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I'm building an outdoor shelter and I'm wondering what would be:

  1. The maximum beam span for the type of wood/material used such it can support the roof weight and not sag in the middle,

  2. Suggestions on other materials (beams or otherwise) or construction techniques that you'd recommend I use instead.

The current beams as currently designed are two standard 2x10's sandwiched together.

The roof is 30°. The trusses are 2x6's which will have four blocking bars between each set of trusses. The roof trusses are currently 20" apart OC.

The distance I have it currently span is 9.5', but I'm interested in increasing that distance, and knowing about how far I can reasonably go.

The plan for the roof is 1/2" plywood with tar paper and shingles.

Here is a picture to help illustrate what I had in mind. (Note: I do have plans for diagonal braces between the columns and the beams, I just didn't bother to illustrate it.)

Outdoor shelter

Micah B.
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    I'm voting to close this question as off-topic because this is better suited to DIY.SE – Carl Witthoft May 14 '18 at 17:56
  • Your local code enforcement people will tell you what you need. Their opinion is really the only one that matters. You submit a sketch to get the building permit. If you ask them in advance, they will probably tell you to buy one of the books they sell at Lowes and Home Depot. Depends on the neighborhood. – Phil Sweet May 14 '18 at 21:03

1 Answers1

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This is an unstable frame and can not support any load for variety of reasons.

The rafters have a horizontal outward force over the 2-2x10 beams which is not capable of offering any lateral resistance. However this can be remedied if you provide horizontal tie beams connecting the rafters at their two bases like an A frame, say of 2x4 lumber with enough nails to counter the roofs horizontal force. Then the 2-2x10s can be supporting the rafters' vertical load easily.

The other problem is the connection of columns to the roof. It needs to be laterally braced somehow. For example by a pair of 4x4 diagonal bracing at 2 feet off-centre from corners of the roof to columns.

Also it is advisable to use one single beam of 4x10 instead of sandwiching to 2x10s.

If you use composite light weight roofing shingles and 1/2" sheathing, this tool-shack can be as big as approximately 10x12 feet. Rough estimates indicate by using 4x12 beams instead of 2-2x20s the width of the shack can increase to 14 feet. Many cities' building departments have pre approved hand outs with plans and details for such structures.

Same issues apply to other materials such as light gauge steel or alum sections.

kamran
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  • If the 210's are glued - would they be ok compared to 410? – Solar Mike May 14 '18 at 05:42
  • @SolarMike, depends on what glue and what quality workmanship. Yes, may be. There are manufacturers in the market that laminate bands of hi quality Doug-Fir horizontally or vertically and the end result is even stronger than Dense Select Structural rating at reasonable prices. However 2=2x10 nominal, add up to 3" width but a 4x is 3-1/2" wide. – kamran May 14 '18 at 06:22
  • Only asked as I can look up at a laminated beam holding my roof up :) and it seems very common - perhaps swiss workmanship helps... – Solar Mike May 14 '18 at 06:31
  • Thank you for the explanation. I do have plans for diagonal braces between the columns and the beams, I just didn't bother to illustrate it. – Micah B. May 14 '18 at 14:01
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    @MicahB. Thank you for beautiful 3d model. is there any self study guide sketch-up? – kamran May 14 '18 at 17:08
  • @SolarMike, My home was built on 61 here in CA coast. Couple of exposed glulam ridge beams still look beautiful. – kamran May 14 '18 at 17:31