How double glazing installation works

Double glazing installation follows the same path whoever you use: a survey to measure every opening, a few weeks while the windows are made, one to three days of fitting, then a certificate and guarantee in the post. Knowing each stage helps you spot a firm that cuts corners, and tells you what to check before you pay the balance.

The survey

After you accept a quote, a surveyor visits to measure each opening exactly. Windows are made to measure, so this is the most important visit of the whole job. Use it to agree, in writing:

• which way each sash opens, and which windows need fire-escape hinges;
• where trickle vents go, if the old windows had them;
• which panes need toughened or laminated glass;
• the frame colour inside and out, and the handles;
• what happens if they find rot, a cracked lintel or a bay that needs propping.

Ask for the survey details in writing, and check them against the quote. Any change in price should be explained now, not on fitting day.

Manufacture

The windows are made to the survey sizes, usually within a few weeks. uPVC is often quickest. Aluminium, timber and unusual colours can take longer. Meanwhile, clear the area around each window inside, and think about blinds and curtain poles, which come down for fitting.

Double glazing installation day

A typical team of two fits several windows a day, so a three-bedroom house takes one to three days. For each window, the fitters:

1. remove the old sash and frame, cutting it out if necessary;
2. check the opening, and repair the sill or lintel if needed;
3. fix the new frame into the wall, level and square, with packers and fixings;
4. glaze the sashes and adjust them so they open and lock smoothly;
5. seal the frame inside and out, and fit trims or cills;
6. make good the plaster and tidy up.

Good firms work one room at a time, so the house is never left open, and they protect floors and furniture. In addition, they take the old windows away.

Before the fitters leave

Walk round with them and check every window:

• each one opens, closes and locks without force;
• the seals are continuous, with no gaps at the corners;
• the glass and frames are clean and undamaged;
• the trickle vents work;
• the inside reveals are made good as agreed.

Note anything wrong in writing and agree a date to fix it. Don’t pay the balance until the snags are sorted.

After installation

The installer registers the work with the council through FENSA or CERTASS, and you receive the FENSA certificate by post within a few weeks. The guarantee, ideally insurance-backed, arrives separately. Keep both with your house deeds.

How long the whole job takes

From accepting a quote to the certificate arriving usually takes one to two months. Most of that is manufacture. The disruption at home is short: a day or two for most houses, a little longer for a large house, sash windows or a bay.

If something goes wrong

If a window leaks, sticks or mists up, contact the installer first and put the complaint in writing. Your consumer rights require the work to be done with reasonable care and skill. The Planning Portal explains what the work has to meet. For typical prices, see uPVC windows, then get quotes.