French Casement Windows in Marylebone, London
Every french casement windows project we deliver in Marylebone starts with a senior surveyor on site — measuring, listening, and specifying to the character of Marylebone Village, Portman Estate and the wider London area. French casement windows with twin opening sashes and no central mullion — the widest clear opening in the range.
French Casement Windows designed around sash-heavy period stock, communal-window agreements and RBKC / Camden conservation planning.
Marylebone's Georgian townhouses off the High Street and the Portland-stone mansion blocks along Marylebone Road need timber-alike sightlines. We install throughout W1 and NW1 with drawings prepared for Westminster planners and managing agents.
SpecificationSix-chamber uPVC or thermally-broken aluminium profile · shoot-bolted centre meeting stile · argon-filled A+ glazing · Yale multi-point locking
Why Marylebone homeowners choose South East Windows & Doors.
Marylebone surveys, London experience
A senior surveyor visits every Marylebone project in person — no call-centre, no sub-contracted quoting. We understand sash-heavy period stock, communal-window agreements and RBKC / Camden conservation planning because we install across London every week.
Made-to-measure french casement windows
Every french casement windows we install in Marylebone is manufactured to the survey — not selected from a stock list. That's why the finish, sightlines and thresholds match the property.
Postcode-covered: NW1, W1
Weekly installs across NW1, W1 and the surrounding London area, with parking, protection and clean-down handled by our own crews. Insurance-backed 10-year guarantee on every french casement windows project.
What sets our french casement windows apart in Marylebone.
No Central Mullion
Both sashes meet on a shoot-bolted centre stile that opens with them — the aperture is completely clear when both are open, unlike a standard 2-light casement.
Widest Clear Opening
Up to 1.6m of clear width on a standard aperture — the widest opening on any hinged window we supply, and a compliant Doc B fire escape on habitable first-floor rooms.
Kitchen & Dining Room Favourite
The natural choice above a sink or over a garden view — throw both sides open and the view is uninterrupted.
Available in All Three Ranges
In uPVC, thermally-broken aluminium or heritage flush-casement — same principle, three material finishes to suit the property.
PAS 24 Secured Locking
Multi-point espagnolette locking on both sashes with shoot-bolts top and bottom — as secure as any single-sash casement, tested to PAS 24:2016.
Astragal & Georgian Bar Options
Full bar and glazing options — a French casement can carry the same period detailing as a fixed light of the same size.
What Marylebone homeowners tell us.
"Four quotes, one honest conversation. Their surveyor spent two hours explaining trade-offs — no other firm came close on either detail or clarity."
"Nine windows swapped across a Victorian first-floor flat. Zero mess, done in three days, and the acoustic laminate has genuinely changed how we sleep."
"The sliding sashes are indistinguishable from the originals — the conservation officer signed off first time. Immaculate site management too."
Common questions from Marylebone homeowners.
- Do you install french casement windows in Marylebone?
- Yes — South East Windows & Doors installs french casement windows across Marylebone (NW1, W1) and the wider London area every week. Every project is surveyed, manufactured and installed by our own teams.
- How long does french casement windows installation take in Marylebone?
- Most Marylebone projects run to a two-to-eight week lead time from signed quote to install, depending on manufacture. Once on site, a typical french casement windows install completes in one to five working days with full dust-sheet protection and clean-down.
- Do you handle conservation-area planning in Marylebone?
- Working across London means understanding period detail, party-wall etiquette and permit parking as well as we understand glass. We schedule dust sheets, protection and clean-down like a good building firm should. We prepare planning-ready drawings with matched sightlines, glazing-bar depths and hardware for Marylebone projects that require them.
- What guarantee covers french casement windows in Marylebone?
- Every french casement windows installation in Marylebone is covered by our insurance-backed 10-year guarantee — parts, labour and finish. Aftercare is direct with the installing team, not a call centre.
- Can I see recent french casement windows work near Marylebone?
- Yes — we can share recent french casement windows case studies from across London, including projects in Marylebone Village, Portman Estate and neighbouring towns. Ask your surveyor at the on-site visit.
- What thermal performance does french casement windows achieve in Marylebone?
- Energy-efficient french casement windows installed across Marylebone, London achieve whole-window U-values of 0.9–1.4 W/m²K, with the exact frame and glazing specification confirmed after survey.
- How is a French casement different from a normal 2-light casement?
- A normal 2-light casement has a fixed mullion between the two sashes — you always see the vertical bar. A French casement has no mullion; the two sashes meet on a movable centre stile that opens with them, so when both are open the aperture is completely clear.
- Are they secure without a central mullion?
- Yes — the meeting stile has shoot-bolts at the top and bottom that engage into the outer frame, and the active sash has multi-point espag locking. The whole assembly is tested to PAS 24 and provides the same security as a standard casement.
- Can I have Georgian bars on a French casement?
- Yes — astragal and Georgian bars in 18mm or 25mm, applied or through-frame, are available on both sashes and any fixed lights above. Popular on flush-casement French windows in period properties.
Also serving french casement windows near Marylebone.
Same french casement windows, same team — installed across neighbouring towns in London and beyond.
Related windows for Marylebone homes.
Book your Marylebone survey.
Tell us about your Marylebone project. A senior surveyor will call within one working day to arrange a free on-site visit and fixed quote for your french casement windows.