IWI Plasterboard Directly on Block Work

[Gaf]

Aware this is probably not the ideal way of doing it, but if you had to, what’s the best way of affixing IWI directly to block work? As in no void behind the boards.

 

Reason is a potential issue with architect forgetting to allow for battens/dot-dab thickness in room calculations. House went up based on external wall measurements so now internal walls are all 2.5cm thinner with dot-dab method (5cm across walls). Not end of the world, but want to know what option there is with direct affixing to blocks. I’ve seen a screw in method but also read this risks breaching airtightness if not done correctly.

[MikeGrahamT21]

They can definitely be mechanically fixed direct to blockwork with no gap.

 

 

Depending on how willing your installers are, instead of using dot-dab method, you could use full bed method with same adhesive, plus the mechanical fixing as per guide above.

[torre]

Soudal plasterboard foam adhesive can be compressed pretty tight to blockwork, but aren't you only going to save the depth of a dab, say about 10mm per wall like this? If your blockwork isn't perfectly flat maybe not even that much.

 

(It does stick well though and goes a long way)

[Redbeard]

I cannot remember from your other thread(s?); have you done a parge coat? 

 

Agree with @torre re adhesive squirty-foam, and with their caveat if the blockwork is uneven. Do it in full-perimeter beads with cross-hatchings as suggested on the other thread and potential air movement behind the boards will be limited even if you do not have a parge coat (but 'belt and braces' suggests you should).

[Gaf]

3 hours ago, torre said:

Soudal plasterboard foam adhesive can be compressed pretty tight to blockwork, but aren't you only going to save the depth of a dab, say about 10mm per wall like this? If your blockwork isn't perfectly flat maybe not even that much.

 

(It does stick well though and goes a long way)

 

Currently the dabs are adding 25mm. The PIR on the boards is 25mm for reference (attached image).

 

Blockwork was snooker table flat. Looking along an >18m long wall, there wasn’t one block out of line. Block work was excellent. 

 

2 hours ago, Redbeard said:

I cannot remember from your other thread(s?); have you done a parge coat? 

 

Agree with @torre re adhesive squirty-foam, and with their caveat if the blockwork is uneven. Do it in full-perimeter beads with cross-hatchings as suggested on the other thread and potential air movement behind the boards will be limited even if you do not have a parge coat (but 'belt and braces' suggests you should).

 

There is a parge coat. Yeah I’m posting a bit at the minute to make sure Im on top of what’s being done in site now. 😬