Leaking Double Glazed Windows Repaired in London

Water coming in at a window is worth sorting quickly, because it damages sills, plaster and flooring, and can lead to damp and mould. Double glazed windows and glazed doors are designed to let some water into the frame and then drain it straight back out. Leaks happen when that drainage is blocked, when seals and gaskets have worn, when the outside sealant has failed, or when a sash has dropped and no longer closes tight. Mark traces where the water is getting in and repairs the cause.

Drainage slots cleared and checked
Worn gaskets and sash seals replaced
Bifold and patio tracks, alignment and glass
Fixed price confirmed before any work starts
Send a photo or call

The most common cause of a window leaking at the bottom is blocked drainage. uPVC and aluminium frames have small slots along the bottom outer edge, often covered by little flaps. Rain that gets past the outer seal runs down into the frame and out through these slots. When they fill with dirt, insects or old sealant, the water has nowhere to go and overflows inside, usually at the bottom corners. Clearing and testing the drainage is often all a leak needs.

Worn gaskets let water past the glass. If the rubber round the glass has shrunk at the corners, rain driven against the window can track in along the edge of the sealed unit. Replacing the gaskets cures it. Worn or flattened sash seals let water in round the opening part when wind drives rain at the window. A sash that has dropped on its hinges won't press evenly into its seals, so it may leak along one edge; realigning or rehinging fixes that.

Some leaks come in around the frame rather than through it. Cracked or missing sealant between the frame and the wall lets water run behind the frame and show up on the inside reveal or under the sill. Resealing the outside perimeter stops it. A cracked glazing bead can also let water in at the edge of the glass, and is replaced with a new one.

Glazed doors leak in the same ways, plus at the threshold. Patio and bifold tracks have their own drainage that can block, and worn threshold seals let water in at floor level. Our guide to water leaking through a window covers what you can check yourself, and window seal and gasket replacement explains the seal work in more detail.

It helps to note when the leak appears. Water that only comes in during driving rain from one direction often points to a seal or drainage fault on that side. Water that appears in any rain, or runs down the wall below the window, is more likely to be the outside sealant or the sill. Those details, with a photo, make the visit quicker.

How the repair works

1. Describe the leak Where does the water appear, and in what weather? Photos of the frame and sill help.
2. Find the cause Mark checks drainage, seals, sealant and alignment, then confirms a fixed price before work starts.
3. Repair and test The cause is fixed and, where possible, tested with water so you know it's sorted.

Frequently asked questions

Why is water coming in at the bottom of my window?

Usually the drainage slots in the bottom of the frame are blocked, so rain that gets into the frame can't drain out. Worn seals and a dropped sash are the other common causes.

Can a leaking double glazed window be repaired?

Yes. Most leaks come from blocked drainage, worn gaskets, failed sealant or poor alignment, all of which can be repaired without replacing the window.

Is the water coming through the glass?

Almost never through the glass itself. It gets in around the edge of the glass, through the frame drainage, or round the outside of the frame where it meets the wall.