Balconies and roof terraces across West Sussex

Guide price

£2,100–£3,600

Survey

Free for new and replacement roofs

Quote

Fixed, in writing

Coverage

England, Wales, Scotland, NI

How much does balcony or terrace waterproofing cost in West Sussex?

Guide prices including VAT at South East rates. The fixed price comes after a free survey for new and replacement roofs.

Which flat roofs are common in West Sussex?

Flat roofs in West Sussex sit on lock-up garage blocks on estates, newer estates where the first extension roofs are now being replaced and 1930s semis with flat-roofed garages and kitchen extensions. Much of the South East sits in the drier Thames catchment at roughly 730 mm of rain a year, so the usual failures are at joints, upstands and outlets rather than from sheer volume of rain. Approximate 1991–2020 regional averages based on Met Office data.

Building regulations in England

Replacing more than half of a roof over a heated room usually counts as renovating a thermal element, so it is insulated to current standards and notified to building control. Renovated roofs over heated rooms are insulated to around 0.16 W/m²K where that's feasible, and new extension roofs are built to 0.15 W/m²K. In West Sussex the application goes to Crawley Borough Council, Worthing Borough Council, Arun District Council and 4 other councils. More on the rules.

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.

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.

Which towns in West Sussex do we cover?

• Crawley
• Worthing
• Bognor Regis
• Littlehampton
• Horsham
• Haywards Heath
• Chichester
• Burgess Hill
• East Grinstead
• Shoreham-by-Sea
• Lancing

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