DIYbanter - View Single Post

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.

3. Add new 4x2 joists to the top of the old ones, inline, attaching
with glue and screws.

Yeah, this was my original plan, and looks like being what I'll end up
doing after all, possibly using the poly vapour barrier mentioned by
Doctor Drivel in
ews.net also.

4. Add new wood on every other joist This will cause damage to the
ceiling, as the differing loads will try to mildly corrugate the
non-flexible plaster ceiling. Expect cracking and damage.

OK, I appreciate now that this is a bad idea.

Dave