Workshop floor insulation

My workshop is being erected in a couple of days.

It's to be insulated throughout. The floor will be plywood over a pressure treated frame.

I was thinking of covering this first ply floor with 50mm Kingspan or Celotex then 12mm ply for the finished floor. To save some funds could I substitute the Kingspan / Celotex for 50mm expanded polystyrene? would this produce more 'bounce' in the floor when working and would it be strong enough for long term use?

Opinions please.

Martyn

Reply to
Count de Monet
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My workshop has 50mm of normal white expanded polystyrene as insulation, overlain by 6" of reinforced concrete, which has 18mm of OSB3 screwed down then painted with Screwfix floor paint. Utterly no signs of movement, sinking or whatever despite having several machines weighing from 3/4 up to 4 ton sitting on it, and a 4 ton fork lift not infrequently running on it for the last couple of years.

I also rejected Kingspan on cost / performance issues

AWEM

Reply to
Andrew Mawson

In message , Count de Monet writes

My shed floor is concrete, then a waterproof membrane just in case, then white expanded foam, then plywood and finally some oldish carpet on part of it. Has a lathe, milling machine plus 3 decent work benches, and I've run up boat engines etc etc on it with no trouble. I think it was done about 15 years ago.

Reply to
Bill

One possible way to cure tendency to bounce & sink would be to fit upright strips of plywood between the edges of the polystyrene sheets.

NT

Reply to
Tabby

This suggestion does depend on what you are using the workshop for. I've an recently self built workshop and didn't bother with any insulation under the concrete - it is after all a workshop and unless you've got deep pockets and can afford to heat it 24/7, it's going to be chilly when you first go out there so warm clothing is going to be the order of the day in winter anyhow, and you don't normally sit around in a workshop, so domestic level of temperature and insulation aren't necessary.

Yes the wall and roof insulation is necessary for background heating, but I went for the interlocking rubber floor mats from Costco and the likes; really kind of the feet and anything you drop (though the latter do tend to bounce into the hidden depths!). They are 600mm square and are around =A310 for a pack of 6 (or is it 8?). Rob

Reply to
robgraham

Polystyrene is very cheap.

NT

Reply to
Tabby

Sadly, ripping up a floor to lay it under, is not.

Reply to
The Natural Philosopher

The workshop will be mainly used for my IT business so I will be spending a lot of time sitting at a bench hence my need for an insulated floor. My only concern with the polystyrene is it's strength and if I should go to the next thickness ply to help stop any 'bounce' when walking on the floor.

I like the pieces of cut ply along the edges of the polystyrene suggestion.

Martyn

Reply to
Count de Monet

Then normal T&G flooring grade chipboard would be fine. As long as the existing floor is flat and level just lay the polystyrene and lay the chipboard on top. No need for fixings even as it can't fall anywhere!

Mike

Reply to
MuddyMike

My workshop floor is 18mm ply on 25mm tiling battens on concrete with DPM under. Battens laid at 16" pitch with 25mm cheap polystyrene in between. More than adequate for substantial woodworking machines being wheeled around and no bounce/sag in the last 5 years. Easy on the feet too! Good draughtproofing and similar insulation on the walls means I need very little heat in a 30 sq metre workshop even in winter depths.

Bob

Reply to
Bob Minchin

I would not use styrene except inside screed. Horrible fire risk, and it dissolves in many common solvents.

If you have a prelaid floor, use carpet, or studwork, rockwool or celotex between and board over.

Reply to
The Natural Philosopher

under concrete its not a fire risk, but under plywood it is,. and it gives off poisonous fumes. Will nobody ever sleep there (and smoke) If it burns down would other buildings catch fire from it? [g]

Reply to
george [dicegeorge]

I was told by Jablite that polystyrene is permitted below any type of ground floor.

Reply to
stuart noble

Firstly that may be economical with the truth, and secondly if so its a glaring error in the regs.

I've seen EPS in a fire. Trust me, you really don't want it anywhere near you. Black toxic smoke.

Also, any cellulose solvent you spill destroys it in seconds. Acetone, Xylene, MEK, all eat through it like lightning.

It's a good insulator, but it needs to be encased in something liquid- and fire-proof.

Reply to
The Natural Philosopher

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a flame retardent.

May not be true of all polystyrene.

MBQ

Reply to
Man at B&Q

It will be fine. The ply will spread any load to such an extent that the polystyrene will support it. BTDTGTTS.

More likely to sag between supports spaced out like this.

MBQ

Reply to
Man at B&Q

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> Contains a flame retardent.

But not easy to find. Sounds like the fire retardant is an optional extra, so hardly an off the shelf item

Reply to
stuart noble

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