Roof window installation, flat roof lanterns and dormer repairs across Basingstoke. Correctly flashed, properly weathered, and fitted to the tile profile on your actual roof.
Tell us the job in 30 seconds. No pushy sales, no call-out fee.
Velux and skylight installation in Basingstoke costs £1,200–£3,000 fitted for a standard roof window including flashing kit and internal finishing. Flat roof lanterns run £1,800–£4,500. Dormer window repairs are priced per scope, typically £600–£2,400 depending on the extent of flashing and timber work.
Honest advice
Is Flat Roofing the Right Fix?
Flat roofs fail in a small number of predictable ways, and which one applies decides whether a patch is sensible or simply postpones a replacement at extra cost.
Water still standing on the surface 48 hours after rain has stopped
Bubbling, blistering or splitting across a felt surface
A damp line appearing along one edge of the ceiling below, usually at a wall junction
Felt that is over 15 years old, regardless of how it looks
A deck that feels soft or springs underfoot
When it is not the answer: If the covering is under 15 years old and the failure is one identifiable split or puncture over a sound deck, a localised repair is the honest answer at a fraction of replacement cost. Read the full guide.
A roof window is a pitched-roof unit set into the plane of the tiles, weathered with a flashing kit matched to your specific tile profile. Velux is the dominant brand and the one we fit most, though Fakro and Keylite units are equally sound and sometimes better value. The critical detail is the flashing kit: a unit specified for slate fitted to a deep-profile concrete tile will leak, and no amount of sealant fixes it.
A flat roof lantern or roof light sits on an upstand kerb built into a flat roof, most commonly over a kitchen extension. The waterproofing junction between the kerb and the flat roof membrane is where these fail. We build the kerb, dress the GRP or EPDM fully up and over it, and set the unit onto that — rather than sealing the unit to a flat deck and hoping.
Dormer windows are a different job again. A dormer is a small structure projecting from the roof slope with its own roof, cheeks and multiple flashing junctions. On Basingstoke's stock they appear on loft conversions across most estates and as original features on some 1930s and earlier properties. They fail at the junctions, almost without exception.
We also fit blackout and thermal blinds, electric openers and rain sensors as part of installation, which is considerably cheaper than retrofitting later.
Local Detail
Roof Windows Across Basingstoke's Housing
Loft Conversions on the 1960s–70s Estates
The trussed rafter roofs used across Popley, Winklebury, South Ham and Buckskin were designed as structural triangles, and cutting any member without engineering input compromises the whole roof. This matters directly for roof windows: a standard Velux fits between existing rafters at 600mm centres without structural alteration, but anything wider needs a trimmed opening with proper structural support.
We size to fit between the existing rafters wherever possible. Where a larger unit is genuinely wanted, the opening is trimmed with new timber sized to carry the load and the work is notified to building control. What we will not do is cut a truss member and hope.
Chineham, Lychpit and Beggarwood: Kitchen Extension Lanterns
Flat roof lanterns over rear kitchen extensions are common across the newer estates and are the single most frequent roof light job we quote. Many of the original installations from the 1990s and 2000s used a sealant-dependent junction between the lantern kerb and the flat roof covering. Those are now failing at 20–25 years, typically appearing as a damp line along one edge of the lantern reveal internally.
The fix is to strip back the covering, rebuild the kerb, and dress new GRP fully up and over the upstand before setting the unit. It costs more than resealing and it is the last time it needs doing.
Old Basing and the Top of Town: Conservation Constraints
Roof windows on the street-facing elevation of a property in the Old Basing conservation area will generally not get consent, and on a listed building certainly will not. Conservation-grade units — low-profile, black-finished, with a central glazing bar to mimic a traditional rooflight — are sometimes acceptable on rear elevations. We advise on what is likely to be approved before you commit to anything, and we would always recommend an informal conversation with the Basingstoke and Deane conservation officer first.
Dormer Failures on Beggarwood and Hatch Warren
The 1990s–2000s estates have a high density of dormer detail as part of their design, and dormer-to-main-roof flashing is where the volume housebuilders of that era most often cut corners. Lead substitute or mastic was used in place of proper stepped lead on a great many of these. They are failing now, and the symptom is damp appearing on the ceiling directly below the dormer junction.
Pricing
Velux & Skylight Prices in Basingstoke
Prices include the unit, the correct flashing kit for your tile profile, installation, internal plasterboard reveal and making good. Structural trimming and building control notification, where required, are itemised separately.
Standard roof window (fitted)
£1,200–£1,900
Fits between existing rafters; includes flashing kit and reveal
Large roof window (fitted)
£1,900–£3,000
Requires trimmed opening and structural support
Conservation-grade rooflight
£1,600–£2,800
Low-profile black finish with central bar; Old Basing
Flat roof lantern
£1,800–£4,500
Includes kerb construction and full membrane dressing
Flat roof light (fixed dome)
£900–£1,800
Simpler unit for garages and utility extensions
Replacing an existing Velux
£850–£1,500
Like-for-like swap; new flashing kit always included
Dormer flashing renewal
£600–£1,400
Stripping mastic or lead substitute and dressing new code 4 lead
Dormer repair (cheeks & roof)
£1,200–£2,400
Where timber and covering both need attention
Electric opener retrofit
£280–£520
Considerably cheaper if specified at installation
Blinds (blackout or thermal)
£120–£260 each
Fitted at installation
Roof windows fitted between existing rafters need no structural alteration. Anything requiring a trimmed opening on a trussed rafter roof will need structural design and building control notification — we handle both and itemise them clearly.
Key Fact: Building Regulations Approved Document A requires that any alteration to a trussed rafter roof — including trimming an opening for a roof window wider than the existing rafter spacing — be designed so the structural integrity of the roof is maintained, with truss members never cut without engineered support. Source: Building Regulations Approved Document A — Structure
Thinking about a roof window? Free survey and honest advice on what your roof will take.
Clear steps from first call to completed work. No call-out fee, no obligation, and a written quote before anything starts.
1
Free Survey and Roof Assessment
We measure the rafter spacing, identify your tile profile for the correct flashing kit, check the internal ceiling line, and confirm whether structural trimming is needed.
2
Quote and Specification
The quote names the unit, the flashing kit matched to your tiles, glazing specification, and any structural or building control work. Blinds and openers are cheaper specified now than retrofitted.
3
Installation
Tiles are stripped back, the opening formed, the unit set and the flashing kit dressed into the surrounding tile courses. Internally the reveal is boarded and finished ready for decoration.
4
Weather Test and Handover
We water-test the installation before making good internally, register your manufacturer warranty and hand over operating instructions and your 10-year workmanship guarantee.
Ready to start? Call 0125 624 2410 for your free survey.
The process
From First Call to Sign-Off
1. Free survey and deck assessment
We check the covering, probe the deck for rot and delamination, measure the existing falls and inspect every upstand and outlet.
2. System recommendation and quote
GRP or EPDM chosen on the roof's shape, use and access — not on which costs more. Strip, deck, insulation, membrane and trims all itemised.
3. Strip to deck
The old covering comes off completely. We never overlay: it hides deck rot, adds weight and voids the manufacturer guarantee.
4. Deck repair and falls
Failed timber replaced with marine-grade plywood, and drainage falls built in with firring strips to at least 1:40.
5. Membrane and water test
GRP laid wet to a seamless shell, or EPDM fully bonded and mechanically terminated. We water-test drainage before handover.
Timescales
Typical Timescales
Job
Typical duration
Porch or bay top
1 day
Single garage
1–2 days
Rear extension
2–3 days
System-built integral sections
3–5 days
Deck replacement
+1–2 days
GRP resin needs above roughly 5°C and dry conditions to cure, which limits winter scheduling. EPDM tolerates cooler weather and is often the practical winter choice.
Access
Access, Scaffolding & Permits in Basingstoke
Most flat roofs are reached from a tower or ladder with edge protection. Scaffold is specified for: first-floor and above, any roof with a walk-on requirement, and anywhere edge protection cannot be safely tower-mounted - always itemised in your written quote, never a hidden extra, and we arrange it.
Most Basingstoke estate housing has generous verges and driveway space, so scaffold and skips drop straight onto private ground. The older streets around the Top of Town are the exception, with narrow frontages and controlled on-street parking. Pavement scaffold and skip permits go through Basingstoke and Deane Borough Council; allow a few working days on streets like Wote Street, Church Street, New Street where space is tight.
Pricing
What Flat Roofing Costs in Basingstoke
Job
Typical range
Notes
Porch or bay top
£650–£1,200
Minimum-job pricing applies
Single garage — EPDM
£1,200–£1,900
One-day fit, 20-year guarantee
Single garage — GRP
£1,500–£2,400
Rigid walkable finish, 25-year guarantee
Extension roof — EPDM
£2,000–£3,400
Simple rectangular areas
Extension roof — GRP
£2,400–£4,200
Preferred where upstands or outlets are involved
System-built integral sections
£2,400–£4,800
South Ham, Popley — new deck and rebuilt falls
What moves the price
Area, and the fact that small roofs carry proportionally higher setup cost
System choice — GRP runs roughly 25 to 40% above EPDM on like-for-like area
Deck condition, which is unknown until the old covering is stripped
Detail complexity: upstands, outlets, roof lights and pipe penetrations
Whether insulation is being upgraded at the same time
Worked example: Three integral flat sections on a system-built semi on Crossborough Hill, South Ham: strip, new marine ply deck, rebuilt falls and GRP throughout — £4,100 including VAT over four days.
A 10 to 20% deposit on material order for flat roof work, balance on completion after the water test. Nothing before materials are on site. All prices include VAT.
Covering RG21, RG22, RG23, RG24 and surrounding postcodes.
Guarantee
The Guarantee in Plain Terms
GRP carries a 25-year manufacturer guarantee and EPDM 20 to 25 years, both alongside our written 10-year workmanship guarantee.
Covered: workmanship for 10 years, in writing, transferable if you sell.
On top: manufacturer warranties on materials (terms vary by product).
Not covered: storm or impact damage - that is an insurance matter, and we will document it for your claim.
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
Noise during strip, and GRP has a distinct resin smell for a day that disperses quickly. Access to the room below is unaffected. You do not need to stay home for external work - we just need power and access agreed in advance.
EPDM installs in most conditions. GRP needs a genuinely dry window, so we schedule it around the forecast rather than pressing on and producing a finish that fails. Basingstoke sits on chalk downland at around 80 metres, so drying is quick after rain but frost nights run longer than the Hampshire coast.
Customer Reviews
What Basingstoke Homeowners Say
★★★★★
"Two Veluxes in the loft conversion. They sized them to fit between the existing trusses rather than cutting anything, which another firm had blithely offered to do. £2,700 for the pair, fitted and finished."
Amanda N. · Woodbury Road, Hatch Warren
★★★★★
"Lantern over the kitchen extension had leaked along one edge since we moved in. They stripped it back, rebuilt the kerb and dressed the GRP right up and over. Bone dry through the winter."
Adrian B. · Redwood Close, Beggarwood
★★★★★
"Dormer junction was mastic, not lead — original builder's shortcut. Proper stepped lead fitted for £1,100 and the ceiling stain has finally stopped spreading."
Joanne K. · Chestnut Walk, Lychpit
FAQ
Frequently Asked Questions
£1,200–£1,900 for a standard unit fitted between existing rafters, including the flashing kit, internal reveal and making good. Larger units needing a trimmed opening run £1,900–£3,000 plus structural design where required.
Usually no — roof windows on most Basingstoke properties fall under permitted development provided they do not project more than 150mm beyond the roof plane. Conservation areas and listed buildings are the exception, and street-facing elevations in Old Basing will generally need consent.
Yes, and most Basingstoke estate housing has exactly that. A standard unit fits between existing rafters without structural alteration. Anything wider needs a trimmed opening with engineered support — never a cut truss member left unsupported.
Almost always because the original installer relied on sealant between the lantern kerb and the flat roof covering, rather than dressing the membrane fully up and over the upstand. It typically fails at 20–25 years. The fix is rebuilding the junction properly, not resealing it again.
On rear elevations, sometimes, using a conservation-grade unit — low-profile, black-finished, with a central glazing bar. Street-facing elevations are unlikely to get consent. We advise on what is realistic before you commit and recommend an informal conversation with the conservation officer.
Yes — it costs £120–£260 per unit fitted at installation versus considerably more as a retrofit, because the internal reveal is already open. The same applies to electric openers and rain sensors.
Yes. A like-for-like replacement costs £850–£1,500 including a new flashing kit, which we fit as standard — reusing a twenty-year-old flashing kit on a new unit is a leak waiting to happen.
