My garage floor is sinking. Who do I call?
Usually, start with
Concrete slab repair / leveling professional
If part of the garage floor has changed elevation but the rest of the garage appears stable, a concrete slab repair or leveling professional commonly evaluates the slab condition, the amount and pattern of movement, and whether the slab may be a candidate for a concrete repair or leveling approach.
Change course if
You see cracks or movement in the walls too
If movement appears to extend beyond the garage floor, foundation or structural expertise may also be relevant.
There is a water problem near the sinking area
If water pools nearby, runs toward the garage, or appears to be washing soil away, drainage expertise may also be relevant.
The concrete is badly broken or falling apart
If the slab is extensively broken or deteriorated, a concrete repair or replacement professional may be relevant.
These conditions can overlap. A professional who evaluates the property can determine what is happening and what repair, if any, is appropriate.
Who handles what
Concrete leveling / slab repair
Evaluates garage floors that have sunk but may still be suitable for stabilization or leveling.
Foundation / structural
Evaluates movement that may involve more than the garage floor.
Drainage
Evaluates water that is collecting, flowing toward the garage, or contributing to erosion around the area.
Concrete repair / replacement
Evaluates concrete that is badly cracked, broken, or deteriorated.
What might be happening
The visible sinking tells you that part of the floor has moved. It does not, by itself, establish why it moved. Changes in the material supporting the slab, water movement, or deterioration of the concrete can be relevant in different situations, and more than one condition can be present at the same time.
Useful things to notice
Whether the movement seems limited to the floor
Movement elsewhere in the garage is useful information for the professional evaluating the condition.
Whether water collects or flows nearby
Recurring pooling, runoff, erosion, or water moving toward the garage can help a professional understand the site conditions.
What the concrete itself looks like
Cracks, broken areas, surface deterioration, and changes in height are useful to document before an evaluation.
Before you call
Have a rough idea of when you first noticed the change and whether it seems to be getting worse. Note any recurring water nearby or movement elsewhere in the garage.
Useful photos include a wide view of the garage floor, the affected area, any cracks or height changes, the wall-to-floor edge, the garage-door threshold, and nearby exterior drainage conditions.
Before you fix the visible symptom
Cracks and gaps can be consequences of movement. Filling, coating, or covering the visible symptom does not establish why the floor moved. If movement appears to be continuing, or water may be involved, an evaluation can help clarify the condition before cosmetic work is undertaken.
References
American Concrete Institute. ACI 302.1R-15, Concrete Floor and Slab Construction, Chapter 5.
American Concrete Institute. ACI 201.1R-08, Guide for Conducting a Visual Inspection of Concrete in Service.
Suprenant, Bruce A., and Ward R. Malisch. Should Slabs Rest On or Be Attached To Foundations? Concrete International, 2010.