Garage Insulation

[duke666]

Hi all,

I'm about to start insulating my garage using 50mm battons and celotex on the floor and walls.

Question is, do I need to put a DPM under and behind these?

Thank you.

 

[Mr Chibs]

Is it single skin brick garage? if so you may be better fixing the celotex straight to wall.
You could use battens on top, to secure the PIR to the wall, then when you plasterboard fix these boards to the battens. cables can be run in the gap created. You won’t need to bother with any DPC

 

[duke666]

Hi, thank you for your prompt reply.

Yes, single block walls with double width column.

The gap that is left for the cables, can I add additional rock wool in here as I have an abundance of it left from the roof?

And no DPM required for the battons on the floor either?

Thank you.

 

[Mr Chibs]

You’re welcome.

If you are running electric cables on top of the PIR boards, then don’t fill the cavity with rockwool, as you don’t want it around the cables.

You might not need any battens on the floor, as you could just ‘float' the floor on top of PIR (depending on floor type and thickness of PIR, what are you thinking of using?)

If you do use battens, would be wise to put DPM down, you can lap it up the walls before you apply the insulation boards to the walls.

 

[duke666]

That's interesting about the cables.

Until about 10 years ago I was in office build and refurb. T&E was always in the rockwoll within the drywall.

 

[robinbanks]

you don’t want it around the cables

You can insulate cables no problem, so long as you're prepared to calculate how it has reduced the current carrying capacity and swap the breaker protecting the cable out for a smaller one that will carry on providing adequate protection for the reduced amount

If this then causes you a problem boiling two kettles at the same time then c'est la vie; reduce appliance draw, fit larger cables and a bigger breaker or change the installation method to improve the CCC and fit a bigger breaker