Green Building Forum - compacfoam. Sun, 19 Apr 2026 03:33:51 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191048#Comment_191048 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191048#Comment_191048 Fri, 06 Dec 2013 16:50:21 +0000 woodgnome Need some for thresholds in new build and would like to compare prices.

Thanks]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191079#Comment_191079 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191079#Comment_191079 Sat, 07 Dec 2013 10:20:24 +0000 scrimper compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191086#Comment_191086 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191086#Comment_191086 Sat, 07 Dec 2013 17:07:10 +0000 davidfreeborough
David]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191471#Comment_191471 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191471#Comment_191471 Fri, 13 Dec 2013 16:03:46 +0000 scrimper
Basic requirement is for something to sit underneath some timber sash windows, straddling the cavity, just behind a stone cill.

Any cheaper ideas!?!]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191472#Comment_191472 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191472#Comment_191472 Fri, 13 Dec 2013 16:15:39 +0000 Triassic
Isover do a high density EPS! http://www.isover.com/Our-solutions/Insulation-materials/Polystyrene-insulation]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191477#Comment_191477 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191477#Comment_191477 Fri, 13 Dec 2013 16:37:20 +0000 willie.macleod compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191480#Comment_191480 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191480#Comment_191480 Fri, 13 Dec 2013 17:45:48 +0000 scrimper compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191481#Comment_191481 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191481#Comment_191481 Fri, 13 Dec 2013 18:19:44 +0000 daserra compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191483#Comment_191483 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191483#Comment_191483 Fri, 13 Dec 2013 18:30:32 +0000 Saint Posted By: willie.macleodExtruded polystrene will have a higher compressive strength than expanded (i.e. look for XPS instead of EPS)
Yes exactly Willie there's XPS available in 500kPa and 700kPa compressive strengths so that's around 0.5N/mm2 and 0.7N/mm2 both with a better thermal conductivity than the Compacfoam at that sort of strength, somewhere around 0.029 W/mK]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191493#Comment_191493 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191493#Comment_191493 Fri, 13 Dec 2013 20:45:47 +0000 Ed Davies Posted By: Saint500kPa and 700kPa compressive strengths so that's around 0.5N/mm2 and 0.7N/mm2The “around” here made my smile. Like 500 g is around 0.5 kg. But only very approximately, you understand?]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191496#Comment_191496 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191496#Comment_191496 Fri, 13 Dec 2013 21:51:59 +0000 scrimper compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191501#Comment_191501 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191501#Comment_191501 Sat, 14 Dec 2013 00:40:47 +0000 Saint Posted By: Ed Davies
Posted By: Saint500kPa and 700kPa compressive strengths so that's around 0.5N/mm2 and 0.7N/mm2
The “around” here made my smile. Like 500 g is around 0.5 kg. But only very approximately, you understand?
ED, yes good point, not sure where the "around" came from, I think I was originally going to go Kgf/m2 to add gravitas then got distracted....:sad:]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191509#Comment_191509 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191509#Comment_191509 Sat, 14 Dec 2013 09:28:39 +0000 owlman
I use it as in floor insulation under concrete, but do you think if you shaped it, tanked it, with something like a tanking slurry to create a key, you could then skim/render it to create a shaped plaster form that would take weight, with a timber tread on it,- steps for instance? Just an idea.]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191529#Comment_191529 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191529#Comment_191529 Sat, 14 Dec 2013 13:27:39 +0000 woodgnome compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191558#Comment_191558 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191558#Comment_191558 Sun, 15 Dec 2013 09:28:22 +0000 Saint Posted By: owlmanI use it as in floor insulation under concrete, but do you think if you shaped it, tanked it, with something like a tanking slurry to create a key, you could then skim/render it to create a shaped plaster form that would take weight, with a timber tread on it,- steps for instance? Just an idea

Just remember the tanking product shouldn't be oil based, the XPS will "melt"
As for coating it with a render type product for external use there are several companies that make replacement sills and the like with EPS coated with a reinforced cementitious skin but for higher tougher specs they'll use XPS]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191585#Comment_191585 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191585#Comment_191585 Sun, 15 Dec 2013 18:25:46 +0000 owlman I have a couple of interior steps up, to create in either side of a split level room. I thought of making them with serpentine shaped risers and normally I'd use timber and plywood to create the basic form. It just occurred to me though that they may look nice plastered with oak treads. and instead of using a thermo-crete type block for the basic form, this stuff may be easier to shape. Getting the plaster/render to stick would be the problem, some sort of scrim base may be a solution.]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191620#Comment_191620 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191620#Comment_191620 Mon, 16 Dec 2013 11:16:17 +0000 davidfreeborough Posted By: woodgnomeAre you able to fix the XPS the same way as the Compacfoam? I need to drill and bolt the compacfoam to the edge of my slab as support for doors and sliders.I don't know of any other insulation which will take a fixing of this type. If you use XPS then you'll need to put it in a pultruded fibreglass channel or box.

David]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191801#Comment_191801 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191801#Comment_191801 Tue, 17 Dec 2013 21:35:17 +0000 djh Posted By: owlmanGetting the plaster/render to stick would be the problem, some sort of scrim base may be a solution.
For EWI, mesh is commonly used over EPS, and I think XPS too. Even chicken wire can work.

Posted By: davidfreeborough
Posted By: woodgnomeAre you able to fix the XPS the same way as the Compacfoam? I need to drill and bolt the compacfoam to the edge of my slab as support for doors and sliders.
I don't know of any other insulation which will take a fixing of this type. If you use XPS then you'll need to put it in a pultruded fibreglass channel or box.

When boatbuilders want to take a high load in a soft area like a balsa or foam core, the trick is to scoop out a larger area to spread the load and then fill it with epoxy plus filler. It has to be said that these are usually sandwich panels and they do leave as much of the skin in place as possible. But using resin-filled holes is commonly used in soft building materials too, so it might be worth trying with XPS, depending on how much the load is.]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191925#Comment_191925 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=191925#Comment_191925 Thu, 19 Dec 2013 13:42:07 +0000 Cav8andrew compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262094#Comment_262094 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262094#Comment_262094 Thu, 12 Oct 2017 13:59:47 +0100 Doubting_Thomas
Posted By: Cav8andrewPurenit by Puren should match the properties of Compacfoam.


this isn't quite true. The compacfoam gets a better lambda value (0.046 for CF200) against Purenit (0.087) for example.

What I'm struggling with is how to know which section profile to use below our triple glazed sliding doors and windows.

Purenit give their compressive strength in MPa, whereas Compacoam talk about Compression stress in N/mm² at 2 & 10% compression and allowable stress etc. The Internorm installers have told me that they can remove the standard purenit section that the threshold comes with and fix directly into a compacfoam ground instead. Since our windows are sitting out in the insulation zone, this makes sense as we can pre-fit the compacfoam in advance.

The GBS sell 100mm wide lengths at 50mm, 75mm and 150mm depths. My feeling is the 75mm should be more than enough, but it would be great to confirm this with some numbers.

Has anyone here had any experience with this approach or found some equivalent properties?]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262099#Comment_262099 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262099#Comment_262099 Thu, 12 Oct 2017 16:46:04 +0100 djh Posted By: Doubting_ThomasPurenit give their compressive strength in MPa, whereas Compacoam talk about Compression stress in N/mm²

1 Pa = 1 N/m² so 1 MPa = 1 N/mm² (ask google if you don't trust me :)

The Internorm installers have told me that they can remove the standard purenit section that the threshold comes with and fix directly into a compacfoam ground instead.

I don't know what 'the standard purenit section' is. Is it a simple rectangular section? What size is it?

I understand why you might want Compacfoam/Purenit underneath a door threshold (what is the threshold itself made from?) but why do you want it underneath the windows? Why not mount the windows directly in the main insulation?

Some drawings would help me understand, for one. I don't understand why the depth (=height?) is arbitrary? Why isn't it determined by the geometry?

You understand that 2% of 75 mm is 1.5 mm - I wouldn't want that much movement in my threshold, for example, so what's the actual load and strain under the threshold?]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262147#Comment_262147 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262147#Comment_262147 Sat, 14 Oct 2017 11:44:43 +0100 Doubting_Thomas Posted By: djhI understand why you might want Compacfoam/Purenit underneath a door threshold (what is the threshold itself made from?) but why do you want it underneath the windows? Why not mount the windows directly in the main insulation?

Sorry I should have explained, generally windows will be supported in a timber 'picture frame' arrangement but the doors are in the same zone. I'm not proposing to use the Compacfoam everywhere, just at ground level where frames would otherwise bear onto the softer below-slab insulation.

With all credit to Internorm and Isoquick respectively, I've attached a side by side of their details. From what I can make out (there's no direct label) the striped blocks below the extrusion profile on the B&W detail are purenit.

Scaling that detail based on the threshold profile, I've managed to extrapolate that the purenit bits are about 140mm deep so it looks like I ought to plump for the 150mm depth Compacfoam to be safe...

Posted By: djhwhat's the actual load and strain under the threshold?


Not quite sure how I work that out, but what I do know is Purenit has a compressive strength of 7.1 MPa. Compacfoam 200 has
Average stress at 5%: 2.56 N/mm2
Average stress at 2%: 1.91 N/mm2
Modulus of elasticity in linear-elastic range (E-Module): 102 N/mm2
Recommended stress level (under service load): 1.01 N/mm2

Are you asking how heavy the doors are likely to be? I'm going to try and get that confirmed this week.]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262148#Comment_262148 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262148#Comment_262148 Sat, 14 Oct 2017 12:23:37 +0100 djh Posted By: Doubting_ThomasWith all credit to Internorm and Isoquick respectively, I've attached a side by side of their details. From what I can make out (there's no direct label) the striped blocks below the extrusion profile on the B&W detail are purenit.
Thanks for the drawings but they are too small to read.

And yes, you need to find out how heavy the doors are and how much of that weight is supported by the threshold (could be any proportion from 0% to 100% depending on the type of door). Then use that weight to work out the stress, check that it is within the working limit, and calculate the resulting strain and use that to adjust levels if necessary. Hopefully the strain is near enough zero to ignore.

Who suggested the Compacfoam CF200, as opposed to 100, 150, 300, 400? Whoever that is, I'd check with all the other professionals involved that they're happy for that person to design the threshold and just go with whatever they say.]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262204#Comment_262204 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262204#Comment_262204 Tue, 17 Oct 2017 09:52:21 +0100 gravelld Posted By: djhI understand why you might want Compacfoam/Purenit underneath a door threshold (what is the threshold itself made from?) but why do you want it underneath the windows? Why not mount the windows directly in the main insulation?Do you mean using brackets, or a plywood box? Using Compacfoam looks easier than the latter. Might also be more secure than the former for larger glazing expanses?]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262314#Comment_262314 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262314#Comment_262314 Thu, 19 Oct 2017 13:58:26 +0100 Doubting_Thomas
Got some weights...

The entrance door is 1m wide and weighs 81kg
Sliding door is 2.6m wide and weighs 260kg plus an 88kg sliding leaf
Full height window is 1.7m wide and weighs 127kg

Whilst the entrance and window are both on hinges (i.e. distributed load), I'd expect the sliding door to bear down solely on the threshold so it's probably the worst case scenario.

So if I understand

Posted By: djhAnd yes, you need to find out how heavy the doors are and how much of that weight is supported by the threshold (could be any proportion from 0% to 100% depending on the type of door). Then use that weight to work out the stress, check that it is within the working limit, and calculate the resulting strain and use that to adjust levels if necessary. Hopefully the strain is near enough zero to ignore.


Stress = applied force / cross sectional area

348kg = 3413 N and the cross section is 0.15d x 0.2w = 0.03m²

Stress = 113757 N/m² or 0.113757 N/mm²

The 'elastic modulus' is apparently 2% from elsewhere on Compacfoam's website, but I don't know if this is Young's modulus or how to get from this to the strain. Is it just 0.11/0.02?

If so it would be 5.7 and nowhere near zero...

Help!]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262317#Comment_262317 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262317#Comment_262317 Thu, 19 Oct 2017 15:14:31 +0100 goodevans
I thick that 2% number indicates the deformation the foam can take and still remain elastic (i.e. not permanently deformd) - if that is true elsewhere on the site gives you a stress limit to remain in that 2% deformation limit. the Youngs modulus would be that stress divided by 0.02 i.e. cf200 the 2% compressive load is 1.91 N/mm2 which indicates a YM of 95.5 N/mm2

Caveats - the is no info on tensile properties - so bending behavior is not known, and EPS will suffer from so creep keep well within the 2% deformation load.

I can't make it out but there seems to be a big angle bracket fixed to the ground and supporting the foam this will be a big thermal bridge removing the advantage of the compacfoam - post a bigger picture and I'll be able to comment further.]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262325#Comment_262325 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262325#Comment_262325 Thu, 19 Oct 2017 16:21:38 +0100 djh Posted By: Doubting_ThomasWhilst the entrance and window are both on hinges (i.e. distributed load)
The door and presumably the window are fastened to and supported by the jambs at the side, not by the threshold. In particular, the jamb at the hinge side carries all the weight.

Stress = applied force / cross sectional area

348kg = 3413 N and the cross section is 0.15d x 0.2w = 0.03m²

0.15d x 0.2w doesn't sound right. It should be the width of the door times its thickness, 2.6 x 0.2 I presume = 0.52 m²
So the stress is 3413/0.52 = 6563 N/m² or 0.0066 N/mm², which is way less than the max working stress of 1.01 N/mm².

The modulus of elasticity, E, is given at http://www.compacfoam.com/26-compressive-strength.html and for CF200 is 102 N/mm², so the strain = 0.0066/102 = 6.4 e-5 and with a height of 150 mm that gives a displacement of 0.01 mm which seems very tolerably low.

But what Paul said about the need for bigger pictures of the details.]]> compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262331#Comment_262331 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262331#Comment_262331 Thu, 19 Oct 2017 18:31:29 +0100 Doubting_Thomas compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262332#Comment_262332 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262332#Comment_262332 Thu, 19 Oct 2017 18:40:19 +0100 Doubting_Thomas compacfoam. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262333#Comment_262333 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11503&Focus=262333#Comment_262333 Thu, 19 Oct 2017 18:44:56 +0100 Doubting_Thomas
https://www.greenbuildingstore.co.uk/products/compacfoam-200/#prettyPhoto

I'd be interested to know people's opinions on the threaded bar - this is presumably necessary to tie it into the slab in case the insulation below deforms. I'm assuming there's more than one flavour of threaded bar on the market, so any tips on what to go for would be welcome too.]]>