"John Rumm" wrote in message
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Keith Dunbar wrote:

You must forgive my ignorance of the names of all the funny bits of roofs
....
(maximise screen to view this best)

THese pictures only really work if you use a non proportional (e.g.
courier) font to draw them and view them....


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| oooooooooo | | ooooooooo |
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There is just about room for a 4' width of chipboard at "ooooooooo"

Where would I be best (i.e. cheapest) going to for this PIR board?

A specialist insulation provider probably. One of the outfits that can
supply "seconds" would be good for this application.

How strong is it?

Fairly stiff - stronger that expanded polystyrene for example.

Can one stand on it?

If it is laid flat on the floor then yes. If you are laying it across
joists then I would not stand over the centre of the span unless it had a
board over the top.

I would need lots of quite long screws to fix the flooring to the joists.

Probably.

Is there any reason why I should need to. Could I create a sort of raft
of flooring above the PIR?

If you have a reasonable area of it, and the covering will remain in one
lump without fixing then a raft would work.



Just out of interest, what is the current requirement for loft insulation -
in inches of glassfibre?

Keith