The Messy Silicone Mistake
Rainwater pooling on an internal timber window sill causes immediate panic.
Homeowners instantly blame the external perimeter silicone sealant. They smear thick, messy layers of fresh sealant all over the outside brickwork join. This extra silicone looks ugly and completely misses the root mechanical issue. The leak continues during the very next rainstorm because the water is coming from inside the frame itself.
The Hidden Plastic Trough
Double-glazed window frames do not form a completely waterproof barrier at the outer rubber seal.
Small amounts of heavy rain naturally bypass the external gaskets during a storm. This is a deliberate part of the window design. Every uPVC frame features an internal plastic collection trough engineered specifically to catch this tracking water before it reaches the house walls.
The Clogged Weep Holes
Small rectangular drainage slots sit at the bottom of the internal plastic track.
These hidden weep holes channel the trapped water straight out through the bottom of the external frame profile. Years of window usage fills this channel with dead flies, roof moss, and fine brick dust. This debris packs down into a solid plug, leading to a uPVC window frame drainage holes blocked situation. The trapped water has nowhere to go. It builds up inside the plastic trough and spills straight over the internal lip onto your timber window board, rotting the wood.
The Wire Clearing Method
Clear the internal path using a simple physical tool.
Open the window sash fully to expose the bottom track. Locate the small rectangular cutouts in the plastic floor. Push a thin piece of garden wire or a stiff plastic cable tie straight into the slot to break up the debris plug.
Rake the packed moss and dead flies out of the channel completely. Pour a small cup of clean water into the trough to verify the flow. The water must exit onto the external cill instantly. Check the external face of the frame to ensure the outer plastic weep hole covers are not clipped shut or painted over.
Trade Counter Advice
Stop wasting money on tubes of useless exterior silicone.
Pop down to 78 Alma Road to get the right advice on window maintenance. Our trade counter team can show you exactly where the hidden weep holes sit on different frame profiles. Call the team directly on 01202 533126 for trade assistance.
