Thread: Measure concrete slab thickness

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.

Originally Posted by Slunnie

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

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

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.

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.