Celotex floor

[Ed209]

I am currently splitting my garage in half so one half is going to be approximately 8x8 office, The floor is concrete and not obviously damp
and fairly level I was just wondering if I could get away with a couple of sheets of 50mm Celotex and put some floor grade chip board over that. have also considered using floor leveller first but floor is not too bad at worst 10mm here and there.
Thank you


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[Phil Pascoe]

If you're not putting in massive machinery, why not?

 

[MikeG.]

Even if you were putting machines on it, that's a standard floating floor and will be fine. Just be sure to glue the T&G joins, to leave a 5-10mm gap to the walls, and hold the whole thing down with a well fixed skirting all round.

 

[banjerbill]

I have done exactly this in my garage and have had no problems. The floor is rock solid and warm underfoot.

 

[Ed209]

Brilliant news I will do the same in my summer house thats been erected for well over a year and still no floor ( batons and T&g stacked on patio, well seasoned. T&G supplied with summer house but not very good quality, and the Mrs. wants carpet in there anyway as she has commandeered it as a sewing room now we have three grandchildren.
Do I need to leave expansion gap for Celotex or butt it up to edges to prevent creeping?


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[MikeG.]

No, the Celotex goes right to the edge.

There should be a VCL (sheet of polythene) on the warm side of the insulation........ie on top of it. So concrete-Celotex-polythene-chipboard working from the bottom up.

 

[banjerbill]

I did not leave a gap but did not scribe it to the edges either.

I personally would not put carpet in a summerhouse as I would think mould would be a problem. I tiled mine, perhaps you could do the same and fit a large rug that could be stored elsewhere in winter. Or perhaps you plan to keep it heated.

Bill

 

[Peter Sefton]

No, the Celotex goes right to the edge.

There should be a VCL (sheet of polythene) on the warm side of the insulation........ie on top of it. So concrete-Celotex-polythene-chipboard working from the bottom up.

I have this in my school workshop, very warm and kind to both feet and tools, paint mine each year with Coo-Var paint

Cheers Peter

 

[monkeybiter]

My professionally built extension, 'L'-shaped around two sides of the house, was floored on this way, 100mm Celotex topped with glued T+G chipboard flooring, quite disappointed. There is bounce in at least one area of regular traffic and the ~6'x6' bathroom floor has two hairline cracked tiles in the centre.
IMHO this method is best used with joist-like supports resting on the concrete and stopping the chipboard from compressing the insulation, and I will likely do this as a retrofit at some point in the future.

 

[Ed209]

I have a big roll of DMP 4x25M would there be any advantages to putting some down before the Celotex then some more on the Celotex before the 22mm chipboard?
I doubt very much that the existing garage floor has a DPM fitted already.
Also I assume I am ok to use heavy gauge DPM instead of a dedicated vapour barrier sheet?


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[Beau]

I did similar with just jablite some years ago ( would use celotex now) Only problem that I have seen was visiting a workshop with 18mm flooring chipboard over jablite and he had a Felder with a wheel set. The presure of the wheels on the flooring crushed the chipboard due to the point loads and the jablite not withstanding it. Celotex may be tougher but a consideration to bare in mind.

 

[Ed209]

Well here’s what I did: On further examination there was a raised area of approximately 12mm in height the length of the garage about 350mm wide where at some time in the past a new drain had been laid.
Material I already had DPC 300 gauge and several 8x4 sheets of 25mm polystyrene.
So instead of £50 worth of floor leveller compound I first laid the DPC sheet, then the polystyrene to absorb the level, 50mm Celotex (Wasn’t actually Celotex brand) Then I put some more DPC on that then, my 22mm 2x8 chipboard flooring.
All good so far and nice level warm floor.


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[TFrench]

I did similar with just jablite some years ago ( would use celotex now) Only problem that I have seen was visiting a workshop with 18mm flooring chipboard over jablite and he had a Felder with a wheel set. The presure of the wheels on the flooring crushed the chipboard due to the point loads and the jablite not withstanding it. Celotex may be tougher but a consideration to bare in mind.

As far as I'm aware, jablite is a flooring product and a much higher density than standard celotex.

 

[MikeG.]

As far as I'm aware, jablite is a flooring product and a much higher density than standard celotex.

You're getting two products mixed up. Jablite is a polystyrene. They have a denser version for flooring, but polystyrene is very different indeed to PIR insulation such as Celotex, which is a much stronger product. Celotex is certainly suitable for use under a floating floor, and if there are failures is more likely because of inadequate chipboard (18mm instead of 22, for instance) rather than because of the Celotex.

 

[TFrench]

Just looked on their website and you're right -sorry. At work we always call the heavy density stuff jablite - I didn't realise they make a lighter weight one!