I am looking into building a grill/smoker cover for my back yard and below are the plans I've drawn in Sketchup. My question is, Can 2x4 14ga rectangular tubing span this gap without adding another support leg in the middle? The only weight will be the slanted "rafters" and a polycarbonate roofing material that looks exactly like tin (similarly light). Other than the front and back "beams", everything else will be 2x2 square tubing. I attempted to use all of the deflection and span calculators out there but I just can't seem to figure it out. Probably why I changed majors away from engineering..... but that is another discussion.

this calculator seems to work well.

http://www.atc-mechanical.com/calculators/tube-size-using-structural-properties/

make sure to allow for uplift and anchoring so it doesn't end up in the pasture or neighbors yard.

calculator indicates a 2x4 14 ga with 15 ft span will support max beam load of 399 lbs with a deflection of L/360.

Architelico said:

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calculator indicates a 2x4 14 ga with 15 ft span will support max beam load of 399 lbs with a deflection of L/360.

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Architelico,

Thank you for that! Forgive my ignorance, so based on the calculator, the beam would support 399lbs across its entire length? Is that considering the entire "roof" structure or just a single point? I would assume that the 2x2 tubing and roof material wouldn't exceed that but I will verify if that is true or not. Also, I have planned for another 2x4 tube along the back side that WILL have a center support in place. So I would assume that the combination of ANOTHER 2x4 beam and a center leg there, should be more than enough to support the 'roof'?

Also, I definitely will have this anchored extremely well through the metal bars/skids along the bottom. They will be screwed to my existing deck, extensively.

Thank you once again for all of your help!

Also want to add, if I add the angled pieces 6" from the end to help "support" the beam, shouldn't that theoretically increase the allowed load weight since it is "shortening" the beam length?

In short, if I can keep the overall weight of the short rafters and the roof material below 300 lbs, then I should be good to proceed with this design?

And where do I send my Architecture Consultant fees to?

Technically this beam supports 1/2 of the roof load.
Include the rafters and roofing material, and any load from climbing on it to install the roof. Also the weight of someone hanging from the beam while you are BBQing

Personally I would also do an eye test when I picked up the material and make sure a 15' stick seems strong enough and was stiff enough.

Not an engineer, but my initial thought is that should be more than strong enough. This is all welded together? Seems like it would be pretty dang solid.

You need to make that a tad deeper than ~3.5 ft if you have the room.

There is a tad more room but not much. It is between my patio and a fence. Are you concerned about being top heavy with a narrow base?

It will be screwed down to the deck to help some.

Thanks for everyone's insights!

I suspect that shade for your grill wont be very effective unless deeper...depends on the lot. ~3.5 foot seems shallow if using it for shade.

Also, the key to this thing to not lifting off to space in the first windstorm is how you anchor to your deck. You'll need to bolt the hell out of it.

Is this thing getting welded joints?

Yes welded! And it will fit the front just under the eave of my house and against a fence behind it. So the shade portion is mostly just straight down and mid afternoon onto my covered concrete patio. Since it will be under the eave of my house I don't think wind will be too much of an issue, especially where it will live and where we are in TX.