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Install a Velux roof window.
Velux or Roto roof window — cut into pitched roof, flashing fitted, weather-sealed.
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Costs, timelines, pitfalls and the right questions to ask before any roofer starts on roof Window (Velux) Installation.
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Top tips
Hiring a roofer, without the regret.
Four moves that separate a smooth job from a nightmare.
Wrong flashing for tile
EDW for concrete tile, EDL for slate, EDJ for low-profile. Wrong flashing leaks within months.
Structural cut incorrect
Without proper trimmer, adjacent rafters sag. Always cut + trim.
Condensation on glass
Inadequate room ventilation. Trickle vent on the Velux itself helps.
Cheap Chinese copies
Generic roof windows lack quality flashing systems. Always genuine Velux or Fakro.
Costs & timeline
Know what it costs. Know when it ends.
Indicative UK ranges and a typical week-by-week schedule.
Cost range
By job type
Inc. VAT · 2026
Source: NMT quotes
Source: NMT quotes
Velux manual standard size, supplyMK04 / MK06 size
£350–£700
Velux solar-electric, supplySolar charge, app control
£550–£1.2k
Velux Integra electric, supplyMains powered
£700–£1.4k
Flashing kit (tile profile)EDW for tile, EDL for slate
£120–£300
Single Velux fitted (during re-roof)Cheapest option
£800–£1.5k
Single Velux retrofitIncluding access and tiles
£1.2k–£2.5k
!
Quote spread is typically ± 18% — always get 3 quotes.
Timeline
Semi-detached full re-roof · week by week
Typical
4 phases · 3 wk
4 phases · 3 wk
W1
W2
W3
Scaffold erection
Strip + felt + battens
Tile + ridge + verge
Flashings + snags
!
Schedule slips on dependencies — pad each phase by 10–20% for real-world delays.
At a glance
Infographic · VideoThe Roofer briefing.
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Roofer explained
Velux and Fakro roof windows bring natural light into lofts, conversions and bathrooms. Expect to pay £800–£3,500 for a UK Velux installation including frame, flashing kit and labour. Best fitted during a re-roof — saves access cost.
What Does the Work Involve?
The roofer marks out the opening on the roof, cuts the existing tiles and felt, cuts the rafters (with a structural trimmer fitted to support adjacent rafters), fits the Velux frame plumb and square, installs the flashing kit around it (specific to the tile profile), re-tiles around the unit, and finishes the internal liner and architrave. Electric Velux units need wiring by a Part P electrician.
Typical Costs
| Item | Low (£) | High (£) | Notes |
|---|---|---|---|
| Velux manual standard size, supply | 350 | 700 | MK04 / MK06 size |
| Velux solar-electric, supply | 550 | 1,200 | Solar charge, app control |
| Velux Integra electric, supply | 700 | 1,400 | Mains powered |
| Flashing kit (tile profile) | 120 | 300 | EDW for tile, EDL for slate |
| Single Velux fitted (during re-roof) | 800 | 1,500 | Cheapest option |
| Single Velux retrofit | 1,200 | 2,500 | Including access and tiles |
| Sun tunnel installation | 500 | 1,400 | No structural cut needed |
| Electric wiring (Part P) | 150 | 400 | Integra wiring |
How Long Does It Take?
During a re-roof: 2–3 hours additional time per window. Standalone retrofit: 1 day per window. Sun tunnels: 4–6 hours.
DIY or Professional?
Professional. Cutting rafters needs proper structural trimmer detail. Flashing must be correct for the tile profile. Building Regs notification needed (sometimes).
Choosing the Right Tradesperson
Velux Approved Installer (for warranty) or general roofer. Confirm flashing kit matches the existing tile profile. Get the warranty in writing — 10 years standard.
UK Regulations
Approved Document Part L — U-value requirement (1.4 W/m²K or better). Part B — escape window in some habitable rooms. Part F — ventilation continuity. Building Regs notification through the FENSA scheme (Velux Approved Installer can handle).
Common Problems
- Wrong flashing for tile: EDW for concrete tile, EDL for slate, EDJ for low-profile. Wrong flashing leaks within months.
- Structural cut incorrect: Without proper trimmer, adjacent rafters sag. Always cut + trim.
- Condensation on glass: Inadequate room ventilation. Trickle vent on the Velux itself helps.
- Cheap Chinese copies: Generic roof windows lack quality flashing systems. Always genuine Velux or Fakro.
Frequently Asked Questions
Velux or Fakro?
Velux: market leader, more flashing options, wider range. Fakro: cheaper, equivalent quality, slightly fewer accessory options. Both are good choices.
What size Velux do I need?
Standard sizes: MK04 (78 × 98cm), MK06 (78 × 118cm), MK08 (78 × 140cm). Choose based on room size and ceiling type. Manufacturer's online calculator helps.
Manual or electric?
Manual: cheapest, hand-cranked. Solar-electric: self-powered, app-controlled, weather-sensitive (auto-close in rain). Integra (mains): full smart-home integration.
Sun tunnel vs Velux?
Sun tunnel: brings light from roof to ceiling without a full structural cut. Cheaper, no ventilation. Velux: full window with opening, ventilation, more light, more cost.
How long does a Velux last?
Frame and glass: 25–30 years. Hinges and seals: may need replacement at 15–20 years. Velux service kit available.
Building Regs needed?
Yes — usually. Velux Approved Installer handles this through FENSA. Standalone installs need building notice or full plans application.
This guide was written with AI assistance and is intended for general information only. Prices are estimates based on UK averages and may vary by region. Always get at least three quotes and consult a qualified professional before starting any work.
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