Wall Waterproofing

Damp walls are the most misdiagnosed problem in Pune buildings. The visible symptom — a patch, blistered paint, a white bloom, a musty smell — is nearly identical whatever the cause, and the four causes need four different treatments. Repainting is the standard response and it fails every year, because paint is not the problem. Leakproofs by Betterwork treats internal and external walls across Pune and Pimpri-Chinchwad, and the survey is designed to tell these apart before anything is specified.

Four causes, four different answers

• Lateral seepage. Rain driven against an external wall passes through porous plaster, cracks or failed pointing and emerges inside. Follows rainfall — worst during and just after the monsoon, dries out afterwards.
• Rising damp. Groundwater drawn up through the wall base by capillary action. Confined to the lower part of the wall, typically under a metre, with a fairly level tide mark, and it does not dry out in summer.
• Condensation. Warm humid air meeting a cold surface. Worst in unventilated corners, behind furniture and on north-facing walls; associated with black mould rather than salt.
• A leaking service. A concealed supply or drainage line. Localised, constant, and unrelated to weather.

The tests are simple. Does it track rainfall, or persist through a dry May? Is it at the base with a level line, or high on the wall? Is there efflorescence — salt crystals — or black mould? Salt indicates water moving through masonry; mould indicates surface condensation. Our diagnostic note covers this in full: rising damp versus seepage versus condensation.

Why treating the inside is usually the wrong instinct

The damp shows inside, so the temptation is to treat inside. But an internal coating on a wall being wetted from outside is negative-side work — water arrives at the back of the coating and pushes it off, exactly as it does in a basement. It also traps moisture inside the masonry, which accelerates salt damage to the plaster.

Where the cause is lateral seepage, the durable fix is on the external face: repair the cracks, make good the plaster, and apply a breathable water-repellent or an elastomeric exterior system that keeps liquid water out while letting vapour escape. Internal treatment is a fallback for walls with no external access — a shared party wall, a boundary wall built up against — and there it should be a system formulated for negative pressure, not ordinary damp-proof paint.

Breathability is the detail everyone gets wrong

A wall needs to dry. Sealing both faces with impermeable coatings traps moisture in the masonry, where it does more damage than the original seepage — plaster blows, salts crystallise inside the wall, and the failure reappears somewhere else along the same wall.

The correct exterior system resists liquid water while remaining vapour-permeable. This is why a cheap solvent-based sealer over a damp wall so often makes matters worse within two seasons, and why the sequence matters: fix the water entry, let the wall dry, then finish.

Cracks, and which ones matter

Not every crack needs the same response. Fine hairline crazing in plaster is cosmetic and a good elastomeric coating will bridge it. A crack that is straight, continuous, wider than about 2 mm, or that runs through the masonry rather than just the render is structural, and coating over it is concealment. Those are cut out, filled, and where movement is ongoing, treated as a joint rather than a defect. See joint treatment.

Rising damp: what actually works

Rising damp needs a barrier at the base of the wall, not a coating up it. That means a chemical damp-proof course — injected at close centres along the wall base to form a continuous barrier — followed by removal of the salt-contaminated plaster and re-plastering with a salt-resistant render. Skipping the re-plaster is why injected DPCs get a bad reputation: the barrier works, but the old plaster is loaded with hygroscopic salts that keep drawing moisture from the air and the wall keeps looking damp.

Efflorescence and paint failure

The white crystalline bloom on a damp wall is salt left behind as water evaporates. Brushing it off and repainting achieves nothing while water is still moving through the wall. Paint peeling, blistering or shedding in sheets is almost always a symptom of moisture behind the film rather than a defect in the paint — which is why the third repaint fails as quickly as the first. Background: efflorescence causes and treatment.

External walls on tall buildings

On a high wing the constraint is access. Rope access is faster and cheaper than scaffolding and is fine for coating and sealant work, but it cannot carry heavy preparation — hacking off failed plaster needs a platform. That decision changes the price materially and should be settled at survey, not on the first morning.

What we quote

Exterior wall treatment in Pune typically runs ₹60–150 per sq ft depending on the system and the amount of plaster repair, with chemical DPC priced per running foot of wall. Leakproofs by Betterwork surveys with thermal imaging and moisture metering to establish which of the four causes is actually operating, then prices the answer to that. Eligible completed work carries a written ten-year warranty on the treated area, with exclusions stated on the estimate before you approve it.