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ssahley

Need advice for anchoring a gazebo to pavers with a concrete base

ssahley
8 years ago

We have a very large paver patio and want to cover a portion with a cedar gazebo that has an aluminum roof. When we had our patio built we went with a more expensive option of having concrete poured beneath it (with footers) rather than using sand and gravel. This being said our pavers are discontinued so we REALLY don't want to cause damage to them but we have the base to support the structure. My husband is refusing to drill into the pavers to anchor the gazebo, and am saying it's a must for safety, plus we plan to run electrical to it for a TV so if it moves - that will cause a big issue. The gazebo is over 300lbs but the roof is not vented which I believe helps with wind gusts. We are in Ohio - and get gust at times up to 50MPH, but that is more the exception rather than the rule. Sooo can we have this structure put up safely without anchoring it???


Comments (11)

  • szut (Zone 6 - MA)
    8 years ago

    How large is the gazebo? Based on that you can calculate the force on the roof with 50mph gusts.

    Personally I wouldn't do it without anchoring...

    Could you put on the corner of your patio and anchor 3 legs outside the patio?

  • szut (Zone 6 - MA)
    8 years ago

    You can find more info on calculating wind force here:

    http://www.vishaypg.com/docs/11874/vpg-07.pdf

    or here:

    http://www.wikihow.com/Calculate-Wind-Load

    I did a quick calculation totally speculating on how your gazebo might look...

    F = 0.63 * Area * Velocity^2 * DragCoefficient

    To determine area

    • I assumed 4 rectangular legs at 4" wide and 8ft tall.
    • I assumed a roof that sits on these legs that is 8ft wide and on average 1ft tall (so maybe 1.5ft at peak and 6" on the edges)
    • Then I converted that into meters to get a total area of 1 sq meter for the four legs (4"/12"*.3048*8ft*.3048 * 4 legs) and another 0.74 sq meter for the roof (1*.3048 * 8 *.3048).

    I used a coefficient of drag of 1.4.

    I converted your 50mph to 22.35m/s

    I then calculated the force to be: 764 newtons or 172lbs

    Other variations:

    1. if I change the wind to be 72mph then the force is 352lbs.
    2. If I change the area of the roof to increase by 6" and leave the wind at 50mph then the force is 208.6
    3. If I change the size of the gazebo to be 12ft wide (with 1ft roof and 50mph winds) then you get 208.6lbs
    4. If I should be using the 2 as the drag coefficient vs 1.4 because of the long/narrow nature of this structure then at the original dimensions and wind the force is 245lbs

    Also the above is not taking into account the "lift" created on the roof (similar to what makes a sailboat move).

    So even with a 300lb structure IMHO it will move - it is just a matter of when.

    Disclaimer: I was doing quick calculations so it is possible I incorrectly converted something from ft to meters, etc. Please check this on your own!

  • ssahley
    Original Author
    8 years ago
    last modified: 8 years ago

    The gazebo is 12 X 12. Your math is far beyond what I could have come up with. Thank you so much! My husband likes to shortcut things and is worried about our pavers and drilling through them into the concrete beneath. I have seen other posts about people putting the legs into pots and adding concrete to the bottom to add weight with good results. Then adding dirt and plants to the top. Thoughts on this option?

  • szut (Zone 6 - MA)
    8 years ago

    Assuming 12ft square - the largest area for wind would be on the diagonal which translates that 12ft to closer to 17ft... (diagonal would be sqrt(12*12 + 12*12)). This brings the area of the roof up to 1.6 sq meters. (Again assuming the outside edge is 6" and the peak is only 1ft 6".)

    With that, assuming a 72mph wind gust (32.187m/s), and a drag coefficient of 2 (the safer and probably more accurate choice) the force is 754lbs.

    I also didn't take into account the area of any side netting, your TV screen (since I don't know) which could also potentially be blown on (unless it hides in the roof in which case the area of the roof is likely much higher).

    And the above doesn't have any safety margin or take into account lift which can be a significant force.

    So assuming 300 lb gazebo you would need 113lbs per leg to hold it down without any further safety margin.

    Again I would bolt her down.

    Or if you really want try it and see what happens. But use a cheap old TV just in case and make sure if the structure moves/crashes that it doesn't hurt the patio or anyone nearby.

    This is my opinion but I tend to overbuild for safety and longevity reasons. Others might advise differently. I have never seen gazebos (either temporary ones like the canvas ones or permanent ones which it sounds like you are describing) not anchored, but google searches show that others have had luck with temporary gazebos (the cloth ones) that aren't anchored but simply weighed down.

  • ssahley
    Original Author
    8 years ago

    I really appreciate your thoughts and math here. I am absolutely in agreement about bolting down, now to convince the hubby!

  • tj_shopper Eng
    2 years ago

    Hi. Just wondering what you ended up doing with your gazebo. Did you bolt it down? I'm in Frankfort, Illinois and am considering getting the Yardistry 12 x 14 gazebo from Costco. I believe it's about 600 pounds. I already have a paver patio and would like to bolt it down but not sure how to do it. Thanks.

  • 3onthetree
    2 years ago

    You cannot fasten to the loose-laid pavers. You would have to install footings under the pavers to attach to. Better call the Building Dept to get their take, as Frankfort is VERY strict about anything and everything you do to your home, even repairing.

  • tj_shopper Eng
    2 years ago

    Sounds like you know Frankfort lol! Ugh - I really don't want to take apart my landscaping for this. I thought we could drive a stake through the pavers to secure it to the ground. Also, it being 600 pounds, I thought it might be okay. Thanks for your insights.

  • Edward Mosher
    2 years ago

    How did this turn out? I have the same issue.


  • tj_shopper Eng
    2 years ago

    I have not done it yet. The gazebo just went on sale at Costco and we purchased it. It is currently sitting in my garage. I did contact Frankfort Building Department. They said I definitely needed a permit, even though we are putting it up ourselves with some help from family. The permit said that we need concrete footings. I'm going to see if my landscaper can help us with this as they put in the pavers. They might have to tear apart my pavers to do the concrete footings and then repair the pavers. I don't know and I won't know until we start on the project later this spring/summer.


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