Renewing a flat roof in Cwmbran usually means stripping the old covering back to a sound deck, correcting the falls so water runs off properly, and laying a modern membrane such as EPDM rubber. The work is common here because so much of the town's housing, built rapidly from the late 1940s onwards, used flat and shallow-pitched roofs over extensions, garages, porches and some main dwellings.
Why so many flat roofs across the new-town estates
Cwmbran was designated a New Town in 1949 and grew quickly through the 1950s and 60s. The estates at St Dials, Coed Eva, Fairwater, Greenmeadow and Llanyravon were built to standardised designs, and flat or low-pitched roofs were a cheap, fast way to cover homes, outbuildings and the link sections between properties.
A flat roof covering is simply the waterproof layer over a near-level deck. Many original roofs used built-up felt — layers of bitumen felt bonded together. Felt has a finite life, so a steady proportion of these roofs reach the point of renewal at any given time.
Later additions added more flat roofs to the stock. Single-storey rear kitchen extensions, garage roofs and dormer cheeks on loft conversions all tend to be flat or shallow, so even modern-looking homes often carry a flat section somewhere.
What ageing 1960s flat roofs tend to show
Why so many flat roofs across the new-town estates Cwmbran was designated a New Town in 1949 and grew quickly through the 1950s and 60s.
Old felt roofs fail in fairly predictable ways. Spotting the signs early often makes the difference between a straightforward renewal and dealing with rotten timber underneath.
- Blistering, cracking or bare patches where the felt has perished under UV and frost.
- Ponding — standing water that never drains — usually caused by inadequate or worn falls.
- Staining, damp patches or a musty smell on ceilings below the roof.
- Soft or springy areas underfoot, suggesting the deck boards have absorbed water.
- Splits at upstands, around rooflights and where the roof meets a wall.
Cwmbran's exposed, often wet Gwent weather accelerates this. Roofs facing the prevailing south-westerly weather tend to degrade first.
Choosing a covering for an extension or garage
For domestic flat roofs in the area, the common modern choices are EPDM rubber membrane, single-ply PVC, glass-reinforced plastic (GRP, a fibreglass coating) and modern torch-applied felt. EPDM is a single sheet of synthetic rubber, often laid in one piece on smaller roofs, which removes most seams and tends to be hard-wearing.
The right option depends on roof size, shape, the number of penetrations such as soil pipes or rooflights, and budget. A roof with awkward corners or several upstands suits a membrane that can be dressed around them cleanly. A simple square garage roof is well suited to a single EPDM sheet or a GRP layer.
Whatever the covering, roof falls and drainage matter most. Building regulations expect a minimum fall so water reaches the outlets rather than pooling. Where an original roof was laid dead-flat, firrings — tapered timber battens — are usually added during renewal to build in the necessary slope.
How a renewal is sequenced
A typical flat roof renewal on a Cwmbran property runs through a clear order of steps:
- Strip the old covering and inspect the deck and timbers beneath.
- Replace any rotten or soft boards and joists.
- Add or correct firrings to set proper falls towards the outlet.
- Fit insulation where the work brings the roof up to current standards.
- Lay the new membrane and bond or weld the seams.
- Dress the covering into upstands, trims and around any rooflights.
- Form the drainage detail at the outlet or gutter and test that water clears.
Like-for-like repairs on existing roofs rarely need planning permission, though listed buildings and conservation considerations are exceptions worth checking with Torfaen County Borough Council. A reroof that alters insulation or structure may fall under building control, so it is worth confirming what applies before work begins.
Reviewed: June 2026