Sash windows in Northwest London — the problems we get called about
Northwest London is layered: Edwardian terraces through Willesden and Cricklewood, conservation-area villas in Hampstead Garden Suburb, the older mansion blocks of St John's Wood and Maida Vale. Different periods, different rebates, same windows ageing the same way — draughts you can feel, paint flaking off the bottom of the cill, the sash sticking in its box.
We specialise in sympathetic restoration — traditional joinery alongside the modern bits that earn their keep. Twenty-five years on sash and casement frames, the last decade or so heavy across Brent, Camden, and Westminster's northern fringes.
What we see most often in Northwest London houses:
- Rotten window frames where rain has worked into the cill or the bottom of the stiles.
- Heat loss through single glazing — a typical U-value around 5.0 W/m²K, against a modern wall at ~0.3.
- Persistent draughts and rattling from worn parting beads and seals.
- External noise from the North Circular, the West Coast Main Line, and the trunk roads through Brent.
- Condensation buildup on cold internal glass, leading to staining and decay around the cill.
Restoring wooden windows in Northwest London
Ageing wooden windows in Northwest London homes often suffer draughts, wear, and inefficient insulation. We focus on sash and casement restoration and the upgrades that come with it — keeping the proportions, fixing the issues.
Draught excluder installation
Fitting tailored brush seals and excluders into the stiles, meeting rails, and cills. Closes the gaps cleanly; cold air stops walking in around the sash.
Wooden window sill repair
We splice-repair decayed cills and bottoms: cut out the rot back to sound wood, scarf in matched joinery, treat the surrounding timber, prime and paint. The cill is structurally the same cill, with a new section spliced in where the old one had failed.
Wooden window frame repair
The same approach across the rest of the frame — stiles, meeting rails, head. Matched joinery, splice in, prime and paint. We don't replace what we can save.
Double-glazing retrofit for Northwest London sash windows
Northwest London homeowners with traditional sash windows often face climbing energy bills, particularly the older mansion blocks on single glazing. Our retrofit service drops vacuum-insulated glass units into the existing sash frames. U-value at the glass falls from ~5.0 to ~0.7 W/m²K — triple-glazed thermal performance inside an 8 mm unit.
Retrofitting sash, casement, and bay windows
The retrofit applies across the period stock — sliding sashes, side-hung casements, multi-pane bays. Different mechanics, same principle: keep the timber frame, swap the glass, gain the thermal performance.
Our service area in Northwest London
The boroughs and neighbourhoods we cover across NW London:
For North London — Barnet, Enfield, Haringey, Highgate, Muswell Hill — see our North London page. Our home county is Hertfordshire.
Frequently asked questions
Is planning permission required for reglazing in listed properties?
In most cases, yes — listed building consent rather than planning. We handle the application, with the glazing specification chosen to meet conservation standards while preserving the historic appearance of the building.
What brands of vacuum glazing do you work with?
LandVac and FINEO are our usual specifications — both slim-profile, both with U-values in the 0.4–0.7 W/m²K range, both proven on heritage retrofits across Northwest London.
Does the retrofit also help with draught-proofing?
Yes. Sealing gaps and dropping in vacuum-insulated glass closes most of the cold-air paths through the window at the same pass. We almost always do draught-proofing alongside a retrofit because it's cheaper to do once.