Hi,

I just want to run this concept by you experts to make sure the advice I am being given is reasonable.

We are building a small 10x15 shed/garage on an existing concrete slab that doesn't appear to be reinforced and is cracked and is settling in places.

What I am looking at doing is instead of ripping out the old slab and pouring a completely new slab, is to frame and pour a new slab over the top of the old one, reinforcing the new one with rebar, preparing the surface of the old slab so they adhere together, and epoxying some vertical pieces of rebar into the old slab, allowing those pieces to adhere to the new pad like little bolts.

Is this a reasonable solution? I would like to avoid having to pour a new pad if possible.

Thanks!

Hi ludogg

If u live in an area that gets cold weather, u would need footings under slab that go below frost line. If not slab will heave from frost.

Good luck

Chuck

Hi ludogg. Not necessary to epoxy anything here. Just use a hammer drill into old crete several places and pound the rebar pins in the dead weight from new crete will hold it in the hole.

New slab should be min 4 inches thick with 3/8 rebar in it 16x 16 square. Not 3 1/2 " 2by width. you want the rebar to have 2" min centered in the slab.

Look at the old slab as dirt at this point and the new slab as a base pedestal for the shed to sit on. The pins at this point is to stop and shear movement of the old slab. (separating). The new slab doesn't need the old to support it in any way other than a place for compression

No adhesion is necessary at all between the slabs other than the shear factor

In the trades we call it a free floating pad/slab. 10x15 is small. Even if the moisture gets between the slabs the upper slab will be the bottom on the boat that can float.

My only side thought here is will the extra 4' of crete be a factor for ramping into the garage

Pouring slabs for 30 years.

I live in an area where it freezes 48" into the ground, no footings are required for a slab but the edge of the slab is about 5" thicker than the rest of the slab (thickened slab) Post #2 is not taking into account that a slab floats and requires no footing. While I agree with 21boats pour thickness and other details I would recommend that you tear out the old slab since it has failed and will continue to move. A 4" pour is totally sufficient for a garge floor so why pour it over a bad floor. Its like putting lip stick on a pig, I still won't kiss it. Like 21 mentions, the extra thickness will make the entry awkward as will the floor meeting the walls and what about your garage door?

Hi Ballengerb1

With the slab floating, won't this effect the structure put it?

Chuck

Yes, your structure must be fairly light such as a garage or single story home. This is the building standard around most of the country and I have never been questioned by a building department when I submitted my plans. A thicken edge is all that's required.

Thank u for info. Try to learn something new every day. Keeps u young. LOL

Thank again

Chuck