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Thread: pergola anyone?

  1. #1
    Join Date
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    pergola anyone?

    ok i guess this would be my frist post here and i have to start somewhere soooo... my backyard deck is 23ft x 16ft and the wife says she wants a pergola above it. I will need 3 or 4 beams 23-24 ft long to span the lenght, there is no option of spanning the other direction and no chance i will put support post in the middle of my deck. does anybody here have and experience making their own glue lam beams? i was thinking 4-6x 3/4 by 7 1/2 inch strips of plywood glued, then encasing it in cedar with some west system 2 part epoxy. am i way off base here or do i get a second and third mortgage on the place and just order 4 solid cedar beams?

  2. #2
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    Might work, but I think I would bolt them together also. Just to be on the safe side. Recess the head and nut, then cover it with the cedar. I would even go as far as just to use 2x10's or something. That is the way basement beams used to be done. Long as you could keep the water out of it, I really don't see a problem.

    Oh and welcome.
    If you don't take pride in your work, life get's pretty boring.

    Rule of thumb is if you donít know what tool to buy next, then you probably donít need it yet.

  3. #3
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    thanks steve i thought about solid wood 2x8 or 2x10 but came to think that plywood is way more structurally stable and if im not mistaken a beam made of plywood 7 1/2 inches by 4 1/2 inches (6 layers thick x 3/4 inch) should be darn close to tank proof? idk just a thought

  4. #4
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    Well you also need to think about snow loads up there, where I really don't have to here. Hopefully one of the northern guys will see this and chime in.
    If you don't take pride in your work, life get's pretty boring.

    Rule of thumb is if you donít know what tool to buy next, then you probably donít need it yet.

  5. #5
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    Glue lam beams are not meant for outdoor use. Youy are going to need on heck of a chunk of timber to spaned over 20'. I dont think I would even try to spand that with out getting someone with exp in support loads.

  6. #6
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    the beam will be in a totally weather/waterproof enclosure, the west system epoxy is the same stuff that the wood boat builders use and the weightload is not much 40 or so 2x8x16 cedar planks on their edge so no snow load or waterload just their weight i could even put fiberglass matt under the epoxy but i really dont think that it would need it

  7. #7
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    I would tend to agree here with Al, delamination due to moisture/humidity would be your big enemy. You don't need a post directly in the center, but a pair of posts with a beam spanning their top for the long beams to lay crosswise onto would help. (clear as mud???) Pergolas don't really hold much of a snow load as they aren't a solid roof, only slatted for shade correct? What about a gazebo over half of the deck?
    By the way, welcome to the family!!
    Jon

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  8. #8
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    that is the plan just a slatted roof. You think that delam would be a problem even if its totally encased in a fiberglass resin without the cloth? I would much rather see the cedar than the fiberglass mesh so i would skip the cloth

  9. #9
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    Yes, I think delamination would happen eventually. Snow and ice sitting on top of the beams, a warm day, wet puddles, freezing cold night causing a crack to develop, water seepage, a couple of days later warm again, laminated beam soaking up water through the crack in the fiberglass, freezing night again, delamination occurring. Might be years before you realize it, but don't think I would take the chance. Around here many of the old electric poles were cedar. If you could get a sawyer to square up a cedar telephone/electric poles for you then you would be in business.
    Jon

    God and family, the rest is icing on the cake. I'm so far behind, I think I'm in first place!

    Host of the 2015 FAMILY WOODWORKING GATHERING

  10. #10
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    there is an idea sure but here they are all tamarac poles hmmm

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