Window Fitter
UK& Surrounding Area

Sliding patio doors in UK cost between £800 and £2,000 fitted, depending on the width, frame material and glass specification. Bi-fold doors are more expensive, typically £1,500 to £4,000 for a three-panel set. All patio door installations must comply with building regulations, and a FENSA-registered fitter will handle the certification for you.

Condensation between the panes means the sealed unit has failed — the airtight seal has broken, allowing moisture inside. This cannot be repaired; the glass unit needs replacing. The good news is that you usually only need to replace the glass unit, not the entire window frame. A replacement sealed unit typically costs £80 to £200 per window depending on size.

Look for FENSA or CERTASS registration, which confirms they can self-certify building regulations compliance. Membership of the Glass and Glazing Federation (GGF) is an additional quality mark. Check that they carry public liability insurance of at least £2 million and ask for references from recent local installations. Avoid any fitter who cannot provide a registered scheme number.

Bay window replacements in UK typically cost between £800 and £1,500 depending on the number of panels, frame material and whether the bay structure itself needs repair. A three-panel bay in UPVC with A-rated double glazing sits around £1,000 to £1,200. If the bay roof or supports need work, expect additional costs of £300 to £800.

In most cases, no — replacing windows like-for-like does not require planning permission. However, if your property is in a conservation area or is a listed building, you may need approval before changing window styles, materials or colours. Ground-floor windows must also meet building regulations for fire escape requirements. Your FENSA-registered fitter should advise you on any restrictions.

Yes, modern replacement windows come with significant security improvements over older designs. Look for windows with multi-point locking mechanisms, internal beading (glass fitted from inside so it cannot be removed from outside), anti-lever hinges, and laminated or toughened glass. Secured by Design accredited windows meet police-approved standards for burglary resistance.