Kingsman or Celutex

I used Quinntherm in 70mm thickness because they all seemed to have a consistent thickness, essential if you have a floating floor. The sheets of Celotex in Wickes had a slight undulating thickness.

Nonsense. The void below the insulation and flooring joists still needs to be ventilated.

There must be no gap(s) between the insulation and the floor.

Which will shower you with PIR dust !!!.

Bosch make a special 4 inch cutting blade with a smooth knife edge that fits any compatible jig saw.

Or sharpen the back of a hacksaw blade into a knife, stick a handle on one end and cut them carefully.

Lay some fine guage chicken netting over the joints and loop down so that the PIR board is held tighly up against the flooring.

I read that score'n'snap may not give a straight edge on thicker boards. So you would likely have gaps where the insulation is thinner, and harder to butt pieces together or have a tight fit against joists.

You can get special insulation hand saws:

For power tools there's this sort of thing, but it ain't cheap:

Theo

I used these

They were a lot cheaper when I bought mine (usual pack of 4)

Strange. Most new houses of that era had solid ground floors.

Only if the temperature is over 1000C, as in Grenfell when covered in aluminium/plastic/aluminium cladding.

Under a floor or protected by plasterboard and they are fine.

Andrew

Yes.

panels between woodwork, foil tape over the top of it all. Its just to stop vapour getting to cold joists, that's all

almost anything if you fill any gaps with expanding foam :-)

snip

Far and away the easiest I've found is an old (but still sharp) non-serrated kitchen knife, 9" or so blade. Makes a neat job of anything up to 50mm (at least - that's the thickest I've tried).

hich at present is a suspended T&G floor on 100mm joists. I am looking at f ixing 25 X 25 battens to the bottom of the joists and dropping 75mm foam in sulation in between the joists. Any advice regards preferences between King span or Celutex or is it just a case of whichever I can get at the best pri ce?

After a bit of research Celotex( note correct spelling) is out with a P/A r atio of 0.7 and a resultant maximum U-value of 0.24 to comply with Part L, the only products they had were 100mm and 110mm thick and would cause some difficulties since my joists are 4" deep.

So it's Kingspan, again two products Kooltherm 103 which I would need a 90m m thickness or the higher performing Thermafloor T70 where a 75mm thickness will give me a u-value of 0.22. Using the T70 allows me to use my preferre d method of supporting the panels using 25X25 battens.

Now just need to phone around and get some prices. I have tried to get some online but most of the insulation stockists seem to want you to send in yo ur quote and then give a price plus you can only buy them in batches usuall y 3 or 4 boards and of course Sods Law I only need 3. Might try a few local builders merchants who I have seen stocking foam insulation but suspect th ey may not have extensive varieties so it will be pot luck. Anyway just tho ught I would pass on my findings for anyone else contemplating doing the sa me.

Richard

Quinntherm comes in 70mm thickness which was ideal for my insulated solid floor after removing the screed and screwing 3x3 battens onto the slab.

Back to my circular saw proposal. Having produced your 400/600mm wide slabs, you could easily rebate the sides to accept your battens and use what I suspect will be much cheaper and more available Kingspan/Celotex. Now we are all used to wearing face masks, you can do the job on the lawn:-)

They will burn in high enough heat, although they should not sustain a flame on their own.

One of the risks in rooms that are fully insulated, it that they can reach a combustible temperature much more quickly than an uninsulated room. So a small fire can spread to spontaneous ignition of other things in the room quite quickly.