What is terrace waterproofing?
Terrace waterproofing is the protection of a flat roof slab against rain and standing water. It covers the main roof surface, the junctions with parapets and walls, rainwater outlets, pipe and cable penetrations, water-tank plinths and any service ducts that pass through the roof.
Depending on the condition and use of the terrace, the system may be a cementitious or acrylic elastomeric coating, a liquid polyurethane membrane, a torch-applied bituminous membrane with protection, or a combination, sometimes over an existing brickbat coba layer that is still sound.
Benefits
- Stops top-floor ceiling leakage and dampness
- Corrects ponding by restoring falls to rainwater outlets
- Seals parapet junctions, outlets and penetrations, the usual leak points
- Heat-reflective finishes can reduce roof surface temperature
Common problems and applications
Problems it solves
- Ceiling leakage and damp patches in top-floor flats during rain
- Cracked or hollow brickbat coba with water trapped beneath it
- Ponding water due to lost falls or blocked outlets
- Gaps at the parapet-to-slab junction and cracked parapet plaster
- Leaks around water-tank supports, solar frames and antenna fixings
- Peeling, chalking or blistered old coatings
Where it is used
- Housing society terraces and staircase head-rooms (mumties)
- Commercial and office building roofs
- Industrial and warehouse RCC roofs
- Accessible terraces with tiled or paved finish
- Lift machine room and overhead tank roofs
Our terrace waterproofing process
Inspection and diagnosis
We map leak points inside the top floor, check falls and outlets, sound the existing coba for hollowness and identify cracks, junction gaps and failed previous treatments.
Decide what stays and what goes
Sound coba can sometimes be retained and treated. Hollow, waterlogged or broken layers are removed back to a sound surface.
Surface preparation
Cleaning, crack filling with polymer mortar or sealant, repair of damaged concrete and formation of coving at parapets and upstands.
Falls and outlets
Screed is corrected where water ponds and outlets are opened up, cleaned and fitted with a proper collar so the membrane seals into them.
Waterproofing application
The specified primer and system are applied in the required number of coats or layers, with fabric reinforcement at junctions, cracks and outlets.
Water test and finish
A flood or ponding test is carried out where the slab allows, followed by the protective or reflective top coat, tiles or screed.
Materials and systems used
- Liquid polyurethane membranes
- Elastic, seamless and UV-stable grades for exposed terraces with movement and complex details.
- Acrylic elastomeric and heat-reflective coatings
- Light-coloured coatings for terraces that are mostly closed to foot traffic, helping to keep the roof cooler.
- Polymer-modified cementitious coatings
- Flexible two-component coatings used under tiles or screed and on sound substrates.
- Bituminous membranes
- APP or SBS sheets with protection screed or tiles, for large or heavily used terraces.
- Polyester or glass-fibre reinforcement fabric
- Embedded at junctions, cracks and outlets to strengthen the coating where movement is highest.
Products are selected from the approved specification. Coverage, thickness and curing follow the manufacturer's current data sheet.
Why professional waterproofing is important
Many terrace jobs fail within a couple of monsoons because a coating is painted over a wet, hollow or cracked base, or because parapets and outlets are left untreated. Water then travels under the new layer and comes out exactly where it did before.
A professional terrace job starts with checking what is underneath, fixes the falls and junctions first, and uses a system rated for UV exposure and the level of foot traffic. Done properly, it also protects the roof slab reinforcement, which in older Mumbai buildings is often the first structural element to show corrosion.
Why choose us
- Diagnosis before quotation
- We find out whether the problem is the coba, the junctions, the outlets or the slab itself before we price anything.
- No paint-over shortcuts
- We do not coat over hollow or waterlogged layers. Where retention is possible, we say so and explain why.
- Experience with society terraces
- We work around residents, water tanks and solar installations, and plan work to finish before the monsoon.
- Written method and records
- You receive the method statement, product details and inspection records for the society file.
Read more about our team and how we inspect and record work.
Frequently asked questions
What is the best waterproofing for a terrace in Mumbai?
For an exposed terrace with foot traffic, a UV-stable liquid polyurethane membrane with fabric reinforcement at junctions, or a bituminous membrane under a protection screed or tiles, gives the most durable result. For terraces that are mostly closed, an elastomeric heat-reflective coating over a sound, well-sloped base is a lower-cost option.
Before choosing, the falls, rainwater outlets, parapet junctions and the condition of any old brickbat coba must be checked, because a coating laid over a wet or hollow base will not last through the monsoon.
Should old brickbat coba be removed before terrace waterproofing?
Not always. If the coba is sound, well bonded and has proper falls, it can be cleaned, repaired and coated. If it sounds hollow, holds water or has lost its falls, removing it is usually the only lasting solution. We sound-test the surface during inspection.
What is the best season for terrace waterproofing in Mumbai?
October to May, when the slab is dry. Most systems need a dry substrate and dry weather for application and curing. Book the inspection early, because demand peaks in April and May.
Can you waterproof a terrace that has tiles?
Yes. Options include sealing and coating over sound tiles with a compatible system, or removing tiles and waterproofing the slab. The choice depends on tile condition, bonding and where the leaks originate.
How long does terrace waterproofing last?
Service life depends on the system, the substrate, maintenance and exposure. A properly applied PU or membrane system with protection lasts considerably longer than a single coat of paint-on coating. We explain the expected maintenance for the system we recommend rather than quoting a blanket guarantee.
Do you also treat the water tank on the terrace?
Yes. Leaks from overhead tanks and their supports often appear as terrace leaks. See our water tank waterproofing service.
