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Housing - Renovation: EWI detailing

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    • CommentAuthorRedDoor
    • CommentTimeNov 8th 2014
     
    Scaffolding goes up next week for EWI on solid stone walled mid-terrace property in S Wales. Would the insulation normally be extended down to the equivalent of under the internal floor joists given that they are themselves some 300mm above the external ground level? Contractor says that they have to go to the existing drip strip which for some reason is down to the internal floor level only (i.e. some 175mm higher) on that wall. On the rear-most wall they'll go down to normal drip strip height above the ground level as there's no existing strip and owing to the slope of the plot this is some 600mm below the internal joists
  2.  
    I would suggest going down to ground level all around. It will reduce the cold bridge you will otherwise get if you stop the EWI just below the internal floor level. What plans do you have for insulating the suspended floor?

    Several posts on here about the non-issue of taking EWI over the DPC.

    Hopefully FT and Tony will be along to add their tuppence.
    • CommentAuthorRedDoor
    • CommentTimeNov 9th 2014
     
    This is a GDHIF job so as it's mainly funded by the voucher we are not perceived to be the customer. I've tried to get the surveyor to agree to the obvious but he says that if the job is audited then it wouldn't be to the Wetherby spec and then they wouldn't be paid.
    Plan is to insulate the suspended floor with (working void to room) 25mm PIR, membrane, warmcell between joists then original floorboards. Sheeps wool at external wall edges and the membrane Orcon'd to plastic strip bedded on the void walls. No tape as experiments with a blue fabric tape (expensive and sold for the job) resulted in the tape failing within weeks.
    • CommentAuthorTriassic
    • CommentTimeNov 9th 2014
     
    You could phone Wetherby and ask their opinion.

    If all else fails get the work done and then lodge a complaint that it's been done incorrectly and you are concerned about cold bridging and condensation.
    • CommentAuthorRedDoor
    • CommentTimeNov 9th 2014
     
    Monday morning - call to Wetherby.
    My point really is that I shouldn't be having to do this. The system should be spec'd to insulate the walls and not leave us with potential cold layers against internal timbers. Just because the property is on a hill and the bottom of the 3 walls aren't at the same ground level shouldn't make it difficult. I can see that taking it to the rafters in the roof would be a challenge.
  6.  
    My EWI which was Green Deal funded has numerous issues that I've picked up on from here.

    However, as it was a freebie and the whole house needed rendering anyway at the rear I can't really complain as it was essentially a bonus.
    • CommentAuthorRedDoor
    • CommentTimeDec 10th 2014
     
    Tomorrow, I hope to meet the contractors' rep on-site and I want to point out a detail that I think will be important, but maybe others can persuade me otherwise.
    The neighbouring flat roof has it's pitch down towards the vertical face of the EWI - so the flashing is directing rainwater to the edge of, and behind, the EWI. What would be best here to deflect the water into the gutter?
    • CommentAuthorn2e4ewi
    • CommentTimeDec 21st 2014
     
    Lookup John Hemphill at a company called EWI Pro, say number came from me sure he will be able to advice, if you have a system provider in hand they should be able to advice just double check with the aforementioned
    • CommentAuthortony
    • CommentTimeDec 22nd 2014
     
    Flashing looks dead odd to me, it should only need to cap the felt up-stand.

    needs to be fail safe so no water can get into your wall. likely not going to be a problem should have been pulled out from behind the eps already though.
    • CommentAuthorRedDoor
    • CommentTimeDec 22nd 2014 edited
     
    I should have added more detail to this as the image is not clear.
    One single wall shared by two properties. Rhs has the EWI cladding. Lhs has glass-fibre roof with lead flashing ( and all covered in debris ). In the centre is the gutter and this is because the slope of the flat roof is down from left to right.
    The flashing solution would be to create a corner, perhaps let into the insulation. However, that still wouldn't seal the gap under the flashing above the deck bearing in mind that water is flowing over the deck from left to right.
    Correcting the obvious mistake may be possible (who builds flat roofs with pitch to the party line?) but I was wondering if there was a different solution.
  11.  
    This is typical of the new 'details' needed for a whole raft of EWI scenarios. Anywhere where there is lead conventionally cut into a wall is a nightmare; as the EWI is generally outboard of where the lead is cut in. - allowing water ingress (if that makes sense?)

    The answer is usually to form new lead goods (which can often involve welding). Fibreglass is also an option especially if the flat roof is glass.
    Unfortunately in your case the lead needs to be installed prior to the insulation to create an effective seal. Other than that you will be relying on the render and a silicone seal
  12.  
    Resurrecting an old thread just for the title.

    Retrofit EWI:

    What are your favourite, and least favourite, details, and what details are you still unhappy with in terms of their ability to last the life of the system?

    Perhaps I'll start:

    Favourites:

    - Roof properly extended at eaves and verge as required to fully cover (and sufficiently oversail) the EWI or

    - Well-formed bespoke 'cappings', either 'self-built' of lead/lead alternative (if sufficiently durable) or purpose-made of welded alu.

    - Use of expanding foam tape at openings and 'ends'.

    - 'Main wall' EWI sits directly (not on a base-rail) on top of a slightly-recessed 'plinth' of 'below-DPC' (whether or not there actually is a DPC) EWI, which may or may not be of a different material (as discussed in other threads). A drip should be incorporated, and if there is anything between the 2 layers I would suggest I strip of expanding foam tape and several beads of adhesive Pu foam, rather the 1 strip of expanding foam tape (and a lot of air 'approved' by some system providers.

    - Adhesive/meshed beads to adhere to window. Silicone seal over.


    Least favourites:

    - Systems which stop at 'DPC level', even when the DPC is an injected one *above* floor level.

    - Silicone as the *only* seal at openings.

    - 'Industry-standard' cappings where eaves and/or verge cover is not provided by the roof, installed with silicone as the only long-term weather seal, and often installed below first floor ceiling level.

    - 'Silly' details of all types. A few examples include EWI cut out for cables, road-signs, because the installer did not provide a flue extension, etc. etc.

    - EWI stopped above flashings on bays or offshots.

    I am sure I will come up with more!

    Nick
    • CommentAuthorgravelld
    • CommentTimeAug 26th 2018
     
    The trouble with some of your favourites (e.g. no base rail) is that if they contravene the system then you're out of luck if you want a guarantee - then the only alternative seems to be DIY, which is hardly feasible in most cases.
  14.  
    I take your point, gravelld, but the BBA Cert for the system I am currently using does not cover the below-ground installation anyway. However their guarantee will cover everything above that, and they are happy in effect, from a g'tee point of view, to treat the plinth layer (with a drip) in lieu of a base-rail.

    I feel the 'systems' are sometimes too inflexible, and some of the standard details (and, to be fair to the standard details, the way they are sometimes installed by people with no understanding of thermal by-pass, thermal bridging etc.) are less than ideal. Too much reliance is placed on a gob of mastic.
    • CommentAuthorbxman
    • CommentTimeAug 26th 2018
     
    Angle the window reveals with the windows set now so far back into the structure both view and light levels are substantially reduced and that little bit of insulation you lose does very little actual insulation out there .

    the PVC sills are not that clever but like everything so much depends on the care taken by the installer .

    I have now gone below ground level but used FOAMGLAS® Insulation below the damp course and covered it with artificial roof slates

    Remember BBA's involvement in Grenfell and draw your own conclusions .

    Sadly in modern day life most people are only in it for the money .
    • CommentAuthorgravelld
    • CommentTimeAug 26th 2018
     
    Posted By: Nick ParsonsHowever their guarantee will cover everything above that, and they are happy in effect, from a g'tee point of view, to treat the plinth layer (with a drip) in lieu of a base-rail.
    Cool, can you whisper the system?
  17.  
    Posted By: Nick ParsonsFavourites:

    - 'Main wall' EWI sits directly (not on a base-rail) on top of a slightly-recessed 'plinth' of 'below-DPC' (whether or not there actually is a DPC) EWI, which may or may not be of a different material (as discussed in other threads). A drip should be incorporated,

    What is the purpose of a 'drip'

    Without a 'drip' rain hits the wall, runs down the wall and into the ground next to the wall and is catered for by what ever manages the rain water.

    With a 'drip' rain hits the wall, runs down the wall to the drip and then falls into the ground 2cm from the wall and is catered for by what ever manages the rain water.

    I can't see any advantage in providing a 'drip'
    •  
      CommentAuthordjh
    • CommentTimeAug 27th 2018
     
    Drips stop water running back along the horizontal surface and getting into any small cracks (and then expanding said cracks when it freezes).
  19.  
    P-in-H, I cannot help but agree with you! But with both EPS systems I have used, there was a different render for the 'main EWI area' and the underground/'splash-up' zone, so there would have t be a junction of some sort anyway. When I was an extra pair of hands on a job with Udireco wood-fibre, the 180 wood-fibre met 180 EPS directly, with no drip.
  20.  
    Posted By: djhDrips stop water running back along the horizontal surface and getting into any small cracks (and then expanding said cracks when it freezes).

    With EWI The only horizontal surface would be the one created by the 'drip'. So if the 'drip' is there it is needed - because of itself and if it is not there it is not needed
  21.  
    Ah, djh, I think we must have posted in the same instant - I had not seen yours, and P-in-H's reply to you reminds me I perhaps missed out a bit of info. The 'plinth' layer is 130, vs the 150 of the 'main' EPS, so there is a horizontal surface.
    •  
      CommentAuthorfostertom
    • CommentTimeAug 29th 2018
     
    I also abhor drip or in fact any discontinuity in the EWI face or body, just above GL. Of all locations, in that splash zone it ought to be seamless. So Nick, why did you put it in your 'good practice' shortlist?
    • CommentAuthorbhommels
    • CommentTimeAug 30th 2018
     
    To be meaningful the "likes" and "dislikes" should have a cost tag attached.
    The additional cost of having EWI continuity between above and below DPC is relatively low, whereas a roof extension or overhang just to cover EWI, or custom welded flashings, increases the system cost massively.
    • CommentAuthorgravelld
    • CommentTimeAug 30th 2018
     
    Again - depends! For roof extension - just extending gables is definitely a cost but it's not too bad according to my research (less so eaves).

    Meanwhile, the impact of insulating below the DPC can be significant if it means moving drains etc.
    • CommentAuthorbhommels
    • CommentTimeAug 30th 2018
     
    @gravelid: My point was that all these nice-to-haves significantly increase the price of a system for which the economical case is shaky enough as it is.
    The examples you give are a perfect illustration of this. Extending gable ends cannot be done cheaper than a certain, significant amount, whereas sub-DPC EWI can be made as expensive as you wish if you make relaying drains (seriously?) part of it. It only goes one way....
    • CommentAuthorgravelld
    • CommentTimeAug 30th 2018
     
    Are you referring to the contents of the drain or the financial cost? :wink:
  27.  
    Sorry for the delay. I have been working away.

    Fostertom wrote:

    "I also abhor drip or in fact any discontinuity in the EWI face or body, just above GL. Of all locations, in that splash zone it ought to be seamless. So Nick, why did you put it in your 'good practice' shortlist?"

    I perhaps worded that badly. The bit I like is not to use a base-rail with almost a guarantee of thermal discontinuity between the 'main' EWI and the base layer.

    The recessing of the base layer was simply a repetition by me of what most system providers seem to 'recommend'. I took the view that, if there is to be a recessing of the base layer, a drip to carry water (running down the face of the 'main' EWI) away would be preferable to no drip, and a possible capillary 'turning in' of moisture into the gap.

    I take your point FT re the 'splash zone', and to that end had already stepped it down the sloping gable so that there is a *minimum* 300mm splash-up zone.

    (My original 'like': - 'Main wall' EWI sits directly (not on a base-rail) on top of a slightly-recessed 'plinth' of 'below-DPC' (whether or not there actually is a DPC) EWI, which may or may not be of a different material (as discussed in other threads). A drip should be incorporated, and if there is anything between the 2 layers I would suggest I strip of expanding foam tape and several beads of adhesive Pu foam, rather the 1 strip of expanding foam tape (and a lot of air 'approved' by some system providers.)
    • CommentAuthorwookey
    • CommentTimeJun 21st 2019
     
    What's a favoured detail for pipes coming through the EWI?

    Wetherby provide one: https://www.wbs-ltd.co.uk/wp-content/uploads/2016/10/EWI-SILICONE-18.pdf but it's nothing fancier than 'EWI and render up to the pipe, then silicone round the pipe'. For internal pipes we use gaskets such as pro-clima's roflex. Shouldn't there be something a bit more long-term reliable than surface silicone for the outside? i.e maybe something like those gaskets built in to the render system at the mesh layer?
  29.  
    Yes, I don't see why you should not make your own grommets out of EPDM. Squirty-foam round the pipe, fit the grommet, glued to the insulation. Fit 'collar' of mesh over, to cover all joints, lightly bedded in a very thin layer of base-coat. Then proceed with main base-coat/mesh layer as usual.
    •  
      CommentAuthordjh
    • CommentTimeJun 22nd 2019
     
    Posted By: wookeyFor internal pipes we use gaskets such as pro-clima's roflex. Shouldn't there be something a bit more long-term reliable than surface silicone for the outside? i.e maybe something like those gaskets built in to the render system at the mesh layer?

    The internal gasket is there because the airtightness and/or VCL is usually internal. Incidentally for pipes I found it more convenient to seal internally using lots of short lengths of stretchy tape (Siga Rissan) rather than pre-made gaskets. For both my insulated MHVR ducts and ducted plumbing runs it was easier to create a seal.

    Externally the render just seals fairly tight to the insulated ducts in my case and the terminal covers it to make it neat. I'm not too worried about how tight the seal is. The duct slopes slightly down of course to encourage liquid water to run outwards. But I'm not concerned about air or vapour tightness so I have no need of a seal.

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