Bay Window Repair in Wellington

A bay is exposed on three faces instead of one, which means three times the weather and a set of corner joints that have to stay sealed for a century. On a Mount Victoria or Thorndon villa, or a Brooklyn or Island Bay bungalow, the bay usually faces the street and therefore the prevailing weather. That is why bays rot before the rest of the joinery does.

Corner joints are where bays leak

The vertical joints between the front pane and the returns are the weak point. Original detailing relied on paint and putty, and after decades of movement the joint opens. Water then runs down inside the mullion and comes out at the sill or into the wall below.

We open the joint, cut out the failed material, treat any soft timber and reseal. Sealing over the top of a joint without opening it traps water inside the mullion.

Sagging heads and settled bays

Some bays are cantilevered and not supported from below, and after a hundred years the head can sag enough to bind the sashes. That is a structural question rather than a glazing one, and we will say so.

What we can do is diagnose whether a sticking bay sash is the frame settling or simply the hardware and paint, which is far more often the case.

Double glazing a bay

Bays are excellent candidates for retrofitted double glazing because they are large, single glazed and face the weather. Each sash is machined for the unit and rebeaded, and the original glazing bars stay in place.

Weight is the thing to check. A large bay sash with a double glazed unit in it is considerably heavier, so cords, weights or stays get upgraded at the same time.

Bays, and why they fail first

Three faces of weather

A bay is exposed on three elevations instead of one and relies on vertical corner joints staying sealed for a century. When they open, water runs down inside the mullion and appears somewhere else entirely, often in the wall below rather than at the sill.

That is why a bay can look sound from outside while the framing behind it is wet.

Opening a joint properly

The failed sealant has to come out, the timber behind has to be checked and treated, and the joint has to be reformed before anything is resealed.

Running a bead over the top of a failed joint traps water inside the mullion where it cannot dry, and it is the most common bad repair we are called out to undo on a bay.

Bay Window Repair at a glance

Common faults

Rotten sill and mullion feet, open corner joints, sagging head

Leak repair

Joint opened, failed sealant removed, timber treated, resealed

Rot repair

Scarf repair into sound timber, profiles matched

Double glazing

Retrofit into existing sashes, hardware upgraded for weight

Character areas

Detailing matched for Thorndon and Mount Victoria heritage rules