Garage slab over slab
Garage slab over slab
(OP)
Have 2 car garage, 24x24, foundation settled and takes water
on one corner that has dropped and cracked, about 4x4 section. Would like to pour concrete over exisiting slab, without tearing down structure. Only use it to park one car. Can it be done? If so, any suggestions for preparation and framework?
on one corner that has dropped and cracked, about 4x4 section. Would like to pour concrete over exisiting slab, without tearing down structure. Only use it to park one car. Can it be done? If so, any suggestions for preparation and framework?






RE: Garage slab over slab
It may be wise to investigate the reason for the failure prior to doing anything. Pouring concrete over the existing concrete could cause larger problems due to increased load.
RE: Garage slab over slab
RE: Garage slab over slab
Besides, it's damn near impossible to get a truck-mounted rig "close enough" to the corner of a garage (or any structure.) Roof overhangs, telephone and electrical lines, etc. are a real problem in raising the boom. Sometimes a Bobcat with a little backhoe is all that's needed -
Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.
RE: Garage slab over slab
As to the part of your question about placing new concrete on top of existing concrete - it is often refered to as "white topping" and it can work, if done properly AND the existing slab is in good conditon. After you have corrected the stated subsurface problems, consider placing new concrete in the repaired area only to match the elevation of the existing slab. After proper curing, place the new slab (uniform thickness) over the entire 24 x 24 area, match all joints in the existing slab. If joints do not match, over time the new slab may develope "reflective cracking" at locations more or less above joints (and crakcs) in the existing slab.
There are two schools of thought about the contact area between the old & new concrete. Some say to isolate the two slabs from each other, perhaps with polyethylene sheet or sand layer. Other say to attempt to get a bond between the the old and new concrete. My expereince has been to just make sure the old concrete is very clean, then place (and cure) the new slab.
RE: Garage slab over slab
As far as pouring atop an existing slab, it's very difficult to get a proper bond and prevent cracking and spaulling off. It might be better to cut out a section, see the problem and backfill with compacted gravel and pour a new portion of slab on sound bearing.
RE: Garage slab over slab
Pouring the 4x4 section back would probably be the same cost (not including the cost to fix the settlement issue) as pouring a concrete top.