Replacing glass in doors may seem straightforward, but it is easy to get it wrong without the right experience. Poor installation affects more than just the appearance of your door. It can cause safety issues, reduce energy efficiency and lead to costly repairs.

Here are three of the most common mistakes made by inexperienced installers, and how to avoid them.

1. Choosing the wrong type of glass

Selecting the correct glass involves more than just measuring the size. Glass must meet specific safety, performance and building regulation standards, especially when used in doors.

Thickness matters

Many inexperienced installers assume all glass is the same, but doors typically require glass between 3mm and 6mm thick. Thinner panes may not withstand daily use, particularly in busy households or areas exposed to weather.

Safety glass is essential

UK building regulations require safety glass, such as toughened or laminated glass, to be used in doors and in any glazing within 800mm of a door opening. This includes both external and internal doors. Toughened glass is always required for internal doors where the glass is near a door, to reduce the risk of injury in case of breakage. Using standard annealed glass may seem cheaper but it significantly increases the risk of injury and does not comply with safety standards.

Poor thermal performance

Using single glazing in external doors can lead to condensation and heat loss. Double-glazed or energy-efficient units should always be considered for front and back doors to improve insulation and reduce energy bills.

2. Inadequate sealing or weatherproofing

Failing to properly seal a new glass pane is one of the fastest ways to shorten the life of a door. Moisture, draughts and even structural damage often begin with poor weatherproofing.

Using the wrong compounds or sealants

Different door materials require different products. For example, traditional timber doors may need linseed oil-based putty, whereas UPVC or composite doors often require specific silicone-based sealants. Using the wrong material can lead to leaks and failure of the seal.

Overlooking weatherstrips

A properly fitted weatherstrip around the glass helps block air and water ingress. Generic strips are often used as a one-size-fits-all solution, but they may not match the door’s design, leaving gaps and reducing effectiveness.

Ignoring drainage

External doors need appropriate drainage to direct water away from the frame. If drainage channels are missing or blocked, water can pool and damage wooden frames or compromise the integrity of sealed units.