Is It Possible To Waterproof Over An Existing Old Waterproofing

Removing waterproofing membrane sheet from roof slab

It’s a very common occurrence where a lot of homeowners been asking this frequently. Many believe that applying the new waterproofing on top the old would enforce the old waterproofing system, such as patching up areas that shows tear and wear. In reality, it is not as simple as wear and tear and there may be other waterproofing failures from the old system that are not visible.

Why is it not recommended to waterproof on the old waterproofing system?

Waterproofing system are not as simple as it is, as some may consist of multiple type of waterproofing membrane.

The main component which is the waterproofing membrane that diverts the water away, can be easily damaged and goes through wear and tear after some time. More often than not, these damage on the membrane is not easily visible during the application of it.

Methods to remove the old waterproofing system

Existing waterproofing system membrane can get rid of applying one of these method:-

  • Chemical application
  • Scraping off waterproofing membrane

We usually recommend to get the professionals to remove the membranes to avoid any damages to the substrate / screeds which could make the situation worst.

When to apply a new waterproofing membrane?

You will be able to identify the failure of waterproofing membrane by looking at the surface of it. Commons sign to look out for is when the area is rough with some sort of distortions, inconsistencies in the surface which is not fully flat, leakages of water or water dampness below of the waterproofing membrane surfaces.


There are times where one can repair it by themselves if the failure is due to small spots of the waterproofing membrane. However if the surface is on areas that are hard to reach, it is recommended to consult professional waterproofing contractors.

Need more information and waterproofing contractors professional advise?

If you would like any further advise  about waterproofing, please contact us or send us an email to . Our friendly team of waterproofing specialists pride themselves on providing great service and will be delighted to help.

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