Insulating a floor

Postby stiz » Fri Nov 02, 2007 1:27 pm


I am planning to put a raised floor at the back of my garage (2.4m x 2.4m) to create a utility area. I have spoken with the local planning dept and I understand that when I eventually separate this area from the garage with a stud wall I will need to go through development control. But for now, I'm just putting in a suspended floor.

The question is, how do I best insulate the floor (so that I won't have to take it up when I do the full conversion).

Building Control have agreed that I can lay 4x2 beams on the exisiting concrete floor (which I have assumed already has a DPM) and use T&G chipboard sheets. For insulation, they have simply told me to meet the necessary U values (which I had to look up for myself!) and will not give me specific advice on this.

My plan was to use polystyrene sheets, but I have read that these are more suitable for under concrete floors due to the fire risk and that I need to consider air flow and the risk of water leaking from the washing machine as well.

Can anyone please help:

1. what's the most cost effective insulation for this and what thickness should I use to meet BC requirements - eg the polystyrene is 50mm thick, but can't get any info on what U value this gives me - would it be safer to put down 2 sheets?

2. Do I need to allow for airflow under the insulation and if so, is it acceptable for me to create some air holes/grooves in the beams to achieve this?

3. Should I take any further precautions as this is a 'wet' area?

Many thanks!
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Simply Build It

Postby blackcat » Thu Nov 08, 2007 10:04 pm

ok one of the best u value at the moment is a product called kingsan but not that cost effective as for dpm in the floor i dout it you could put polythene under the beams first for air flow can"t see the point make sure you use moister resistent chipboard glue all the joints with pva skirting around the edge to hold it all down hope this helps
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