Raising kitchen floor by a few centimetres...

[jeds]

The insulation will mould itself to small deviations so if the tiles are flat you won't need levelling compound. Frank makes a good point. You should leave a minimum 8mm gap all round the perimeter for expansion.

 

[dpm_dpmartin]

I had envisaged that expansion gap for the chipboard - is that the case for the insulation board as well?

Let's say the board is 25mm thick and the room is 1,000mm wide (it isn't) then I was going to cut the insulation board to 950mm (1,000mm - (25mm x 2)) and lay it centrally, then have 2 pieces of 25mm board turned on their side so that the foil was facing vertically (to stop "cold bridging")... is that right... or should I do that but still have an 8mm gap around?

 

[dpm_dpmartin]

Oh, and just to be clear on the approach to layers that I was going to take. It was:

22mm T&G Chipboard
25mm Insulation Board
4m x 3m 1,200ag DPM sheet
Level Tiles

If that's not then exactly level (what are my chances? little to zero, right?) of raising it up a little bit more... and what with? Should I put something else on top or should I be taking it up and laying some sand or asphalt down above the tiles first, to then make it?

22mm T&G Chipboard
25mm Insulation Board
4m x 3m 1,200ag DPM sheet
[SOMETHING ELSE?]
Level Tiles

I very much appreciate everyone's assistance here.

 

[theprinceofdarkness]

Please don't use ashalt, you can't roll it inside a house, you can't get it flat as you require. I can't see the problem, if your main floor is floorboards, you just make your new floor as close as possible, then run over the joint with a coarse sanding disc to taper any 1mm step across 12" or so. Your foam will compress by .5mm or so over the next 5 years. If you are thinking about a 3mm step, then its a lot of sanding. Its a difficult thickness, too thin for hardboard, too thick for a layer of lino/plastic flooring. Don't be tempted by the thicker foam filled flooring, its will be soft and compress. Wood veneer would be good but ultra expensive.
Frank

 

[dpm_dpmartin]

OK, ta. But if I'm over 3mm then it'd be hardboard I should use? Makes sense.

 

[dpm_dpmartin]

Guys, can I pester you again just to ask whether this insulation board and chipboard should both be cut so there is a ~10mm expansion gap around the edge of the room, like I know to do with the laminate flooring itself?

I was going to cut the insulation board so it was snug (but with a 25mm 'frame' of turned edges, with the foil facing sideways). I had not yet thought about the T&G chipboard... I'm guessing, it's wood, so it will need to expand like laminate?

 

[jeds]

No expansion gap needed for the insulation. If you need to make up levels use a latex compound. Unless your floor is very damp I wouldn't bother with a dpm, just use a 1200g vapour layer over the insulation which will do both jobs.

 

[theprinceofdarkness]

The foam will not expand at all, over its life time it shrinks. Just make sure that any bent boards have enough room to straighten (3mm?). The P5 will expand, again not as much as 10mm X 2 over 3m. A half of that would be enough. Laminate board is an unknown quantity, the manufacturers say 8mm, is this across a 1m wide corridor or along a 10m corridor. The irony is that for the manufacturers its an easy test to find out the exact figure, say .8mm along its length (1m) and .3 across its width then add 2mm. Measure up and calculate the gap. Its really only a nasty way for them to sell their quadrant capping strip, which then moves your furniture a further 15mm inwards into the room. A much nicer way would be to undercut the skirting boards.
Frank

 

[dpm_dpmartin]

I've removed all skirting boards!

 

[dpm_dpmartin]

This stuff...

http://www.wickes.co.uk/Bostik-Cempolatex-Floor-Levelling-Compound-25kg/p/224669

...where in the layers? Inbetween the insulation board and chipboard?