All Expanding Foam is Equal?

[DIYWell]

Ok, so my grand plan is to seal some yet to be discovered gaps. Assume the likes of joist ends where they enter the masory and the wind whistles through after decades of shrinkage etc, and around windows when I peel off the UPVC trim the fitters used and I find gaps big enough to stick fingers or small children into.

But aren't all cans of expanding foam equal? Ok, ignore the fire rated ones. And the sticky ones. But why is "No nonsense" £7 but FM330 £12? Both appear to do the same job. Is there some hidden technical detail I'm missing?

 

[noseall]

Ok, so my grand plan is to seal some yet to be discovered gaps. Assume the likes of joist ends where they enter the masory and the wind whistles through after decades of shrinkage etc, and around windows when I peel off the UPVC trim the fitters used and I find gaps big enough to stick fingers or small children into.

But aren't all cans of expanding foam equal? Ok, ignore the fire rated ones. And the sticky ones. But why is "No nonsense" £7 but FM330 £12? Both appear to do the same job. Is there some hidden technical detail I'm missing?

There are different types of foam, yes. We tend to buy more of the low-ex adhesive foam these days as the rate of expansion is lower and more predictable. Gap filling foams expand a lot more.

 

[Ivor Windybottom]

They all seem to be capable of sticking to your skin for at least a week and ruining all your clothes.

I suspect there's a degree of mug premium. As with so many things, some just want to buy the reassuringly expensive one so they're happy to take their money. E.g. I'm pretty sure that Sika and Everbuild are identical with most glues and adhesives, as they're the same company but Sika usually has the premium price.

I've never had any issues with any No Nonsense product. But if you were charging a customer £10,000s for a job then you might check they weren't watching while you used it and bagged up the empties straight after.

Cheap or posh, a mist spray of water before use into whatever you're filling improves expansion and adhesion.

 

[Ivor Windybottom]

Check you're not inadvertenly creating damp bridges while squirting into cavities. Theoretically possible, I don't know how much of a real-world risk it is.

 

[opps]

They are not all equal.

Expanding foam that doesn't stick to things

I recently purchased a gun grade expanding foam from my local decorators' merchant. They had the Soudal foam and the BondIT Megafoam. My first task was to fill a 8mm wide and 6mm deep channel in a concrete window sill. The replacement sliding sash window had a lot of bounce in it. I decided to...

www.diynot.com

I would guess that the FM330 has a smaller hole structure. It cites superior sound/air insulation. I have no idea if that is just marketing or not.

As @noseall says they also have differing expansion rates. I am inclined to think that the ones with lower expansion rates will have better sound/temperature rating, again, I am only guessing.