DIY Doctor UK DIY Forums

Hi all,

Firstly, apologies for the essay! There's no easy way of summarising this but I'd really appreciate it, if you do have the time, if you could take a look. Thanks.

I posted earlier in the year regarding a problem we were having with the ground floor of our new build David Wilson home. Basically the room was freezing, felt draughty and cold at floor level etc... We recorded temperature and generally where it was 21/22 degrees in the centre of the room it was only 17 degrees at carpet level. See https://www.diydoctor.org.uk/forums/view ... highlight=] for more details on that.

Anyway, builders replaced the rads in the lounge which doubled their size. But we still had a problem so they came out last week and inspected insulation under concrete screed in the lounge, in the cavity wall and in the suspended floor void. Result was that everything was ok apart from the fact that a layer of insulation is completely missing in the floor void below the house.

Apparently there should have been a layer of foil type insulation on the underside of the ground floor (ie across the top of the void, attached to the concrete, between the suspended floor joists). This was missing! Also, there were massive gaps (missing breezeblocks basically) around where the airbricks feed the void which mean that all the cold air from the void can come straight back out and up the cavity walls - hence us finding the lounge walls were always freezing!

Anyway, they are going to fill the gaps around the air brick feed into the blockwork and then come back to us with a solution for replacing the missing insulation in the floor, whatever that may be. They can't get back into the void obviously so I assume it'll involve laying something on top of the screed inside the house.

However, we don't know where we really stand on this. Firstly, surely NHBC and local build control have signed off the house in which case I assume we have some comeback there? Is there anywhere else we can turn to for advice?

Basically how major is this? Should we be considering the legal route or simply let them solve the problem? We're really concerned that whatever they do won't be good enough and certainly won't last as it won't be part of the fabric of the house and may wear out in years to come, thus devaluing the house.

Also, do any of you recognise this building practice - e.g. floor void, foil insulation, concrete base, polystyrene insulation, thin plastic sheeting and then the concrete screed? The builder said that this technique was used only for 4 months or so and they changed technique because it caused so many problems. I assume they uprated the insulation below the screed?

Any thoughts/advice/information would be appreciated - even a lesson on how suspended floors in modern houses should be insulated would be great.

Thanks
Mark

Contact NHBC directly, as it would seem that it is their mistake.

tanz1978,
I assume you have a suspended concrete beam and block floor. Normally these will be the blocks and beams covered with a concrete screed, DPM, insulation and a top covering of either concrete or floorboards.
Did you see what depth of insulation was present under the floor screed?
end

Yeah it's a suspended block and beam floor. The insulation in the floor was under the concrete screed, they drilled down and i guess it was 30-40mm down maybe a little more. I read the screed needs to be 60mm thick to make it strong enough so it doesn't crack?

They have come back to us and said they're looking for a "suitable material" to lay over the concrete screed/under the carpet to replace the missing insulation. This doesn't sound ideal to me as I'm sure wear and tear over the years will reduce its effectiveness. Also where it'll only run up to the internal walls it will not cover the entire surface area of the floor and so might not be as effective.

Think I'm going to try to get an independent survey out of them as i think this is pretty serious stuff!

I would have thought the missing insulation would have been 2" thick, which would create more problems.
I think it would be advisable to employ a surveyor, but tell NHBRC that you intend to do so, and bill them for the costs as youare not happywith their response.But tell them in advance of doing so to see what their response is.
You could also visit CAB for the legal angle.
HTH

Why not go to HMG Planning Portal and download the current regs.
L1a Conservation of Fuel and Power in New Dwellings.
Once you know what should have been done you are much better equipped to present your case

tanz1978,
From your description the only sound way to solve the problem is for the screed to be removed, the correct depth of insulation to be installed and the screed relaid.
The builder will not like this but you should try to persuade them that it is the correct solution. You may find the builder washes his hands of the whole thing and passes the responsibilty to the NHBC.
Get the NHBC involved they may be able to apply pressure on the builder.
end

Thanks for all your help and advice on this. I've just sent them a letter saying how "disappointed" we are, etc... Also saying that we intend to instruct an independent surveyor and we'd hope they would cover the cost blah blah so we'll see what they say to that.

I'll check out the regs - the house was completed before April 2008 so I believe the regs are different and since April last year they've really tightened up on the conservation of energy side.

One thing with removing the screed and relaying - won't the internal walls need to be taken out and rebuilt so the insulation can be installed continuously across the entire floor? That just sounds like a total nightmare to me!! But if it's the only way to fix this properly then it'll have to be done!

tanz1978,
won't the internal walls need to be taken out and rebuilt - depends on how the walls were constructed, load bearing walls should not be bearing on a screed with insulation under it.
end

Do visit the Government site, the current regulations are there and you can down load them for free.(just look further down)
Also, people like Jablite, etc have good web sites and available literature where you can see what they recommend as a solution using their products.
As I wrote earlier, the more you read, the better you are able to press your case.
It may well be worth getting a solicitor to threaten court action.
Try something novel, ask the building inspector for advice.

Just as an update... they've kindly offered to pay for an independent survey and have also said they would fix anything that the survey additionally hightlights! Pretty happy with that so now just got to find a suitable surveyor!

tanz1978,
Once you have found a surveyor don't forget to ask whether they have professional indemnity insurance, what the limit of the insurance is and check out whether it's current.
end