Source of seepage
External wall
Monsoon rain driving through outer walls
How water travels
From the source to your wall.
Wind-driven monsoon rain soaks the outer face of brick or block walls. Hairline cracks in the external plaster, gaps at the junction between the RCC frame and the infill, and open joints around pipes and AC brackets let water in. It moves through the wall and shows on the inside face, most often on the side facing the prevailing monsoon wind.
When it shows: During and just after the monsoon, most on the side facing the prevailing wind.
The pattern it leaves
- Damp on the inside of external walls on the monsoon-facing side
- Diagonal or horizontal patches following the line of a beam or column where infill meets the frame
- Damp that appears during or after heavy rain and fades in the dry months
- Efflorescence and crumbling plaster in the same spots year after year
- Damp around where external pipes, AC brackets or cables pass through the wall
How it's confirmed
Meter, thermal, eyes.
- Meter readings across external walls compared with an internal dry reference wall
- Thermal scan showing cool areas at frame and infill junctions and around penetrations, with each one confirmed by the meter, because draughts through gaps can also create cool patches
- Visual check of the external face where it can be seen from windows, balconies or the ground: cracks, peeling external paint, and plant growth
- Comparing walls on the monsoon-facing side with the sheltered side
Who is usually responsible
It depends on where the water starts.
- Society or association
- Usually responsible for external walls as part of the building's structure and common areas, under the society's bye-laws, which vary.
- Builder (within defect period)
- In a new building, rain entry through external walls brought to the builder's notice within five years from the date of handing over possession falls under Section 14(3) of the RERA Act, 2016. Your state's rules may differ.
- Owner
- Usually responsible for openings they have made, such as new AC brackets or pipe holes, and for interior repairs.
Typical repair approach
What a fix usually involves.
Described for understanding, not as a recommendation. Megahedge does not do repairs or recommend contractors.
- 01Filling and sealing cracks in the external plaster, especially at frame and infill junctions
- 02Re-plastering badly cracked or hollow external plaster
- 03Applying an external water-repellent coating or exterior paint system suited to the wall
- 04Sealing around pipes, brackets and cable entries
- 05External work is usually done from scaffolding or a rope access setup in the dry season, then interiors repaired once dry
Questions buyers ask
Can I waterproof my external wall myself?
External walls in an apartment building usually belong to the society, so work on them generally needs its approval. Check your bye-laws, which vary.
Will interior waterproof paint help?
It does not stop rain coming in from outside, and it can trap moisture in the wall. The outer face needs to be fixed.
How do you tell rain entry from condensation on an external wall?
Rain entry usually reads wet into the plaster and follows cracks or junctions, worse after rain. Condensation sits on the surface, often in corners and behind furniture, with high room humidity. A meter and a hygrometer together usually separate them.
Find the damp before you pay for it.
Book a moisture and thermal inspection. Report on WhatsApp within 24 hours.