building gazebo in backyard


This is a question for the builders/engineers/handymen of the forum.

I'm building a 3.5 x 3.5 gazebo with hip roof. The 4 posts will be bolted onto slab. How thick should my slab be? Do I need expansion joints? I'm concerned if I partition the slab, it might shift and affect my posts. Is it possible to have slab in 1 piece by going thicker?

Also, ground is on a slight slope. Does slab need to be dead set even in thickness? Should I allow a layer of blue metal and plastic under slab to allow water run off?

Thanks a million.

did a similar build, on a 6% slope, anchored the slab in place by digging 12" diameter 2' deep post holes at the corners, to also ensure the bolt down would be strong enough,
of course at the time I was installing FTA satellite dishes on poles for $$$, so had a post hole digger,
normal, If you have a hammer every problem is a nail
before making a 2" slab. Looking back, it worked,
the slab remained anchored in place the relief lines havent cracked.
I would be doing a small footing approx 300mm deep under where the posts are going to be bolted.

These photos are of my own gazebo and how I did mine using copper logs.It measured 5 metres by 8 metres in the end.:D


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Gday Pat82

100mm slab should be plenty thick just make sure you use steel mesh to prevent the slab from cracking. The mesh should sit in the middle of the slab, so 50mm from the top and bottom, You can do this using mesh chairs( little plastic chairs you sit the steel mesh on to keep it 50mm off the ground). It should also be 50mm in from the edges of the slab. Having plastic is a good idea as it will stop moisture soaking up from the ground, I wouldnt worry about the blue metal. It doesnt matter if the slab is thicker in sections but it will matter if its thinner than 100mm. Keep in mind its cheaper to just get the ground to the right level using well compacted dirt.

Hope this helps mate

Thanks for the replies guys.

So does it mean I do not have to use expansion joints for a 3.5 x 3.5 slab?

Yeah thats right no expansion joints needed on a slab that size. The steel mess will stop it from cracking.