Usually 2 to 4 in of low-strength concrete placed over subgrade so rod busters and waterproofers can work on something clean, dry and flat, or poured in crawlspaces to keep out moisture and rodents. It carries no structural load and is often unreinforced. Drawings often call the working-slab version a mud mat or mud slab.
Heard on the job
Throw a rat slab in the elevator pit so the waterproofing guys have something clean to stick to.
Also heard as
- mud slab
- mud mat
- working slab
- blinding
Related terms
Vapor retarder
A plastic sheet under a slab on grade that slows ground moisture from rising into the concrete.
CLSM
Controlled low-strength material, the soupy flowable fill poured into trenches and voids instead of compacted soil.
Dobie
A small precast concrete block, often with tie wire cast in, used to hold rebar up off the ground.