Celotex

[John Whitworth]

OK...the garage conversion is actually happening. All of the external building work is complete. :-)

I've now got to do the floor. I was going to lay 50x125 wooden beams at

400crs, and infill with Celotex XR3120. But when the guy from Building Control came to inspect the external building works, I spoke to him and he suggested to me that it would actually be far easier for me, if I simply laid the Celotex wall-to-wall (without the timbers), and then put a damp-proof membrane over the top, then topped it all with 22.5mm T&G chipboard, which is glued together. He said that if done this way, the floor will move a micron in it's lifetime.

So that's what I'm now doing - I'm not going to argue, especially if it's making my life easier. However, I have a wee problemette...

The Celotex is 2400mm x 1200mm. The garage is 4900mm x 2480mm internally. Effectively, having laid four slabs of Celotex, I would have 100mm gap at the end, and 80mm gap at the side. So I need a fifth slab of Celotex. I'm no expert, but I do wonder whether cutting what would be thin slivers of Celotex (compared to the 2400x1200 slabs), and slotting them in at the sides is really the way to go. Or whether I should aim for less complete slabs, but overall, bigger slabs wherever used.

I hope that makes sense? Does anyone have any idea? I will then also have a similar problem with the T&G floorboard, but with that, I can see definite benefits to cutting them in half, as then I can put the flat sides of the boarding next to the wall (well, 6-10mm away).

Cheers

JW

[fred]

In article , John Whitworth writes

Distribute the gaps, 3 x 33mm in the length and 3 x 27 in the width then fill them with squirty foam.

[AJH]

if you are gong to dry line the walls then the 100mm & 80mm gaps won't matter will they? Using expanding foam would be very messy and expensive.

[John Whitworth]

If I could dryline the walls before the council inspected, then it would be OK. ;-) But they want to inspect the floor insulation & damp proofing before I can continue. I agree about the expanding foam. Sounds a bit messy. I've ordered 5 Celotex slabs. I will just have to puzzle out the best way to fit them in.

JW

[John Whitworth]

I'm not keen on the sound of that. It sounds a bit messy - and I've no guarantee that the council will OK it.

JW

[fred]

In article , John Whitworth writes

There's no need to apply it like silly string. Cured foam cut flush and covered with 3" foil tape is ideal for the job. The insulation will be bonded together to form a single sheet so will be better than loose with fillers. If the BCO was ever to notice he would not object.

[AJH]

No problem the building inspector and gaps as they won' be part of the floor, they will be under the walls. Try speaking to him about it. If he insists on full width insulation then simply cut 80mm and 100mm Celotex strips it's dead easy with a saw, I have cut strips as narrow as 12mm in my loft space.

[John Whitworth]

Thanks. I've decided to do just that (cut strips), but fred's post prompted me to wonder if the thin strips might be better in the middle. So I'm actually going to lay the four complete slabs in each corner, then complete the centre of each axis with cuts of 2400x80, 2400x80, 1280x100 and 1200x100 from the fifth slab.

I want to go wall-to-wall to be honest, as I did read somewhere (Knauf site I think), that bottom of wall gaps are one of the problem areas for insulation. And I've already ordered the fifth slab of Celotex! ;-)