Window Repair in London: When to Fix or Replace Your Windows

When moisture appears between your window panes, it signals a broken seal. This condensation traps water vapour inside the sealed unit and, while it doesn't affect window function immediately, it does reduce insulation and visibility. In London's damp climate, this problem is especially common in older double-glazed windows installed 15–20 years ago.

Repair costs typically range from £150–£400 per window, depending on frame type and accessibility. The technician will remove the sealed unit and replace it with a new one, preserving your existing frame. However, if your window frames are also deteriorating, a full replacement (£400–£1,200 per window) may offer better long-term value. Most repair jobs take 1–2 hours per window, and results are immediately visible.

Sash windows are iconic in London properties, but paint build-up, warped wood, and degraded pulleys often cause them to jam. Wooden sashes stuck in the down position are frustrating and reduce ventilation; metal-framed sliders accumulate dirt in their tracks and become difficult to operate.

A sash window repair typically costs £80–£250 and involves cleaning tracks, lubricating mechanisms, replacing worn cords or springs, and sometimes carefully scraping old paint. If pulleys are broken, add £40–£100 per pulley. For severe warping or cracked wood, the sash itself may need replacement (£200–£500 per sash). This is almost always cheaper than replacing the entire window frame, which can exceed £1,500 in period properties.

Rotting window frames are common in London's wet climate, especially around wooden sills and mullions exposed to rain. If rot is caught early—when it affects only the outer inch or two of wood—specialist repair contractors can cut out the damaged section and splice in new timber, then re-seal and repaint. Early-stage frame rot repair costs £120–£350 per window.

However, if rot has penetrated the core structural timber, repair becomes unreliable and replacement is the safer choice. Signs of advanced rot include soft wood that crumbles under pressure, significant pest damage, or frame movement. A full window replacement in this case (£600–£1,800 per opening) prevents future water ingress and protects your building's integrity. Have a surveyor assess the extent before committing to repair.

Damaged handles, hinges, locks, and stays are among the quickest and cheapest window repairs. A broken casement hinge might cost £15–£50 in parts plus £40–£100 in labour. Window locks and security hardware typically cost £20–£80 to replace. Even tilt-and-turn mechanisms, which sound complex, usually cost £60–£150 to repair or replace.

These repairs are worthwhile at almost any window age, as they restore functionality and security without touching the frame or glass. Most hardware issues can be fixed within 30–60 minutes. If your window otherwise performs well, replacing a single component is a smart investment.

In London, the rule of thumb is: if repair costs exceed 50% of replacement cost, or if your window is over 20 years old and requires multiple repairs, replacement often makes better financial sense.

A single foggy-glass repair (£200) is sensible. But if the same window also has a rotting frame and broken hinges, total repair costs might reach £500–£600, creeping towards a replacement at £700–£1,000. Factor in energy savings too—modern windows with A-rated glazing reduce heating bills by 10–15%, which pays back the investment over 10–15 years, especially in older London properties with poor insulation.

Consider your timeline: repair is faster (1–2 days), replacement is slower (3–7 days depending on frame type). If you're selling soon, a targeted repair may suffice; for long-term occupation, replacement often delivers better ROI and peace of mind.

Getting multiple quotes is essential because repair feasibility and cost vary widely depending on your window type, frame material, and the surveyor's assessment. ProvenQuote connects you with vetted, local window repair specialists who visit your London property, diagnose problems on-site, and provide transparent fixed quotes within 24–48 hours.

When requesting a quote, mention the window type (timber sash, uPVC casement, metal-framed, etc.), the specific problem, and whether you're flexible on repair vs replacement. Reputable contractors will never pressure you into replacement—they'll explain the pros and cons of each option. Always ask about guarantees (typically 5–10 years for sealed units, 3–5 years for labour) and whether they're insured and trading standards registered.