- Guide price
- £1,650–£2,850
- Survey
- Free for new and replacement roofs
- Quote
- Fixed, in writing
- Coverage
- England, Wales, Scotland, NI
Belfast at a glance
- Largest towns
- Belfast
- Postcode areas
- BT
- Building control
- Belfast City Council
- Neighbouring areas
- County Down · County Antrim · County Armagh · County Tyrone
- Guide price region
- Northern Ireland (−12% on West Midlands rates)
How much does balcony or terrace waterproofing cost in Belfast?
Guide prices including VAT at Northern Ireland rates. The fixed price comes after a free survey for new and replacement roofs.
| Job | Guide price inc VAT |
|---|---|
| Balcony (12 m²), liquid-applied, scaffold | £1,650–£2,850 |
| Single garage (18 m²), EPDM rubber | £1,400–£2,450 |
| Extension (20 m²), GRP, new deck + insulation | £2,650–£4,750 |
Which flat roofs are common in Belfast?
Flat roofs in Belfast sit on low-rise post-war blocks of flats, 1960s and 1970s link-detached houses with flat-roofed garages and porches and 1930s semis with flat-roofed garages and kitchen extensions. 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 Belfast the application goes to Belfast City 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.
How long does it take to waterproof a balcony?
A small balcony is typically waterproofed in two to four working days, plus time for scaffold if it is above ground floor. Liquid and GRP systems need dry weather and cure time between coats, which sets the pace.
The balcony door will be out of use while the membrane is laid and curing, and the room behind may be noisy while old paving or screed is broken out. If the team needs to work through the house, we agree a route and protect floors. Larger terraces with paving or decking take longer, because the finish has to be lifted and reinstated. Resin systems smell while they cure, so nearby windows are best kept closed.
Which towns in Belfast do we cover?
Balconies and roof terraces in Belfast: questions
Which towns in Belfast do you cover?
All of Belfast. The main towns have their own pages below, and if yours isn't listed we still cover it: send your postcode and we'll confirm.
How much does balcony or terrace waterproofing cost in Belfast?
£1,650–£2,850 for a 12 m² balcony in a liquid-applied system including scaffold, at Northern Ireland guide rates including VAT. The fixed price comes after a free survey for new and replacement roofs.
Which council handles building control for a flat roof in Belfast?
It depends on where the roof is: in Belfast that's Belfast City Council. 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. We confirm which applies at the survey.
Do you install balustrades?
Our work is the waterproofing and drainage. We detail the membrane around balustrade fixings so they stay watertight, and we can advise on where posts should be fixed.
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.
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