to use in spring and autumn (unheated/uninsulated) for yoga/spare bunkroom and the like.
In the dining room we wish to keep the feel/look of the room with the white soffit between dark chestnut beams.
So I'm looking for a insulating board that can be cut specifically to each gap fixed to underside of deck and then lined with heavy duty lining paper and painted.
At 40mm thick (or so) it will improve a great deal the insulation and we can retain the very nice cherry boards above intact.
I have considered at length taking these up, but after various thoughts and investigations and experience am unlikely to be persuaded otherwise!
Any and all suggestions very welcome
Cheers
Andy
bty I have considered aerogel but after gaining a quote I'm looking for something much cheaper.
-]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15825 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15825 Wed, 01 Aug 2018 18:29:58 +0100 RoseMill_DandR http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15819 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15819 Mon, 30 Jul 2018 01:46:03 +0100 smudger
I'm looking at options to tidy up the internal walls during renovations. We already have external wall insulation and we are at 0.30 U value. Its likely to be 30-50mm insulation internally, which would not increase interstitial condensation (if permeable open) and be accommodated within the loss of room space.

There is a lack of info on websites on the fire resistance / flammability of the materials. Apart from personal safety (noxious fumes) we live rurally so 30 mins for brigade response likely.

Refs to class O (spread of flame) and EN13501 (without referencing classification).

Options being considered are Celotex or XPS (Marmox for bathrooms/block walls) or wood fibre / cork for breathable sections. Some reference class E which 'could lead to flashover'. Only Rockwool promotes its A1 rating which makes me suspicious of the others.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15781 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15781 Wed, 27 Jun 2018 11:18:55 +0100 gravelld
In the case of dwellings with unused space (e.g. a loft) I wonder if a hybrid solution is achievable? Install ducted MVHR to the first floor, running the ducts in the loft, and maybe single room units in the ground floor.

Anyone heard of this, is it possible to "balance" such a system?]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15726 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15726 Mon, 14 May 2018 09:00:05 +0100 ordinarybod
We are thinking to ask the tiler/plasterer to dry-line the external walls with insulation board, as well as the skeilings (the flat part of the ceiling has a thick layer of loft insulation on it). Does this sound a good idea? Should we also dry-line the flat part of the ceiling and the internal walls as well?!

Been reading others comments and now I’m worried about cold spots and interstitial condensation –any advice welcome, we have no expertise in building matters and are pretty baffled!! Thanks.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15734 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15734 Wed, 16 May 2018 22:35:57 +0100 Dominic Cooney
We are just starting a new Barn Conversion project.
I would appreciate some advice on various issues as it progresses...

The walls are 500mm thick sandstone.
There is a badly created window opening put in approx 1960's with a concrete lintel on the outside face and one on the inside face, with bits of timber in between (now rotten).

We have replaced the outside lintel with a dressed stone lintel to match the original lintels over the doors.
In the process of tidying up the badly created opening the window will be very slightly wider, which we have allowed for with the size of the stone lintel (150mm overlap on each end)

What sort of lintel should we install to replace the rest of the bodge job with?

The stone lintel is 130mm thick/deep so there is approx 370mm of wall thickness to support and then finish off internally with some insulation and plasterboard.

The length of the lintel is 1800mm (1500mm wide window opening once all tidied up and plumb!)

A single Catnic type steel lintel of the closest size suitable (heavy duty? extra heavy duty?) or several concrete ones side by side to fill the wall thickness?

Any thoughts anyone?]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15735 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15735 Wed, 16 May 2018 23:17:22 +0100 SarahLW Whilst doing this I would like to increase the property’s green credentials as much as my budget will allow. I have cavity walls but would like to bring them to a renovation u value.
I have been looking for suppliers of external wall insulation but drawing a blank in this area, my architectural technician is suggesting internal insulation and cavity wall insulation but don’t really want to lose the space and my understanding is external wall insulation is better due to potential issues with condensation with internal insulation and cavity wall insulation.
Current build is brick cavity walls with timber suspended floors, 4 inch joists around 350 centres
Also trying to decided between insulating between the joists and using spreader plates for underfloor heating or taking out the joists, using hardcore to fill void (around 500mm) insulation and screed system.
I would like to use bamboo flooring throughout the house.

Can anyone help please?

Main questions
Any external wall insulation suppliers in Dorset?
Is worth paying the extra for external wall insulation I will need to render with a 0.7 m band of brick slips (planning permission). I have got one price from Welsh company of around £15,000. They will install from ground level to soffits, have asked for Kingspan kooltherm to keep insulation to 50mm to reduce amount soffits would have to be extended.
Any advantages/disadvantages to the different ufh system for ground floor.
If I go with screed can I use eps for insulation in the floor rather than celotex to reduce the required amount of hardcore ( my understanding is this would require me to double the thickness of insulation to 200mm but not sure if it would take the weight)]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15684 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15684 Fri, 20 Apr 2018 14:45:26 +0100 SpaceTofu
Undergoing some renovation, i.e. a wall has been knocked off and creating one unique space from two rooms.
The room at the back used to have a cold pitched roof, will now have a flat warm roof and the RSJ will be exposed.
How to read the image below: the grey shapes are the walls (double skins), the black blocks are the padstones and the red rectangular is the steel; where there are gaps between outer and inner leaf stands for a small cavity.

The steel is sitting halfway on the external padstone, will this cause thermal bridging?
I suppose some TB will be happening, but is it indeed an acceptable thermal bridging (as that's how it is always done according to builders) or is it going to be very compromising?
If it is very compromising, how to minimise thermal bridging as much as possible, seeing the steel is actually already in situ and builders are very adamant that there is nothing to worry about and are laying bricks at the moment?



Thanks]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13972 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13972 Mon, 18 Jan 2016 10:56:40 +0000 lineweight
So, establishing it as a performance specification, against which actual performance can checked with a blower test on completion makes sense.

However, that only really works for newbuild. In most extensions or refurbs the newly constructed parts of the envelope generally enclose spaces that can't easily be sealed off from the rest of the (presumably more leaky) building.

So a blower test can't really be done.

What's the best strategy in this situation? Visual inspections at various critical stages before insulation etc is covered up?

I'd be interested to know how people have got on with this. Have you found that writing this into building contracts scares builders away - or have you found resistance to your suggestions that they need to improve their standard of work in order to achieve a reasonable level of airtightness?]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15649 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15649 Sat, 31 Mar 2018 12:09:30 +0100 biggerbyfar
Has anyone here had experience that they could share with Unger Diffutherm UdiReco or UdiIN Reco systems, or the Pavadry system? Pavadry requires dry-lining with plasterboard and gypsum skim whereas UdiReco is a direct plasterable surface.

Having boarded a room with pavadry I have found a few issues - there doesn't seem to be any anchors compatible that are thermally broken. I also found it difficult to get the boards level. The UdiIN Reco appeals because (I believe) it doesn't require a levelling base coat as it has a mouldable fibre backing that can flatten out any bumps. Also the front board comes with countersunk mounts so that thermally broken anchors can be used. I haven't double checked but it also seems that I could go back to the brick and save a bit of lost space from adding the insulation. One of the biggest tasks with my pavadry project was reinstating the lime base coat, which I wished I'd never hacked off. I had no idea of the amount of materials involved, and couldn't find anyone to do it, so did it myself :cry:

Any thoughts about any of these systems appreciated.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15610 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15610 Tue, 06 Mar 2018 19:32:43 +0000 acobite@yahoo.co.uk
About to start plastering most of the walls in our renovation. The house is mid-terrace, but it joins an older house where the roof is perpendicular to the roof of the terrace, so the ridge of our house hits the middle of their ridge, giving us two valleys (T shape in plan).

After heavy rain a section of our downstairs party wall becomes visibly damp. Not dripping, but darker than the surrounding stones which remain dry. I've been into the attic, and onto the roof, and can't see any signs of damp, or water ingress. Our neighbour also says his side is fine.

Aside from re-roofing the whole house, not really sure what to do..

So my question is; if I plaster over this part of the wall, which occasionally sweats, will the lime plaster fail?

Thanks in advance.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15623 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15623 Mon, 12 Mar 2018 17:32:36 +0000 jamesingram I've a friend whos looking for the best solution for HWS , with the restrictions on any external changes the choices are very limited (no PV, ASHP, Solar thermal)
Space heating the goal would be insulation, the idea of E7 thermal store came to mind , but seems better to invest in insulation, airtightness etc, (lets leave that for now)
for HW my first thoughts would be a main pressure cylinder with 2 immersions high Standard/low E7, which is the obvious standard solution.
anyone got some better ideas
here's the brief

Hot water design

Aim: Adequate cost-effective hot water provision to suit house being enlarged from 3-5 bed.

Current design is:
• All electric (no other fuel to property)
• “Economy 7” dual tariff meters
• HW cylinder is 1500 x 450 Economy 7 vented
• House heating supplied by two storage radiators (not sufficient!!)
• Bathroom shower is currently “Aqualisa Quartz Smart – gravity pumped” – good.
• Shower room shower is unknown (hidden behind tiles and not working properly).

Factors to consider:
• No change to external appearance of house permitted (alternative heating sources not practicable).
• New house heating will be provided by electric under-floor (to ground floor) and by electric skirting radiators (first and second floors).
o Hot water provision will be independent from house heating
o House heating will be mostly in use outside “Economy 7” hours.
• Expected use of house is single person, part-time (typically one cloths wash, one dish wash, five showers per week). However want to have solution that will adequately cope with typical household of four people (for when guests visit or for when house is sold).
o Want capacity for at least three “good power” showers in the morning (current tank can provide for two only). Bath infrequently used.

Layman’s thoughts:
• Will need to move hot water tank anyway
o Option to change to more efficient type of system?
• Ideal solution will probably have limited or nil hot water storage capacity (to minimise unnecessary heating)
• When second floor is added, showers on first floor will not need to b]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7182 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7182 Fri, 25 Mar 2011 12:31:52 +0000 jms452
The EWI fitters recommend a glazier do this – Glaziers know nothing about EWI so I will be moving the existing windows DIY.

The concept I wanted to air was creating a frame of treated timber around each opening (of the same internal dimensions as the opening) into which the window will be screwed and sealed into as shown below.

When we change the windows of the house all I have to do is make sure that the glaziers get the windows the right size and screw them into the wood.

Any snags with this approach that I should be aware of or suggestions for the best timber and treatment to use? This has to last 25 years minimum!]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15513 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15513 Fri, 19 Jan 2018 20:10:53 +0000 chrip
I have just bought a brick built - ex railway cottage/bungalow built around 1850ish which is a full renovation job.

But the first thing to do will be to stop the water penetrating the building.

There is sandtex type paint which needs to be removed and air-brick problems - see photos.

Also the property has been empty since last July.

Is there any ideas/recommendations on any further causes or remedies i should take?]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15587 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15587 Thu, 22 Feb 2018 19:16:27 +0000 nbishara
I've got a 1925 solid walled semi by a canal (so pretty humid). After much deliberation, we decided to go for breathable Ewi - and to take off the cement based render and internal gypsum plaster.

However, a (thoughtful) builder has pointed out to me that not only do we have sand and cement mortar, which I knew, but the bricks are apparently london brick company flettons - or commons...but definitely very hard and arguably fairly impermeable.

Said builder noted it was worth checking out whether there was much point using more breathable (& more expensive and less insulating) insulation (probably wood fibre), as well as lime based render, hacking off plaster, replastering with lime plaster etc when we have relatively impermeable bricks and mortar.

So, this is me checking...are lbc commons/flettons sufficiently impermeable to negate the advantages of breathable Ewi? It might be worth noting that we're planning on replacing wood suspended floors with insulated concrete slab, with have a slate dpc that's been bridged with render and there's still. I sign of rising damp, we do have mouldy issues ATM but hope to achieve sufficient airtightness for mhrv to be effective.

Really appreciate any advice/comments/suggestions or experiences,

Thanks,

Tania]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15545 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15545 Fri, 02 Feb 2018 11:26:02 +0000 RedDoor
The situation is that the wall drops below the door threshold level and is below ground on the outside (street pavement) but is open to the space under the suspended ground floor.

Because of this, over the decades ( the original pavement would have been below the poured dpc one assumes) the original joist timbers have rotted. To remedy this we built a dwarf wall inboard of the wall to support new timbers with sufficient space to drop the IWI all the way down passed the joist ends and into the underfloor space.

Since this has taken place over the course of a few years (ahem! http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11175&page=1#Item_9) ideas have changed as we've moved on. In the main room (now, I can see this clearly but I hope that I can describe it so that it can be pictured) the IWI goes down the wall below the joist level, finishing below the joists but a strip was left out at skirting board level. The membrane was drawn through under the joists and above the supporting dwarf wall, pulled up above the joist ends and secured to the wall with the final strip of IWI at skirting level. However, at the door in the hallway, there's no wall at skirting level!

So, I was thinking of drawing the membrane through under the joists, up against the wet wall under the door step and then trapping it directly to the stone threshold with an improvised upvc capping. Insulation could then be slipped down into the gap between the joist ends and the (now membrane covered) wall.

All this is complicated by the presence of the dwarf wall and the question of how I properly seal the membrane to the rough stone walls in the corner where the joist is hard up against the wall..... another discussion!

But does anyone have any comments on the opening question?]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15543 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15543 Thu, 01 Feb 2018 15:37:50 +0000 oink
I've moved into an old stone cottage and am looking to get wood flooring in the living room. The floor is concrete, no idea when it was laid. The chap who will be installing the wood floor has tested the concrete and the moisture readings are high; upto 85%. He has suggesting using ARDEX DPM 1C to protect the floorboards.

My concern is the 'breathability' issue. I'm a complete novice to old buildings but have been trying to educate myself, albeit slowly! Despite having cement pointing externally there doesn't seem to be any damp issues in the walls but my concern is that by stopping evaporation of moisture through the floor it could divert it to the walls, where it would then have trouble finding a way out. I did ring ARDEX and the chap on the phone reassured me that their product doesn't stop moisture passing through, it just controls the rate to a level low enough to protect the floor, while still allowing the moisture through and therefore not forcing the moisture into the walls. He really did sound knowledgeable but I thought it almost sounds too good to be true.

I was just wondering if anybody had experience using a liquid dpm in an old house, or more particularly, if anybody has had any problems using one? Or if someone had any advice for me?

Thanks in advance,

Joe]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15523 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15523 Wed, 24 Jan 2018 01:05:24 +0000 Duffer
I'm a newbie so apologies that these questions might sound dufferish (hence the name!)

We have recently bought a late, late Victorian or super-early Edwardian semi. It has loads of original stuff which is exciting but also entails a lot of repairs!

Whilst we're getting some floor joists repaired in one of the ground floor rooms, we're thinking of having underfloor insulation put in. There's only a small crawl space so this will entail having the floor up. For info - the crawl space (from the bottom of each joist to the floor) is 700mm max so, we gather, not enough space to do the job from below (although I went and had a roll around in there last night and found it to be a lovely cave but I guess I wasn't trying to do work!) The room we have so far inspected has a clear void and we've already cleaned 110 years of dust out of the vents which sit at joist-level.

We've found a builder who seems to be sensitive to old buildings and green measures (he's done a lot of church renovations, apparently) and he seems good to work with. We're not sure about the spec that he's proposing for the underfloor insulation though so it would be wonderful to get some views on the specifics so that we can have a more sensible conversation with him.

He's proposed what seems to be the usual insulation between the joists but with some additional flourishes which we're curious about. This is his proposed construction:
Chicken-wire between joists holding some kind of insulation TBC (we will insist breathable, hygroscopic etc) with building paper on TOP of the joists and then on top of that wpb weyrock flooring and then, optionally, floorboards. To accommodate the added layer of Weyrock he plans to cut off the bottom 18mm of the skirting boards.
There are a few things which are worrying us a bit about his spec:

(1) He's proposing to get rid of the floorboards and replace with wpb weyrock flooring which seems to be a moisture resistant chipboard. To be fair, the floorboards are only original in around two thirds of the room - the other third is not original and the replacements don't match. The room is, in any case, carpeted at present and will stay so for the foreseeable. His other suggestion is to put in the chipboard and then add the floorboards on top, slicing the bottom off the skirting board. We've been reading around this and haven't really come across chipboard before in this application. --> Our question is --> How beneficial is the chipboard? Would it be madness to have the work done and not add the chipboard? Is there anything we could use in place of the chipboard that would be less deep (and thus take away less skirting)? If the chipboard is to reduce drafts, can we instead seal?

(2) We have another couple of downstairs rooms which we're tempted to have insulated at the same time but in those rooms, the floorboards are exposed but not original, we think - we'd love to stick with exposed floorboards in this room but if we could reinstate something a bit more like what might have been here before, that would be a bonus. I'm particularly precious about the skirting boards being reduced in height as they're gorgeously deep at present. So, here, we're wondering - whether anyone knows of any material that would offer the benefits of the chipboard (whatever they may be, presumably reducing airflow) but with the looks of pitch pine or similar. Probably a pipe dream but if anyone is going to know, it's going to be you people, by the looks of things!

(3) He's proposing to use wire mesh between the joists. Most of what I'm reading suggests plastic mesh - are there any issues about wire?

Any experiences, knowledge and suggestions gratefully received.

Thanks for your time.

F]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15504 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15504 Mon, 15 Jan 2018 13:43:48 +0000 Victorianeco
This might be too big for our local joiners personally

I have a grade 2 listed building in Cardiff which requires over 50 windows of considerable size

Thanks]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15450 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15450 Mon, 11 Dec 2017 21:25:02 +0000 Kenny_M Just joined the forum today. Moved into an 1800’s detached sandstone house with flat roof rear extension built in 1989 about a year ago. The last year has mostly involved dealing with things like internal damp issues, repairing cast gutters, blocked downpipes, sealing up gaps at windows, reopening blocked under floor vents and a host of other diy jobs, and my main shelling out of cash has been for a mason to repair some of the ashlar stonework cornice and some stone at the front and to rebuild a chimney which was taking in water (one part of the dampness issue, the other part seems to have been mainly internal condensation (sash windows were all painted shut and no vents in bathroom and kitchen).

My next step is to attempt to improve the energy efficiency and trying to decide what to do first. The GCH boiler is a quite old Ideal Mexico Super RS 125, which was allegedly 73% efficient when new, but presumably not now. This boiler is a bit of a workhorse and has lasted around 30 years, but the amount of heat coming out of the flue is criminal!

The other side of things is insulating the fabric of the building. Despite the fact that the old part of the house still has single glazing and no insulation, it seems that it’s the ‘modern’ part that is the weak point. When I got up this morning before turning heating on it was 7 degrees C in the south facing 1980’s extension, but 12 degrees in a North facing room in the original house which has single glazing but had the wooden shutters closed all night. I wandered around the house this afternoon with an IR gun and was getting varying readings from -2 to zero degrees C on the outside walls, but on the double glazing pane around +5 degrees C, and parts of the frame were reading around +8 degrees C. I know that replacing double glazing is not usually the most cost effective thing to do, but this seems to be where most of the heat is leaving the house so I am wondering if I should go there before attempting to insulate walls. I think the issue in the extension is the amount of glass. It’s an L-shape and the sitting area is the bit that juts out, which means 2 out of the 3 outside walls of the sitting area are glass (patio door and windows). My gut feeling is that replacing the old DG windows will have the most impact in terms of comfort, they are old, unusually small gap, and were draughty before I silicone them up.

One concern is that I do intend to insulate the walls eventually and I am concerned that this might be the wrong way around to do things, in terms of insulating the reveals. Is it better to do get the walls insulated first, then get window fitted taking into account any narrowing caused by insulating the reveals. Sorry I don’t know a lot about this so apologies if I am talking nonsense!

Anyway, sorry for the long story, from my look around so far this seems like a good forum with a lot of experienced people so I would really appreciate any comments and pointers.

Cheers
Kenny]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13038 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13038 Wed, 28 Jan 2015 11:04:06 +0000 gravelld
I want to start addressing ventilation. RH in many rooms is consistently around the 70% mark; I want to get this down to 60% as a maximum. Condensation is a problem and as I have been draught proofing we are beginning to see mould on window frames and in window reveals.

The house, despite my air tightness work so far, is probably still (air) leaky. So what is the best methodology to go forward? Should I try to start an MVHR project, knowing it's going to cost us while the house is leaky? Should we go for SRHRV and do rooms as and when?

Some house details:

• 1950s build, masonry cavities


• All cavities filled, although some with fibrous batts


• Cold roof, 270mm rockwool


• Zoned heating, only 40% of the house is heated typically


• Three (count 'em!) extensions


• Three bathrooms, two toilets, all dumb 'hole in the wall' extraction (although I did install an Iris fan in one toilet).


• One kitchen, one utility room, neither with extraction or cooker hood filter

Any thoughts would be appreciated, I'm not expecting one true answer but more a bit of guidance as to what to look at, what to measure etc.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15467 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15467 Thu, 21 Dec 2017 14:47:57 +0000 GarethC
I've got period cornices and all sorts of 'stuff' on my walls, so 'proper' IWI would extremely expensive and disruptive, and I'm worried about it causing condensation problems.

Would affixing just thin insulated plasterboard (15mm celotex + 12.5mm plasterboard) to my external walls be a good idea? Calculator suggests that this would reduce the U-value from 1.1 to about 0.55. A decent improvement, and am I right that by not lowering the U-value by 'too much' I'd reduce the chance of condensation issues?

Also, instead of removing the cornices, the insulation could just finish where the cornice starts. Given it would only encroach by an inch, I don't think it would be noticeable. I -might- even be able to get away without removing the skirting boards as they're quite thick. i.e. thin insulation would basically make it all a lot easier and cheaper to do.

Of course, I'd end up with a strip at the top and bottom of walls which was un-insulated if I did this, so is it a stupid idea? Greatly appreciate any advice.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14381 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14381 Fri, 08 Jul 2016 11:10:34 +0100 smudger http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15435 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15435 Tue, 05 Dec 2017 20:00:41 +0000 kayserasera
I have a question about vapour barriers, energy efficiency and avoiding problems with interstitial or room side condensation. I would really appreciate any helpful comments regarding how to approach our project to get good value, design and low risk with regard to damp and good energy saving. I know that our situation is not ideal design wise because it is a conversion. I’m hoping to do the best in the circumstances.

Our barn footprint is approx. 22m by 11m. It’s being split into two homes, with bedrooms being created in the roof space, like a dormer bungalow, with velux windows.

The original wall construction is cavity wall 1980’s vintage, with reconstituted stone mock stone effect on the outside and breeze blocks on the inside. There are internal breeze block piers along the interior of outside wall at intervals for support ( no original internal walls for support ) Design is to be open plan interior.

So far we have had a new internal cavity wall dividing the two dwellings, new attic roof trusses installed with 22mm chipboard floor deck. Each bedroom has a velux triple glazed window. The roof has a permeable membrane felt, with reused concrete pantiles

Insulation: We were not keen to use cavity wall insulation because of possible damp problems sometimes reported. The plan is to use 100mm celotex to internally insulate the outside walls. The surface of the celotex would then be in line with the breeze block piers. We are then thinking of putting either foil backed plaster board or insulated plaster board over the breeze block piers and the celotex so that the wall appears smooth without piers sticking out into the room.

We will be insulating between the roof trusses with 150mm celotex equivalent wedged in.

We have discussed with the builder about whether having a complete continuous vapour barrier connecting the celotex in the rafters with the celotex lining the masonry walls is a good idea or not. Obviously the celotex has foil backing, but how important is it, for example, that the breeze block piers should have some kind of membrane over them which is then taped to the adjacent celeotex foil so the membrane is continuous from floor, around the walls to roof ridge?

One reason not to be obsessive about taping is that I am concerned about interstitial damp and room side damp. We do not plan to have a heat recovery unit, although I might consider individual extractor fans in bathroom etc to have heat recovery in them.

Also do you think the breeze block pier with less insulation than the adjacent wall might be problematic for interior condensation (thermal bridging) ? I know it’s not ideal but it’s a trade off of looks and less cost against any effects of thermal bridging.

I would like to know how some experienced people on this forum would approach vapour proof barriers etc in this instance. i.e. what needs to be membraned and taped or is that kind of fussiness more relevant to single skinned walls?

It would be really helpful if you can be specific as possible about what you would tape( if at all) and what membrane you would use to connect up to the celotex foil, and what extra insulation measure you might think wise. Somebody said that foil is better membrane than plastic as plastic can encourage condensation ?]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15426 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15426 Sat, 02 Dec 2017 12:11:29 +0000 Mynamite http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13679 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13679 Fri, 25 Sep 2015 16:36:58 +0100 Victorianeco
I was contemplating getting a modern composite door, but do like the original for.

Links to products appreciated.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15415 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15415 Sun, 26 Nov 2017 13:40:24 +0000 Dabbler I've noticed a couple of firms supplying chimney systems that draw the air for the stove down the chimney alongside the exahust flue (eg POUJOULAT efficience). These are all rigid systems for new build. Has anyone seen a flexible flue system for retrofit?
I'd imagine them having a specialist terminal, then dropping a second smaller pipe for the air supply down alongside the flue liner.
There are probably very good reasons why they don't, the care needed to make certain the flue is large enough, the care needed to avoid kinks when fitting etc. But it would be a lot simpler than running a air pipe through the sub floor to the outside.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1264 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1264 Mon, 18 Feb 2008 09:35:23 +0000 villagedefender
I moved into my new house last night, and hey presto we had the coldest night of the year.

Well, apart from the radiator in my room not working we survived.

Anyway, a portion of the ground floor is only single skin brick, what would you suggest for insulating the walls?]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2924 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2924 Wed, 12 Nov 2008 13:40:31 +0000 Esphino
I am renovating a house in Mid Wales and need some help regarding the way I install the Kingspan/Celotex insulation. As it stands I plan to install 120mm of kingspan/celotex in the following way 40mm between the rafters and then 80mm over the rafters with plasterboard over that.

My problem is that I am unsure of how I should attach the 80mm boards to the rafters, I could use 100mm screws but then I am faced with the issue of how I would then attach the plasterboard to the insulation as this would need 110mm dry wall screws at least to get through the insulation into the rafters.

Can the pir and plasterboard be bonded together and if so what would be the best product to use for this?

Any help on this would be much appreciated]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14060 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14060 Tue, 16 Feb 2016 23:49:21 +0000 skaffen
After lurking and reading around the forum for a few weeks, I'm looking for advice on my proposed plan for insulating attic rooms in our Victorian house. Built 1877 it's one half of a semi that then had another house built directly adjacent, but at a lower level, a few years later.

- External Wall 1 - 4.2m x 2.75m high (with a corner taken out due to slope of roof)

This is a gable end wall, with the roof and attic of next door about half way up the wall. Currently brick covered with original (lime?) plaster which is very sound.

I plan to dot and dab Cellotex PL4000 65mm+12.5mm over that wall.

- External Wall / Ceiling Slope - 6m x 4.3m (3.3m of sloping ceiling and 1m of vertical solid wall)

Spanning the width of the front of house this is about 1m of solid wall before the ceiling slope which extends 3.3m to the 'flat' part of the ceiling.

The 1m height of solid wall

Plan -> Dot & Dab Cellotex PL4000 65mm+12.5mm

*Sloping ceiling wall* has approx 1.5" of latch and plaster over 64mmx85mm rafters with approx 380mm centres. Beyond that are slate tiles on battens. Slate tiles are 99% sound.

Plan -> Remove lath & plaster. Insert 80mm Cellotex GA4000 board between rathers. Tape joints with metallic tape. Fix Cellotex PL4000 65+12.5mm plasterboard over the GA4000 & rafters.

*Flat ceiling*

This is approx 3m x 6m and extends over the other attic room and a landing/stair space. Lath & plaster (very sound) onto 3" x 2" joists with 15" centres. Above that, rafters with slate tiles on battons. Very drafty. Signs of a few missing tiles. There was no access to this loft space, when I cut a hole to inspect, the big surprise was that the loft space ran the full length of both our house and our mirror image 'twin' next door. There is no dividing wall.

Plan -> Roll out 380mm width strips of Knauf Earthwool 100mm between joists. Overlay at 90 degrees with 200mm Knauf Earthwool, for 300mm total thickness.

A few questions.

1. Is there any point in removing the (sound) plaster from the solid external wall before dot & dabbing the Cellotex PL4000 on top?

2. I plan to push the Cellotex between the rafter on the sloping wall up into the loft space to abut the 300 mm of mineral wool. Is that a good idea?

3. Am I going to have problems with condensation? I plan to have a shower in the room (with an extractor venting outside).

4. Will thermal bridging be a big problem from the external gable wall to the internal solid wall that forms the rear wall of the room? Anything I can do about that?

Happy to hear thoughts on more effective / cheaper alternatives!

I have some photos here https://www.icloud.com/sharedalbum/#B0N5ON9t3FY1xg

Regards.

Greg.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15398 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15398 Thu, 16 Nov 2017 14:16:03 +0000 Seret
https://photos.app.goo.gl/jmfsyULSKzelFtke2

Basically what this guy's done is cut the board up into chunks and then randomly stuff them into the void under the floor in a big jumble. Massive air gaps everywhere, no vapour control layer, none of the insulation actually in contact with the floor. Mindboggling.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12599 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12599 Sun, 28 Sep 2014 20:16:49 +0100 Victorianeco
I assume the preferred method would be to stud the walls at 400 centres using 3x2 or 2x2? Insulate inbetween using PIR then insulate infront of the studs with further PIR?

I wanted to keep the breast wall as a feature so to speak but not sure this is practical, just insulate over as above?

Thanks]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14797 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14797 Mon, 02 Jan 2017 08:30:25 +0000 Pigglet The plan is to lay a 80mm UFH limecrete slab over Geocell insulating aggregate and finish with a sandstone floor pointed with lime grout.

Basic floor slab spec is non woven membrane, geocel, nonwoven membrane, geogrid (will expand on this) UFH pipes, Limecrete slab.
I've got so far as getting the geocel down and wackered however this has been rather tricky as the lumps of geocel are quite large and being light they move around easily. I took my time to ensure the fill was spot on level using a rotary laser and long levels (note, this took a lot longer than with dolomite or similar).

As soon as I tried to wack it down the wacker started pushing it around. I tried 3 different wackers, ranging from a little amman wacker to a large forward and reverse wacker I use on road work. The smallest and lightest worked best. (large wacker wasn't really practical in such a small cottage but wanted to see if it would help with compaction)

The supplier stated that the geocel should compact by 25%, it has not compacted by anywhere near this amount, probably around 12% in reality hence my trying the large wacker. I didn't want to keep running the wacker over it as after a few passes it didn't seem to compress any further and I was worried about shaking a 300 year old terrace to pieces!

Having got this far the next issue I can forsee is that the geogrid provided by the supplier for the purpose of attaching the underfloor heating pipes to is nothing more than thin flexible plastic fencing mesh.
As the geocel is effectively a loose fill even after wacking there is no way of anchoring this mesh down and as such I am sure that when I try to lay and cable tie the UFH pipe to it, will just lift and distort due to the UFH pipes tendency to want to spring straight. I think I'm going to have to shell out for some steel reinforcing grid to clip the pipes too.

Has anyone else done this and is so what were your conclusions? Any tips or tricks? Based on experience So far I'm less inclined to go down this route again in a small building due to the difficulty of getting a level Geocell base for the slab.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15349 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15349 Tue, 17 Oct 2017 14:57:22 +0100 owlman It got me thinking about the gutter brushes "hedgehog" type. They are about £13 for a 4M length, expense apart are they any good, anyone got experience?

P.S. I bought some small metal baskets that now fit into the downpipe top]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15340 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15340 Thu, 12 Oct 2017 21:58:09 +0100 tony
I heard a target of 1,000,000 homes per year for twenty years

Interesting, anyone know any more details?]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15341 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15341 Fri, 13 Oct 2017 01:39:45 +0100 gyrogear
(new set-up = 3 x Tinox GM, tempered Low-E glazing, 2.5 m2 each. ( Weight not stated...)
Including tubular-steel support structure (3mm thick walls...)

Problem now arises re how to fix through 100mm EWI & into block wall...

The sketch suggests using threaded 20mm SS bar & is the only suggestion received so far...

Despite my reservations for the suspension principle, period, I feel inclined to suggest thinner mild steel bar, inclined *upwards* into the blockwork; with steel-tube sleeves inside foam-filled PVC liners through the EWI, & big washers, for anti-compression etc.

Photo shows old installation, pre-EWI...

all / any opinions welcome.

gg]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15075 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15075 Mon, 01 May 2017 12:52:24 +0100 newcastlerenovation Velfac and Allan Brothers are about same price - i got a special May offer from Velfac !
Olsen slightly more
Rationel quite a bit more - extra £4,000
We are looking at aluclad - u values are similar - we are retrofitting existing windows.
Any comments on quality, style, reliabilty/delivery times, ease of retrofitting, aftercare with these companies ? Is it worth spending more on the Olsen or Rationel windows ?
Thanks for any comments.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15321 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15321 Fri, 29 Sep 2017 09:31:47 +0100 acobite@yahoo.co.uk
Recently bought a mid terrace house built 1863. After lifting the carpets, linoleum and slate slabs, we discovered a compacted earth floor. Initially quite surprised, but after doing a bit of research it seems like these were the norm. We've dug a couple of exploratory holes and the foundations don't go very deep, so a suspended floor is not an option.

So the choices we have so far are;

a) leave the earth/slate down and live with a breathable/cold floor.

b) dig down far enough to put in a dpm/concrete slab and float a floor on top, making for a warmer floor, but compromising breathability, and potentially sending more moisture into the walls.


Would rather use as little concrete as possible, so would love to hear if anyone has any alternatives.

Thanks]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15327 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15327 Mon, 02 Oct 2017 09:27:05 +0100 Leedjc
I'm laying slate down on our limecrete floor, but want to darken the mortar used for the grout. Has anyone done this? I know a pigment can be used for plaster, but can't think of any good reason why it can't be done for a grout mortar as well. Or is there some other way this should be done?

Thanks
Lee]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15274 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15274 Sun, 03 Sep 2017 16:18:26 +0100 girdersofbabel
I wonder if you could help. I am renovating a bathroom in a Victorian house, and my builder has proposed an unorthodox detail. Having sought advice from a few suppliers, I got confused as they are all saying different things, yet I'm sure that this sort of situation must arise often in practice and can be easily resolved...

The attached drawing shows the detail, with tiling over an existing ground floor which is part suspended timber joists and part suspended concrete slab on brick sleepers.

Our builder has proposed the construction shown on DETAIL 1, with new plywood substrate laid over existing floor joists (item 5), and a layer of cement board on top bonded to the plywood with the tile adhesive.

To deal with the joint between concrete and timber substrates, he proposes to oversail the cement board over the concrete (item 6a) and to pour self levelling screed (e.g. Mapei Ultraplan Renovation) over the concrete to bring it level with the cement board (item 7). A second layer of cement board will then be laid on top, again bonded with tile adhesive and fixed down with extra screws (item 8). A liquid waterproof membrane (e.g. Mapei Aquadefence) then goes on top (item 9), then the tile adhesive and tiling. The theory is that this avoids having to have a movement joint between the two substrates which could be problematic for water penetration.

Is this detail acceptable, from your point of view? If so, what thickness of cement board is OK to use? Can I get away with 6mm, or should it be 12mm?

Also, do you think the plywood base is adequate (18mm marine grade ply)? Some suppliers are adamant that I need 2 layers of plywood which seems excessive. The existing timber joists are 45x95mm @400cc. The tiles are 9.5mm porcelain.

Would be most grateful for any tips and advice!]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15234 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15234 Wed, 16 Aug 2017 12:11:14 +0100 SpaceTofu
we have a period terraced house, with extension at the back, double glazing. Overall pretty well doing in terms of condensation / damp.

However, I noticed the other day that the 3 or 4 1kg pack of salts (yes, I know. I love bulk saving offers) have absorbed LOADS of humidity. They are stored in cupboards that are well above 1.50m height from the floor. Further, the external wall on the back is south facing, although it doesn't see much direct sunlight due to the extension of the next door neighbour.
When we cook we always turn on the fan and we do not believe there is any broken pipe in the vicinity. The back of the cupboard looks alright and not rot, if a pipe would have burst I would have expected to see rotting wood.

I do want to warn at this point that when we were still house hunting and having developed a penchant for period houses, I did back then a lot of reading into rising damps, the myths and the facts.
I am therefore a "rising damp" skeptical, although I do recognise that with certain materials / constructions it can actually happen.

The kitchen is in the rear extension bit and is actually sitting on a floor of solid concrete (the "main" building is sitting on raised wooden floors).
The kitchen did have some rising damp interventions a good five years ago, as we came to know when purchasing the property.
The report mentioned things like "Conductivity meter tests gave patterns normally associated with rising damp (sharp cut-off) in those ground floor walls shown in the attached plan; this is probably due to the lack of an effective DPC " and "the plaster on the walls marked in the plan looks significantly decayed . This condition is likely to be a product of residual salt, which might be hygroscopic"
The work ultimately carried out was "to drill and inject a chemical DPC, hack off and re-plaster as above specification (plaster will be hacked off to a min height of 1 metre and replaced to our spec in the area marked in the plan. Sand and cement with ratio 3:1 will be used and incorporating a waterproof/salt inhibitor in the gauging solution)"

My questions now are:
- with the (little) details provided, do you think I am witnessing actual rising damp?
- if the above is true, leaving aside poor workmanship, how is it possible that after solely 5 years of that chemical DPC carried out we are witnessing rising damp?
- I was reading back in the days that once can purchase "salt tester" (I do not remember the correct name) and other cool gadgets to DIY check for rising damp. Are those readings actually relatively easy to carry out and interpret for a novice?
- last but not least. Do you know any good damp expert, i.e. that does recognise that rising damp exists but only in 5% of the houses? We live in the Bristol area

Thanks!]]>