Weatherproof windows

Weatherproofing & durability

British weather is the real test of a window. Wind-driven rain, damp winters and the constant cycle of warming and cooling will find any weakness a frame has — and a window that shrugs all of it off for decades is never an accident. It is the sum of good design, the right exposure rating, working drainage and, above all, a proper fit.

Where weather gets in

Water and draughts rarely come through the glass; they come through the joints. The usual routes are the perished weather seal around the opening sash, the mastic joint between the frame and the wall, and blocked drainage that leaves rain standing where it should run away. Each is fixable, and each is worth understanding before you assume a window is beyond help. Draughts in particular are often a seal or hardware issue rather than a frame one.

Drainage: the detail that saves the window

Look along the bottom of any modern frame and you will find small slots — the drainage, or “weep”, holes. Their job is to carry away the water that inevitably finds its way in, before it can sit against the sealed unit and shorten its life. Keeping them clear is the single most valuable habit in our window maintenance schedule, and it is why a poorly drained window fails years before a well-drained one.

Exposure and the right specification

Not every window faces the same weather. A sheltered inner-city elevation asks far less of a frame than a coastal gable or an exposed hillside home, where wind-driven rain is relentless. Windows carry weather ratings for exactly this reason, and a good installer will specify to your exposure — a heavier gasket, better drainage, a tougher finish. If you are weighing which frame copes best where you live, our comparison of window material lifespan is the place to start, and you can see the options in this overview of window styles compared.

Fit is everything

The best window in the country will leak if it is fitted badly. A square, level, properly sealed and drained installation by a registered fitter is what turns a durable product into a durable window. Condensation and damp on the reveals often trace back not to the window but to how it was bedded into the wall. When you come to price the work, compare local installers and ask specifically about how they weatherproof and drain the opening. For the wider question of when weathering has gone too far to cure, see our hub on when to replace your windows.