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Velux, Skylights & Dormer Windows in Portsmouth

Velux and skylight installation, roof lights and dormer windows across Portsmouth. Coastal-grade flashing is essential here — standard zinc corrodes in salt air. We install and flash correctly for the south coast, on pitched and dormer roofs alike.

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Velux and skylight installation in Portsmouth costs £1,200 to £3,000 per window in 2026, with dormer windows priced per scope. Coastal salt air demands upgraded flashing kits — standard zinc corrodes fast here. We install roof lights and dormers on pitched and flat roofs with correct coastal detailing. Free survey — call 0239 307 1334.

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Velux, Skylights and Dormers in Portsmouth

Adding natural light to a loft or top-floor room is one of the most popular Portsmouth home improvements, and it covers three related but distinct jobs: fitting a Velux or other roof window into a pitched slope, installing a flat rooflight into a flat or low-pitch roof, and building or reglazing a dormer window that projects from the roof. Each involves cutting into the weatherproof envelope of the roof, and each lives or dies on the quality of the flashing that reseals it. In Portsmouth's coastal environment that flashing specification is not a detail — it is the difference between a dry installation and a leak within a few winters.

Why Coastal Flashing Matters Here

A roof window is only as watertight as the flashing kit that seals it to the surrounding roof. Manufacturers supply standard flashing kits rated for typical inland conditions, but Portsmouth is not typical inland — salt-laden air corrodes standard zinc flashing components years ahead of their expected life. On Portsmouth installations we specify upgraded coastal or copper flashing kits as standard, because a window that leaks two winters after fitting costs far more to remedy than the modest upgrade cost. This is exactly the kind of local specification a national installer following a standard fitting manual will miss.

Loft Conversion Activity Across Portsmouth

Portsmouth's tight island geography, where extending outward is often impossible, has made loft conversion and rooflight installation especially common — and different areas convert differently. The larger Victorian and Edwardian properties off Albert Road in Southsea and the bigger houses of Old Portsmouth suit full dormer conversions that add real floor area. The dense two-storey terraces of Fratton and North End more often take rooflights or modest dormers within permitted development. The 1930s semis of Cosham and Drayton have generous, simple roof structures that accommodate standard Velux sizes cleanly. We assess the roof structure and the planning position before recommending rooflight, dormer or full conversion for each property type.

Dormer Windows on Portsmouth Terraces

A dormer projects from the roof slope to add headroom and light, and on Portsmouth's Victorian terraces it is the standard route to a usable loft room. The roofing challenge is the dormer's own roof — usually a small flat roof facing directly into coastal weather — and its junctions with the main slope, which are prime leak points if flashed poorly. We build dormer flat roofs in GRP fibreglass for coastal durability, not felt, and flash the cheeks and junctions with upgraded materials. On party-wall terraces we also manage the rafter configuration at the shared wall, which dictates where the dormer can sit. Conservation area properties in Old Portsmouth and parts of Southsea may need planning consent for a visible dormer — we establish that before quoting.

Rooflights on Flat and Low-Pitch Roofs

Beyond pitched-roof Velux windows, Portsmouth's many flat-roof extensions and dormers take flat rooflights that flood single-storey rear rooms with light. These sit on an upstand kerb built into the flat roof, and the waterproofing detail where the kerb meets the membrane is critical — on a coastal flat roof it faces standing water and salt exposure. We install rooflights as part of a GRP or EPDM flat roof so the kerb and membrane are a single integrated system, rather than retrofitting a rooflight into an aged felt roof where the junction will inevitably fail. Getting the flat-roof and rooflight specification right together is how you avoid the ponding leaks that plague poorly detailed installations.

How Much Do Velux & Skylights Cost in Portsmouth?

InstallationCost GuideNotes
Velux / roof window supplied & fitted£1,200–£2,000Coastal flashing kit included
Large / centre-pivot roof window£1,800–£3,000Bigger units, coastal detailing
Flat rooflight (on new flat roof)£1,400–£2,800Integrated GRP/EPDM kerb
Dormer window (build, per scope)£3,500–£9,000+GRP dormer roof, coastal flashing
Dormer reglaze / window replacement£800–£2,000Existing dormer
Coastal flashing upgradeIncludedStandard on all Portsmouth work

Roof windows installed within permitted development must not project more than 150mm beyond the roof plane, under the General Permitted Development Order.

Source: General Permitted Development Order

Free Velux & Skylight Survey in Portsmouth

We assess your roof structure and planning position, specify coastal-grade flashing, and quote in writing for Velux, rooflights or dormers. No call-out fee.

Call 0239 307 1334
Reviews

What Portsmouth Customers Say About Our Rooflight Work

★★★★★

"Two Velux in our Cosham loft — they fitted upgraded coastal flashing without me asking and explained why standard zinc corrodes here. Bone dry through two winters."

Helen R. · Cosham, Portsmouth
★★★★★

"Dormer on our Southsea terrace loft conversion — GRP roof, proper flashing at the cheeks. They handled the conservation area check before quoting. First class."

Mark T. · Southsea, Portsmouth
★★★★★

"Flat rooflight over our kitchen extension — they built it into a new GRP flat roof rather than cutting into the old felt. Floods the room with light, no leaks."

Susan A. · Fareham
Honest advice

Is Velux Skylights the Right Fix?

A flat roof problem usually shows as a damp patch on the ceiling below, ponding water that never drains, or a felt surface that has blistered, split or lifted at the edges.

When it is not the answer: If the deck is sound and only a seam has failed, a targeted repair may hold rather than a full re-cover Read the full guide.

Warm deck versus cold deck flat roof build-ups compared layer by layer
Building Regulations push new habitable flat roofs to warm-deck construction.
Local factors

Local Factors in Portsmouth

Solent salt air and exposed Channel weather corrode fixings and lift tiles faster than inland Hampshire. Portsea Island's dense Victorian terraces mean rear elevations are often reached only through tight alleys, and front scaffold needs permit-controlled pavement space. It is why we specify marine-grade fixings and correct lead codes as standard on Portsmouth roofs — the coastal environment punishes anything less.

The process

What to Expect: Velux Skylights in Portsmouth

1. Survey

We assess the covering and, critically, the deck condition underneath — the biggest cost variable on a Portsmouth flat roof.

2. Written quote

An itemised quote specifying the system — GRP, EPDM or felt — and any deck replacement, priced upfront.

3. Scheduling

We book the work and arrange access; most flat roofs are a one to three day job.

4. The work

Strip, assess and replace any rotten deck, then lay the chosen coastal-grade membrane with proper upstands and drainage falls.

5. Cleanup & sign-off

Site cleared, waste removed, and your 10-year workmanship guarantee issued alongside the membrane manufacturer warranty.

Timescales

Typical Timescales

JobTypical duration
Small flat roof / porch1 day
Garage-sized GRP or EPDM1–2 days
Large or multi-level flat roof2–4 days
Deck replacement (add-on)+1 day
Dormer flat roof1–2 days

GRP needs dry, workable temperatures to cure — we schedule around the forecast and never lay over a damp deck.

Access

Getting Safely onto Portsmouth Roofs

Most flat roofs work from towers or a small scaffold; access is straightforward on single-storey extensions and garages. Scaffold is specified for: first-floor and above flat roofs, or where edge protection is needed for safe working - always itemised in your written quote, never a hidden extra, and we arrange it.

Portsea Island's dense Victorian terraces mean rear elevations are often reached only through tight alleys, and front scaffold needs permit-controlled pavement space. Pavement scaffold and skip permits go through Portsmouth City Council; allow a few working days on streets like Albert Road, Fawcett Road, Marmion Road where space is tight.

Guarantee

Your Guarantee, Explained

The flat roof carries a 10-year workmanship guarantee; GRP and EPDM membranes carry manufacturer warranties of 20–25 years on top.

If a fault appears in covered work, we come back and put it right. No quibbling, no re-charge.

Good to know

Living Around the Work

One to three days of work over a single roof area, minimal internal disruption — we protect the space below and clear all waste. You do not need to stay home for external work - we just need power and access agreed in advance.

EPDM can be laid in most conditions; GRP needs dry weather to cure properly, which we plan around Portsmouth's coastal forecast. Solent salt air and exposed Channel weather corrode fixings and lift tiles faster than inland Hampshire.

Prefer to talk it through? A local Portsmouth roofer will answer — call 0239 307 1334.

FAQ

Frequently Asked Questions

A Velux or roof window supplied and fitted costs £1,200 to £2,000, with larger units £1,800 to £3,000. Coastal-grade flashing is included as standard — essential in Portsmouth's salt-air environment.

Standard zinc flashing kits corrode years early in coastal salt air. We fit upgraded coastal or copper flashing as standard, because a leak two winters after fitting costs far more than the modest upgrade.

Dormer windows are priced per scope, typically £3,500 to £9,000-plus for a built dormer including its GRP roof and coastal flashing. Reglazing an existing dormer costs £800 to £2,000.

Roof windows within 150mm of the roof plane are usually permitted development. Dormers on principal elevations, and any roof change in conservation areas like Old Portsmouth, may need consent. We check before quoting.

Yes — best done as part of a new GRP or EPDM flat roof so the kerb and membrane are one integrated system. Retrofitting into aged felt creates a junction that will eventually leak.

GRP fibreglass, not felt — the small dormer flat roof faces direct coastal weather and needs the seamless, salt-resistant durability GRP provides. We flash the cheeks and junctions with upgraded materials.

Yes — seal failure, flashing and full replacement. See our dedicated Velux repairs page, or call 0239 307 1334 and we'll advise whether repair or replacement is the better option.

Related Services

Related Roofing Services in Portsmouth

Velux RepairsLoft Conversion RoofingFlat RoofingRoof RepairsLead RoofingRoof InspectionsRoof ReplacementGuttering
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