Improving a workshop (ex-garage) - floor and doors

When we moved in we found that the back half of the garage had been turned into a dog grooming parlour. The floor was 50mm expanded polystyrene over the original concrete, then covered with T&G flooring. To get the car in the garage, I took down the dividing wooden stud wall, and parked the front of the car on the parlour floor. I've been doing it for 11 years, and the polystyrene is still at 50 mm.

Use insulation and board, but leave holes where the machines are to go and then fill those holes to floor level with concrete?

Thanks, that's interesting. Quite a while ago I did some work in a kitchen where the T&G floor was just sat on insulation board, but it had sagged in the middle, hence my caution.

Yes, I'd wondered about that but some of the machines are on castors and occasionally need to be moved a few feet. I guess the pads could be larger than needed, but I rearrange things from time-to-time and wouldn't want to be tied.

I wonder why it had sagged (if it wasn't on concrete, perhaps whatever it was on had sagged underneath!). I just checked, and the compressive strength of EPS is at least 70kPa (around 10psi). Insulation board should be double that. So although I can understand indentation from, eg castors or narrow legs, I can't understand sagging over a larger area. FWIW, I guess if I had put the car tyre directly on the EPS, then it would almost certainly have crushed it (I reckon it works out at about

When making my mancave I used 75mm PIR over the concrete floor and topped it with 18mm chipboard T&G glued together with a PIR glue. Nothing has moved or sagged despite at the moment it contains all the fixtures and fittings for the bathroom refurb.

Does the insulation make much difference?

Of all the things I did at my last place, 50mm underfloor celotex seemed the least effective. Difficult to tell objectively, but maybe 1-2C difference between uninsulated (but carpet and thick underlay) and insulated. So I'm wondering whether to bother at the new house.

Something like PIR boards under a decent thickness of sheet material to spread the load, it surprisingly crush resistant. However If you wanted a stiffer floor, then you could insulate and screed over it with 2" of fibre reinforced concrete. (assuming you can cope with the loss of headroom and the extra step in the floor)

An inner sliding insulated door perhaps (the "door" being nothing more than a lump of insulation board with a skin of wood product encapsulating it well enough to allow it to be "hung")

Dunno, but it seems a requirement in modern solid floors to insulate below the concrete and I have seen it done in projects where out buildings are converted into living places in those cases like mine the insulation is installed above the concrete and a floating timber floor on top.

The height is about 2.7m so headroom isn't an issue, but I'd prefer not to mess around with concrete because of having to empty the place and then wait for the humidity levels to drop.

Yes, that's sort of what I had in mind but I can't think how to get them to seal adequately when in position. I doubt that brush strips would work well enough, and sliding rubber seals would be a pain to set-up and maintain. Insulated bi-fold doors (closing onto seals) might be a better option, but I'd prefer not to have to keep the door area clear. Tricky!

Beam and block floor. In the workshop and garage I just painted it; in the office there's a layer of insulation, then a chipboard floor.

Andy

Yes, helped a mate with a living room solid floor - building regs required

Mine are suspended timber with easy access - so it would be easy, if only I could convince myself it'd be worthwhile.

If you only need occasional access do you need anything as sophisticated as brush strips or sliding seals? I have in mind just building another stud wall in 2 or 3 sections in front of the second door but screwed to one another and the studs either side; foam strip where they join to keep the wind out; and coach screws to withstand better the repeated use of impact driver to fit and remove.

EPS/XPS is feeble stuff. PIR is tougher but I wouldn't put industrial machinery on it. 2 alternatives are wood with insulation between, putting the heavy machines on the wood. Another is lightweight concrete blocks, they insulate reasonably & withstand more load than PIR. Whether it's enough for a lathe depends. Flooring sheet does spread load, but not very well. All kinds sag under load, loading the insulation under it.