Problem with building regs

ComicGeek

Your builder would build what you have designed in compliance with building regulations. But the fact is that this Part L1B compliance calculation is to do with your design, so I really don't see it being the builder's responsibility to do this.

I do these kinds of calculations - I don't do them for less than £300-400 + vat depending on building size, so you'll be lucky to get it done for £130 or so. The calculation has to include the whole of the existing house, so I would need to undertake a site survey at least 90% of the time as the detailed information I need for the calculation isn't normally provided by the client (ie detailed floor plans of the existing, heating systems, insulation details of existing (or sufficient information to estimate), window opening sizes etc..

The assessor should do their own U-value calculations using the confirmed insulation products. As long as your builder has built to, or better than, the maximum allowable U-values under Part L1B of the building regulations, it would normally be fine - I haven't yet had a project (and I've completed hundreds) where I've had to spend any more client's money to get it to work.

So don't panic, and just get someone to complete the Part L1B calculations for you. Building Control should be able to give you a contact if you don't have one - our local inspectors put a lot of work our way as they know that we will sort it out and make their lives easier.

sw_jay

Newuser1987 wrote: »

Are you not speaking to the builder? Just ask him what has been used. Then call the manufacturer of the insulation and they will do the calculation for you. All could be resolved in a matter half hour.

Have you done the calculation I mentioned in my post already? You mentioned 25% rule but you probably haven't allowed for the existing openings.

Ok so I have done some measurements. Hopefully you can confirm whether I still need U values based on this.

Floor area of new extension - 9.45m2
Floor area of existing kitchen/diner - 24.5m2
Total of both = 33.95m2
Total area x 0.25% = 8.48m2

Existing doors/windows - 5.94m2

Total floor area - 25%+ existing doors/windows = 14.42m2

Total area of glazing in new extension is 8.26m2

snowcat75

Last EPC and SAP Calc on a new dwelling cost me (barn conversion) for nearly 300 sqm £138 inc VAT.... Some assessors want wildly more, there are online company's who will do you the calcs for this sort of money online, send them your plans and they send the paperwork back.... Its a tick box exercise IMHO pointless but BC will want to see it.... For me it was £138 of pointless paper, but wasn't worth doing battle with BC.


When I built my other place I had the same thing, and paid for someone to come out and charge me 4 times more...… You live and learn.

Newuser1987

sw_jay wrote: »

Ok so I have done some measurements. Hopefully you can confirm whether I still need U values based on this.

Floor area of new extension - 9.45m2
Floor area of existing kitchen/diner - 24.5m2
Total of both = 33.95m2
Total area x 0.25% = 8.48m2

Existing doors/windows - 5.94m2

Total floor area - 25%+ existing doors/windows = 14.42m2

Total area of glazing in new extension is 8.26m2

Just send this calculation to your building control officer and this will satisfy the 'over glazing' comment. But you certainly shouldn't need any SAP calcs now.

The building elements still need to meet current U-Value requirements. So the Building Control officer may still ask what insulation was installed if they were not able to inspect themselves. But as I say it is very easy to do the U-Value calculation if it is needed. Once you know the insulation that was used.

An example of an online calculator:
https://www.rockwool.co.uk/technical-resources/tools/u-value-calculator/

a.turner

sw_jay wrote: »

Thanks for the replies so far. We didn’t use an architect. We considered it but after speaking to the builder he told us he didn’t require full architect plans for what is a fairly small extension. My partner is CAD trained so she drew up some plans and we discussed the design with the builder. Unfortunately due to our inexperience we knew nothing about U Values and were under the impression that the builder would take care of that side of things. We have upgraded the insulation to 100mm and installed a warm roof to compensate for the amount of glass so I am hoping it won’t be a problem. It’s just working out how to do the U Value report that is causing me the problem as it’s not something I’ve ever had to do. Basically I’m clueless and would rather leave it up to the professionals.

It was the building inspector who mentioned that we would struggle to sell. Unfortunately I have separated from my partner during the course of the build so we need to put the house on the market as soon as we have completed everything. Hence why I’m a little bit panicked about not getting building regs signed off!

Who did the structural calculations for the roof lantern?

sw_jay

a.turner wrote: »

Who did the structural calculations for the roof lantern?

The structural engineer. We have submitted his report and calculations to building control

Mistral001

sw_jay wrote: »

I have it in writing

I would get a solicitor involved. It could depend on the wording of all the written information you got from the builder and someone neds to study that all. Note building law is a bit quirky and not like consumer law so getting legal advice from someone knowledgeable and experienced in building law would be advisable.

sw_jay

Newuser1987 wrote: »

Just send this calculation to your building control officer and this will satisfy the 'over glazing' comment. But you certainly shouldn't need any SAP calcs now.

The building elements still need to meet current U-Value requirements. So the Building Control officer may still ask what insulation was installed if they were not able to inspect themselves. But as I say it is very easy to do the U-Value calculation if it is needed. Once you know the insulation that was used.

An example of an online calculator:
https://www.rockwool.co.uk/technical-resources/tools/u-value-calculator/

I’ve emailed this calculation to building control so I will see what they respond with.

ComicGeek

sw_jay wrote: »

Ok so I have done some measurements. Hopefully you can confirm whether I still need U values based on this.

Floor area of new extension - 9.45m2
Floor area of existing kitchen/diner - 24.5m2
Total of both = 33.95m2
Total area x 0.25% = 8.48m2

Existing doors/windows - 5.94m2

Total floor area - 25%+ existing doors/windows = 14.42m2

Total area of glazing in new extension is 8.26m2

No, that's not correct (assuming you're in England)

Floor area only of extension = 9.45 m2
So allowable glazed area = (9.45 x 0.25) + 5.94 (existing doors/windows) = 8.30m2

Total area of glazing in new extension has to include the glazed roof lantern as well - if your figure of 8.26m2 glazing is correct and includes the roof lantern then you're fine. If not, then your options are to do an area weighted average U-value calculation or a whole building SAP calculation - either way, get someone who knows what they are doing.

ComicGeek

snowcat75 wrote: »

Last EPC and SAP Calc on a new dwelling cost me (barn conversion) for nearly 300 sqm £138 inc VAT.... Some assessors want wildly more, there are online company's who will do you the calcs for this sort of money online, send them your plans and they send the paperwork back.... Its a tick box exercise IMHO pointless but BC will want to see it.... For me it was £138 of pointless paper, but wasn't worth doing battle with BC.


When I built my other place I had the same thing, and paid for someone to come out and charge me 4 times more...… You live and learn.

If you have someone else who can establish the strategy for compliance with building regulations, then no problem going for the cheapest option. But recently I worked out that on average we save our clients £1,600 on build costs per dwelling because we put together the best strategy and tick the right boxes. The cheapest assessors will always pick the options that are simplest for them, not the best for the client.

It's not just about cost - it's value for money and added value.