The concrete slab in my garage/shop has sunk a few inches where it meets a wood floor. The low area is worse next to the wood floor and then tapers out to where it should be in about three feet. I also have a few low spots in other areas of the slab, not horrible but very annoying. I would like to level up the entire slab. I know it won’t be perfect but I’m hoping I can get close. What type of product can I use to do so? Gypcrete? Something else? How should I prepare the slab to achieve the best adhesion for the resurfacing? Thanks
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Pictures are always helpful
If I interpret your explanation correctly, only a small proportion of the entire floor slab has sunk. If so, then there must be visible cracks of some consequence.
How old is the garage?
Was it an addition to the house or is it an outbuilding?
Sounds like poor subbase prep for the floor.
Putting a topping over it, especially if that topping has to feather to zero thickness, might offer a short-term fix but not likely a permanent fix. Slab jacking could raise the original and then you will need to epoxy the cracks.
Need to see pics showing good vs bad before commenting further. Preferably with a visible tape measure in the image.
Yes, there is a line of cracks in the slab a few feet past the sunken area. The garage is attached to the house. I know the slab was poured during the winter months and I'm sure you're right about the poor subbase prep. I have not been able to find any slab jacking services in my area, (Homer Alaska) so that's not an option for me. The garage was built in 2005. I'll try to get some pictures posted. The other low spots in the slab won't show up in pictures. they're just shallow depressions that hold puddles of water when a vehicle is inside thawing out. Thank you
If you really want a permanent fix, demo the existing floor slab in its entirety.
Excavate the subbase material down a couple feet in the areas where the slab sunk. Replace with a good gravel placed in 6" lifts thoroughly compacting each lift. Run a plate compactor over the entire area.
Plan your new slab with at least 1/4" per foot slope down towards the overhead door. Make sure top of the subbase material matches that slope so you're placing a uniform thickness slab. Depending on the overall dimensions of the slab you may need to divide it into 4 panels by control joints (sawcut if it can be done within the correct time frame) or use metal keyways to divide the panels.
It may not be a good time of year for this kind of work, especially in your climate zone.