CMW Roofing & Renovations
Flat Roof Repair
Portsmouth
CMW Roofing & Renovations carries out flat roof repair and replacement across Portsmouth and the surrounding area. Portsmouth's dense housing stock includes a large number of terraced properties, extensions and outbuildings with flat roofs — many now leaking or past the end of their felt lifespan. We install GRP fibreglass systems across the PO1–PO6 postcode area.
GRP Flat Roofing in Portsmouth
Portsmouth has a high density of terraced housing, with many properties featuring rear extensions, outbuildings and bay window roofs covered in traditional felt — a system that lasts around 10–15 years and fails at the lap joints between sheets.
We replace failing felt across the PO1–PO6 postcodes with GRP fibreglass, which has no joints to fail and carries a 20-year manufacturer guarantee.
Repair or replace, we'll always tell you honestly which your roof actually needs.
How we install your GRP flat roof
- Strip and inspectThe existing felt is stripped back to the deck and the boards checked for rot, movement or damage — any that aren't sound are replaced first.
- GRP trims and universal primerGRP edge trims are fixed around every perimeter and upstand, then a universal primer is applied across the full deck to seal it ready for the laminate.
- Matting and resin laminateFibreglass matting is laid into catalysed resin and rolled out to remove any air, bonding into one seamless, jointless layer across the whole roof.
- Sand, dust off and topcoatOnce the resin has cured we sand it back, dust it off and roll on the topcoat (matched to the system) for a hard-wearing, UV-stable, colour-fast finish.
Where the deck is sound and only a localised area is leaking, we can carry out targeted GRP repairs rather than a full replacement — we'll always give an honest recommendation on which is better value. Every installation includes a written workmanship guarantee alongside the manufacturer's 20-year product guarantee.
What we cover
Full flat roof replacement
Old felt stripped, deck boards inspected and replaced where needed, full GRP system installed from bare boards up across Portsmouth PO1–PO6.
GRP trims and upstands
GRP edge and drip trims fixed to all perimeters and upstands before the laminate goes down, for a weathertight, clean-edged finish on Portsmouth flat roofs.
Universal primer and matting
A universal primer seals the deck, then fibreglass matting is laid into the resin across the whole roof — one continuous layer with no joints to fail.
Sanded and topcoated
Once the resin has cured, the laminate is sanded back, dusted off and topcoated — a seamless finish with no lap joints or seams, removing the most common failure point on Portsmouth flat roofs.
Deck board replacement
Rotten or damaged boards identified at strip-out stage and replaced before the new system is laid, ensuring the 20-year guarantee is not compromised.
Flat roof leak repairs
Targeted GRP repairs for Portsmouth properties where the deck is sound and only a localised repair is needed — repair or replacement assessed on site.
Recent flat roof work
Areas we cover
We cover flat roof work across Portsmouth, Southsea, Fratton, Cosham, Paulsgrove, Drayton, Farlington, and the wider PO1–PO6 area. If you are not sure whether we cover your location, call or message and we will confirm.
We typically respond to enquiries within a few hours and can usually arrange a free site visit and written quote within a few days.
FAQs
Do you cover Portsmouth for flat roof repairs?
Is GRP suitable for a terraced house extension in Portsmouth?
How quickly can you quote for a flat roof in Portsmouth?
What is the difference between GRP and felt flat roofing?
Have a question not answered above?
Call 07876 803 029Get a free flat roof quote in Portsmouth
Call or message for a free, no-obligation quote. We cover Portsmouth and the wider PO1–PO6 area and aim to respond the same day.