Barnet at a glance
- Postcode districts
- N20, N11, N14, N12, EN4, N3, EN5, NW7 and 1 more
- Council area
- London Borough of Barnet
- Building approval
- London Borough of Barnet building control, or a registered building control approver
- Guide price region
- London (+20% on West Midlands rates)
What does a balcony or terrace in Barnet need?
Balconies in Barnet are often re-waterproofed when the ceiling below starts to stain. On many older balconies, the membrane was laid under tiles or screed with no way to inspect it, so by the time the leak appears, water may have been tracking under the surface for a long time.
Barnet's flat roofs are mostly on shops with flat-roofed stores below flats above, with plenty on mansard and dormer loft conversions too. 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 Barnet?
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?
- Written workmanship guarantee, with approvals handled where needed
- New liquid, GRP, single-ply or asphalt waterproofing
- Sealed details at doors, outlets, walls and balustrade posts
- 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?
Balconies and roof terraces in Barnet: questions
Do you cover Barnet?
Yes. Barnet is part of our London coverage, including postcode districts N20, N11, N14, N12, EN4, N3 and 3 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 Barnet?
Where the work needs approval it goes to London Borough of Barnet 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 Barnet?
£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.
Can I put decking straight onto my flat roof?
Not directly onto the membrane. Decking needs a supporting system that spreads the load and lets water drain, and the roof must be checked for the extra weight.
Is a roof terrace heavier than a normal flat roof?
Yes. Paving, people, planters and furniture all add load, so a structural engineer should confirm the roof can carry it before a terrace is formed.