I have decided to install a lowered ceiling in my kitchen, partly to avoid
having to repair it considerably, partly to install downlighters, but
mainly to hide the ducting for the cooker hood which is 6" flexible
aluminium tubing.

My question is what size wood to use for the joists which will cover a span
of approx 2.5m.
If necessary I could support the joists along the middle by a batten fixing
to the existing ceiling.
If I were to use 9.5mm plasterboard can I get away with less substantial
joists than using 12mm.

--
Chris Melluish

Chris Melluish wrote:
I have decided to install a lowered ceiling in my kitchen, partly to avoid
having to repair it considerably, partly to install downlighters, but
mainly to hide the ducting for the cooker hood which is 6" flexible
aluminium tubing.

My question is what size wood to use for the joists which will cover a span
of approx 2.5m.
If necessary I could support the joists along the middle by a batten fixing
to the existing ceiling.
If I were to use 9.5mm plasterboard can I get away with less substantial
joists than using 12mm.


2x3 would be good. 2x2 would just work, 1.5x2.5 would be better than
2x2.

9.5 vs 12mm: not significantly. 12mm offers better sound insulation,
fire resistance and durability, and is hardly any more expensive.

If you support them half way along, 2x2 would be plenty.


If you _really really_ want to cut down on wood use, if you support it
every 2' you could even use bamboo canes supporting a cardboard
ceiling. Treat with fire retardant and lining paper. Wonder if anyones
ever done that!


NT