Islington at a glance
- Postcode districts
- N1, N5, N7, EC1V, EC1R, EC1, EC1Y, EC1M and 3 more
- Council area
- London Borough of Islington
- Building approval
- London Borough of Islington building control, or a registered building control approver
- Guide price region
- London (+20% on West Midlands rates)
What does a balcony or terrace in Islington need?
Balconies in Islington 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.
Islington's flat roofs are mostly on mansion blocks and purpose-built flats with large flat roofs, with plenty on Victorian and Edwardian terraces with flat-roofed back additions 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 Islington?
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 |
How are thresholds, drainage and paving handled on a terrace?
They are designed together, because most balcony leaks start at the door threshold, a blocked outlet or a fixing driven through the membrane. Getting those three right matters more than the brand of membrane.
Thresholds: upstands are usually 150 mm above the finished surface, but a level or low step-out door cannot always achieve that. Where the upstand has to be reduced, extra protection is needed, such as a drainage channel at the door and a fall away from it, and the membrane must still run up and under the door sill.
Drainage: every terrace needs a reliable way off for water, with outlets sized for the area and an overflow if one outlet could block. Outlets under paving need access for cleaning.
Inverted roofs and pedestals: on an inverted roof the insulation sits above the waterproofing and is held down by paving or ballast, protecting the membrane from sun and foot traffic. Adjustable pedestals lift paving slabs level above the falls, so water drains underneath and the surface stays flat. Balustrade posts are fixed through upstands or side-fixed where possible, with every penetration sealed into the membrane.
What's included?
- Strip-out of the failed membrane and deck repairs
- 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
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 Islington: questions
Do you cover Islington?
Yes. Islington is part of our London coverage, including postcode districts N1, N5, N7, EC1V, EC1R, EC1 and 5 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 Islington?
Where the work needs approval it goes to London Borough of Islington 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 Islington?
£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 you waterproof a balcony without lifting the tiles?
Sometimes a liquid system can go over a sound, well-bonded surface, but if water is already getting under the tiles they usually have to come up.
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.