Insulating concrete floor

[numnum]

Hi

I'm looking for a bit of advice and excuss my lack on knowledge on correct DIY names

My boyfriend has insulated the house we've bought. He's took lots of advice from a number of folk and construction suppliers he's been dealing with.

The way he's done it is:

Put Damp Proofing down

on top of that laid a wooden border round the rooms then strips across the floors (cant remember the type or size of wood)

then in between that he has laid the polystyrine

then put chipboard or plywood or some kind of wood on top and nailed it into the border/strips (excuse my lack of DIY names)

is this how you would do it?

[AlBags]

Sort of ..
Was it a suspended timber/floorboarded floor before all this?
Or some sort of solid floor?

[numnum]

it was a concrete floor. solid and cold

[Count-A-Strong]

Is this on top of the concrete?

[numnum]

yes, its on top of the concrete

he has left a bit of room at the edges for it to breath

[Count-A-Strong]

The joists (strips) may act as a 'cold bridge' making the cold from the concrete transfer to the boarded floor but it should help a bit

[numnum]

i see.

we'll be putting good underlay and carpets on top so hopefully that will also help.

the rest of the house will be kingspaned, including the roof so that should also make up for any coldness from the strips

[AlBags]

What thickness is the timber floor?
What thickness is the insulation/batten layer?

[The Builder]

As Al says ........... sort of ........... I've done this many times, but polystyrene is not the best insulator. Better than nothing of course, but foam boards like Celotex or Kingspan are over twice the insulation value.
Technically, it really needs a vapour check (thin polythene) put over the insulation, under the flooring. The reason is, without it, water vapour in the air can get down to the cold concrete and condense on top of your damp-proof membrane. Water could accumulate there. Not a good thing even if you've used treated timber.

[numnum]

hi

i've just looked out a bill for what i think will be the flooring order:

uniply 1.22x2.44 x12mm WBP

polystyrene Insulation 25mm (2400x1200)

wws treated 25x50mm

i'm not sure if this is all for the floor order. does the sizes make sence?

i'm just a bit worried now about the polythene backing. the floor is laid

[AlBags]

So that's 37mm height batten plus ply with 25mm polystyrene. Then floor on top.

Builder is correct .. technically .. but so long as the room is pretty dry, not a wet room, etc ...you are not likely to get much of a problem for quite a long time. Good it is WBP Ply and treated batten.

[numnum]

thanks for all your advice

it is the whole house he's done. thankfully he's not yet done the floor of our en suite which i'll mention to him to get the polythene for that

at the moment he has done the livingroom, hall and 2 bedrooms.

theres still the kitchen, main bathroom, 2 porches, 1 bedroom and ensuite to do so i'll get some polythene ordered

the whole house will be damp proofed and well insulated once finished so hopefully there will be no dampness once we're finished with it.

we also took out 2 lumbs which were letting water into the walls, concrete aswell so that will make a huge difference as well

[AlBags]

Good luck then!

[The Builder]

Don't give him a hard time over that vapour check business. Al's quite right. It's minimal, and probably won't happen. It's just that Al and I, being "in the trade", feel we have to point these things out if we want to keep our "cred"........ :o)