Seepage around a window is almost never the glass. Six checks to run in May that save you a repaint in September.
Every July we take calls about water coming in around a window. In nearly every case the glass and the frame are fine — the failure is at a joint, a drain or a seal. All six of these checks take an afternoon.
1. Clear the drainage slots
Look along the bottom of the outer frame for small slots. They are the drainage path, and they clog with dust and insect nests. Push a thin wire through and flush with water. A blocked slot turns the track into a bathtub that eventually overflows inward.
2. Check the external sealant bead
Run a finger along the joint between frame and masonry. Silicone that has gone chalky, cracked or is peeling at an edge has stopped working. Cut it out completely and re-bead — do not lay fresh silicone over old.
3. Inspect the gaskets
Open each sash and look at the rubber. It should be soft and springy. Flattened, shiny or cracked gasket is no longer compressing, which is why the window whistles in wind. Gaskets are a replaceable part; ask for a service visit rather than living with it.
4. Test the drip groove above the opening
Externally, above the window, there should be a projection or a groove that throws water clear of the wall face. If a painter has filled it, water now runs down the wall and into the head joint.
5. Tighten and adjust the hardware
A sash that has dropped a few millimetres no longer compresses evenly along its length. Most hinges are three-dimensionally adjustable; half a turn brings it back square.
6. Look at the sill slope
The external sill must slope away from the building. Flat or back-sloping sills — usually a tiling error — pool water against the frame indefinitely.
If you have run these and water still comes in, book a service inspection. The cause is usually visible in fifteen minutes on site.
