I have a very old, all brick garage. At one time was an ice storage building and parts of a brewery. The concrete is original and very pitted, brittle, etc. Wondering if anyone has experience putting new concrete (4+” pad) directly over original slab? I have 20’ roof so height isn’t a problem.
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New concrete over old?
- Thread starter House_74
- Start date
Where do you live?
any extreme temperatures hot/cold/wet
only issue I can think of is bonding/keying into the old slab, you could drill a ton of 3 inch deep X 3/8 holes, ( thinking like 12/16/18 inch centers ) and epoxy in some bolts, rebar or all thread into old slab with say 3inch sticking up / out into the new poured concrete so the 2 slabs are stuck together, that would make it so no areas can separate. A flood, muddy dirt or water can make hollow spots and cause a failure.
i would also dowel ( 24inch spacing )into all brick walls so the new slab is tied to the floor and walls, keep in mind you’ll also need some room for expansion so some 1/2inch foam tape or felt board around the perimeter and then caulk that joint / gap. Think if a swimming pool and a patio slab there is a joint around the pool coping. In high heat (expansion ) the new slab could expand and damage the brick walls…
As an example-
on concrete industrial buildings ( tilt up style ) we tie footing rebar dowels, wall rebar dowels and slab rebar dowels with a concrete pour strip after the walls are lifted and set in place with a crane, that makes a strong and tight connection for the 3 independent items.
i hope I didn’t confuse you with the last part it’s slightly off topic
any extreme temperatures hot/cold/wet
only issue I can think of is bonding/keying into the old slab, you could drill a ton of 3 inch deep X 3/8 holes, ( thinking like 12/16/18 inch centers ) and epoxy in some bolts, rebar or all thread into old slab with say 3inch sticking up / out into the new poured concrete so the 2 slabs are stuck together, that would make it so no areas can separate. A flood, muddy dirt or water can make hollow spots and cause a failure.
i would also dowel ( 24inch spacing )into all brick walls so the new slab is tied to the floor and walls, keep in mind you’ll also need some room for expansion so some 1/2inch foam tape or felt board around the perimeter and then caulk that joint / gap. Think if a swimming pool and a patio slab there is a joint around the pool coping. In high heat (expansion ) the new slab could expand and damage the brick walls…
As an example-
on concrete industrial buildings ( tilt up style ) we tie footing rebar dowels, wall rebar dowels and slab rebar dowels with a concrete pour strip after the walls are lifted and set in place with a crane, that makes a strong and tight connection for the 3 independent items.
i hope I didn’t confuse you with the last part it’s slightly off topic
I poured 6 inches of concrete over an existing slab when I rebuilt a 10’ by 16’ storage building. The original slab was level or slightly below the existing exterior grade so it flooded with heavy rain.
The existing slab was in pretty good condition condition so I formed to the same footprint and poured right on top with no tie-in. I built the shed right on top as it’s 6” above grade and has a foot on concrete total. I did rebar the new slab on chairs to keep the bar centered
It’s been fine
The existing slab was in pretty good condition condition so I formed to the same footprint and poured right on top with no tie-in. I built the shed right on top as it’s 6” above grade and has a foot on concrete total. I did rebar the new slab on chairs to keep the bar centered
It’s been fine
billconner
Well-known member
I'd add a vapor barrier and perhaps insulation, and pour on that. I believe it's less likely to crack from shrinkage as it cured if it's unrestrained.