Flat Roofing in Jersey
Flat roofing in Jersey covers a huge range of buildings, from single-storey extensions and garages to garden rooms and commercial units, and getting the detailing right at the edges is what separates a roof that lasts from one that fails within a few years.
We install and repair flat roofs across the island using modern single-ply and GRP systems as well as traditional felt, choosing the right build-up for the size of the roof, the amount of foot traffic it needs to take and how exposed it is to wind and rain.
What the job involves
We start by assessing the existing deck, whether that's timber, concrete or an older asbestos-cement board, and check the falls to make sure water is draining correctly rather than pooling. Poor falls are one of the most common causes of premature flat roof failure, so we address this at design stage rather than simply overlaying a new membrane on a flawed structure.
Installation involves fitting insulation above or below the deck depending on the build-up specified, then the waterproof membrane itself, with careful detailing at upstands, rooflights, pipe penetrations and roof edges where most leaks originate. Trims and edge details are dressed and mechanically fixed or bonded according to the manufacturer's specification for that system.
Repair work involves locating the source of a leak, which on a flat roof isn't always directly above the visible damp patch, then cutting out and patching the affected area or, where the covering has reached the end of its life, recommending a full overlay or strip and replace.
Common problems we fix
Flat roofs in Jersey face a specific set of issues linked to weather exposure and age of covering.
- Ponding water from inadequate or reversed falls
- Blistering and splitting on older torch-on felt roofs
- Perished upstands and flashings around parapet walls
- Wind-driven rain and storm damage lifting membrane at exposed edges
- UV degradation on roofs with long, unbroken southerly exposure
- Failed detailing around rooflights and soil pipes letting water track internally
- Moss and algae growth holding moisture against the membrane on shaded roofs
- Corrosion of old metal edge trims on coastal properties from salt air
Materials and standards we use
For new installations and full replacements we mainly specify SikaPlan single-ply membrane and GRP fibreglass systems, both of which give a durable, low-maintenance surface with a long service life and good resistance to UV and standing water compared with older felt products.
Torch-on felt is still a suitable option for some smaller roofs and budgets, and we fit it correctly with the right number of layers and properly lapped and sealed joints. All flat roof work is carried out with attention to current good practice for falls, insulation placement and detailing, and any related fixings on adjoining slate or tile sections are finished to BS 5534.
How much does it cost in Jersey
Flat roof pricing depends heavily on the roof's overall size and its pitch or fall, since a larger area or one needing tapered insulation to correct poor drainage takes longer and uses more material. Access is another factor, particularly for roofs above extensions with limited scaffolding room or where materials have to be carried through a house.
The condition of the deck once uncovered can change the price too. Rotten timber or damaged boarding found during strip-out needs replacing before any new covering goes down. The choice between single-ply, GRP and felt also affects cost, as does freight to the island for specialist membrane systems, and any requirements around listed or registered buildings where visible detailing needs particular care.
We provide a free, written quote for every flat roofing job so you can see exactly what's covered before work begins.
Frequently asked questions
- Which is better, single-ply or GRP?
- Both perform well when installed correctly. Single-ply membrane suits larger or more complex roofs with lots of detailing, while GRP fibreglass gives a seamless, hard-wearing surface that's often preferred for smaller roofs, balconies and roofs that will take foot traffic.
- Why does my flat roof keep leaking in the same spot?
- This usually points to a detailing fault rather than the membrane itself, such as an upstand, pipe penetration or edge trim that was never sealed correctly. We trace the actual source before repairing, since patching the visible symptom without finding the cause rarely fixes it long term.
- Can you just repair a small area rather than replace the whole roof?
- Where the membrane is otherwise sound, yes. We'll assess the overall condition and age of the covering and give an honest recommendation on whether a patch repair or full renewal is the better long-term option.
Related roofing services
See finished work across the island in our roofing gallery.
Get a free, written quote
Call 07797 773536, message us on WhatsApp or send the quote form. We reply within one working day. Monday to Friday, 08:00 to 17:00.
info@watertight.je · La Commune, Jersey, JE2 7HS