Roof & RC Slab Waterproofing
Flat roofs and RC slabs work hard. Thermal cycling, ponding, planter loading and foot traffic all attack the same membrane. The right system depends on substrate condition, exposure and the finish on top — green roof, planter, paver, walkway or service deck. We size the system to the loading, not to the cheapest data sheet.
Common defects we treat
- Damp ceiling on storey below an exposed roof or terrace
- Bubbles or wrinkling on existing membrane
- Standing water around floor traps and rainwater outlets
- Stained or efflorescing concrete soffits beneath planter boxes
- Cracking at parapet upstand and slab-wall junctions
Method on site
Site survey and water trace
Roof inspection, fall direction check, rainwater outlet condition, parapet upstand integrity and substrate moisture. Existing membrane condition recorded before removal scope is decided.
Substrate preparation
Removal of failed membrane, grinding of laitance, repair of cracks and honeycombing, formation of haunches at slab-to-upstand junction, priming of substrate where the data sheet requires.
Membrane installation
Sheet membrane heat-welded with overlaps per data sheet, or liquid system applied in two coats at right angles. Full continuity at parapet upstand, around floor traps and at expansion joints.
Flood test
Outlets plugged, slab flooded to a marked depth and held for 24 to 48 hours. Soffit inspected for fresh staining. Test result recorded before protection screed is laid.
Protection layer and finishes
Protection screed, geotextile, drainage cell, root barrier or paver pedestals applied to suit the final finish. Membrane is never exposed to direct foot traffic or planter loads.
Materials we use
- Torch-on bituminous sheet membrane (APP/SBS)
- Liquid-applied PU and acrylic membranes
- Cementitious crystalline systems for selected concrete decks
- Drainage layer, root barrier and protection screed for green/planter applications
Deliverables to the client
- Roof condition report with photo record
- Method statement aligned with SS 637
- Flood test record and protection layer specification
- Maintenance note covering outlet cleaning and joint inspection