It rains hard on a Tuesday night. By morning there is a damp streak under the bedroom window, a few drops on the sill, and a wet curtain edge. Dry spell, no problem. Next heavy shower, same spot. Most people wipe it up and wait. That is how a small gap turns into a stained wall, a swollen wooden frame and peeling paint.

We cannot diagnose a window from a description, and sometimes the water is not coming from the window at all. This guide helps you work out where it enters, using nothing but a torch and a few minutes after the next rain.

Why the gap around the frame is the weak spot

A window frame sits in an opening in the wall. The joint between frame and wall is sealed with sealant or mortar, and both age. Sealant can shrink, crack or peel from the frame edge. Mortar can crack where the frame and masonry expand and contract differently. In wind-driven rain, water is pushed sideways into any opening, so a gap that stays dry in straight rain can leak in a storm. That is why the problem looks occasional.

A ten-minute check

  1. Look at the joint around the frame, outside first. Check the sealant line for cracks, gaps, or sections lifting from the frame or the wall. Hairline cracks in the plaster running from the frame corners are common entry points.
  2. Check the sill. The outer sill should slope away from the window and have a drip edge or groove underneath so water drops off instead of running back to the wall. A flat or back-sloping sill holds water against the frame.
  3. Clear the track drain holes. Aluminium and uPVC sliding windows have small drain slots at the bottom of the outer track. If dust and paint block them, rain collects in the track and spills inside.
  4. Look above the window. A cracked lintel edge, missing drip groove or a blocked sunshade drain can send water down the face of the wall into the frame. Our guide on cracked sunshade slabs covers this.
  5. Test it. On a dry day, have someone pour water from a mug along the top of the frame and then the sides, one section at a time, while you watch inside. Wait a minute for each section. Note which one leaks.

Tip: photograph the damp patch and mark its edge in pencil with the date. If it grows after the next rain, you know the entry point is still open.

Window gap or something else?

Not every wet window is a window problem. A damp patch that appears under the sill but not at the frame edge can come from a crack in the wall above, a leaking pipe or a terrace issue higher up. If the stain sits well away from the frame, read our guide on seepage fixing before you buy sealant.

What to do first

  • Clear the drain slots in the window track with a thin brush or a stiff wire. It costs nothing and fixes more leaks than people expect.
  • Do not seal over wet or dirty joints. New sealant needs a clean, dry, dust-free surface. Sealing over wet plaster or an old failed bead can trap water and push the leak elsewhere.
  • Do not repaint yet. Stop the entry first, then let the wall dry fully. Our wall dryness test shows how to check.
  • Protect curtains and wooden frames. Wipe the sill after rain and keep an eye on swelling at the bottom of wooden frames.

Electrical safety. If water runs down near a switchboard, socket or light fitting, keep clear and have an electrician check it before using it again.

Where LoklFix fits

We trace where the water is entering and fix that: frame joint sealing, crack treatment around openings, sill and sunshade waterproofing, and external wall treatment. If the real cause is a plumbing line or a structural crack, we will tell you straight rather than sell you a coating. Related: efflorescence and peeling paint and wall seepage cost.

Window leaking every time it rains hard? Send photos on WhatsApp, or call +91-8123083393 for a free inspection this week.

Frequently asked questions

Why does water come in around my window only during heavy rain?+

Wind-driven rain pushes water into any gap between the window frame and the wall. If the sealant has cracked or shrunk, or the sill has no slope or drip edge, water finds the gap only in heavy or sideways rain, which is why the leak looks occasional.

Can I just apply silicone around the frame myself?+

A fresh bead can help if the old sealant is the only problem, but only on a clean, dry, dust-free joint. Sealing over wet plaster, an old failed bead or a blocked track drain can trap water and move the leak elsewhere.

Should I repaint the damp patch under the window first?+

No. Find and stop the entry point first, then let the wall dry fully. Paint over a wet wall peels and hides the source.