Single Story Extension - few issues…

[JakeJam]

Hello, my wife and I are in the process of having an extension built on our semi-detached house. The work is fairly advanced but we’ve got some issues and the builders are not communicating very well with us (or Building Control). It is a timber frame with outer brick skin, tiled sloped roof, and the back wall has been opened into the new structure. The architect drew up plans in brick and block, and never updated them to reflect the change to timber frame but he did mention using 140mm timbers. The builders have erected the frame made using 2x4” with 2x6” for roof rafters. The roof is 15 degree pitch, tiled with two velux windows. The structure is watertight at present, building control are happy with the foundations & structural side (including steel to make opening to house which was designed by a structural engineer).
Building control advised the builders to check with manufacturers for U values. Builders have used rock wool in the walls and wingspan in ceiling and insisted that they’d done this plenty of times before and it’s never been an issue w/BC. They weren’t bothered about contacting manufacturers so I did (only had an response from wall insulation ppl) and they advised that the current wall insulation won’t get near the 0.18 required u value (that’s R value of 5.56). I asked them what I would need to do to get there and they said to add 65mm thick insulated plasterboard which is not feasible.
As I said the builders don’t seem to be communicating very well. The boiler (combi), which needs to be moved, was switched off over the weekend as the flue opening is inside the house so we have no hot water (no electric showers either).

I’m really frustrated and very stressed out as the builders (and I) really want to crack on with the work, but I feel BC won’t sign it off if we can’t show proof that it will achieve U values. Any advice would be greatly appreciated.
Thanks

 

[^woody^]

You'd be wise to stop any further work until the issue is resolved to the satisfaction of the inspector. Don't allow any further covering up, in case things need to be opened up or altered.

Likewise, no further payments communicate that to the builder.

 

[JakeJam]

Thanks Woody, I had a feeling that would be the best course of action. I’m getting a woodburner fitted on Wednesday in a corner of the extension which I’ve built the hearth for and have also rescheduled that work 4/5 times during the course of the build. If the walls need to come out then the hearth (that I built for it) will be too small. It’s left me in a really funny position, and I’m not sure the builders are that bothered about the BC - but as you said, that completion payment isn’t going anywhere until it’s complete.

 

[noseall]

Hello, my wife and I are in the process of having an extension built on our semi-detached house. The work is fairly advanced but we’ve got some issues and the builders are not communicating very well with us (or Building Control). It is a timber frame with outer brick skin, tiled sloped roof, and the back wall has been opened into the new structure. The architect drew up plans in brick and block, and never updated them to reflect the change to timber frame but he did mention using 140mm timbers. The builders have erected the frame made using 2x4” with 2x6” for roof rafters. The roof is 15 degree pitch, tiled with two velux windows. The structure is watertight at present, building control are happy with the foundations & structural side (including steel to make opening to house which was designed by a structural engineer).
Building control advised the builders to check with manufacturers for U values. Builders have used rock wool in the walls and wingspan in ceiling and insisted that they’d done this plenty of times before and it’s never been an issue w/BC. They weren’t bothered about contacting manufacturers so I did (only had an response from wall insulation ppl) and they advised that the current wall insulation won’t get near the 0.18 required u value (that’s R value of 5.56). I asked them what I would need to do to get there and they said to add 65mm thick insulated plasterboard which is not feasible.
As I said the builders don’t seem to be communicating very well. The boiler (combi), which needs to be moved, was switched off over the weekend as the flue opening is inside the house so we have no hot water (no electric showers either).

I’m really frustrated and very stressed out as the builders (and I) really want to crack on with the work, but I feel BC won’t sign it off if we can’t show proof that it will achieve U values. Any advice would be greatly appreciated.
Thanks

It sounds like your builders are making it up as they go along and are unaware of the (thermal) rule changes that occurred back in June 2022.

Who's idea was it to change the design from blockwork internal skin to timber frame? Did the build the timber frame first and sheath it etc?

 

[noseall]

You'd be wise to stop any further work until the issue is resolved to the satisfaction of the inspector. Don't allow any further covering up, in case things need to be opened up or altered.

Likewise, no further payments communicate that to the builder.

Agree.