"Raise the loft floor by 175mm on top of ceiling joists, ensuring insulation is not squashed and U values are maintained. NOT suitable for habitable rooms as the product is designed to fit on top of ceiling joists in boarded lofts used as storage".
Would you trust it?
What's the recommended spacing? Not going to be that cheap. Wouldn't a lightweight fabricated I or rolled U-section be better?
Maybe, on two provisos:
1) It is screwed to the joists below to prevent lateral slippage2) The false floor on top goes "wall to wall" to prevent shear of the whole structure.
The reason for that conslusion is it is approximately the same structure as a computer room false floor and they are OK unless you take out a big square and leave a small island dangling in the middle :)
As we're "back to basics" here, a cross joist is the usual solution - only downside is the fact it makes running pipes harder.
It doesn't say but I wouldn't be happy at much over a foot. I guess you actually put them along the joints in the 22mm chipboard loft boards so that's every 400 odd mm. There will be movement in those boards...
They would also have to be fixed to the ceiling joists and how do you fix the loft boards down? Screw into the tops of these things?
Any why 175mm? OK on top of your standard 100mm ceiling joist you get
275mm, just a little less than the recomended 280mm of insulation but boarded over you don't need 280mm as the boards also provide insulation...I did some vague maths on this the other week. 100mm glass fibre covered with 22mm chip is not that far short of the recomended level, certainly as good as 200mm glass fibre and not worth the agro of fitting say 50 or 100mm cross joists IMHO.
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