What causes water to seep through a cement slab?

Answer by  GilFinn (2065)

A common cause of this problem is water flowing towards the house. The area under the slab is usually a base made up of gravel and sand. The water will flow under the slab and wick up through the concrete. Make sure you have positive runoff away from the slab.

Answer by  bl834 (1317)

Cement isn't waterproof by itself, it needs a coat of sealant. If it hasn't been sealed properly or if there are cracks in the slab, water would easily be able to penetrate.

Answer by  Fritz (608)

I would say there was not enough gravel fill put in under the concrete before it was poured, There really is not much you can do expect break it up and pour the slab all over again.

Answer by  Amber40 (24961)

Well concrete itself is porous like most other rock based substances. When water is trapped behind it the small hole in the material actually allow the water to slowly flow through it similar to a sponge. To stop this the concrete needs a physical water barrier. Typically in the form of a plastic or paint.