"Dave Page" wrote in message
...
wrote:

Lets review the options.

1. Lay new joists on old at 90 degrees This will leave you with a very
weak floor, as well as being a pain to insulate.

Hmm, why would this lead to a weak floor? I figured that laying the new
joists at 90 degrees to the old ones would spread load across the old
joists, and laying the new floorboards across the

This method has the advantage that I can space my new joists at 400mm
(the pre-cut width of the insulation roll) rather than having to deal
with the existing 350mm joist spacing, and means that I can do the loft
in fewer "strips" of insulation (three or four as opposed to a dozen).

Other people have commented that insulation roll is "supposed" to be
laid *across* the joists. I have to assume that this precludes flooring
the loft space, and that if I want to floor my loft space, I'll need to
lay the roll *along* the joists.

Lay insulation between the joists and another layer 90 degrees to that.

I have seen a loft floor raised over 1 foot by using short pieces of 4X2.
all the same length. These were on end on the existing joists vertically,
and secured by small angle pieces. On top on the 4x2s long lengths of 4x2s
were laid and 6" screws driven in. These were secured to the gable end wall
by joist hangers, which also takes weight off the ceiling. The odd cross
brace was inserted so the floor did not wobble, and the chipboard laid on
top being well screwed down. The chipboard tightened up the whole floor.
MDF was used around the loft hatch, which also added rigidity to the floor
too. Easy to do if you have a chop saw and an Impact Driver. This gap was
filled with spray-in Warmcell insulation, which also makes the ceiling
air-tight too. Warmcell has the equiv performance of Rockwool that is 25%
thicker.