Measure concrete slab thickness

Get a template of the desired hoist, drill some holes to measure the concrete thickness. Concrete only has to be 100mm thick.

If you're going to drill it to test the thickness, drill the same size hole as the anchor system requires as a 20mm drill will punch the bottom out of the slab earlier (effectively lessening the slab thickness that the anchor is holding into) than say a 5mm bit because it mightn't be the risk of the hoist cracking through the slab but more so the risk of the anchors pulling out if the load is too far out of balance fore and aft.

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Originally Posted by Slunnie

See if the council has the engineering papers for the shed. It should be specified shouldn't it.

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Good idea! As the shed slab was done 30 years ago I have doubts the council was ever involved. But worth checking.

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Originally Posted by Saulman1010

Id be thinking a plate under the posts, twice or three times the post size to spread the weight rather than the risk of pushing through an unknown slab thickness. Also i would use 15mm stainless allthread and chemset them into the slab. I would not use dynabolts and they can vibrate loose. I regularly hang 1200 x 1800 sheets of glass vertically on 2 mounting points with ss allthread and chemset - imagine not only the weight but the wind loads.[emoji3]

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Agree. We chemset the s/s anchor bolts for a 17m x 5m carport we erected recently to be sure it wasn't going anywhere, as it gets windy up here sometimes too :-)

Google some info on it.
What depth of concrete is needed for installing a car hoist?

This site says 100mm of reinforced concrete is the bare minimum.

They recommend 140mm at 35mpa. A normal house slab is 20-25mpa, your concrete infill will be lucky to be 20.

Then they go on about cutting out holes at 300x300 for footings. I'd still go 1x1x1 with 25mm min high tensile all thread concreted in but that's me.

Hope it's nice and thick then you will be laughing!

Why not drill the test holes where the lift mount holes have to go - if the thickness is OK then simply proceed.

I've been building a shed for a couple of months now. It ain't small, has a mezz in the gable part (6m at the peak) with a skillion that is about 11x6m, 4M high.

Part of it is over an existing slab (100mm) that I had done a few years ago.

The engineering drawings specified for some totally over the top footings incorporated with the slab (existing and extension). The biggest were 600 dia and 1300 deep.

This might sound like a big deal but in reality it isn't.

Had to cut 6 700 x 700 holes in the existing slab (took about 40 mins), a mate with an excavator drilled all the 600mm holes (16 in total) to varying depths (850 to 1300) in an hour max.

Concreter used 4 bits of rebar in each of the cut holes drilled into the existing slab (half a hour) and the whole lot got poured, including 70 odd square metres of new slab in less than half a day.

Point is you only need 2 pads mated to your existing slab. Even if you go way over the specs it is still no big deal to cut the slab and dig for the pads for whatever the specs say or more and rebar it to the existing slab and keep the existing flat floor.

Yes I have pics of my build for the shed thread, but it ain't going to be for the PC.

cheers, DL