Living with it · 23 Oct 2026 · 4 min read
Your first monsoon in a new flat: what to watch
The first monsoon is the real test of a new flat's waterproofing. What to watch room by room, how to record it, and why it matters for your defect window.
A new flat handed over in the dry months has not yet been tested by rain while you are living in it. Bathroom waterproofing, window sealing, terrace coating and external plaster all get their first real trial in the monsoon. Whatever shows up in those months is the most useful evidence you will ever have, because it is still early in the builder's defect liability window.
Before the rain starts
- Take dated photos of every wall and ceiling in the flat, especially walls behind bathrooms, external walls and ceilings. These are your baseline.
- Clear the balcony and utility drains and check the floor slopes towards them.
- Check window weep holes are open and sliding tracks are clean.
- Note your possession date and work out your window with the defect liability deadline calculator.
- Move wardrobes and heavy furniture a few centimetres off the external walls if you can.
What to watch, room by room
| Where | What to look for | Likely source |
|---|---|---|
| Ceilings, top-floor flats | Patches near the edges after heavy rain | Terrace |
| External walls | Damp patches, bubbling paint, especially on the rain-facing side | External wall plaster or cracks |
| Below windows | Wet sills inside, stains running down from the corners | Window frames and sills |
| Walls behind bathrooms | Damp at skirting, swelling at door frames | Bathroom waterproofing or grout |
| Ceilings below the bathroom above | Rings, drips, rust stains | Bathroom floor of the flat above |
| Balconies | Water standing, or running into the room | Floor slope or drain |
The pattern tells you a lot. A patch that appears during or right after heavy rain points to the outside of the building: the terrace, the external wall or a window. A patch that grows regardless of the weather points to plumbing or a bathroom. A patch that appears a day or two after rain and then fades slowly is often water working its way through a wall or slab, and is worth watching closely through the next few spells of rain.
How to record what you see
- Photograph each patch the day you notice it, and again every week, from the same spot.
- Note the date, the weather in the days before, and whether the patch is growing.
- Keep a simple log: room, location, date first seen, what it looked like.
- If water is coming in, record it on video with the date visible.
Send the builder a written notice as soon as you see a defect, even mid-monsoon. Under Section 14(3) of the RERA Act, 2016, defects notified within five years from the date of handing over possession should be rectified without further charge within 30 days. A repair attempted during heavy rain may not hold, so ask the builder to record the defect now and confirm a repair date once the weather allows.
What not to do in the first monsoon
- Do not repaint a patch. You remove the evidence and the paint will not hold.
- Do not let a contractor open up a wall or floor before the builder has seen it, if it is within the defect period.
- Do not seal a balcony drain or window weep hole to stop water. It will find another way in.
If you are away
Many buyers, and most NRI buyers, are not in the flat for the first monsoon. A relative can take weekly photos, but small changes are easy to miss and a leak under the kitchen sink can run for days. Humidity sensors on the walls of most concern and leak sensors under sinks give you a record with dates without anyone being there. See NRI buyers for how remote buyers handle this.
After the monsoon, compare your photos with your baseline. Anything that changed is worth a written notice to the builder, even if it has dried out by October.
Monsoon Watch rents you humidity and leak sensors with WhatsApp alerts for the season, followed by a post-monsoon re-scan.
Find the damp before you pay for it.
Book a moisture and thermal inspection. Report on WhatsApp within 24 hours.