If you have a flat roof on an extension, garage, or outbuilding that’s started leaking, you’ve probably already discovered that getting a straight answer about what replacement costs is harder than it should be. Most guides give you a range so wide it’s useless — “€1,500 to €9,500” tells you almost nothing useful when you’re trying to decide whether repair or replacement makes more sense.
This guide gives you something more useful: honest, specific, Wicklow-relevant pricing broken down by system, by property type, and by the factors that genuinely push costs up or down — based on what the DJ Roofing team actually charges on flat roof replacement jobs across County Wicklow in 2026.
This is worth addressing before getting into costs, because it’s specific to this county and this moment — and it explains why the DJ Roofing Wicklow team is carrying out more flat roof replacements across Wicklow right now than at any other point in the business’s history.
The majority of homes built across County Wicklow’s residential estates between approximately 1985 and 2005 — and there are a very large number of them, across Bray, Greystones, Newtownmountkennedy, Wicklow Town, Arklow, Rathnew, and everywhere between — were built with rear extensions. Those extensions almost universally have flat roofs. The flat roof systems installed on those extensions — almost exclusively built-up felt in that era — had a designed service life of 10–15 years.
Those roofs are now 20–40 years old.
The original felt on the vast majority of these extension flat roofs across Wicklow has either already failed or is in the late stages of its useful life. Some homeowners know this because they’ve had leaks. Others don’t know yet because the felt is deteriorating from the inside out — splitting, blistering, and losing its waterproof integrity in ways that aren’t immediately visible from the surface but that allow water to penetrate the insulation beneath during rainfall.
This is why flat roof replacement is such a live topic in Wicklow right now. It’s not a niche job. It’s a maintenance cycle that a significant proportion of Wicklow homeowners with 1990s extensions are either already dealing with or about to face.
Before any conversation about cost, the most important question is whether your flat roof actually needs replacing or whether targeted repair is the right approach. This affects the budget significantly and it’s where honest contractor advice matters most.
Repair is almost certainly the right option when:
Replacement is the right option when:
The team at DJ Roofing Wicklow assesses this at the inspection stage and gives a straight answer. If repair is the right call, that’s what is recommended — even when replacement would earn more.
The material you choose for the replacement is the single biggest variable in cost after roof size. Here’s an honest breakdown of each system, what it costs, and what it delivers.
Built-up felt and torch-on modified bitumen systems are the traditional and cheapest flat roofing option. A quality torch-on system, correctly installed with the proper number of layers and adequate fall to the drainage outlet, will perform for 10–15 years.
This is the system that was standard on Wicklow’s 1990s extensions — and it’s also the system most likely to be reaching end of life on those same extensions right now. It’s worth being direct about this: felt is the cheapest upfront option, but it has the shortest lifespan of all the flat roofing systems available. Replacing like-for-like felt on a 2026 flat roof replacement means you’ll be in the same position again in 10–15 years.
For homeowners on a tight budget, or where the extension is likely to be demolished or substantially renovated in the medium term, felt is a legitimate choice. For most Wicklow homeowners replacing a flat roof they want to last, EPDM or GRP delivers substantially better value over the life of the roof.
Cost range: €55–€75 per m² installed, excluding decking replacement where required.
EPDM — ethylene propylene diene monomer — is the DJ Roofing team’s most commonly recommended flat roofing system for residential extensions across Wicklow, and with good reason. It is the default system for flat roof replacements in Ireland in 2026 among contractors who are not simply recommending the cheapest option.
EPDM is a single-ply rubber membrane supplied in large sheets that minimise the number of joins in the finished roof — and joins are where flat roof failures most commonly begin. It handles thermal movement — the expansion and contraction that every flat roof experiences with temperature changes — without cracking. It is highly UV resistant. It tolerates occasional foot traffic better than GRP. And a correctly installed EPDM system carries a manufacturer warranty on the membrane itself of 20+ years, with a realistic serviceable life of 25–30 years in Irish conditions.
The cost variation within this range reflects several factors: whether new OSB decking boards are required beneath the membrane (usually yes on a replacement job where the old decking has deteriorated), the complexity of the edge detailing and upstand work around the perimeter of the roof, and whether the drainage outlet and associated pipework need replacing as part of the job.
Cost range: €85–€120 per m² installed, excluding new decking where required. New OSB decking adds approximately €20–€35 per m² where needed.
GRP — glass reinforced plastic, commonly called fibreglass — creates a rigid, seamless roofing shell across the entire roof surface. When correctly installed to manufacturer specification, it is completely waterproof with no joins or seams through which water can enter the main field of the roof. Its expected lifespan is 25+ years.
GRP is particularly popular on extensions where the flat roof surface will be walked on regularly — a balcony above a ground-floor extension, for example — because the rigid surface handles foot traffic better than a rubber membrane. It is also highly resistant to impact damage from falling debris.
The trade-offs compared to EPDM are that GRP requires specific resin and glass-fibre materials for any future repairs — incompatible products applied to a GRP surface create adhesion failures that peel away quickly and leave the original defect unresolved. It is also slightly less forgiving of thermal movement on very large roof areas than EPDM. And GRP installation requires more skill and preparation than felt or EPDM — the surface must be correctly primed, the laminate layers applied correctly, and the topcoat finish completed properly — making the quality of the installer more critical.
Cost range: €95–€130 per m² installed, excluding new decking where required.
Here’s what flat roof replacement realistically costs on the most common property types the DJ Roofing team works on across County Wicklow in 2026. All figures are for a full replacement — strip, new deck where required, new membrane, edge detailing, and drainage — and are VAT inclusive.
The most common flat roof replacement job across Wicklow. A standard rear kitchen or living room extension with a straightforward flat roof, no complex parapets, and a single drainage outlet.
At the lower end: EPDM on a small extension with sound existing decking.
At the upper end: GRP on a larger extension where new OSB decking, new drainage outlet, and upstand detailing at the house wall are all required.
Larger flat-roofed extensions — whole-house rear extensions common in Wicklow’s 1990s housing estates — fall into this range. The cost reflects both the larger membrane area and the proportionally longer perimeter requiring edge detailing.
Garage flat roofs are straightforward jobs in most cases — typically a single flat section with simple perimeter detailing. The wide range reflects the variation in garage sizes and whether the existing decking needs replacing.
Dormer flat roofs are smaller in area but often more complex in detailing — the junction between the dormer flat roof and the surrounding pitched roof requires careful flashing and membrane work. This complexity is reflected in the per-m² cost, which is typically higher than for a simple extension flat roof of the same area.
Outbuildings vary considerably in size and construction quality. Where the existing structure is sound, replacement is straightforward. Where the supporting structure has deteriorated alongside the roof membrane, additional timber or structural work increases the scope.
Larger flat roofs — commercial units, large agricultural buildings, or extensive residential extensions — are quoted individually based on the specific site, access requirements, membrane system, and drainage configuration.
When the team quotes a flat roof replacement in Wicklow, the price covers:
Full strip of the existing roof covering — old felt, membrane, or system fully removed and disposed of. Overlay — fitting new membrane over old — is never recommended and never quoted as a full replacement.
Inspection of the existing timber deck — once the old covering is stripped, the deck boards, joists, and supporting structure are fully exposed and inspected. Any rotten or delaminated decking is identified and replaced before the new membrane goes on.
New OSB or plywood decking where required — the standard approach on most replacement jobs where the original decking has deteriorated.
New membrane installation — EPDM, GRP, or torch-on system as agreed, installed correctly to manufacturer specification.
Perimeter and upstand detailing — the critical edge and junction work where the membrane turns up against walls, parapets, and the main roof above the extension.
Drainage outlet replacement — the flat roof drain is replaced or serviced as part of the job, ensuring correct drainage.
Fall assessment — confirming the roof has adequate fall to the outlet. Where fall is insufficient, this is flagged and, where feasible, addressed as part of the replacement.
Site clearance — all stripped materials, debris, and waste removed. The site is left clean before the team leaves.
VAT at 13.5% — all quotes are VAT inclusive on residential properties over five years old.
Beyond system choice and roof size, these are the factors that consistently push costs beyond the base range on Wicklow jobs:
Decking replacement. The most common additional cost on older extension flat roofs. Where the original chipboard or OSB decking has absorbed moisture over years of felt failure, it must be replaced before the new membrane is laid. On a roof where the felt has been failing for several years, some deck replacement is extremely common. Where the full deck requires replacement the additional cost is typically €20–€35 per m².
Parapet walls and complex perimeter detailing. Extensions with parapet walls — the raised edges on all sides rather than simple eaves — require more extensive upstand detailing than a simple eaves-to-wall configuration. This adds labour and material cost.
Rooflights and skylights. Each rooflight in the flat roof requires individual upstand and flashing detailing. Additional rooflights add both material and labour cost.
Access and height. Extensions on two-storey properties are higher to access than those on single-storey sections. Where scaffold or more complex access is required than a standard ladder, this is reflected in the quotation.
Poor drainage fall. Where the existing flat roof has been installed without adequate fall to the drainage outlet — creating permanent ponding — correcting this as part of the replacement involves additional timber work to create the fall, which adds to the scope.
Isolated rural location. Properties in remote parts of Wicklow — out toward Tinahely, Shillelagh, Donard, and the upland areas — may involve additional transport time and material delivery costs that affect the final price compared to town-based projects.
This is an honest recommendation based on the specific conditions the team observes across the county — not a sales pitch for the more expensive system.
In a typical year across County Wicklow, a flat roof will go through numerous thermal cycles — expanding in summer heat, contracting in winter cold. It will be rained on hundreds of times. It will sit under standing water if drainage is even slightly compromised. It will face occasional frost, occasional hail, and occasional extended periods of damp conditions that give felt little chance to dry out between rain events.
Built-up felt handles these conditions adequately for 10–15 years when correctly installed. But correctly installed felt flat roofs are the exception rather than the rule on Wicklow’s 1990s extensions — many of the ones the team strips back show inadequate falls, insufficient layers, and poor perimeter detailing that has reduced the effective lifespan below even the 10-year minimum.
EPDM handles all of the same conditions more durably, with no seams across the main field of the roof, genuine manufacturer-backed longevity, and a performance ceiling that is demonstrably appropriate to the Irish climate. The additional upfront cost over felt on a standard extension replacement is typically €500–€1,500 depending on size — and it buys 10–15 extra years of reliable performance before the next replacement cycle.
The team doesn’t refuse to install felt. But where a homeowner is replacing a flat roof and planning to be in their property for more than 10 years, the honest recommendation is always EPDM or GRP.
Two options that come up regularly when homeowners are looking for a cheaper solution than full replacement:
Targeted repair. As outlined at the start of this guide, targeted repair of specific failure points on an otherwise sound membrane is a legitimate and cost-effective approach. The key phrase is “otherwise sound membrane.” On older Wicklow extension roofs where the felt has been deteriorating for years, there rarely is a single failure point on an otherwise sound system — there are multiple simultaneous failures because the whole membrane is at the same stage of deterioration. Repairing one point on this kind of roof resolves nothing and costs money without addressing the underlying problem.
Overlay (new membrane over old). Some contractors offer to install a new EPDM or GRP membrane directly over the existing felt rather than stripping it back. This is cheaper in labour — the strip is the most time-consuming part of a flat roof replacement — but it creates several problems. It adds weight to the existing roof structure. It traps any existing moisture in the old felt beneath the new membrane, where it continues to affect the deck. It prevents any assessment of the deck condition. And if the existing felt is bonded to a deteriorating deck, the overlay follows the deck rather than creating a flat, even surface.
The DJ Roofing team always carries out a full strip on replacement jobs. Where a homeowner specifically requests an overlay, Sean explains the reasons it isn’t recommended before making any decision to proceed.
Flat roof replacement on a residential property more than five years old is subject to VAT at 13.5% in Ireland — the reduced rate that applies to renovation and repair work on existing homes rather than the 23% standard rate. All DJ Roofing Wicklow quotations are provided VAT inclusive, so there are no arithmetic surprises on the invoice.
Where a flat roof replacement is being carried out on a new build or a property under 5 years old, the standard 23% VAT rate applies.
A quote given without inspecting the existing deck. The condition of the deck beneath the membrane is the most important factor in determining the true scope and cost of a flat roof replacement. Any contractor quoting without checking the deck is guessing — and that guess will either result in an inflated quote or an underdone job that doesn’t address the actual condition of the roof structure.
An overlay offered as a full replacement. If a contractor quotes a “replacement” without stripping the existing felt, it isn’t a replacement. Ask specifically whether the quote involves a full strip.
Incompatible repair materials on GRP roofs. If you have an existing GRP flat roof that has been previously repaired with bitumen-based products or silicone sealant, ask the contractor about their approach. These materials don’t bond correctly to GRP and the team will need to address the previous repair before any new work can be guaranteed.
A very low quote. Flat roofing done correctly requires adequate preparation, quality materials, and proper perimeter detailing. A quote that comes in significantly below the ranges in this guide almost always reflects one of three things — cheaper materials, inadequate scope, or a contractor working without proper insurance. None of these delivers value in the long term.
If your flat roof is leaking, showing visible deterioration, or simply hasn’t been assessed in the last few years — call Sean today for a free inspection and a clear, honest quote.
The team covers all of County Wicklow and carries out flat roof replacements in EPDM, GRP, and felt on extensions, garages, dormers, and commercial properties across the county.
DJ Roofing Wicklow — honest, reliable roofing across County Wicklow. Call Sean directly for a free quote.
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