Garage Conversion advice

20 Dec 2011
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United Kingdom
Hello all.

I'm converting my integrated single garage into a usable room over the next few months and am looking for some advice.

I have applied for building control and have a builder bricking up the old garage door and fitting a new window. Part of the garage sticks out from the main building so he is also going to insulate and re-felt the external roof, which I believe will keep the council happy.

I need to raise the floor by 165mm and have plenty of space to lower the ceiling to give me a height of 2400mm for the room height.

I am planning to fix joists around the inside of the wall and use joist hangers to attach 47x95mm joists across the garage. The garage is roughly 2.5m wide. I will then use 100mm Celotex boards between the joists, plywood, underfloor heating mat, laminate floor. I've checked with the council and the tiny gap (around 20mm) under the insulation will be acceptable.

As the ceiling of the garage will be either insulated on the outside or under a bedroom, I don't think I need to insulate the ceiling so was planning on using wall attached joist hangers with smaller joists and plasterboard attached directly to it.

Finally I will do the walls. They are all double brick cavity walls with a 2' gap between the bricks. The council have said 50mm insulation will be fine, so I'm planning on using batten with rockwool inbetween, plasterboard on top.

Obviously there will be services work throughout the process. The additional electrical sockets and lights first fix will be done before anything else.

I need to know if I should do the floor or ceiling first? And if i've missed anything obvious?

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