On 18 Nov, 13:46, wrote:
Part of our kitchen has a sloping ceiling; plasterboard nailed to the
sloping roof rafters.
This section is not insulated.
What is the best, and what is the easiest way to do it? Should I
take off the plaster, lower the ceiling by 3 inches, and pack between
the joists and the extra space with fibre - a relatively big job....
or could I successfully take an easier route; drill holes and inject
something - expanding foam maybe?

Thanks

Tony

Did something similar recently in our kitchen.
Put 25 mm celotex between the 3" joists - held in place by friction
(leaves a 50 mm airspace between insulation and roof tiles).
Put 70 mm celotex over the joists - held in place by a few long screws
with large washers.
Cover joints in celotex with aluminium tape.
Covered over with foil backed tapered edge 12.5 mm plasterboard - held
in place by 100 mm plasterboard screws from toolstation.co.uk
(Screwfix don't appear to sell them).

If you want more insulation (I think about 160 mm is recommended?)
then attach batten e.g. 50mm to the rafters and fill the space
between rafters with 100 mm celotex then overboard with 60+ mm of
celotex. I would have done this but the sloping parts of the ceiling
were quite small and I stuffed the large void/attice above the sloping
parts with glass fibre insulation.