Cavity 10mm wider than insulation?

[Moonshine]

 

🤣 got a refund on them

[Tetrarch]

My architect specified 90mm Kingspan K106 (at £44 per sq m) for a 100mm cavity. The specified tape is also extortionate at £68 per 50m roll

 

My builders found this almost impossible to fit because it requires an absolutely flat internal face and then a "snot-free" finish without sufficient space to get tools or fingers in. This is a stupid specification and the Building Control guy agreed when he came to inspect. We're having K-Rend so he was not as concerned, but his recommendation was to use a 110mm cavity as a miniumum to avoid these problems.

 

I assume that Kinspan use their specificiation because that is the only way that the models give the necessary u-value, architects and designers then take this as written without any regard to the installation practicalities

 

Regards

 

Tet

[Iceverge]

On 30/03/2024 at 11:29, Tetrarch said:

assume that Kinspan use their specificiation because that is the only way that the models give the necessary u-value, architects and designers then take this as written without any regard to the installation practicalities

 

Kingspan don't care. They just want to sell their extremely expensive insulation. 

[goodbyegti]

On 30/03/2024 at 09:29, Tetrarch said:

My architect specified 90mm Kingspan K106 (at £44 per sq m) for a 100mm cavity. The specified tape is also extortionate at £68 per 50m roll

We had the same spec. The tape doesn't even stick very well and melts off in the sun. I had to keep patching more on. Tongue and groove boards seem a much better design. I just can't imagine the tape sticking for long.

 

Our builder washed the 10mm cavity with a hose to keep it clear. Not that it mattered a huge amount with the render.

 

 

Edited April 7 by goodbyegti

[Iceverge]

I would rather eat a breeze block than use rigid boards in a cavity wall. 

[tuftythesquirrel]

8 hours ago, Iceverge said:

I would rather eat a breeze block than use rigid boards in a cavity wall. 

Wise words, if only I had known...

[FirstTimeSelfBuild]

reignighting this, primarily out of curiosity.  My architect has suggested 100mm fullfil kingspan, and my brickie has quoted accordingly, and his quote seems higher than I would have expected (i am awaiting further quotes). 92sqm (including below dpc) 4 weeks of work brick and block for an extension wrapping around 3 sides of the house 14k (no VAT) all ground floor but scaffolding will be needed. Based on previous messages is the full fill hard interlocking PIR insulation a huge PITA hence the high quote and would 100mm rockwool be preferred (certainly would be cheaper). Or is it not that simple, considering the extension will need to meet certain thermal insulation criteria (i havent scoured building codes just yet).

[Canski]

21 minutes ago, FirstTimeSelfBuild said:

Based on previous messages is the full fill hard interlocking PIR insulation a huge PITA hence the high quote and would 100mm rockwool be preferred (certainly would be cheaper)

Yes it is a PITA for brickies. But if you can’t increase your cavity size and need to meet the design criteria you are stuck with it.