The house I moved into had a concrete patio with a roof already put on it. The craftmanship on the roof is pretty terrible, but it does the trick nonetheless.

The roof is made of 2x4 joists with plywood on top and tarpaper on top of that It's roughly 24 feet long and 9 feet wide. I don't think it weighs very much and it's not pitched very much at all. The previous owners used two 12-foot 4x4s as the header. this header is held up by a 4x4 in each corner, one in the middle and a random one off center that really serves no purpose.... So it's supported by 4 columns, but only 3 would really be needed.

I want to replace the 4x4 header with something that can span almost the whole width of the porch. I wouldn't mind moving the support columns in by 2-3 feet on each side and then the span would be 18-20 feet.

Could I pull this off with two 2x8 or 2x10s glued and screwed with plywood between them? I have heard of metal headers used for carports that can have a very long span... Would one of those be better?

I don't want to tear it down and completely rebuild it. Just want to make it flow better and not feel like we are in a jail of columns.

For piece of mind on a 24' span, my preference would be to use LVL's (Laminate Veneer Lumber) instead of regular lumber. You can purchase LVLs from Home Depot or other major lumber stores.

I did some calculation and the total weight of the roof is probably around 850 to 900 pounds... which comes out to around 5 pounds per sf.

One side is attached to the house the the side with the 4x4 header has 4 columns under it.

I would love to reduce this down to 2 columns... and I was wrong... The header would need to be 22 feet total length. The span could be 16-22 feet total.

So many words.... so few pictures

Keep forgetting to take some! Got ya tonight!

LSL Laminated Strand Lumber can get you there too, less cost than an LVL

Excuse the terrible qualities of those pics. The sun was right above my roof line, so it made for a terrible glare. The HDR feature on the iphone was really put to the test on those.

Dual 2x6 beam 10' away from the house can span 7' if you're building a deck with people on top and designing for 50 lbs/ft^2. For roof loads, go with 22 lbs/ft^2. Gets you to 16 foot span.

Dual 2x8s get you to 20' span before they should start sagging for a roof. If you're not going to replace the 2x4s and decking though, they are undersized for roof design and your beams will not be the weak link in the system. So stretching them out a little farther than 20' shouldn't be a problem. Just make sure to keep people off the top, not because of the beams, but because of the 2x4 "joists."

agnerd said:

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Dual 2x6 beam 10' away from the house can span 7' if you're building a deck with people on top and designing for 50 lbs/ft^2. For roof loads, go with 22 lbs/ft^2. Gets you to 16 foot span.

Dual 2x8s get you to 20' span before they should start sagging for a roof. If you're not going to replace the 2x4s and decking though, they are undersized for roof design and your beams will not be the weak link in the system. So stretching them out a little farther than 20' shouldn't be a problem. Just make sure to keep people off the top, not because of the beams, but because of the 2x4 "joists."

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Awesome info. Thanks!