Garage conversion with single skin walls...freezing!

[DottyD83]

Hi, we recently bought a property that had a lovely recent garage conversion... it was one of the reasons we loved the property. It is currently a spare bedroom with lovely sharps fitted wardrobes and a new ensuite bathroom. However it has come to light that the room has the original single skin walls so is freezing in winter. It has a massive radiator, but as soon as the heating goes off all the heat disappears. We have had to get an electric heater for overnight when guests stay over. We would like to make the room into a playroom/spare sitting room with sofa bed for guests, but it will need to be better insulated. My husband says it will cost a fortune as everything will have to be ripped out (inc wardrobes and bathroom), walls better insulated, replastered etc.....Has anyone had experience of this and know how much we're talking roughly?? Or if there is a cheaper option. It's such a shame as everything is so new. Husband also reckons the wardrobes will have to be made smaller as the walls will be thicker so I imagine that will be expensive!!

It really sucks that your vendor didn't inform you of this before purchase. This would have been known to them. This is an example of how people aren't truly adding "value" to their properties. It is BS and you have to check these things and vendors need to provide evidence the renos they've done have been built to modern standards and comforts.

The costs of internal wall insulation could run between 15-30k for a single garage given current expensive reno running costs. I've recently been quoted this for the house I am purchasing that has a garage that isn't renovated. I'm in SE London.

When was the conversion done? If recently then it hasn't been converted with the correct building regs approval and therefore is effectively not a legally habitable room. This should have been queried in conveyancing when you bought the property.

We have done a conversion recently and have had to double insulate all external walls and the floor was dug down, insulated and then screeded. All was inspected by the Building Inspector and lits of photos recorded.

Really!! A sheet of 120mm celotex is £50, do the maths on materials and you will find that quote is very pricy. Labour is expensive of course but knocking off plaster, adding insulation and boarding is easy so doesn't need a particularly skilled worker to do it.

Insulate it externally?

I know right! That's what we were quoted by 3 traders. They gave different prices in that range and we think trades people are really taking advantage of the current "renos are expensive" climate. We are going to hold off until we get a more concrete quote. It isn't something we absolutely need right now anyway... maybe OP you can consider whether it's a room/extension you use regularly right now? Can you leave it for awhile until costs come down?

Do update us what quotes you get.

Btw @Ilovemyshed you mentioned you took photos. How often did you do this? I think this is a good idea to collect evidence? Were your workers ok with it? Thank you

how much do you think is reasonable to pay for labour (exc material costs)?
I'm planning a full house reno and literally the project manager lol

Labourers £150/day, skilled trades £200-300/day

All in renovation costs £1500-£3000 psm depending on spec

Surely this was picked up on survey or was it marketed without the inclusion of this room / bathroom ?

Surely it needed building regs, did you see any paperwork. For the time being I would put down thick rugs and thick wall hangings and anything in the wardrobes could get damp and cold so put them in clothes covers and storage boxes.

Exactly this! We converted our garage a couple of years ago and it needed huge amounts of insulation to comply with building regs. I'm so thankful, it is now pretty much the warmest room in the house.

I’m converting my detached single skin garage using an internal frame, celotex, plasterboard to the walls, raise and insulate the floor, and put a partition wall up to create a hobby space at the back. With additional wiring, lighting, cat6 cable to provide internet, and paying tradespeople to do the actual work it’s costing me about 4k. I plan to use it as an office/hobby room so will be worth every penny. I’ve no plans to do a change of use but it’s being done to building regs anyway.

My previous house had a huge integral garage that had been converted in the same way yours had. It was bloody freezing all the time even in summer. In winter I had to run 2 oil radiators along side the actual radiator. I might as well have set fire to my money. I think your husband needs to come round and pay to have it done properly. It’ll be worth it.

Yes agree. I’ve gone top spec with a lot of extra sockets, high speed internet and maxed insulation. The labour for the actual insulating is going to be between 1k and 1500. A skilled DIYer could do that but themself and save the labour charge.

edit labour costs
IT tech £50 ph
Electrician £30 ph
Joiner £20 ph
handymen £15 ph

You can do external insulation if you have access to the outside of the walls and sufficient space. I don't know the comparative costs, but it would preserve the inside dimensions and the decor.

I also don’t understand how this didn’t come up in the survey or in the conveyancing process.

Even if you cheaped out and just had a valuation survey, you solicitor should have asked for the relevant building regs documentation and the fact it didn’t have any (it wouldn’t if it didn’t meet the insulation requirements) should have been an issue.

Or did you just decide it wouldn’t really be a problem and now realise that it is?

They should have a building regs certificate for the conversion, and if this has not been made available/checked you possibly have some recourse with your conveyancer

External wall insulation seems like the best option to keep the interior intact.

Could you put brick wall internally and then make one of the brick walls into a feature wall plastering the other walls ?

@Ilovemyshed does that include all the re-plastering and get it back to looking like a normal room?

I've been through the paperwork and we have a building regs certificate!! We strongly suspect it's single skin as it's freezing and the walls are so thin....The conversion was done in 2018. So either we're wrong about single skin and it is the bare minimum insulation to comply with regs. Or the council inspector made a huge error....how likely is this though?? Any advice on next steps?

@cupcakesarelife. We took photos at all stages and emailed them to building control. They made regular visits also to inspect what they wanted to see.

And the costs per sq m are to finished spec.

How deep is the window and ledge? You’ll know if it’s two walls
2018 is very recent - check the council
planning portal

If it was issued with a completion certificate by building control, there’s nothing you can do. It’s highly unlikely a single skin wall would have been signed off, but inspectors see only a snap shot of the works, and insulation is not a statutory inspection.

You need to investigate the wall build-up and take steps from there.

Maybe check all doors/windows are properly sealed. We had a garage conversion done recently. We saw them put in the double brick walls and tonnes of insulation. It was freezing cold in there so we checked the new door. It hadn’t been tightened properly so the wind was whistling in around it. We also had to have a huge hole drilled into it for ventilation to comply with building regulations as it didn’t come with a trickle vent.

Did you have a survey done?