- Postcode district
- HA1
- Survey
- Free for new and replacement doors
- Typical lead time
- Typically 6–8 weeks for slimline systems after check survey sign-off
- Guide price
- From £5,095 inc VAT
- Nearby
- Pinner, Wembley, Ruislip
- Building rules
- England
Why choose sliding doors for extensions in Harrow?
Most homeowners choosing sliding doors for extensions want the same things: more light, a clear view and a door that is easy to live with.
Where an extension in Harrow faces south or west, ask about solar-control glass, because a wall of glass in a single-storey room can overheat in summer.
For a garden room at the bottom of a Harrow garden, think about access: large glass panels need a clear route from the road to the site.
- Agreeing a fitting date with your builder lets the extension be made weathertight on programme, so plastering and flooring can follow without waiting on the doors.
- A check survey once the opening is built means the door is made to the real dimensions, accounting for any small variation in the brickwork or blockwork.
- Garden rooms benefit from the same approach, with a door sized to the frame and a header designed to carry the roof without pressing down on the door.
Light and sun in Harrow
Sun angles matter for big glazed doors. Around Harrow, midday sun reaches about 62° in summer and drops to about 15° in winter. That low winter sun is free heat through south-facing glass; high summer sun is easier to shade with a roof overhang, and solar-control glass helps where there is none.
Guide prices for sliding doors for extensions in Harrow
These are guide prices for fitted doors, including VAT. They run from an entry-level system to a premium one at the same size; the survey confirms which suits your opening.
| Overall width | Typical panels | Guide price (fitted, inc VAT) |
|---|---|---|
| 2.4 m | 2 panels | £5,995–£7,295 |
| 3.0 m | 2 panels | £6,895–£8,395 |
| 3.6 m | 2 panels | £7,795–£9,495 |
See every size on the sliding doors for extensions page or try the guide price tool.
From survey to fitted door in Harrow
Nothing is ordered until you sign off the surveyed specification. The door is made from the finished opening sizes (typically 6–8 weeks for slimline systems after check survey sign-off), and fitting usually takes 1–2 days, scheduled to the build programme. If you are in Pinner or Wembley, the same process and prices apply.
Rules for sliding doors for extensions in England
Doors in an English extension go through the extension's Building Regulations approval. Under Approved Document L, the total area of windows, roof windows and doors is normally capped at 25% of the extension's floor area plus any openings the extension removes, unless your designer shows compensating improvements; the glass must be safety glazing under Approved Document K.
Specification choices for sliding doors for extensions in Harrow
- Flush threshold. A level floor from inside to out, with a drainage channel set into the patio.
- Solar-control glass. Coated glass for south- and west-facing extensions prone to summer overheating.
- Triple glazing. For low-energy extensions or north-facing walls, subject to panel size limits.
Questions about sliding doors for extensions in Harrow
Do you fit sliding doors for extensions in Harrow?
Yes. We survey and fit sliding doors for extensions in Harrow and across Greater London, including nearby Pinner and Wembley. Start with a guide price online or call us, and we will arrange a free survey for a new or replacement door.
What structural opening size should my builder leave for sliding doors?
Your builder should leave the structural opening size we give in writing for your chosen door, which is the frame size plus a small fitting tolerance on each side and at the head. The exact figure depends on the system and the threshold detail. We confirm it from your drawings early, then check the built opening before the door is made.
How do I get a level threshold in an extension?
A level or flush threshold in an extension needs the finished floor level inside to be set relative to the door sill and the outside paving before the screed goes down. Outside, a drainage channel is needed across the threshold so rain cannot run in. Our thresholds guide explains the options.
Why does the steel beam matter for sliding doors?
The steel beam above an extension's sliding door matters because every beam bends a little under load, and a large sliding door needs a straight, level head to run freely. If the engineer knows a wide slider will sit under the beam, they can design for low deflection. Too much movement can make panels stiff or bind.