Insulation of single brick garage-what to use?

[Happy Bees]

Hello all, I have had several quotes for converting our single wall brick build garage into a home office/play room and trying to decide what is the best way. I want it to be habitable all year round including at night for occasional guests.

What would be the best way to insulate? I gather from my research that option b is a lot cheaper. I will have a builder do this as I am expecting and my husband is not so handy...

a) studs, 90mm kingspan insulation between studs, plasterboard with 12.5mm sound board
b) studs, 100mm roll insulation between studs, plasterboard with 12.5mm sound board (and where do you put a barrier and what type?)

Would using polystyrene boards save some cost while offering better insulation than rolls? (rockwool or similar).

Many many thanks for input, I have searched all past threads and online and am even more confused than when I started. It seems people thing kingspan is the best but it is the most expensive...

 

[foxhole]

You could just use insulated plasterboard, save loosing some internal space.Less work so quicker. Polystyrene is cack compared with other forms of insulation, it’s cheap for a reason.

 

[Happy Bees]

Thanks very much, would something like this then go direct on the bare brick? The video of the product says it has a vapour barrier built in , would this mean that all you need to do is stick this onto the brick, plaster and you are done?

https://www.insulationsuperstore.co...ted-plasterboard-12m-x-24m-725mm-overall.html

 

[^woody^]

Have you put in a building regulations application?

 

[Happy Bees]

Hi, thanks for reply,didn't think we needed it. I have applied for certificate of lawfulness as the garage is existing and we are just changing use. That is what planning dept told me to do. Would certificate of lawfulness triger building regs? We are in Merton, London.

 

[^woody^]

Building regulations are different to and separate from planning regulations and you will need building regulation approval and have the work inspected.

A good way of selecting competent builders is whether they tell you what permissions you need when they quote.

Then you are faced with the a conundrum of whether to employ a designer to specify the correct design and materials, or can you rely on a builder doing a compliant design.

To answer your original question, it will depend on several factors as to what insulation you require and how it is installed. It should not be thought of in isolation, but part of the whole design.

 

[oldbutnotdead]

Kingspan etc has about twice the thermal resistance of rockwool etc. So to achieve the required U value on a half brick wall 90mm PIR or 180mm Rockwool. Rockwool per cubic metre is much cheaper than PIR but installation time is higher- you can dot and dab PIR bonded plasterboard, you have to build a stud wall to use rockwool. Rockwool is better at attenuating sound and is easier to install correctly.
You will need to inform Building Control of this scheme

 

[Leofric]

What have the builders quoted (allowed ) for ?
Are they taking responsibility for the work complying with building regulations ?
If you employ a building designer to obtain bldg. regs approval then builders providing quotations are more likely to be quoting on the same thing !
You would also have a better idea in advance of what you are getting.
Might seem obvious comments but always better to sort these things out before work starts on site in my opinion.

 

[Happy Bees]

Thank you all for very useful input. I have called building regs and they said the building is exempt since it is about 25sqm, detached from main house and not intended as sleeping accommodation. They only thing that will be subject building regs is the connection to the sewer for the toilet-I do have a question on this below please!

They said the minimum required IF it were subject to building regs is celotex/kingspan type thing is 100mm for walls, 80mm for floor and 120mm for celling.

I am trying to keep the cost as low as possible as this is really just a home office....we might have people stay there overnight on rare occasions but not as regular accommodation. I can't afford a designer or high spec...

The key issue I have here is that the builder I know and trust is too busy with bigger projects and is VAT liable. The other guy is a lovely local carpenter and not liable to VAT so it will be considerably cheaper....but this means all the research is down to me to just simply say exactly what I want and to deal with bulding regs myself to save cost.

Any top tips for macerators and leading the pipework into the main foul water please? I know many people say macerators are a big NO go due to the hassle with them when they break but considering this will be mainly used for n.1 (ehm) and only on occasions I was hoping it will suffice....the garage is about 12meters away from the main house and the foul water and cold water connection.

Do we insulate the pipes and burry shallow under lawn?

Thanks again so much!

 

[^woody^]

I want it to be habitable all year round including at night for occasional guests

the building is exempt ......not intended as sleeping accommodation.

Which is it?

If it should have building regulations approval but it does not, then just hope there are no incidents in there such as a fire.

 

[Happy Bees]

Good point woody, thanks. you are right. I am not classifying it as overnight sleeping accommodation to the council as the main purpose is really the home office. By habitable I really meant comfortable -i.e. if I work there all day long I need it to be at least nearly as comfy as the main house no matter how cold or hot it is outside-hence the focus on insulation.
However I do want to be able to have to option for people to sometimes sleep there if we have a full house. Obviously I want it to be safe, electrics are done by a professional electrician with a certificate and I intend to put a smoke alarm in there. I have had a structural engineer look at the shell when we had our extension done and he said it is a solid building with no issues. Am I missing something else here? How else could it be unsafe?

Many thanks

 

[Ian H]

12mtrs of pipe would only need 300mm of fall so if the ground levels aren’t a mile out you could more than likely have a normal drain put in there.

 

[^woody^]

It does not matter what it is called, the criteria is what it is used for.

Any electrician can self-certify works, but that does not mean that it is the correct work. Does it need one or more detectors, smoke or heat or both, their locations? An electrician wont necessarily know this, but can certify that they have been wired in correctly.

The correct materials, escape routes, fire spread from inside to out and outside to in are all part of the fire safety requirements that need to be considered and verified.

And unauthorised work wont be covered by a household insurance policy.

 

[Happy Bees]

Thanks to you both. I will do some more investigating and talking to the council. Maybe one or two more quotes would be a good idea too.