Expanding window tape - how long does it last

[readiescards]

So window fitters A have installed my Internorm windows using a black expanding foam tape, leaving it exposed to the elements on the outer edge.  

Window fitter B has come along and says 'that'll never last mate' you need to cover it in some sealant.

 

I have to admit I'm struggling to believe the expanding foam tape will last 25 years, will it?

[Russell griffiths]

That looks like a big gap for sealant, can they not use a nice trim over it. 

[pauldoc]

I have just had my windows installed. (Ideal combi) they to have this tape on. Various window companies all- velfac, rationel etc all recommend this method. I agree it's hard to imagine it will last and be weather proof but the tapes do have a rating that specs how efficient they are which relates to wind and weather proofing....they are also ridiculously expensive ! In the upside they are neat.  My installer was also not convinced but did admit that was only because he hadn't had call to use them much .

[MikeSharp01]

Why such big gaps? Why is it not possible to make the windows a snug fit in the brick formed orifice? Such large gaps also have the visual effect of making the frames look much bulkier than they need to. @pauldoc I cannot find any life length guarantees on the tapes I have looked at so suspect they won't last unless mechanically protected from UV / Weather etc as if they did have a guaranteed life then it would be in their technical manuals / general advertising. In the ads for the product they show them as very much more compressed than in the @readiescards example also they show them mid frame so that sealant has somewhere to go to cover / protect the tape.

[joe90]

This is another reason I am installing my windows in check reveals, also makes the frame a little less bulky.

[Gone West]

Expanding foam tape is only expected to be water and air tight up to a certain amount of expansion. A tape may be 5mm thick and expand to 17mm but only be weathertight up to 12mm.

[Nick]

Compriband made by Tremco is the industry standard. It is normally specced based on the size of gap to be filled rather than the thickness in its pre-expanded state so assuming your window openings were surveyed correctly, it should have the right weathertightness.

 

They warranty it for 15 years if the installation is registered and installed to their guidelines but who knows what that will mean in practice if your window leaks in 14 years' time. Life expectancy is 25 years on their literature assuming it is this brand that you have.

 

Personally, i like to see a tight 5-6mm expansion gap around a window and a silicone seal regardless of whether there is compriband, EPDM, e.t.c. behind it that should be doing the job of weatherproofing. Reality is that installations are never 100% by-the-book and the more secondary protection you can give to your primary seal, the longer the whole thing will last.

 

I suspect the expanding tape only method is these companies' way of minimising installation time and labour costs.

Edited February 9, 2017 by Nick

[Onoff]

I was going to use Compriband fitting my bathroom window recently but bottled it and used low expansion Soudal foam into a well wetted opening in the end. 

[Jeremy Harris]

23 minutes ago, Onoff said:

I was going to use Compriband fitting my bathroom window recently but bottled it and used low expansion Soudal foam into a well wetted opening in the end. 

 

 

I did the same, then covered the small (5mm max) gap with clear neutral silicone and a length of 6mm x 6mm x 1mm PVC angle as a trim, so you can't see the sealant.  It worked well and left a neat-looking finish externally:

 

[Onoff]

Oh to have a nice square hole to fit the window in! I could have faffed around rendering the ragged brickwork.....but I didn't! This'll have some the new (undrilled) 15x13mm trim stuck on which'll be rendered up to and then a bit of paint. Concerned I might not be able to match the original finish, anyone got a chip pan?

 

 

[MikeSharp01]

Just been to one of the two possible window suppliers and now I know why the tape is there at least for this manufacturer. Essentially, as they explained it to me, it is set back a small distance to create an air gap up the side of the frame to ensure that the ali cladding can breath otherwise moisture would build up behind the ali cladding and not be able to escape. It seals the frame but is not designed to take up slack in the construction because the brakets etc still have to be a slide fit. If you clad / render up to the frame then you have to leave a 2mm gap to allow the alu cladding to breath. A bead of silicone would seal the gap and cause eventual failure of the timber frame. They also told me that it's life expectancy was 25 years, guarantee is 15 years so suspect it is the stuff @Nick describes above, in the open if protected then it should last much longer. Well that is what I was told!

[Jeremy Harris]

Depends very much on the way the frame is made, though.  There's no exposed wood at the outside edges of our aluclad frames, the alloy extrusions are around 20mm deep, IIRC, and then there's a foam-cored PVC frame about 30mm thick, with the timber frame inside that. 

[MikeSharp01]

Yep I guess that's correct they all seem very different the other possible manufacturer does not use the expanding tape on their standard details.