How to prevent concrete roof from Absorbing water

Question

It's winter again and rainwater still collects on my flat roof due to it's bad tilt, Because of that the concrete absorbs a lot of that water into the second floors roof and it's really visible on the roof and the walls. I try to move the water to the gutter when I'm in the house but I don't have time to keep doing that.

My question is : Is there anyway to stop the concrete from absorbing this water, and what are the possible fixes to my my problem ?

and also is there any way to dry the water that got already in the walls ...etc ?

Answer 1

Concrete absorbs water. That’s why it can never be finishing layer in this type of situations. Even if it is properly tilted that wouldn't solve your problem completely. You must protect it. Now, if you want to do it right it's a bit more complex than just putting tiles. If you are short on money you can do just that but it's not proper solution. Firstly you should apply some hydro coating. It should be something that is meant for outside usage. Pay special attention to the edges; places where your slab connects with surrounding walls etc. Than, since under the slab is a living space (which is being heated) you should put some thermal insulation to prevent condensation which also can cause humidity problems. If you use thermal insulation which soaks water you must wrap it around with a foil. Then you can put some metal sheets on top of the roof. Keep in mind that sheets cannot be HORIZONTAL. There MUST be some slope. Again, pay attention on the edges, they should be placed so water cannot find the way in. If you want I can draw some sketches how to do it, but I will need a picture for that.

Answer 2

You can almost eliminate the permeability of the concrete by sealing it with silane/siloxane sealers. Next step up would be roofing material designed for waterproofing flat roofs. (See related: How should I waterproof a concrete roof?) Beyond that you have to establish a pitch to prevent standing water.