Southwark at a glance
- Postcode districts
- SE5, SE15, SE17, SE22, SE14, SE11, SE1, SE8
- Council area
- London Borough of Southwark
- Building approval
- London Borough of Southwark building control, or a registered building control approver
- Guide price region
- London (+20% on West Midlands rates)
What does a balcony or terrace in Southwark need?
Door thresholds are a common reason for balcony work in Southwark. 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 a town like Southwark, flat roofs are commonly found on Victorian and Edwardian terraces with flat-roofed back additions or mansard and dormer loft conversions. 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 Southwark?
For Southwark 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 |
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
- Free survey of the deck, falls, outlets and door thresholds
- 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 Southwark: questions
Do you cover Southwark?
Yes. Southwark is part of our London coverage, including postcode districts SE5, SE15, SE17, SE22, SE14, SE11 and 2 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 Southwark?
Where the work needs approval it goes to London Borough of Southwark 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 Southwark?
£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.
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.
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.