Merton at a glance
- Postcode districts
- SM4, SW20, SW19, CR4
- Council area
- London Borough of Merton
- Building approval
- London Borough of Merton building control, or a registered building control approver
- Guide price region
- London (+20% on West Midlands rates)
What does a balcony or terrace in Merton need?
Balcony membranes in Merton wear out like any roof, but faster where they are exposed to foot traffic, furniture and planters. Once the topcoat has worn through or cracked around posts and edges, a full re-waterproofing usually lasts longer than repeated patching.
In a town like Merton, flat roofs are commonly found on kitchen extensions and roof terraces behind period houses or mansion blocks and purpose-built flats with large flat roofs. 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 Merton?
At London guide rates, a 12 m² balcony in a liquid-applied system including scaffold comes to £2,300–£3,900 including VAT. 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?
- Sealed details at doors, outlets, walls and balustrade posts
- Written workmanship guarantee, with approvals handled where needed
- Lifting and setting aside of existing paving or decking
- Strip-out of the failed membrane and deck repairs
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?
- Sutton · 3 mi
- Wandsworth · 4 mi
- Kingston upon Thames · 5 mi
- Croydon · 5 mi
- Lambeth · 5 mi
- Richmond upon Thames · 6 mi
Balconies and roof terraces in Merton: questions
Do you cover Merton?
Yes. Merton is part of our London coverage, including postcode districts SM4, SW20, SW19, CR4. 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 Merton?
Where the work needs approval it goes to London Borough of Merton 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 Merton?
£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.
What is an inverted roof terrace?
It is a terrace where the insulation sits above the waterproofing, held down by paving or ballast. The membrane stays protected and at a steadier temperature.