Green Building Forum - EWI + Timber Cladding Tue, 19 Dec 2023 06:46:40 +0000 http://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281185#Comment_281185 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281185#Comment_281185 Sun, 07 Jun 2020 20:58:32 +0100 teach_glas
Im not finding much help with this online, or even chatting to insulation suppliers:

My house will be single leaf 215mm blockwork with 200mm EWI. About half of the build will be clad with timber, my problem is that 200mm is to far to mechanically fix the battens for the cladding, there might be significant sagging.

Possible solution: fix a 100mm thick stud externally to block wall (within EWI layer), this way the fixing would only travel trhough 100mm of insulation to meet stud.

Anyone dealt with this kind of thing before?

Thanks a lot, any help much appriciated :smile:



J]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281186#Comment_281186 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281186#Comment_281186 Sun, 07 Jun 2020 21:14:42 +0100 Peter_in_Hungary EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281187#Comment_281187 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281187#Comment_281187 Sun, 07 Jun 2020 21:16:23 +0100 djh
Having said all that, 100 mm studs in a 200 mm insulation layer don't sound that disastrous!]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281188#Comment_281188 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281188#Comment_281188 Sun, 07 Jun 2020 21:22:12 +0100 teach_glas
I foolishly didnt use the search funtion before posting, but found an interesting thread here:

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13358

Your suggestions are covered, but also the possibility of using an I-Beam instead of a stud.. that would yeild less of a cold bridge im assuming?]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281189#Comment_281189 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281189#Comment_281189 Sun, 07 Jun 2020 21:30:16 +0100 teach_glas Posted By: djhIf the EWI is in two 100 mm layers then it is possible to recess battens in the first layer so the screws don't need to be as long. Other possibilities include supporting the battens to support the cladding (assuming there are such!) either from the ground or from the top (eaves or gable). How heavy is the cladding?

Having said all that, 100 mm studs in a 200 mm insulation layer don't sound that disastrous!


Its actually a flat roof with parapet wall (single story). Might be tricky to hang from top with a flying joist or similar?

I like the two 100mm layers idea with recessed battens.. any examples of this being done?


Thanks for the input!]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281196#Comment_281196 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281196#Comment_281196 Mon, 08 Jun 2020 08:57:55 +0100 barney
Regards

Barney]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281198#Comment_281198 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281198#Comment_281198 Mon, 08 Jun 2020 09:17:18 +0100 Nick Parsons
''After the Grenfell Tower lesson I would now think twice about battening straight over 'naked' EWI. If it were me I would do the 2 x base-coats as a bit of a fire-retarder, and as the result is apparently not to be seen, we are back to 2 x base-coats and paint (or not, even - check with suppliers. Certainly one supplier does a lime-based base-coat which can be left as the top coat).''

Of course when I wrote that I was thinking graphite EPS. Also I should have suggested running that past the system provider's tech dept. and BC first. If you are using (completely non-flammable) Rockwool it's less of an issue, though more expensive IIRC, and much heavier in itself.

djh comments above: '' 100 mm studs in a 200 mm insulation layer don't sound that disastrous!''. Surely you could do it with only 50 depth and, if your datum points and measuring ability are better than mine, maybe 50 width?]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281199#Comment_281199 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281199#Comment_281199 Mon, 08 Jun 2020 09:48:19 +0100 teach_glas Posted By: barneyHave a look for a product by "nvelope" - you want to look at the NV 6 range

Regards

Barney

Thanks for this, any idea how they get round the cold bridging effect of all that aluminium?]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281200#Comment_281200 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281200#Comment_281200 Mon, 08 Jun 2020 09:56:40 +0100 teach_glas

Posted By: Nick Parsonsdjh comments above: '' 100 mm studs in a 200 mm insulation layer don't sound that disastrous!''. Surely you could do it with only 50 depth and, if your datum points and measuring ability are better than mine, maybe 50 width?



Do you mean a 50x50mm stud? This would mean the fixing would have to travel 150mm unsupported through EWI.

Is this acceptable?



I'm looking more and more towards 200mm I-Beam studs (at 800 centres?) with OSB sheathing on top to further break thermal bridge.
Similar to this:]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281203#Comment_281203 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281203#Comment_281203 Mon, 08 Jun 2020 10:35:33 +0100 dickster EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281204#Comment_281204 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281204#Comment_281204 Mon, 08 Jun 2020 11:14:01 +0100 teach_glas Posted By: dicksterOr do vertical cladding, no sagging?

Surely the weight will be distributed on the horizontal batten.. which could sag?]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281214#Comment_281214 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281214#Comment_281214 Mon, 08 Jun 2020 14:24:18 +0100 Mike1 EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281216#Comment_281216 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281216#Comment_281216 Mon, 08 Jun 2020 14:45:40 +0100 Nick Parsons
Is this acceptable?''

Yes, I did mean a 50x50 stud, but I envisaged it on top of the first layer of 100mm, fixed with sufficiently stout fixings to keep it all tight. The stud thus has 50mm EPS over it, and the cladding screws are only going through 50mm of EPS before they hit a stud.]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281218#Comment_281218 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281218#Comment_281218 Mon, 08 Jun 2020 15:01:17 +0100 fostertom Posted By: Nick Parsonsfixed with sufficiently stout fixings to keep it all tightTo be clear, the fixings' task is not to 'keep it all tight' as in clamping the batten to the inner EPS so that friction prevents it from sliding down, which it won't reliably - the fixings have to be 'stout' and numerous enough so the act as cantilevers.

Unless following the suggestion of ... who was it recently - djh? ... who suggested 'angling the fixings upward' - gd idea that cd change this whole discourse.]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281220#Comment_281220 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281220#Comment_281220 Mon, 08 Jun 2020 15:34:51 +0100 djh Posted By: teach_glasI'm looking more and more towards 200mm I-Beam studs (at 800 centres?) with OSB sheathing on top to further break thermal bridge.
I'm not sure how the OSB helps? I would just put the membrane over the EPS and screw through that into the I-beam flanges for the cladding.

Posted By: barneyHave a look for a product by "nvelope" - you want to look at the NV 6 range

That looks like Rolls-Royce solution. Any idea of the cost?]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281231#Comment_281231 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281231#Comment_281231 Mon, 08 Jun 2020 18:06:26 +0100 barney
To answer the question on thermal bridges, you don't use that many, and there is a thermal break between the base and the flange and of course, it's supporting a timber stud not a metallic element if you were using aluminium rainscreen instead.

I'll see if I can get a UK cost, but for me, they gave certainty of a solution without faffing around either hanging stuff from rafters or standing it on timber, etc in a bit of a suck it and see approach. That way, I can deal with walls as one aspect and roof as another (from a very big social distance)

Regards

Barney]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281239#Comment_281239 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281239#Comment_281239 Tue, 09 Jun 2020 06:53:47 +0100 bogal2 EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281254#Comment_281254 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281254#Comment_281254 Tue, 09 Jun 2020 11:00:51 +0100 barney
I'm happy that the oak cladding can be observed, everything else is clay block, rockwool, cementitious board and aluminium (or possibly steel) brackets which won't be subject to any insect etc attack.

Basically, I wanted a system that reflects current commercial practice, has certification, and is reasonably fire resistant.

Regards

Barney]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281257#Comment_281257 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281257#Comment_281257 Tue, 09 Jun 2020 11:29:12 +0100 djh Posted By: barneypotential termite problems
Ouch! That makes quite a difference. Even with cement blocks etc, you'll still need regular termite treatment, if the situation is anything like where my wife's family live. Also think about ant-proofing cupboards etc especially food stores, as well as hard surfaces at all entrances.]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281273#Comment_281273 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281273#Comment_281273 Tue, 09 Jun 2020 17:17:56 +0100 barney
From experience of the area, I'm pretty sure there isn't a real problem with termites or ants etc, but I think it's an item in the regional building code for that part of France.

Given that the starting point was hollow concrete block with internal insulation, and sprayed lime render to the outside I'm happy that a move to clay block (keeps the brickie happy), external insulation (keeps me happy), oak cladding with some brickwork (keeps the better half happy) and sprayed lime internal plastering (keeps the plasterer happy). Using non timber commercial hangers with rockwool and fire board seems a sensible way forward

Regards

Barney]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281515#Comment_281515 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281515#Comment_281515 Wed, 17 Jun 2020 18:07:47 +0100 teach_glas Posted By: fostertom
Unless following the suggestion of ... who was it recently - djh? ... who suggested 'angling the fixings upward' - gd idea that cd change this whole discourse.

This is really interesting, I wish there were some examples of this being done to show my engineer!



Posted By: djht sure how the OSB helps? I would just put the membrane over the EPS and screw through that into the I-beam flanges for the cladding.


Does anyone know how much thermal bridging I am introducing with the I-Joists embedded into the EWI? Can anything be done to further reduce this at masonary?

Even if fixing a giant steel screw through the EWI was possible.. im sure this introduses it's own set of (possibly worse) thermal bridging issues?


Thanks so much for all the replies so far, really helpful :smile:]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281538#Comment_281538 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281538#Comment_281538 Thu, 18 Jun 2020 09:54:34 +0100 Ed Davies Posted By: teach_glasThis is really interesting, I wish there were some examples of this being done to show my engineer!
Sorry, can't find any online references but I helped out years ago with a Pavatherm roof which was fixed this way. Long Spax screws at 30° to the roof normal up and down the slope through counter battens, ~200mm of Pavatherm into oak rafters. So it's not an entirely novel idea though I've not heard of it being applied specifically to a wall.]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281543#Comment_281543 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281543#Comment_281543 Thu, 18 Jun 2020 10:57:11 +0100 WillInAberdeen
Unfortunately the deflection (sag) in each fixing is proportional to the moment x length^2 so longer fixings sag more.

If you have the same number of fixings per m2, the weight of cladding carried by each fixing is the same, so the shearing force on each fixing is the same.

The weight of cladding is also carried by pinching the insulation between the frame and cladding, so there's friction between the insulation and cladding. This requires the fixings to compress the cladding horizontally against the insulation. If the fixings are skewed, they need more tension force, to get the same horizontal compression.

To sum up, skewed fixings are longer, bendier and need to be tighter than straight fixings.

I guess this is why carpenters down the centuries have tried to drive fixings straight not skewed!

Edit: the same goes for embedding a batten in the insulation, the two fixings (batten to wall, and cladding to batten) behave mechanically like a single long fixing, in terms of sagging, shear, tension, etc. The batten provides a thermal break in the fixings but it does reduce the insulation thickness a little.]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281549#Comment_281549 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281549#Comment_281549 Thu, 18 Jun 2020 11:39:49 +0100 Ed Davies
In the extreme case, imagine the screw was a piece of rope. Put it horizontally and it won't support the cladding at all other than maybe in tension to hold the cladding against the insulation so friction does the job.

Put the rope at an angle downwards and it's easy to see that can support the cladding, with the reaction to the pressure against the insulation providing the counter to the horizontal component of the tension.

The assumption is that a screw is typically stronger in tension than it is in bending. Yeah, I realise that those are measured in different units so not strictly comparable but you know what I mean. Mostly down the centuries people have been screwing solid things to other solid things - not with something light but not very compressible when the pressure's spread wide enough in between.]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281550#Comment_281550 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281550#Comment_281550 Thu, 18 Jun 2020 11:47:56 +0100 WillInAberdeen
To reduce the compression against the insulation, you can use a rope to hang the cladding from the eaves (or preferably use a thick batten instead of a rope, which can also stand on the floor).

If you support that batten at regular intervals with cantilevers sticking through the insulation, it will be less floppy. It the limit that you have lots of cantilevers, it behaves like the I beam solution.]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281551#Comment_281551 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281551#Comment_281551 Thu, 18 Jun 2020 12:02:49 +0100 Ed Davies Posted By: WillInAberdeenYes, some of the weight is taken in tension, but the fixing is longer, so overall the bending moment is (exactly) the same (see 1st para above).That would be true if the reaction to the compression against the insulation wasn't providing a bending force in the opposite direction.

(Or, for that matter, the second screw in the opposite direction in the case of my friend's Pavatherm roof.)]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281553#Comment_281553 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281553#Comment_281553 Thu, 18 Jun 2020 12:15:51 +0100 fostertom EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281554#Comment_281554 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281554#Comment_281554 Thu, 18 Jun 2020 12:16:13 +0100 djh Posted By: Ed DaviesThe assumption is that a screw is typically stronger in tension than it is in bending.
Mostly screws are rated in tension but not in shear. Coach screws are an exception.

I'm not a mechanical engineer, so I'm not straining my brain too hard trying to understand what you and Will are saying, but to me your rope argument is persuasive. I can see that I could build a wall and hold the cladding and insulation in place entirely with angled ropes as you suggest, so this bending argument must be spurious for some reason I haven't bothered to figure out.]]> EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281559#Comment_281559 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281559#Comment_281559 Thu, 18 Jun 2020 14:40:57 +0100 fostertom EWI + Timber Cladding http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281568#Comment_281568 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&Focus=281568#Comment_281568 Thu, 18 Jun 2020 17:12:38 +0100 WillInAberdeen
The proposal is to treat the skewed screw like a short rope tie, acting with the insulation as a strut, to make a tie-and-strut cantilever. Let's say the screw is skewed upwards at an angle of 30deg as mentioned.

If the weight of the cladding per screw is W, the tension in the 'rope' is W/sin(30deg) = 2W. The compression in the insulation is W/tan(30deg) = 1.73W. These loads are inefficiently high, compared to W, especially as screws aren't great in tension and insulation isn't great in compression. You'd need extra-strong screws and insulation.

But fortunately, as soon as you started to drive the screw, it would act as a little cantilever itself, and support the cladding even before you'd applied any tension at all. You'd probably drive the screw a little further and apply a little tension to keep it neat. That would clamp the cladding against the insulation and create some friction, which would transfer some of the weight of the cladding directly into the insulation, so reducing the load in the screw. The fixing would be secure, long before the tension in the screw had reached 2W, and you'd move onto the next one.

But if you were feeling brutal and did manage to tighten the screw tension to 2W without breaking the head, the friction would be supporting the cladding weight (mu = ~0.5) and the 'rope tie' idea would become redundant, more of a 'clamp'.

If you checked the next day, the insulation would have squashed a little, relaxing the tension in the screw, so it would be back to acting as a stiff cantilever again.

So in summary, the 'rope tie' idea could work if the rope and insulation were strong enough to hold twice the cladding weight, but fortunately the screws are stiff enough that they can act like pegs (cantilevers) and so don't need such high loads. The 'rope tie' idea is appealing but it isn't analogous to how the screws work.

The situation is a bit different on a roof where the weight of the insulation is mainly supported against the sarking by friction. The screws there act in shear, to stop the everything sliding off, and in tension if there's a strong wind lifting everything up.

All this is probably unhelpful for the OP!]]>