Balconies and roof terraces across County Antrim

Guide price

£1,650–£2,850

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 County Antrim?

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

Which flat roofs are common in County Antrim?

Flat roofs in County Antrim sit on shops with flat-roofed rear stores below flats, bungalows with flat-roofed side extensions and dormers and lock-up garage blocks on estates. Northern Ireland averages roughly 1,150 mm of rain a year, spread over many wet days, so a roof that sheds water quickly to clear outlets lasts far longer than one that holds puddles. Approximate 1991–2020 regional averages based on Met Office data.

Building control in Northern Ireland

In Northern Ireland, renovating or replacing a roof over a heated room usually means meeting Technical Booklet F1, and building control should be contacted before work starts. Technical Booklet F1 sets roof insulation at 0.18 W/m²K when a roof over a heated room is renovated or newly built, where feasible. In County Antrim the application goes to Lisburn and Castlereagh City Council, Antrim and Newtownabbey Borough Council, Mid and East Antrim Borough Council and 1 other council. 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 County Antrim do we cover?

• Lisburn
• Newtownabbey
• Carrickfergus
• Ballymena
• Antrim
• Larne
• Ballymoney
• Ballyclare

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