Installing a pet flap in glass is a common request from homeowners with cats or dogs, particularly where doors or windows are fully glazed. One of the most frequent questions is how long the process takes from the first visit through to completion.
Unlike fitting a pet flap into timber or uPVC, glass installations involve additional steps to ensure safety, durability, and compliance with UK glazing standards. This means the process takes longer overall, but it also results in a cleaner and more reliable finish.
This article explains how long it usually takes to install a pet flap in glass, what is involved at each stage, and why the timeline is different from other types of installation.
Glass cannot be altered once it has been toughened. Most modern doors and windows use toughened or double glazed glass, which means holes cannot be cut into the existing unit. Attempting to drill or cut into this type of glass will cause it to shatter.
Because of this, installing a pet flap in glass always involves replacing the existing glass panel with a new one that has been manufactured with a pre cut hole. This is why the installation process takes place over more than one stage rather than being completed on the same day.
The first step is a site visit to measure the existing glass accurately. Precise measurements are essential, as even small errors can result in the replacement glass not fitting correctly.
During this visit, the following will usually be checked:
The size and thickness of the existing glass
Whether the unit is double glazed or single glazed
The type of door or window the glass sits within
The most suitable position for the pet flap
The correct pet flap size for the animal
This visit usually takes between thirty minutes and one hour.
Once measurements have been taken, a new glass unit is ordered from a manufacturer. The hole for the pet flap is cut at the factory before the glass is toughened.
For double glazed units, the glass is sealed to ensure insulation and energy efficiency are maintained. This process cannot be rushed, as the glass must meet safety and performance standards.
Manufacturing typically takes seven to fourteen days, depending on supplier lead times and the specifications of the glass.
Once the replacement glass unit is ready, the installation itself is relatively quick.
On the day of installation, the existing glass is removed, the new glass unit is fitted, and the pet flap is installed and sealed. The flap is then checked to ensure it opens and closes smoothly and sits securely within the glass.
In most cases, this stage takes one to two hours.
No. Existing toughened or double glazed glass cannot be cut or drilled. Any attempt to do so will result in the glass breaking.
For this reason, fitting a pet flap into glass always requires a replacement glass unit with a factory cut hole.
When installed correctly using a professionally manufactured glass unit, a pet flap should not significantly affect insulation. Double glazed units are sealed to reduce heat loss, and the pet flap itself is fitted securely into the glass.
Many modern pet flaps include locking systems or microchip access to prevent unwanted entry.
Installing a flap in glass takes longer than installing one into other materials, but this is due to the safety and manufacturing requirements involved. From initial measuring to final installation, the process usually takes between ten and twenty one days, with the fitting itself completed in one to two hours.
Understanding the process helps set realistic expectations and ensures the installation is carried out safely and correctly.