Kensington and Chelsea at a glance
- Postcode districts
- W8, SW5, SW7, W11, SW10, SW3, W10
- Council area
- Royal Borough of Kensington and Chelsea
- Building approval
- Royal Borough of Kensington and Chelsea building control, or a registered building control approver
- Guide price region
- London (+20% on West Midlands rates)
What does a balcony or terrace in Kensington and Chelsea need?
Door thresholds are a common reason for balcony work in Kensington and Chelsea. Where a door was fitted with a low step-out and no drainage channel, water driven against the frame finds its way under the sill. Re-waterproofing gives the chance to rebuild that detail properly.
In and around Kensington and Chelsea, flat roofs are typically found on Victorian and Edwardian terraces with flat-roofed back additions, and on shops with flat-roofed stores below flats above. The Thames basin is one of the drier parts of Britain at roughly 730 mm of rain a year, but summer heat is the bigger test here: dark membranes on south-facing roofs swing a long way in temperature.
How much does balcony or terrace waterproofing cost in Kensington and Chelsea?
For Kensington and Chelsea we use London rates: £2,300–£3,900 is the guide for a 12 m² balcony in a liquid-applied system including scaffold, VAT included. The fixed price comes after a free survey for new and replacement roofs.
| Job | Guide price inc VAT |
|---|---|
| Balcony (12 m²), liquid-applied, scaffold | £2,300–£3,900 |
| Single garage (18 m²), EPDM rubber | £1,900–£3,350 |
| Extension (20 m²), GRP, new deck + insulation | £3,600–£6,450 |
Which waterproofing system is best for a balcony?
For most small balconies, a liquid-applied membrane is the practical choice, because it is brushed or rolled on and forms one continuous layer around posts, door frames and outlets with no seams to fail. Many systems include a hard-wearing, anti-slip topcoat.
GRP fibreglass gives a rigid, walkable surface and suits balconies left exposed rather than paved. On larger roof terraces under paving or decking, single-ply membranes are common, and mastic asphalt has a long record on concrete terraces and blocks of flats.
The choice also depends on what goes on top. Paving on pedestals protects the membrane, while an exposed balcony needs a system rated for foot traffic in its own right. We specify the build-up at survey.
What's included?
- Lifting and setting aside of existing paving or decking
- Sealed details at doors, outlets, walls and balustrade posts
- Strip-out of the failed membrane and deck repairs
- Written workmanship guarantee, with approvals handled where needed
Building regulations in England
Replacing more than half of a flat roof over a heated room usually counts as renovating a thermal element, so the roof is insulated to around 0.16 W/m²K where that's technically and economically feasible, and the work is notified to building control: the council or a registered building control approver, unless a registered competent person self-certifies it. A roof on a new extension is built to 0.15 W/m²K. Patch repairs, and most unheated detached garages, don't trigger the upgrade. Structural changes, or a new covering that adds 15% or more to the roof's weight, also need approval. More on the rules.
Which nearby areas do we also cover?
- Hammersmith and Fulham · 1 mi
- Westminster · 2 mi
- Camden · 3 mi
- Wandsworth · 3 mi
- Lambeth · 4 mi
- Islington · 5 mi
Balconies and roof terraces in Kensington and Chelsea: questions
Do you cover Kensington and Chelsea?
Yes. Kensington and Chelsea is part of our London coverage, including postcode districts W8, SW5, SW7, W11, SW10, SW3 and 1 more. Surveys and roofs are carried out by vetted roofing teams working under S&K Property Investments and Improvement Ltd.
Who checks building regulations for a flat roof in Kensington and Chelsea?
Where the work needs approval it goes to Royal Borough of Kensington and Chelsea building control, or a registered building control approver. We tell you at the survey whether your job needs it and deal with the paperwork as part of the quote.
How much does balcony or terrace waterproofing cost in Kensington and Chelsea?
£2,300–£3,900 for a 12 m² balcony in a liquid-applied system including scaffold, at London guide rates including VAT. The fixed price comes after a free survey for new and replacement roofs.
How long does balcony waterproofing last?
It depends on the system and how well it is protected. As indicative ranges, liquid-applied systems last 10–25+ years by product and mastic asphalt 30–60, with good maintenance.
Why is water coming through the ceiling below my balcony?
The usual causes are a failed door threshold, a blocked or poorly sealed outlet, or a fixing through the membrane. A survey, sometimes lifting paving, finds the source.