Thread: How thick?

NO, I am not talking about the Prime Minister (at the moment)

I want to lay a concrete pad over an area about 1100 wide by 6 metres long. It will reach from the fence and butt up against the concrete floor of the carport. I will be just used for storage - the cars can't get onto it because of the posts in the way. The distance from the carport to the fence is the 1100mm dimension.
The carport floor is probably 100mm thick and reinforced.

Would 50mm or 80mm thick be enough for the floor? I am thinking of getting the Concrete Taxi in for the job.

I know its over kill for just a storage area but it should be as thick as the carport slab and definitley not less than 75 mm. It should also be pinned to the carport slab by doweling with some reo. You only get one chance to do it right

Thanks Ringtail,
I am a bit confused about the reo. The carport slab has been for years - are you saying I should drill into and push the reo into the holes and then let that be the reo for the storage area?

Yes. Basically, when you dig the area for new slab you expose the edge of the existing carport slab. Come down 50 - 55 mm and drill into the edge of the slab about 60 mm deep and every 300 - 400 mm. Get some SL62 mesh and cut a piece to fit the new slab and cut little bits off the left overs to use as dowels. Cut bits about 250 mm long ( doesnt matter if they have other bits hanging off - ie doesnt have to be a straight piece of bar) as long as there is a staight piece to hammer into the hole that leaves you with a good amount hanging out. To the stub sticking out you then wire tie the mesh for the new slab and support the rest of the mesh on chairs so that you have 40 mm cover at the top and 25 - 30 mm off the ground. Dont forget to put the black plastic down first. Like I said, its sounds like overkill but it costs bugger all more to it properly first time and know that its right. Its going to be there for a long time after all. The doweling means the two slabs should move together so you dont get a big lip sticking up. Run a edging or jointing tool along the join as part of the finishing.

Two different areas in the photos but shows the dowels in the small slab and the mesh placement in the larger slab which is off the side of a existing carport slab, just to give you a idea. Cant see the dowels in the carport slab but they are there

I'd go 100mm thick and SL72 steel mesh reinforced - i like overkill more than saving money though!

Thanks for your suggestions fellas. Today at 7am the Concrete Taxi arrived and the area is now covered with 100mm of Perth's finest mud!! I took your advice and put 5 x 300mm long pieces of 12mm reo into the existing carport slab. I can't see that there will be any "differential movement", which the pinning will prevent, but better do it now rather than have it appear in a year or so and say "##!@% - wish I HAD pinned the old floor into the new one!!!"

Different movement would cause one part of the slab to lift or sink, ,leaving a big step, and fixing it would require digging it up and doing it again. No thanks. I was going to take a photo of the site before the mud went in, but the Conc. Taxi came early so now all the evidence is hidden. Now I can work on enclosing the space and putting on the Colorbond roof.