In message , John
Rumm writes
On 17/10/2012 11:49, GMM wrote:
Sorry chaps, a bit of a long post but I have tried to get all the
essential information in (!) Undoubtedly
there will be something I've missed out, even so....

Couple of thoughts... someone in here reinforced their existing joists
rather than install new.

The other.. don't allow the new timbers anywhere near the lath and
plaster. We once had a chalet bungalow where the previous owners had
stiffened up the old loft floor to take the new bedrooms load. These
joists spanned the outside walls but were not attached to the old
ceiling ones. Inevitably the new timber moved and pinged nail head
plaster off the downstairs ceiling.

--
Tim Lamb