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I am interested in building a 16'x14' pavilion in my backyard and I am just starting the research and design process. I'm interested in a modern-looking pavilion. I'm also interested in not having knee braces and I assume that all steel would be cost prohibitive. I'm tall and since we are building this for shade, we want it to have a lower ceiling and I've had too many experiences hitting my head on knee braces at other people's houses before.

I have tried to research this the best I could, but it hasn't gotten me far. I understand there are shear forces at play and without knee braces, structures like this are prone to sway, racking, and just general instability. I'd really like to avoid these things and have a sturdy, solid structure.

What are the strategies out there for having a sturdy, free-standing pavilion / pergola / gazebo that doesn't use knee braces? Embedded columns in the ground? Steel brackets? Tensioned cables? Steel column bottom sleeves?

This one has a fireplace. I believe that if the fireplace were tied into the structure, it would reduce the shear forces, sway, and racking.

Modern Pavilion without Knee Braces and a Fireplace

These 2 both appear to be completely freestanding. These are what I'd like to better understand. How would these 2 structures not sway or wobble?

Modern Freestanding Pavilion without Knee Braces

Modern Freestanding Pavilion without Knee Braces

Are steel posts the only way? What about steel brackets on lumber or having 1,2,3, or 4 of the columns be masonry? Any thoughts or insights would be great!

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  • Well, unless you use a skyhook then you will need supports and remember steel columns can be clad in wood.
    – Solar Mike
    Commented Jul 21, 2021 at 20:08
  • The question is quite broad and hypothetical (and therefore off topic). You hit on both options--rigid columns or steel brackets.
    – isherwood
    Commented Jul 21, 2021 at 20:21
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    You said you want low ceilings. Does that also imply that you want low columns? Diagonal bracing need not be under the ceiling.
    – isherwood
    Commented Jul 21, 2021 at 20:24
  • For the size, I'll eliminate wood as a feasible alternative. Steel remains the most preferable material, the next will be reinforced concrete. Masonry columns may work, but need to be looked at/sized by an engineer.
    – r13
    Commented Jul 21, 2021 at 21:09
  • Your 2nd 'freestanding' pic has at least 2 solid(ish) walls. Some diagonal bracing hidden in there would probably eliminate most movement.
    – brhans
    Commented Jul 21, 2021 at 22:06

4 Answers 4

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Thanks for posting a picture of our Caribbean pavilion. We achieve proper sheer strength, not from any attached chimney (the one pictured was not attached), but by using massive 16" tall steel boots for the posts, steel connecting the posts to beams, and a steel bracket for the hip rafters. Our Caribbean pavilions are designed for a 50lb snow load!

GROUND SNOW = 50 PSF, DESIGN ROOF SNOW LOAD 42 PSF MINIMUM ROOF LIVE LOAD = 42 PSF WIND SPEED = 150 MPH, EXPOSURE B

For more information check out our website. https://lancastercountybackyard.net/pavilions/vinyl/caribbean/

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Deep foundations will obviate the need for knee braces, get a pile driver in to sink some poles deep into the ground and fix the roof to the top.

masonry will not be strong unless tied to a rigid foundation with reinforcing.

steel brackets on timber posts will work too.

Look at the cost of steel construction, it may not be as bad as you fear. but as this is DIY, the costs assciated with tooling up for steel working may be too much.

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You can actually do this with fixed connections at the base. Simpson has developed a fixed base connection for wood posts. FYI - I am a structural engineer.

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    Welcome to DIY!I am sure there's lots you can contribute here as a structural engineer . Would you care to add some more details to the answer to add depth and breadth from your knowledge and experience (e.g. pictures/screengrabs)? It would make a great read for others, not just the OP. And please take the tour
    – P2000
    Commented Dec 13, 2021 at 17:37
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    Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.
    – Community Bot
    Commented Dec 13, 2021 at 17:38
  • Please provide a product link. While product recommendations are off-topic on this site, I'm not familiar with such a product and would like to learn more.
    – isherwood
    Commented Dec 13, 2021 at 19:15
  • The product in question is the MPBZ, which provides a moment connection when embedded in a properly designed footing. The footing must be large and deep enough to resist the overturning load on the post. The advantage to the MBPZ is that you do not have to embed the post deeply in the concrete (which is the traditional way of transferring moment loads to the footing). This should make the post last longer since it is protected from the wet ground.
    – Trebawa
    Commented Mar 22, 2023 at 16:16
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As others already said you don't really need knee-braces if your posts are set deep enough to prevent horizontal shear.

If that is for some reason not possible (e.g. there already is an existing slab or deck underneath that you won't/can't modify a lot so you have to mount the posts on top of it, there is another option.

You are probably thinking of a knee brace as an angled (about 45 degrees) beam from post to roof-beam. Which takes away from the free standing height.

However you can also use a big steel L-bracket mounted flush against the post and roof-beam. Provided that steel bracket is rigid enough it serves the same purpose. And you can hide it with a thin wood cover if it is an eye-sore. Or maybe not. Some people like exposed brackets.
Likewise you can also add brackets on the bottom of the post with the other side bolted into the slab or deck.

Additionally the anti-shear bracing doesn't have to be from post to roof at all. If your roof is internally braced against shear (e.g diagonal beams or tension cables) it just sits on top of the posts and locks the posts into place. There may be some slight horizontal sway depending on how much flex there is in the posts, but as a whole the thing won't be subject to shear.
This is most likely used in your 2nd picture: an internally braced roof and brackets to attach to the posts.

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