K.t. Joinery Limited

Not much, but not none. Wipe the frames a few times a year, lubricate hinges and locks annually, and keep the drainage channels along the bottom of the frame clear so water can't pool and find its way inside. There is no statutory annual service like a boiler needs.

Repair makes sense for a failed seal (misted double glazing), a worn handle or hinge, or a damaged lock on an otherwise sound frame — usually a straightforward swap. Replacement is the better value once frames are warped, draughty, rotten (on timber) or past roughly 20 to 25 years old, or when several units across the house have failed. Ask the installer to price both where it's borderline.

It's proof the window or door installation meets Building Regulations (thermal performance, safety glazing, ventilation) without a separate council building control sign-off. Without one, selling the property can mean paying for retrospective building control inspection or indemnity insurance, so keep the certificate with your house documents.

This directory holds 406 active window and glazing businesses across 47 towns in County Durham, all from the Companies House register. Bishop Auckland accounts for 28, among the county's busiest. About 42% of County Durham's registered window and glazing firms were incorporated in the last three years, so weigh incorporation date and FENSA/Certass registration, not just company age.