Velux Windows — Installation, Flashing and Costs for Salisbury Homeowners

Velux and similar roof lights are one of the most popular home improvement additions across Salisbury's housing stock — adding natural light to loft conversions, attic bedrooms and first-floor extensions. But they are also one of the most consistent sources of roof leaks when installed incorrectly or when the flashing system reaches the end of its service life. This guide covers everything you need to know.

Do I Need Planning Permission for a Velux Window in Salisbury?

Permitted development rights allow most Velux installations without planning permission, subject to these conditions:

• The window must not project more than 150mm from the existing roof slope
• The top of the window must be no higher than the ridge
• Not on the principal elevation facing a highway (front of the house)
• Not on any wall or roof slope of a side elevation facing a highway

Exceptions requiring planning consent:

• Listed buildings — all external alterations require listed building consent
• Salisbury conservation area properties — conservation area consent required
• Properties where permitted development rights have been removed (Article 4 direction)

We check the planning position for your specific property before any installation is confirmed.

Permitted development rules allow rooflights that project no more than 150mm above the roof plane and sit no higher than the ridge — installations exceeding these limits require planning permission.

— GPDO 2015, Class C

Installation Costs in Salisbury (2026)

Type	Supply and install	Notes
Single Velux — standard pitched tile	£700–£1,200	Includes flashing kit
Single Velux — conservation unit	£1,000–£1,600	Low-profile frame for conservation areas
Velux flashing replacement only	£250–£500	Per window, existing window retained
Two-window installation	£1,200–£2,200	Economies on scaffold and access
Velux on flat roof / pitched flat conversion	£900–£1,800	Additional flashing complexity

Why Velux Flashings Fail in Salisbury

The majority of Velux-related leaks we attend are flashing failures rather than window failures. The window itself is rarely the problem. The EDW (Extendable Drainage Window) flashing kit supplied with standard Velux windows has a service life of approximately 10–15 years in exposed Wiltshire conditions — less on south-west-facing slopes or plateau sites like Larkhill and Old Sarum where UV degradation and thermal cycling are more intensive.

The failure modes are:

• Apron joint breakdown: The bottom apron flashing separates from the adjacent tile course, allowing water to track behind the apron
• Side soaker failures: The aluminium soakers on the sides of the frame corrode or lift, allowing water to enter along the window sides
• Top flashing separation: The top counter-flashing lifts from the wall or tile junction in thermal cycling

Conservation Area Installations

Salisbury's conservation areas include specific guidance on roof lights. Conservation-spec Velux units — with slimmer sight lines, grey powder-coated frames and recessed profiles — are generally more acceptable than standard units. The key planning consideration is whether the roof light is visible from public areas and what visual impact it has on the character of the area. We advise on appropriate specifications and carry out conservation area installations regularly.

Dormer vs Velux — Which Is Better?

For converting a loft space in Salisbury, the choice between Velux (roof light) and a dormer extension affects both planning and cost:

Factor	Velux roof light	Dormer
Planning permission	Usually not required	Usually required
Cost	£700–£2,200 per window	£10,000–£25,000+
Head height gained	None	Significant
Natural light	Good	More light, better views
Maintenance	Flashing replacement at 10–15 years	Full roofing maintenance requirements

Last reviewed: 21 July 2026 by Salisbury Roofing Experts