Poorly laid cavity wall insulation

[WakingUp]

We are currently building an extension work involving cavity walls. The builder seem to have done a poor job - the insulations are loose and have not been stuck to the inner leaf. The building control officer is now requesting that this is fixed. I am wondering how to fix it as the construction is nearly complete (at roof level). Some thoughts I had:
1) Fix all the visible ones
2) Introduce an external insulation layer (similar to a warm flat roof) and this will avoid bridging issues but not sure if this would be acceptable to building control
3) Replace the insulation - not sure how?
4) Demolish one leaf, fix insulation and rebuild?

Any practical solutions?

Looking forward to hearing your thoughts. Many thanks

 

[stevie888]

What insulation are you using?

Why are you worrying: this iis up to your builder to sort to BCO's satisfaction

 

[WakingUp]

I am using PIR board insulations. My builder is a friend and hence liabilities are not too well defined.

 

[stevie888]

Friend or not it's up to him to do the job properly: I'd like to think I'd try harder for friends.

I suppose the surest way would be to take down the outer skin, remove the insulation and clean back any snots of mortar (which are likey if the board was floating about). Then replace the insulation with clips on the ties to hold it and rebuild the outer skin.

In the real world though if the required insulation thickness is in place is it really going to matter?

 

[WakingUp]

Yes, a good job will require the work you suggested. It will cost time and money.

Your question on "is it really going to matter" is a good one. I don't have an answer and keen to understand.

 

[Deluks]

Your question on "is it really going to matter" is a good one. I don't have an answer and keen to understand.

Your building control officer has already answered that one for you.

 

[WakingUp]

Your building control officer has already answered that one for you.

The building control officer informed us it needs fixed but would not comment on how or why.
I am now left to figure out a solution. If I don't fully understand why I should fix the issue, the solution options available is a wide range.
The forum could help with understanding the risks of not fixing, additional solution options, pros/cons of the solutions and more.

 

[jj4091]

Is it possible you could fill the cavity between the insulation and outer skin with loose fill vemiculite or some other product, to hold the insulation firmly against the inner skin.

Micafil Vermiculite Loose Fill 100 Litre Bag

100-litre Micafil vermiculite for chemical spill absorption. Buy online with fast delivery for safe industrial handling.

itppackaging.com

 

[WakingUp]

Is it possible you could fill the cavity between the insulation and outer skin with loose fill vemiculite or some other product, to hold the insulation firmly against the inner skin.

Micafil Vermiculite Loose Fill 100 Litre Bag

100-litre Micafil vermiculite for chemical spill absorption. Buy online with fast delivery for safe industrial handling.

itppackaging.com

Thanks JJ. For the sections are still visible, we will exactly as you suggest. I bought PU adhesive. Does vemiculite provide a firmer fit? If there are blocks that are not accessible, are there other solutions?

 

[jj4091]

Can you get an adhesive to the bottom of the cavity?
Gravity and tamping it down as you fill will make vermiculite firmer, but not sure it would need it.

 

[WakingUp]

I agree, adhesive may not always work. By BC agrees to, I would be happy to use vermiculite as alternative.

Is external insulation an option? Would this avoid cold bridging risks and serve the purpose?

 

[endecotp]

Is it possible you could fill the cavity between the insulation and outer skin with loose fill vemiculite or some other product, to hold the insulation firmly against the inner skin.

I think you need to understand what the reason for wanting the insulation held against the inner skin is....

My understanding - and I am not an expert! - is that you want it held against the inner skin exactly because you don't want it in contact with the outer skin. So filling the gap between the PIR and the outer skin with vermiculite would be exactly the wrong thing to do. I think the idea is that water that penetrates the outer leaf can run down the inside without bridging across and making the insulation and inner wall wet.

Someone who knows more, please comment.

 

[WakingUp]

This is a very good point Endecotp. Thanks. Sticking the insulation to the inner leaf should avoid the insulation becoming a bridge and prevent the inner wall becoming wet.

 

[stevie888]

But we frequently full fill cavities!

 

[endecotp]

But we frequently full fill cavities!

Right! So what’s the criteria for when to full-fill and when to partial-fill?