PIR board for block cavity

[gravelrash]

Looking at cavity block wall with external render and timber clad facade so should be no water penetration of cavity. I was looking to build inner leaf first and use full size insulation boards. Does any one have any experience with PIR or phenolic boards...why do the manufacturers seem to make different boards from the same material but for specific jobs ie cavity, floor, roof? 

Seconds and co are selling 150mm Kooltherm phenolic at very cheap prices but not coded as k1** . Anyone know how using the wrong board would affect the build? 

[Russell griffiths]

You cannot use full size boards as the wall ties will get in the way, need to use correct size sheets that match the tie spacing. 

That is why they make those small sheets purpofor the job. 

[PeterW]

You can cut down 1200/2400 boards to 1200/450 which is a 2 block spacing but leaves you with a load of 150mm off cuts. You also need to glue them together with foam as the proper ones are T&G. 
 

I have seen this done - guy near me built an extension like this, laid the blocks himself then insulated and he cut the boards and bonded and taped them - looked pristine when he had done it but took him 4 months to do the blocks and insulation.... brickies has the brickwork up in a week ..! 

[gravelrash]

No you don't need small boards,  Helical ties are put in after so any size board can be used. 

[PeterW]

That is a really expensive way to fix a problem that doesn't need to exist..?? Which ties are you thinking of using..??

[Russell griffiths]

1 hour ago, gravelrash said:

No you don't need small boards,  Helical ties are put in after so any size board can be used. 

Really, so are you doing the blockwork, that will only work if you fit them as a bricky team are not going to stop to start drilling in ties. 

 

[MikeGrahamT21]

If you are wanting to full fill with PIR, you will need to buy a board which is BBA certified to do so.

 

Kingspan do one, as do Xtratherm (CT/PIR).

 

Building control will also need to be informed of this, as they often get a bit funny with full fill PIR (if thats what you are thinking of).

[gravelrash]

I was originally asking if anyone knew the difference between boards and how they are effected by different locations...or is foil backed phenolic board just a foil backed phenolic board

15 years ago you just bought a board, not one specific to a roof or wall or anything else. 

 

[MikeGrahamT21]

On 03/07/2020 at 19:43, gravelrash said:

I was originally asking if anyone knew the difference between boards and how they are effected by different locations...or is foil backed phenolic board just a foil backed phenolic board

15 years ago you just bought a board, not one specific to a roof or wall or anything else. 

 

 

Yeah theres no difference if the foil coatings are the same, there is a lot of different coatings between the boards for different applications.

[gravelrash]

Thanks Mike, a clear and concise answer.