Professional Installation Makes Windows Last Longer
Retrofit or full-frame replacement, sealing, packing and checks: why the quality of installation matters as much as the window itself.
People like to compare windows on Uw values or glazing specs. Yet many problems found after the work come from the installation: leaks, draughts, sashes that rub. A professional installation protects your investment.
Two main installation methods
Retrofit installation
The new window is fitted over the existing frame, which is kept. It is quick and clean, with no masonry work. On the other hand, some glass area is lost and the old frame must be sound.
Full-frame replacement
The old window is removed entirely, frame included. You regain the full glass area and start from a sound substrate, but more masonry and finishing work is needed.
A serious professional recommends the right method after checking the condition of the old frames.
The steps of a careful installation
- Accurate survey of dimensions and substrate.
- Packing at the fixing points to keep the window plumb and square.
- Fixing suited to the substrate: brackets or screws, in sufficient number.
- Continuous sealing between frame and masonry: watertight outside, airtight inside.
- Sash adjustment and closing checks.
- Finishing: trims, cover strips, sills and render repairs.
In France these rules are set out in DTU 36.5, the reference for window installation.
Consequences of poor installation
- Water ingress at the base of the window in driving rain.
- Cold bridges and condensation around the frame.
- Gradual distortion if packing is insufficient.
- Acoustic performance far below what was advertised.
Guarantees
A professional installer is bound by statutory guarantees (completion, proper functioning and, where applicable, the ten-year guarantee). Ask for proof of insurance. To qualify for energy-renovation grants in France, they must also be RGE certified.
Key takeaway
A premium window poorly fitted will perform worse than a decent window perfectly fitted. When comparing quotes, look at the installation details as closely as the product price.