Timber Beam Load

banjolin

Hello,

I am building a car port with a 15ft/ 4.6m opening. It is a mono pitch roof with the high end over the beam. There will be 7 6x2 roof joists resting on the beam (600mm spacing) over the opening to hold 0.6mm corrugated steel sheeting. How do I go about sizing the beam. I have a length of 9x3 that could span it but how do I calculate the load and work out the minimum requirement?

There are numerous US based sites that have calculators but I just don't understand the terminology. Is there an Irish/UK equivalent? Any advice welcome.

Calahonda52

Design is not done here but you need to consider, depending on your location and degree of exposure, both snow loading and wind lift, the latter being more probable as an issue so you need to design that it is well fixed down.
You also need to consider lateral support to the 6 by 2 and additionally to the 9 by 3 if the 6 by 2 are sitting on top of the 9 by 3.
personally I would use a steel beam, maybe 254 by 102 by 22, and sit the 6 by 2 on a filler piece on the bottom flange so as the top of the 6 by 2 are flush with top of beam.

banjolin

Thanks for the reply. I managed to source 2 inch sized galvanised joist ties that will fix to the wall plate at the low end and the beam at the high end. The roof joists are joined in pairs in a ladder fashion and each ladder will be joined to the next with noggings.

I had thought about steel but to be honest it goes against the grain of what I want to achieve. The whole build is timber frame. I have made up 1/4inch steel plates to attach the beams to the uprights/posts to keep the structure rigid as there will be no racking in the openings, so all things considered, fairly secure from a wind shear and uplift point of view. Its the snow load I am most concerned about.

I have attached an image of the design. Its a range of sheds but the 5m car port is my main concern. All the information I have been able to source is about 10x2 and 12x2 size timbers (US) but nothing on 9x3.

PureBred

Hi banjolin,

Did you manage to do this. Interested in how it turned out as doing something similar.

banjolin

Used a 9x3 timber beam to span the 4.8m opening. Its fine. The span is probably 0.5 m longer than recommended if you are going to be jumping up and down on it but I'm not. Two 8x2s slapped together might give you more confidence if you were looking for real strength, but without knowing what you are building I wouldn't make any recommendations beyond what I have said here.

jack of all

A little late with this, but another solution using timber only is two 9x2" joists with a strip of 9" deep 3/4" ply sandwiched between the two, glued and bolted (along the neutral axis) at say 600mm c/cs. I've seen this done and it looks well in addtion to being a strong timber solution.

banjolin

How long a span could that beam cover?

jack of all

banjolin wrote: »

How long a span could that beam cover?

Don't know- that would be one for an engineer! The jobs where I've seen it done it was specified by an engineer and was well over size for the spans involved (domestic builds, nothing over 5m anyway I think). All I do know is the ply really stiffens the beam and minimises deflection over a standard timber beam/ joist.