Garage conversion and Building Control woes

[nelliekins]

Hi everyone,

Well, after a couple of years of umm'ing and ahh'ing, getting prices on knocking a new doorway through into our attached garage, my better half has agreed that we can start on a home cinema conversion!

And now Building Control has pulled the rug out from under our feet! We want to keep the garage door on the front of the property, because

1) we don't want to have a window installed, only to black it out again
2) we don't want to have to dig out foundations and build a wall

But Building Control say (in writing, as a handwritten note included with their "information pack")

"we can keep the garage door, but we'll need to build a double wall inside to satisfy the required U-value".

Is this right? Surely all that is needed is _something_ that achieves a U-value of 0.35-0.45 - that doesn't require masonry, does it?

Can anyone help?

Neil.

[mavice]

Hi

this is purely my understanding of the rules from my experiences.....so....

building control have no influence on how the building will 'look' - that is the job of planning. Their remit is to ensure the building works are done to the building regulations which includes insulation values.

From their words in the letter, why do you think they want you to build a masonary wall ? The double wall mentioned could just as easily be a stud wall with membrane outer, and insulation (and I would recommend soundproofing) and then the inside boarded with plasterboard - maybe 2 layers of plasterboard to afford more soundproofing.


the wall will not be structural as there is obviously a lintel already over the door.

If planning have accepted the plans with the garage door still shown, then you only have to meet the U value to use the room as 'habitable' and how you do this is your choice.

it might be as simple as a telephone call to building control to discuss your intentions

good luck

Mav

[nelliekins]

Hi Mav,

Thanks for responding - I need the help!

I've already confirmed that Planning isn't required - even if I wanted to change the garage door, it falls under "permitted development" (which is a miracle, given all the restrictions in the deeds - apparently, I'm not allowed to keep alligators or crocodiles as pets! )

Originally Posted by mavice

From their words in the letter, why do you think they want you to build a masonary wall ? The double wall mentioned could just as easily be a stud wall with membrane outer, and insulation (and I would recommend soundproofing) and then the inside boarded with plasterboard - maybe 2 layers of plasterboard to afford more soundproofing.

Ah - that makes more sense! I was assuming that they meant a double-leaf masonry (i.e. cavity) wall - which was begging the question "just how small would my cinema conversion end up?"

I take your point on the soundproofing, though - I had been planning to build the wall as follows:

1. membrane
2. 4x2 studwork @ 450mm centres
3. 50mm rigid insulation boards between joists
4. 2 layers of 12.5mm plasterboard

Lots of Googling and scribbling on the back of a fag packet reveals that _should_ have a U-value in the region of 0.2-0.3 (dependent upon the type of insulation boards used).

Originally Posted by mavice

the wall will not be structural as there is obviously a lintel already over the door.

Yep, although this wall of mine is going perhaps 4-6" behind the garage door (I'm going to put a 12" 'flood barrier' of brick & concrete down right behindthe garage door to prevent any ingress of water from coming underneath - just in case!)

Originally Posted by mavice

it might be as simple as a telephone call to building control to discuss your intentions

That's what got me into this mess in the first place - asking silly questions of a Duty Officer over the phone!

I guess I need to just pay attention to the regs for the various areas of consideration:

1. thermal insulation (looks to be covered)
2. sound insulation (2 of the 4 walls are internal, so don't matter; anyone have any ideas for soundproofing the exterior 2 walls?)
3. heating (we're going underfloor electric heating mats - no radiators = maximum space for big comfy chairs!)
4. ventilation (planning to fit 100x100mm inlet and extraction vents into the ceiling, with low-speed fans in the ceiling void in case it gets stuffy)

Anything I've missed?

Equipment to start with will be what I've already got lying around - Sony 1200ES receiver, HTPC as DVD player (MCE box with upscaling S-video input), Infocus SP4805 PJ, B&W P4 fronts, Mission centre and surrounds.

Hoping to come into some money this year , in which case that lot will go into a bedroom in favour of a 3-chip DLP, Dali speakers (7.1) and something like an Onkyo 875 driving it!

But need to build the room first! Hopefully I'll send in the plans in the next couple of days, and be ready to start in a week or so - YAY!

Neil.

[mavice]

hi neil

this site may be useful for soundproofing and insulation

http://www.soundstop.co.uk/index.php

and here is a bit cheaper for insulation

http://www.planetinsulation.co.uk/

[neilball]

For ventilation then look at the single room heat recovery units from Vent Axia - they are designed to run continuously and provide constant background ventilation - gives much better air quality and also places less load on the heating system as the incoming fresh air is preheated. They also also generally quieter than standard fans as they operate at much lower speeds.

[ched]

Good luck with the conversion. We converted our garage into a lounge in our last house, long story as we needed planning permission etc.

But I can tell you that our floor had 2 coats of a paint on bitumen on the floor and partway up the walls to create a moisture barrier (damp course). Then 50mm celotex insulation on the floor then it had concrete on top. This complied with building regs for a new house. We did have a front wall and window fitted.

As for the other 2 external walls I would just use the same technique you are intending to use on the garage door wall. One thing to remember is that insulation is very cheap to put in when you are constructing. If I was you I would double up on insulation as well as keeping the room warm in winter it will help to keep it cool in summer. Remember to insulate the ceiling if you can, it will help with both heat loss and reduce the sound escaping through the roof.
You could also maybe think about putting in central heating powered underfloor heating as an extension to your radiators. I think screwfix sell kits with pumps and control valves. That way you should be using cheaper gas to heat your cinema room.

Gook luck and keep us posted on the progress.

[Banbert]

The planning permission/building regs can be a pain in the ar** cant it.

We spoke to the planning office and told them what we were doing (no external mods at all) and got a letter back from them saying what we planned was fine and that we didnt need planning permission, we would however have to comply with building regs of course.

No problem we thought, so we contacted the building regs people and arranged them to come out when we were at a key stage they wanted to view and started the work.

Couple of days after starting the work we got another letter from the council telling us that we did need planning permission after all due to the deeds and convenants that were in place on the whole housing estate.

We were less than impressed with this situation as we were well into the work now and had to apply for planning permission retrospectively, thankfully it went through without any issues ....... the council wouold have had a real fight on their hands if there had been an issue though !


We left our double doors in place and placed this inside of them.

1. Sealed them in with DPM and flashband
2. Insulation layer
3. Single row concrete block wall.
4. Stud wall with insulation and soundboards over the top of it.

I wouldnt have been happy without the built wall we put in, pictures here >

Double Garage Conversion by a Newbie