Overusing expanding foam - an issue?

[lookseehear]

Our builder seems to be very keen on squirty expanding foam (he keeps talking about all the areas he likes to use it). I have heard not great stuff (it can sag, it can be used to fill bigger gaps than it should really be, it can be a lazy way to get something done etc etc).

 

Is there a general concensus or guidance anywhere about where the appropriate uses for it are? I'm guessing between sheets of PIR is probably a good place because it's probably a similar type of material and the gaps should be small if the PIR has been cut properly. Anywhere that it often gets used that it really shouldn't?

 

Also any brands to look for or avoid in particular?

[Onoff]

20 minutes ago, lookseehear said:

Also any brands to look for

 

Illbrück FM330.

 

The end. 

[nod]

How did we ever manage without Exspady Foam 

We built window frames in tight and filled gaps with bricks and mortar 

[gravelld]

It can definitely be over-used. Cheaper foams don't deal well with movement. Look for the flexible ones, like Soudal Flexifoam. They allow some degree of compression and reshape. But think of it more of a gap filler for other measures than an air tightness provider, as such.

[Blooda]

14 hours ago, lookseehear said:

gaps should be small if the PIR has been cut properly. Anywhere that it often gets used that it really shouldn't?

 

It is often better and more controllable to have larger gap say 5-10mm and then fill with quality foam, rather than trying to get to fill a 1-2mm gap.

All you will end up doing is covering the joint on the surface, with no foam going down the gap, and you may have just used the tape.