Replacing the windows in an existing home

Sales visits and surveys are not the same thing. The sales visit produces a price; the survey measures each opening precisely, checks the brickwork, the lintel above and the sill below, and confirms which way each window opens. Frames are made to those measurements, so mistakes at this stage are expensive to put right.

Use the survey to settle details that are hard to change later: which sashes open and which are fixed, the height of handles for children, restrictors on upstairs windows, obscure glass in bathrooms, and whether old sills are kept or replaced. If a window is being made smaller or larger, that is an alteration, not just a replacement, and may need a lintel or planning advice.

Upstairs, some windows are fire escape routes. The Planning Portal says a replacement must give at least the same potential for escape as the window it replaces. Where an escape window is needed, the guidance sets a clear openable area of at least 0.33 square metres, a minimum width and height of 450 millimetres, and the bottom of the opening no more than 1100 millimetres above the floor. Escape hinges on side-hung casements help achieve this.

Ventilation is the other easily lost detail. If the old windows had background ventilators, the new ones should not leave the room with less. Homes that go from draughty single glazing to tight double glazing without trickle vents or extract fans often develop condensation and mould within a winter, especially in bedrooms and bathrooms.

Most houses are done a few windows at a time, so each room is open to the weather only briefly. The installer removes the old frame, fits the new one on packers so it sits square, fixes it into the reveals, seals the joint, and fits the internal trims or cills. Removing old frames can damage plaster; the quote should say whether making good means filling and trims, or plastering and redecoration.

Timber windows removed from an older house are sometimes set into lime mortar and the reveals can be fragile. In cavity walls, the gap between the frame and the cavity should be closed properly so heat and water do not track round the frame. Ask how the installer deals with both.

A contract signed at your home or at a distance generally carries a 14-day cancellation period for services, but the law excludes goods made to your specifications. Window contracts combine both, so read the cancellation clause before signing and ask when manufacturing starts. A company that pushes for a signature on the first visit with a discount that expires tonight is telling you something.

Keep deposits modest until the survey has confirmed sizes, and ask whether the deposit and the guarantee are insured if the company stops trading. Some competent person schemes offer insurance-backed guarantees; the company should say which applies.

Replacement windows are controlled fittings. If the installer is registered with a competent person scheme such as FENSA or CERTASS, it notifies the work and GOV.UK says you should receive a certificate within 8 weeks of completion. If it is not registered, Building Control has to approve the work, and FENSA points out that it is the homeowner's responsibility to make sure the installation is registered, so agree in writing who applies and who pays the fee.

Ask also for the product details and energy rating of each window, the glazing specification, and the guarantee documents for frames, sealed units and installation.

• a window schedule: size, style, opening and glazing for each opening
• escape windows, restrictors, trickle vents and obscure glass marked
• removal of old frames, disposal and the extent of making good
• certificate route: competent person scheme or Building Control
• payment stages, deposit amount and deposit protection
• lead time and the number of fitting days

Source: gov.uk

Window companies in your area see what you need, but not your name or contact details. The first company to buy the request is the only one that gets it, and it pays Offrano for it; you pay nothing. Before it sees your details, we email you its name, address and phone number.

We cannot promise that a company takes the request, and unsold requests are withdrawn after 21 days. You may turn the quote down. Offrano checks that buyers are registered businesses, not their installations, so look the company up on the FENSA or CERTASS register before signing.