A waterproofing membrane is essentially a thin layer of material that is laid over a surface that needs protection from water leakage or seepage. This waterproof membrane is continuous and stops water to pass through it.

To give you an example, a flat roof will usually have a waterproof membrane laid above the concrete or structural slab and below the flooring. This is to ensure that water is stopped to pass through into the base of the roofing.

The tiles as well as the membrane are usually laid over a filler matter. This material is angled to ensure that water flows towards the drains. Any water that is stagnant as puddles may likely to seep through the slab, so puddles are risky and are to be taken care of at all costs.