Flat Roofing In Weymouth
Is your flat roof holding water or letting it in?
EPDM rubber, GRP fibreglass and felt flat roofs for extensions, garages, dormers and bay windows
Flat roofs have a poor reputation, and most of it comes from flat roofs that were never built to last. Get the fall right, put a decent deck down, choose a membrane that suits the job and finish the edges properly, and a flat roof in Weymouth will happily see out twenty-five years or more. We repair and replace flat roofs on rear extensions, garages, dormers, porches and bays across the town, and we'll be honest about whether yours can be repaired or has simply reached the end.
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What makes a flat roof last
A flat roof isn't really flat, and that's the first thing it needs to get right. These are the details we pay attention to.
01
A proper fall
Water needs a slope to drain. We build in a fall with firring strips or tapered insulation so rain runs to the outlet or gutter instead of sitting in puddles that slowly find their way through.
02
The right membrane for the job
EPDM rubber for most extensions and garages, GRP fibreglass where a hard, walkable finish matters, and torch-on felt where it suits an existing roof. We'll explain why we recommend one over another.
03
A sound deck underneath
Soggy chipboard is behind most flat roofs that bounce or sag. We replace decking with moisture-resistant OSB or exterior ply, so the membrane has something solid to stick to.
04
Edges and upstands done well
Most flat roof leaks start at the edges: where the roof meets a wall, a window or the gutter. Trims, upstands and flashings are where we spend the most care.
05
Warm roof options
If the room below is cold in winter, a warm-roof build puts insulation above the deck, which keeps the room warmer and reduces the risk of condensation in the structure.
06
Repairs where they make sense
A single split or a failed edge trim on an otherwise sound roof can be repaired. We won't push a full replacement unless the deck or the membrane as a whole has had it.
1,000+
Roofing projects completed
5★
Every review we have is five stars
10 yrs
Guarantee on roof replacements
Free
Roof surveys and written quotes
Flat roofs in a sunny coastal town
The Met Office's Wyke Regis station logs around 1,900 hours of sunshine a year, against a UK average nearer 1,400. Lovely for the beach, hard on cheap flat roofs. Ultraviolet light dries out bitumen felt, and summer heat followed by cold nights makes it expand and contract until it cracks. That's why so many older felt roofs on garages and back extensions here look crazed and blistered well before their time.
Wind is the other enemy. A flat roof with poorly fixed edge trims can peel back in a gale, and once the wind gets under a membrane it doesn't stop. We pay particular attention to perimeter fixings on roofs facing the bay or standing high on the hills around Wyke Regis and Preston.
"When we're asked to quote for a leaking flat roof in Weymouth, the deck underneath is usually in worse shape than the covering on top."
How we repair or replace a flat roof
- 1
Survey and moisture check
We look at the surface, the edges and the outlet, and from inside where we can. A soft or spongy feel underfoot tells us the deck has taken on water.
- 2
Written quote with options
If more than one membrane would suit your roof, the quote shows the options side by side with honest notes on lifespan and cost.
- 3
Strip the old covering
Old felt, asphalt or membrane comes off down to the deck. Any wet or rotten boards are cut out and replaced.
- 4
Fall and insulation
Firrings or tapered insulation set the fall towards the drainage point. On a warm-roof build, rigid insulation and a vapour control layer go down at this stage.
- 5
New deck laid
Moisture-resistant boards are fixed down tight with joints staggered, giving a smooth, stiff base for the new membrane.
- 6
Membrane, trims and upstands
The EPDM, GRP or felt system is laid to the manufacturer's method. Edge trims, drip details, upstands and wall flashings are completed and checked.
- 7
Water test and handover
Where practical we run water across the finished roof to check it drains, then clean up, take the waste away and hand over photos of the work.
Ten years on a new roof, written down and signed
When we replace a roof in Weymouth, the paperwork you're handed at the end will, on all but a handful of unusual jobs, include a 10 year guarantee on the work. If yours is one of the exceptions, you'll know at quote stage, not after. It names your address, says what was done and is dated the day we sign the roof off. It covers the installation itself, meaning the battens, membrane, fixings, the slates or tiles and the junctions where the roof meets walls and chimneys. If any of that lets water in through a fault in how it went on, we come back and fix it without charging you.
A guarantee that long only makes sense if the roof is built properly underneath, so it shapes the job from day one. Every slate or tile is mechanically fixed to the current British Standard rather than relying on its own weight, which matters on a stretch of coast where the wind arrives with nothing in its way. Breathable membrane goes on before the battens. Valleys, abutments and chimneys get proper lead or a tested dry-fix system, never a smear of mortar that cracks in its third winter.
Materials carry their own manufacturer cover on top, and that differs from product to product. Your paperwork says which one applies to your roof.
10
Year guarantee on roof replacements
1,000+
Roofing projects completed
What to look for in a flat roofing contractor
They ask about the room underneath
What's below a flat roof changes how it should be built. A garage can be a simple cold roof. A kitchen extension or bedroom over a bay usually wants a warm roof with insulation and a vapour layer. A contractor who doesn't ask is probably quoting the same build for everything.
They're trained in the system they fit
EPDM, GRP and modern felts each have their own adhesives, primers and details. Manufacturers train and approve installers for a reason. Ask which system is proposed and whether the person laying it has fitted that product before.
They talk about the deck, not just the surface
Laying a new membrane over a rotten deck is the most common short cut in flat roofing, and it fails quickly. A good quote says what the deck is made of now and what it will be replaced with if it's not sound.
EPDM, GRP or felt: choosing a flat roof
The three flat roof systems we install, compared on the points customers ask about most. Figures are typical for a domestic roof.
| Comparison point | EPDM rubber | GRP fibreglass | Torch-on felt |
|---|---|---|---|
| Expected lifespan | 25 to 40 years | 25 years or more | 15 to 25 years for modern high-performance felt |
| How it's laid | Single sheet bonded down, few or no joints | Resin and matting laid wet, cures hard | Layers heat-bonded with a torch |
| Foot traffic | Fine for maintenance, not a terrace | Good, hard-wearing finish | Moderate |
| Appearance | Matt black, plain | Smooth, can be coloured | Mineral finish, traditional look |
| Relative cost | Mid | Mid to high | Lowest to mid |
| Best for | Extensions, garages, dormers | Balconies, bays, complex shapes | Matching or overlaying existing felt roofs |
Dormers, bays and the awkward small roofs
Not every flat roof is a big rectangle over a garage. Victorian bay windows along the older streets often have a small lead or felt roof that's been patched many times. Dormer cheeks and tops on loft conversions, porch canopies and the strip of flat roof between two pitched slopes all need the same care at a smaller scale.
These small roofs leak out of all proportion to their size because so much of their area is edge. We give them the same detailing as a large roof, and often finish bays in lead or GRP so they suit the house.
Lead work on bays and dormers
Flat roofing costs in Weymouth
Price depends mostly on size, access and what's found underneath. A single garage re-covered in EPDM sits near the bottom of the range. A large warm-roof extension with new deck, insulation and roof lights is towards the top. Small repairs to trims and splits cost less again.
Flat roofing questions
How long does a flat roof last?
A properly installed EPDM or GRP roof typically lasts 25 years or more, and modern torch-on felt 15 to 25. The old three-layer felt roofs many houses still have were often expected to manage ten to fifteen.
Is EPDM or GRP better?
Neither is better everywhere. EPDM is quick to lay, forgiving of movement and suits most extensions and garages. GRP gives a hard, seamless finish that copes better with foot traffic and complicated shapes. We'll recommend one for your particular roof and explain why.
Can you go over my existing flat roof?
Sometimes, if the existing covering is well bonded and the deck is dry and sound. More often the deck has taken on water, and covering over it simply traps the problem. The survey will tell us which situation you're in.
Why is there water sitting on my flat roof?
Ponding usually means the fall is too shallow or the deck has sagged. Small puddles that dry within a day or two aren't a disaster, but standing water speeds up wear on felt and will eventually find any weakness. Rebuilding the fall cures it.
Do I need planning permission for a new flat roof?
Replacing a flat roof like-for-like doesn't normally need planning permission. Raising its height, adding a roof terrace or changing a listed building is different, so speak to Dorset Council first in those cases.
Can you add a roof light while you're at it?
Yes. Replacement is the best time to add or upgrade a flat roof light, because the upstand can be built into the new deck and sealed properly with the membrane.
Related: Guttering, fascias & soffits · Roof repairs · Roofing costs
What customers around Weymouth say
More than a thousand roofing jobs finished, and every review customers have left us is five stars.
Those reviews are on their way onto this page. Until they land, ask us for photos of recent jobs near you in Weymouth when we come out to quote - seeing a finished roof on a house like yours tells you more than any star rating.
Flat roofing across Weymouth, Portland and beyond
Sort out that flat roof for good
Tell us what's on top and what's underneath, and we'll come and give you an honest view and a fixed price.