I have an old brick patio, cracked in some places. I want to pour concrete over it and stamp the concrete with a texture. What is the thinnest I can go? 1 inch? 2 inch? I have 5000 square feet and need to save as much on materials as possible.
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1Considering that we know nothing about what's under the brick we have to assume a self-supporting slab that will accommodate settling and movement. (Concrete doesn't usually work as an overlay, especially when over an unstable substrate.) 4" with rebar on a 24" grid is my answer. I don't imagine that's helpful. Perhaps you're asking the wrong question.– isherwoodCommented Mar 26, 2018 at 20:57
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I had a professional pour a slab over dirt and they only used 4 inches,– user3561494Commented Mar 26, 2018 at 23:00
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1 Answer
You can go with whatever thickness you like, however, if you want it to last, you need to determine if the brick will continue to settle and crack. If so, thicker is better or your cracks will eventually show up in your slab. 4" would be the best, with expansion joints. You might be able to get away with 3" with more joints, but you'd be pushing it and possibly inviting cracking. A standard sidewalk is 4" thick, and even they crack from settling. 1" is just a skim coat and will definitely crack. You can't make up 4" by using your 2" brick, plus 2" slab. The brick below will continue to move and seperate from the slab, causing more cracking. Your best bet....remove the brick and level, grade, gravel and then pour a new slab, 4" minimum with proper expansion joints. Not cheap however.
What will this slab hold? Heavy weights like a vehicle? If so, you will want 6" minimum.
