Disclaimer: I am not a waterproofing specialist, just sharing my opinion.

hi bcombat,

1. based on your photo, I think it is pretty obvious that the water is seeping out from the cement screed layer. So it is correct that you waterproof the whole slab surface. However, you need to ensure you cover the whole area thoroughly, including the drain. Because if you miss out any small corner or small cracks, rainwater still can seep through.



2. since now you're directly applying waterproof coating on top of your car porch slab, which is exposed. Make sure your waterproof material is meant for exposed coating application. Because most waterproof material is NOT meant for exposed application. They usually will need a protective layer (cement screed layer) to avoid direct sunlight and weather. Otherwise, the waterproof coating will lose its function over time.

3. to quickly examine the effectiveness of the waterproofing coating. you should immediately do ponding test for the slab after the coating is dried.

4. if the problem is persistent i would advise you to engage a professional waterproofing specialist nstead of trial and error on your own. As i know, some provide bituminous membrane installation for upwards of 10 years warranty. they will come to fix any leakages within the 10 years period. at least you get peace of mind for 10 years.

Torch-on membrane is only effective if all the joints and terminations are done properly and the overall installation is carried out meticulously.

However, any small gap between the membrane and your roof slab can allow water to seep through, potentially leading to even worse leakage problems on your roof.

Theoretically all water proofing material has its lifespan. So, it is important that you make sure that your slab has gradient for water to channel to drain efficiently