A bit of advice please...

[Kingo206]

Hi guys,

First time post although unfortunately, not a happy one. We are doing a rear one-storey extension.

We've had continuous bad luck with builders who all just seem to be in it for the money. The first builder we had sort of absconded halfway through, got another builder in who rightly pointed out issues that builder #1 made - and quoted a high amount, to me anyway, to rectify - I just wanted all done with so accepted. So they tore down the inner leafs (blockwork) of both sides and the outer leaf of one (external wal)

In all fairness builder #2 was efficient and sent us pictures and kept us updated, but regardless they still rushed in order to get the money in my eyes. The main issue that building regs pointed out is that because we've used Celotex 100m, but builder #2 installed it incorrectly - The insulation has been 'clipped' against the external brickwork wall, rather than the internal blockwork. So this has to be rectified. Note, our cavity is essentially 130mm (long story), 100mm insulation, 30mm air gap (which should've been between insulation & external wall)

I will get onto them in the morning, but the way things have turned out I'm sure they will ignore and wash their hands of it.

Does anyone have an idea of a remedy or is it the inevitable tear down and hope for 3rd time lucky.

Please see progress image sent by builder #2 attached:

Sighs.

 

[John D v2.0]

Yeah it definitely should have been against the inner leaf, and I don't see how it is going to be fixed other than rebuilding the outer leaf again.
Our builder did similar although the insulation was just floating around loose in the cavity and it was a rebuild job needed.
Did you have a proper agreement and spec for the builder? If everything is in place it will cost them more to walk than to rectify. If you don't get things in place it will cost you a lot more, so make sure you sign a contract before you do any more.

 

[Kingo206]

It won't cost them anything to walk in all honesty, they were contracted to rectify the issues of builder 1 - We are using an independent roofer to complete the work - So it all boils down to morals, and failing that, we go down the legal route.

 

[RandomGrinch]

Others will say if I'm wrong, but would it be possible for the cavity to be full-filled with insulation?

 

[Kingo206]

I also thought this, but maybe because we are using PIR for it to be effective there has to be an air gap?!

 

[RandomGrinch]

I also thought this, but maybe because we are using PIR for it to be effective there has to be an air gap?!

I don't believe so, there are plenty of full-fill systems available, example:

Eco-Cavity Full Fill

Insulation board suitable for full fill cavity wall applications, whilst maintaining a residual 10mm cavity helping resist moisture transfer, aids installation and accommodate mortar squeeze.

www.ecotherm.co.uk

Yours would be unconventional though - it may be worth asking building control if they have any suggestions?

...aah, this system does maintain a 10mm cavity...

 

[John D v2.0]

Some insulation you can full fill but normal pir is not one of them. It's supposed to be kept dry. The air gap wouldn't make a big difference, the foil face might be negated only.

 

[Notch7]

There needs to be an air cavity

I also thought this, but maybe because we are using PIR for it to be effective there has to be an air gap?!

no, the air gap behind external skin is nexessary as part of the damp detailing.

what you have is normal PIR, not designed for “full fill” applications.


When using PIR cavity insulation the internal skin has to be built first, your muppet builder didn’t do that - I bet he did it for a reason: no blocks on site or whatever.

 

[Kingo206]

There's really no excuse, particularly for the side where both the blockwork and brickwork were taken down - I would have given the benefit of doubt for the side where only the blockwork was taken down.

 

[Kingo206]

As I predicted the builder has ignored my messages and didn't answer my call.

What steps do I need to take before considering taking on someone else to re-do the work, whilst ensuring I can chase the builder in the future for my money.

If anyone has a comprehensive link that would be great.

 

[jeds]

Something is a bit odd here? How thick is that insulation? it looks (from the photo) quite a bit thicker than normal for a standard partial fill cavity and not only have they fixed the insulation in the wrong place but the residual cavity is way too small. It's like they have built a 100mm cavity and tried to fill it with a - 80, 90mm insulation? Very odd.

It's hard to believe a bricklayer wouldn't know that partial fill insulation should be fixed to the inner leaf - it is a fundamental and something they would come across almost daily. I wonder if they thought this was full fill and just got the material wrong? That would explain the thickness and the size of the cavity.

What specification or drawing was this builder working from?

 

[Kingo206]

The issue we have is the original builder messed up and didn't inform us, we were working to a 100mm cavity with rockwool insulation, and then the building reg inspector told us (partially incorrectly) that the regs updated to 150mm cavity - with 100mm PIR Celotex insulation. However, we long later discoverd there were other options available with a 100mm cavity that we could have gone with.

The original builder built from the concreted foundation (600mm width, which we were told by building regs to use, however later found for a 150mm cavity , we needed 700mm) up to DPC, and did the block work of both sides, and the brickwork of one side fully, then the other partially. We then realised the errors:

1) He didn't extend the cavity to 150mm, as there was no tolerance to, he did it to the max he could 130mm, but he never told us and continued regardless, as to not disrupt his Christmas money.

2) The brickwork of one side was rushed, hardly used adequate cement.

The new builder then took over, and advised us to remedy with the following:

1) Remove the blockwork of both sides and rebuild. (We removed the blockwork and the builders built up blockwork)

2) Remove brickwork of one side and retain the other. Rebuild Brickwork of the side removed.

There's really no reason why the insulation was not installed correctly to the side that both the brickwork and blockwork were torn down, unless they wanted uniformity to hide the issue?!

Overall everything is okay, except for the insulation.

Building regs came in and said that the cavity air gap just about passes, the minimum is 20/25mm we have 30mm.

I wonder, would it be possible to removed the inner leaf of both sides, and build back up? Remove block, put insulation against block, use clip?

Note: The original builders built the insulation correctly. I genuinely think the new builders hadn't used Celotex in cavity wall before, as it's a new regulation - people typically use rockwool

 

[noseall]

It's like they have built a 100mm cavity and tried to fill it with a - 80, 90mm insulation? Very odd.

Its standard spec' I'm getting from architects since June last year i.e. 90mm insulation in a 100mm cavity.

 

[Kingo206]

Its standard spec' I'm getting from architects since June last year i.e. 90mm insulation in a 100mm cavity.

Mine was originally supposed to be 100mm cavity, but we were advised to increase to 150mm due to regulation.

 

[jeds]

Its standard spec' I'm getting from architects since June last year i.e. 90mm insulation in a 100mm cavity.

Yes, agreed, but that would be insulation designed for full-fill - which that stuff isn't.