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Perimeter expansion insulation


Thorfun

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I've done a search on the forum and couldn't find much detail about recommendations for what to use here. I found this post from @Nickfromwales back in 2017 but the links aren't working any more so it's hard to know what products they relate to

 

 

our liquid screeders have suggest the JG product (https://www.screwfix.com/p/jg-speedfit-jgufhedge-edge-insulation-roll-150mm-x-25m/87019) but this is 4x the price of something like this (https://www.ebay.co.uk/itm/350335173377?hash=item51919a8301:g:XzYAAOSw6dteOuEt&_trksid=p5731.m3795) and twice the price of this (https://www.underfloorshop.co.uk/product/underfloor-heating-edge-insulation-roll-50m-150mm-x-8mm/?gclid=EAIaIQobChMIltDoleCu9QIVy-3tCh1UkgK9EAQYBCABEgJjg_D_BwE). 

 

I would assume that this stuff is pretty much the same (apart from colour) as it's all 8mm x 150mm and so why would anyone buy the JG stuff? is this a case that paying more is not actually a better product?

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1 minute ago, Thorfun said:

lead times and ripping to width put me off this route.


Lead times …? It is a stock item in 99% of BMs including  Wickes … 

 

Ripping it down will take minutes with a hand saw and a piece of 6x1 - it doesn’t need to be perfect. 

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Just now, PeterW said:


Lead times …? It is a stock item in 99% of BMs including  Wickes … 

 

Ripping it down will take minutes with a hand saw and a piece of 6x1 - it doesn’t need to be perfect. 

Jewsons quoted me 4 - 6 weeks when I looked for 25mm EPS100 for insulation under the screed.

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Change your BM. It is a standard product that is available everywhere - just check your local Wickes for stock as a 150mm upstand basically needs one sheet for nearly 20 linear metres of EPS so you don’t need that many sheets. 
 

https://www.wickes.co.uk/Kay-Metzeler-General-Purpose-Polystyrene-EPS70---2400mm-x-1200mm-x-25mm/p/210823

 

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2 hours ago, Russell griffiths said:

is it for expansion or to stop heat loss at the screed edge. 

sorry. didn't see you'd edited this post.

 

it's for expansion only. I have 200mm EPS outside my basement walls that wraps underneath the slab.

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You've two types of insulation. Flexible and rigid. EPS, PIR, etc are all rigid. These are NOT WHAT YOU WANT if its expansion insulation you're looking for and will result in cracking in the slab. You want expansion insulation which you purchase it in rolls like the one you posted in the OP. Expansion insulation is most commonly used in polished concrete floors or other exposed slabs or non structural slabs that have underfloor heating.  They're cheap and available anywhere. Any type will do. Some some with a sticky back to hold in place, some come with a plastic skirt to help connect to the membrane on the flat. It doesn't really matter and any type will do.

 

If its not expansion insulation you want then you can go for 25mm EPS, PIR or whatever you want. If you're drylining internally or have tiles that can cantilever over you can have 50mm thickness. 

 

Who's saying it's expansion you want or need or what type of floor do you have? You need to know for certain if it's expansion or rigid insulation to the perimeter you need. 

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1 minute ago, Dudda said:

Who's saying it's expansion you want or need or what type of floor do you have? You need to know for certain if it's expansion or rigid insulation to the perimeter you need. 

it's definitely expansion that I need. stated on the prep document from the liquid screeders. I have no need for perimeter insulation in the other sense of the phrase. this screed is going in our basement on top of 25mm PIR and ufh pipes. below that is 250mm reinforced slab with 200mm EPS300 underneath that. the walls are 250mm reinforced concrete with 200mm EPS100 externally. so there are no thermal  bridges to rectify and no need for perimeter insulation. 

 

to quote from our pre-install prep instructions:

 

"Expansion Edging and Crack reduction

You should install a minimum 8mm perimeter edging strip around the perimeter of EVERY area to be screeded including in and around door thresholds."

 

so, I'm just going to go for the yellow stuff from eBay that I linked to in the first post. 

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  • 3 weeks later...
On 17/01/2022 at 16:00, Dudda said:

Ya do, that's perfect. No need for EPS or anything else.

the yellow stuff I bought has a 'trim' of plastic with a sticky strip. I presume that is to go on the floor like the picture below?

 

IMG_2437.jpeg.54318d1468d8e1646db065b25f0bfd70.jpeg

 

to stop screed getting underneath and behind the expansion strip?

 

our screeders said to use gaffer tape for that but as this strip has the plastic built-in I presume we can just use that?

 

or does it go at the top to stop screed splashing up and behind?

 

what did others do with that plastic strip?

 

edited to add:

 

the eBay advert call it an overlap strip

 

"25m 150mm x 8mm with self adhesive Overlap & Backing Strip"

 

just doesn't mention where that overlap goes

Edited by Thorfun
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  • 1 year later...

I have put perimeter strips on my internal and external walls (external walls have 60mm PIR, full height, for added insulation acting as vapour layer). Should I swap these out on external walls for PIR? Screed due tomorrow. 

 

Also no movement joints on door openings but now reading I perhaps should have - can't find any perimeter strip stuff available within 50 mile radius at merchants. Is there any substitute I could use?

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1 hour ago, eandg said:

I have put perimeter strips on my internal and external walls (external walls have 60mm PIR, full height, for added insulation acting as vapour layer). Should I swap these out on external walls for PIR? Screed due tomorrow. 

 

Also no movement joints on door openings but now reading I perhaps should have - can't find any perimeter strip stuff available within 50 mile radius at merchants. Is there any substitute I could use?

Screwfix stock it. https://www.screwfix.com/search?search=perimeter+edging+strip

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7 minutes ago, Thorfun said:

Thanks - I bought the last two rolls anywhere within a couple of hours drive on Thursday! Should have ordered another just in case for next day but only getting back round to thinking about it. If the 60mm PIR is fine for the vertical upstands I'll steal some off the external walls and fit across the thresholds before the guys get here in the morning.

 

Also wondering about external doors - we have our doors (in situ) sitting on treated timber but I left them out - should these be 'stripped'?

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not sure I'm qualified to state whether they should or shouldn't. I simply put the edging strip everywhere! every door, wall, partition etc whether they were internal or external. anywhere the screed was going to touch a vertical surface.

 

our screeders also said expansion joints were necessary to reduce cracking. I put 6mm hardboard across the doorways which they said was fine.

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If these are low temp slabs, passive levels, then cracking is really not a big concern tbh. This only becomes a thing IMO when you have thin screeds vs a constructional slab with mesh / fibres etc.

For external doors, the wood will still be a cold bridge plus you should have something for expansion. At the doors this only needs to be something thin such as the foam expansion strip. Have you looked locally on Gumtree etc to see if anyone's got some going begging? For emergency measures you could just bond a couple of layers of bubble-wrap back-to-back I suppose.

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I just used 70mm PIR around the whole perimeter of the house, including at the door thresholds. Which confused the tiler somewhat, as he never seen so much insulation apparently. You get close to linear metres per sheet at 300mm wide.

 

Our slab is 25m long, without any expansion joints, and have had no issues so far, 2 heating seasons later. Did calculate the expected expansion and it was super small, but generally floor is only varies between about 19-20 when cooling and 22-24 during heating.

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7 hours ago, JohnMo said:

I just used 70mm PIR around the whole perimeter of the house, including at the door thresholds. Which confused the tiler somewhat, as he never seen so much insulation apparently. You get close to linear metres per sheet at 300mm wide.

 

Our slab is 25m long, without any expansion joints, and have had no issues so far, 2 heating seasons later. Did calculate the expected expansion and it was super small, but generally floor is only varies between about 19-20 when cooling and 22-24 during heating.

That's reassuring, thanks. I'll maybe rip a wee bit of insulation in the morning and fit it at the door thresholds just for comfort. 

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