Loft Installation question re laying over boards

wildmandy wrote: »

True, but any insulation will work and the first 100mm is the most effective. 170mm thickness should? be placed over the joists (or over the boarding).
Mandy

Should doesn't come into it, I've not seen any regs or recomendations stating such, especially over boards. If the loft is required to be boarded for storage, then the best way is to extend the size of the ceiling joists where the boards are needed by screwing 4"x2" timbers on top of the joists making 8" in total, and "screw" the boards down adding stability to your new joists. If you lay 270mm insulation, the boards will compress it very slightly but not enough to make any noticable difference.

If you have insulation over the loft boards then there is no point in having the loft boards, so why not remove them. Otherwise, if you put anything in the loft onto the insulation, it will will be squashed and its effect negated.
Basically you have to decide between insulation(and thus, less energy costs) or a measure of storage. Which do you want most.
The other alternative is, as has already been suggested, to raise the level of the joist tops to allow another layer of insulation to be added.
I was in my loft today to make start adding insulation. My compromise will be to leave a smallish area near to the hatch, boarded for storage and to double the insulation everywhere else. The other part of the project will be to ruthlessly clear out the accumulated 'stuff'.