How much would a 15×20 foot cement/concrete slab cost, roughly?
Surprising enough, the prep under the slab cost as much as the slab itself. Never skimp on the preparation. You need a good 4-6″ solid well drained compacted base. Access to the slab is important. The more difficult it is to get to the more it will cost. If your slab is a simple broom finish and is relatively easy to get to a good stone or sand base should run about $1 – $1.40 per square foot. The concrete is about the same $1.40 – $1.80 per square foot. Remember in your cost will be damage done by contractors and cement trucks. Make it clear who takes care of this.
