KHIA headerKnow-How in Action


Belzona® Seals Leaking Balcony Roof At World Famous College



Buildings & Structures (BSTR)



Roof Problem Areas (RPA)


Customer Location:

College, Cambridge, UK


Application Date:

August 2013


Application Situation:

An asphalt balcony, used as a walkway, covered with concrete slabs.



The asphalt roof was leaking underneath the concrete slabs, causing water damage to the rooms below. To repair the roof the College was planning to remove the concrete slabs, replace the asphalt roof and then reinstall the concrete slabs.



Belzona® 4131 (Magma Screed)

Belzona® 3131 WG Membrane)

Belzona® 9231 (Surefoot Aggregate)



Asphalt and concrete


Application Method:

Application was carried out in accordance with Belzona Know-How System Leaflet RPA-6. The gaps between all paving slabs were cleaned and filled with Belzona 4131. A fully reinforced Belzona® 3131 system was then applied to weatherproof the area. This was followed by a further coat of Belzona® 3131 blinded with Belzona 9231 aggregate to create a non-slip walkway.


Belzona Facts:

To replace the leaking asphalt roof with new asphalt was expensive, would expose the building to the weather and would take over one week. The Belzona system meant the existing roof substrate stayed intact, the roof coating was completed in 3 days and new Belzona non-slip surface provided additional safety.


Photographs Description

  1. Leaking balcony roof with paving slabs
  2. Close up of paving slab edge
  3. Gaps between  slabs filled with Belzona® 4131
  4. Balcony roof coated with Belzona® 3131 system with 3rd coat incorporating Belzona® 9231 aggregate anti-slip system
Case study pic one


 Case study pic two


 Case study pic three


 Case study pic four


For more information about Belzona visit: