- Guide price
- £1,750–£3,000
- Survey
- Free for new and replacement roofs
- Quote
- Fixed, in writing
- Coverage
- England, Wales, Scotland, NI
Carmarthenshire at a glance
- Largest towns
- Llanelli, Ammanford, Carmarthen, Burry Port
- Postcode areas
- SA
- Building control
- Carmarthenshire County Council
- Neighbouring areas
- Swansea · Neath Port Talbot · Bridgend · Rhondda Cynon Taf
- Guide price region
- Wales (−8% on West Midlands rates)
How much does balcony or terrace waterproofing cost in Carmarthenshire?
Guide prices including VAT at Wales 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 | £1,750–£3,000 |
| Single garage (18 m²), EPDM rubber | £1,450–£2,600 |
| Extension (20 m²), GRP, new deck + insulation | £2,750–£4,950 |
Which flat roofs are common in Carmarthenshire?
Flat roofs in Carmarthenshire sit on newer estates where the first extension roofs are now being replaced, bungalows with flat-roofed side extensions and dormers and 1960s and 1970s link-detached houses with flat-roofed garages and porches. Wales averages roughly 1,460 mm of rain a year, among the wettest in Britain, so we design for steady run-off: proper falls, clear outlets and upstands well above the finished roof. Approximate 1991–2020 regional averages based on Met Office data.
Building regulations in Wales
Welsh guidance is that most re-roofing needs building control approval, so it's worth checking whenever more than a quarter of a roof is replaced or repaired. Renovated roofs are upgraded to around 0.16 W/m²K where feasible, and new extension roofs are built to 0.13 W/m²K under the Welsh Approved Document L. In Carmarthenshire the application goes to Carmarthenshire County Council. More on the rules.
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.
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 towns in Carmarthenshire do we cover?
Balconies and roof terraces in Carmarthenshire: questions
Which towns in Carmarthenshire do you cover?
All of Carmarthenshire. 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 Carmarthenshire?
£1,750–£3,000 for a 12 m² balcony in a liquid-applied system including scaffold, at Wales guide rates including VAT. The fixed price comes after a free survey for new and replacement roofs.
Which postcode areas do you cover in Carmarthenshire?
All of Carmarthenshire, including the SA postcode areas. Send your full postcode and we'll confirm.
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.
Why is water coming through the ceiling below my balcony?
The usual causes are a failed door threshold, a blocked or poorly sealed outlet, or a fixing through the membrane. A survey, sometimes lifting paving, finds the source.
Is a roof terrace heavier than a normal flat roof?
Yes. Paving, people, planters and furniture all add load, so a structural engineer should confirm the roof can carry it before a terrace is formed.
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