Center support beam?

[GPintheMitten]

You said joists. Are you putting a 2nd story floor in or did you mean roof rafters?

Do you have a sketch of what you want it to look like when you're done?

If not then do a sketch and take it to a lumber yard to get some advice. Sometimes a back and forth discussion in person can get you squared away faster.

 

[franklin2]

I may have used the wrong wording. I said "trusses" but I meant floor joists too. You know, the ones that you can lay from one basement wall to the other without having to use metal poles in your basement.

I have seen them made with wood on the top and the bottom with OSB in the middle, they look like wooden I beams. I think they make them out of different stuff and call them "LVL's" or something like that. I believe you can also get them with a 2x4 on the top and the bottom, with 2x4 cross bracing inbetween. These are all very long, very strong engineered joists and would work perfect for a slanted flat roof. I bet you can get them up to 30ft long, maybe longer.

 

[franklin2]

Here's the ones with the OSB in the middle.

 

[franklin2]

Here's the ones with the "X" bracing in the middle.

 

[franklin2]

Here are those laminate beams.

 

[kojo]

GP, I guess I meant rafters, there's not gonna be any weight on the top except for the metal or tin roofing. But, I did find some 20' long 2x10's, I finally found a place that has them longer than 16', which is great because now with those, I shouldn't need a center support brace, I hope. I have drawn up a blueprint myself to kinda go by.

franklin, I like the looks of the LVL's but, I haven't priced them, I was trying to keep the price as low as possible and I figured they were probably pricey.

 

[GPintheMitten]

Check the rafter tables for 2x 10 s to see what they will support on a 20 foot span. Figure your deadload and any snowload for your area if any . Then you can figure the spacing needed.

 

[Pipestone Kid]

Use the manufactured joist as shown in franklin2's first pic. They are stronger, straighter, and lighter to handle. They won't warp or twist and they can be made any length you want. ( the ones with OSB in the center--like an I beam)
No center beam required.

 

[busy dad]

Most places like Menards can order up to 24' lumber for you. I joists are lighter , truss types are lighter too than big deep beams .. If you were meaning beams to support the entire roof , a good steel shop could give you the size required for the span .. 6" beam or two pieces of 6" c channel drilled and bolted is shorter than a similar strength wood beam