Hi all,
I'm a carpenter and I need some help with some structural work I'm doing. Can't get my head around moment of inertia equations and calculations.
The basic problem I have is a customer wants me to build a display room/cubicle approximately 3m x 3m wide with as thin roof structure as possible because it is being built indoors, therefore ruling out "A" frame truss structures. 2x4 inch timber (flat - without an A frame or any other support) will easily hold over a 3m distance but it will sag over time. The complete 3m x 3m roof with appendices will weigh about 300kg (timber frame, plasterboard, plaster, and various display bits the customer wants hanging from the ceiling) and be distributed fairly evenly around the roof structure. I thought angle iron or square tube would be an great way to support the roof structure. The iron/tube will be going on top of the roof spanning end to end and going across (and fixed to) each wooden 2x4 beam which will be spaced 400mm apart. I'm quite happy to put 2 or 3 angle iron lengths across the roof evenly spaced out if required, therefore spreading the weight to around 100kg per angle iron if I use 3.
Any ideas on what size I should be going for? Would square tube be better? Also I'm not overly keen on using steel as drilling it will be a pain. Some deflection is acceptable. The display room will be in use for 5 years after which it will be torn down.
Hi, welcome to the forum.
How constrained are you for the inner wall height? If you can sneak say 2" it would not be visibly obvious but you could then use 2 x 6 instead. It means trimming the drywall though.
Spacing them closer together than the conventional 24-OC, would give you greater overall-stiffness if you are worried about sag over time.
So, I wonder just how tall the ceiling really needs to be. Would 1 or 2 inches really matter or be noticed?
I would certainly notice 1 or 2 inches! Oh wait, that's not ceilings. Yes, it would matter.
Must apologise, the room size is 4m x 4m, not 3 x 3. I did think about 2 x 6 timber. That sort of thickness would probably be the maximum the client will accept, but I still think the sag will get progressively worse over time.
Ok, 4M is about 13.123359580052488 ft. Which, does not seem that far to me for a 2x6 with the 6 vertical...
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