Roof slabs · Sri Lanka
A leaking concrete slab does not get better with time. Water tracks along the reinforcement, stains the ceiling below and eventually corrodes the steel. This guide explains what drives the cost of slab waterproofing in Sri Lanka and which system suits your roof.
4
Membrane systems
2 coats
With mesh where specified
Flood test
Before it is covered
From above
Where water enters
Why slabs leak in the first place
Good waterproofing deals with the cause as well as covering the surface. Click a numbered point to see where leaks start and what we do about each one. A slab that never had waterproofing at construction gets a full membrane system.
Concrete shrinks as it cures, leaving fine cracks that open further with heat and movement.
How we deal with it
Cracks are repaired during preparation, then a crack-bridging flexible membrane goes over the whole slab.
What slab waterproofing costs
Two slabs of the same size can cost very different amounts to waterproof. The rate you are quoted depends on five things, and we put each in writing. For the wider picture, see waterproofing price in Sri Lanka.
Cementitious membranes cost less than polyurea.
Cracks, ponding areas and failed old membranes need repair or removal.
Upstands, drains, pipe penetrations and parapet junctions take the most time.
A roof that will be tiled over needs a different system from one left exposed to sun.
Larger, easier roofs cost less per square foot.
Systems we use
| System | Type | Best for |
|---|---|---|
| Mapelastic Smart | Two-component flexible cementitious mortar, 2 mm film, bridges cracks up to 2 mm | Terraces, balconies, bathrooms, water tanks |
| Mapelastic High Flex | Highly flexible cementitious membrane, crack bridging over 2 mm | Slabs prone to movement and cracking, irregular surfaces |
| Planiseal 288 Plus | Cementitious coating | Below-ground structures, lift pits, tanks, small exposed areas |
| Purtop HA N | Polyurea membrane | Large exposed roofs needing fast, seamless coverage |
Our method
We pond the slab before anything covers the membrane, so you see it hold water before tiles or screed go over it.
01
We find where the water enters, not just where it shows.
02
Cleaning, removing loose material and repairing cracks.
03
Fillets at wall junctions and reinforcement at drains and penetrations.
04
Applied in two coats with reinforcing mesh where specified.
05
The slab is ponded to prove it is watertight.
06
Screed, tiles or a reflective topcoat over the membrane.
Our waterproofing contractors in Colombo page covers the team; for the service in Colombo, see roof waterproofing in Colombo.
The best time to waterproof
Membranes need a dry slab and dry weather to cure properly, so plan the work in the dry months rather than after the first leak. Read more on waterproofing before the monsoon.
Already leaking?
Book the inspection now. Leak tracing and preparation can start while you wait for a dry spell, so the membrane goes down as soon as the weather allows.
Shop the membranes
Our work
Waterproofing, finishes and materials delivered for landmark residential and commercial developments across Colombo.
Assurance
ISO 9001:2015Quality Management System · Certified
CCI Sri LankaChamber of Construction Industry · MemberGood to know
Floors, waterproofing and care guides
We trace where water enters, recommend the membrane and quote it in writing.
Stopped at the surface, where the water gets in.
Mapelastic High Flex
26 kg set
LKR 0
Residential · Colombo 03
