Roof Window Maintenance and Servicing Costs

Roof windows — including products from Velux, Fakro, and Roto — require periodic maintenance to remain weathertight and operate correctly. In UK loft conversions and older properties with original skylights, neglected maintenance is one of the most common causes of interior water damage, yet the cost of a professional service visit is modest compared with the repair bills that follow a failed flashing or deteriorated seal.

Key points

• Professional roof window servicing typically costs £80–£200 per window in the UK (Indicative UK costs, last reviewed 2026-05-07), covering seal inspection, flashing checks, mechanism lubrication, and glazing assessment.
• Flashing replacement — the most common professional repair on older roof windows — typically costs £150–£350 per window depending on flashing type and roof access difficulty.
• Velux recommends annual inspection of seals, flashings, and the opening mechanism; failure to carry out periodic maintenance may affect warranty claims under the product guarantee.
• Glazing unit replacement for misted or failed sealed units typically costs £150–£400 per window, depending on model and specification.
• Any external roof window work must comply with the Work at Height Regulations 2005 and should use appropriate scaffolding or platform access — do not attempt flashing or tile work without proper equipment.

What roof window maintenance involves

A standard annual or biennial service visit covers several components.

External flashing inspection: Checking lead or aluminium flashings for lifting, cracking, or gaps where rainwater may track under surrounding tiles and into the roof structure.

Seal and gasket check: Inspecting weatherproofing seals around the glazing unit and frame for cracking, compression loss, or displacement that allows draughts or water ingress.

Mechanism lubrication and adjustment: Lubricating hinges, stays, and locking bars; adjusting closing pressure where the window no longer seals tightly when shut.

Glazing unit check: Looking for misting or condensation between panes, which indicates a failed sealed unit requiring glazing replacement.

Drainage channel inspection: Clearing debris from internal drainage channels on centre-pivot models that route incidental condensation away from the frame.

Many homeowners can safely perform internal checks from inside the room. External flashing checks, drainage clearing, and tile inspection require roof access and should be carried out by a qualified roofer or window specialist.

Roof window maintenance and repair costs

Indicative UK costs, last reviewed 2026-05-07. Costs vary by roof pitch, window size, model, and access difficulty.

Common problems and their likely causes

Leaking around the frame or flashing is the most common and urgent issue. It is usually caused by lifting or cracked flashing, displaced underfelt at the window perimeter, or degraded sealant at the junction between the flashing kit and surrounding tiles. Water tracking behind the flashing can cause extensive timber rot and ceiling damage if left untreated.

Condensation between panes indicates a failed sealed unit — the inert gas fill has been lost, reducing thermal performance and causing visible misting. The glazing unit itself needs replacing; the frame and flashing are usually unaffected. Replacement units are available from the manufacturer or from specialist glazing suppliers.

Stiff or difficult to open is usually caused by dried-out or corroded hinges and stays, or by a warped frame. Annual lubrication prevents most mechanism issues; frames that have swollen due to moisture ingress may require assessment to determine whether repair or replacement is more cost-effective.

Draughts around a closed window are typically caused by a compressed or degraded perimeter seal. Replacement seal kits are available for most Velux and Fakro models from manufacturer stockists.

Annual homeowner maintenance checklist

The following can be checked safely from inside the room without roof access:

• Open and close the window fully — does it operate smoothly and latch firmly shut?
  
• Inspect the internal frame and sill for water staining, mould, or condensation at the corners
  
• Check for visible misting or fogging between the glass panes
  
• Examine the surrounding ceiling plasterwork for water staining or damp patches
  
• Inspect internal perimeter seals for visible cracking or gaps
  
• Lubricate hinges, stays, and locking bars with a dry PTFE spray or manufacturer-recommended product (avoid oil-based lubricants that attract dust)
  

Arrange a professional external inspection to check:

• Condition and adhesion of all flashings
  
• Internal drainage channel clearance
  
• Tile condition immediately surrounding the window
  
• Visible sealant condition at the flashing perimeter
  

What to ask before accepting a quote

• What specifically will be inspected and serviced during the visit?
• Do you have experience with this brand and model of roof window?
• What access equipment will you use, and is scaffolding required or included in the price?
• Is VAT included?
• Will you provide a written condition report or photographs after the visit?
• What is excluded from the service price?
• If additional repairs are identified during the visit, will you quote separately before proceeding?

When to get professional help

Arrange a professional inspection if you notice water staining on the ceiling or plasterwork below a roof window, or if the window has not been professionally serviced in more than two years. Do not attempt to inspect flashings or work on tiles without proper access equipment — pitched roof work above two metres presents a significant safety risk under the Work at Height Regulations 2005.

Contact a qualified roofer or window specialist urgently if:

• Water is entering the room during or immediately after rain
• The window frame is visibly warped, cracked, or damaged
• Surrounding tiles are displaced or broken
• Internal timber around the frame shows discolouration or early signs of rot

How Housey can help

Housey connects you with local roofers experienced in roof window repairs and flashings, and with window and door installers who specialise in roof window servicing and glazing unit replacement. Request quotes from verified tradespeople in your area and compare them before booking.

Frequently asked questions

How often should roof windows be serviced?

Velux and most other manufacturers recommend a full inspection at least once a year. In practice, many UK homeowners arrange a professional external check every two years and carry out a basic internal inspection annually. Windows older than ten years benefit from annual professional checks, as flashings and seals degrade with age and UV exposure.

Can I service my Velux window myself?

Internal checks — lubrication, seal inspection, and mechanism testing — can usually be carried out safely by a homeowner from inside the loft or room. External checks involving the flashing, drainage channels, and surrounding tiles require roof access and should only be undertaken with appropriate scaffolding or platform access. DIY pitched-roof work is not recommended.

How much does it cost to replace a roof window seal?

Seal replacement typically costs £60–£120 per window when carried out professionally (Indicative UK costs, last reviewed 2026-05-07). Many manufacturers supply replacement seal kits for popular models, which can be fitted internally without roof access — check the manufacturer's website using your model number. Kits for common Velux models are widely available from builders' merchants.

What causes a roof window to leak?

The most common causes are lifting or cracked flashings, failed or displaced perimeter seals, and blocked or damaged drainage channels. Less commonly, a cracked glazing unit, loft condensation, or poorly re-tiled surrounds after earlier work may be responsible. A professional inspection will usually identify the cause before repair work is agreed.

Does a manufacturer warranty cover roof window repairs?

Velux and Fakro typically offer 10–20 year product warranties covering manufacturing defects in the glazing unit, frame, and mechanism. Flashings are often sold and warranted separately. Normal wear, degraded seals, and routine maintenance items are usually excluded. Warranty claims typically require evidence of correct installation and regular maintenance.

Sources and further reading

• Velux UK: maintenance and care guidance — Velux
• HSE: Working at Height Regulations 2005 — Health and Safety Executive
• FENSA: competent persons scheme for window installation — FENSA
• GOV.UK: building regulations approval — GOV.UK