From a rceent conservatory ceiling thread I plan to do something similar and wonder what size timber I’d need to buy for the lightweight ceiling. If anyone can advise that’d be great.

The ceiling will be 4.2 x 5.5m. Screwed into UPVC, possibly with L-brackets. It will have about 40kg of insulation, maybe 10kg of PVC cladding and the weight of the timber itself to support.

I’m thinking of maybe 2x main beams across the 4.2m at 1.8m spacing, then much lighter ones going the other way. Would 3×2 be enough? Basically I guess I’m asking would 3×2 timber 4.2m long support something like 40kg weight across it’s length and hold it’s shape? The insulation will be boards so the weight will be spread out, including at the ends of the beams where it’s attached to the UPVC walls.

Have a look here, there are loads of similar sites/calculators on the web.

http://www.home-extension.co.uk/tech2.html

https://www.jamesjones.co.uk/interactive-span-table

What are you doing?

A flat lightweight conservatory ceiling

Suspended ceiling tiles and a metal grid? Can be a bit too “industrial-look” tho

I’m not sure about suspending from the roof as it’s bound to be tricky screwing up into the plastic and retain any strength