bay window roof replacement in Sunbury (201)

Dormer and roof windows are a great way to bring natural light, ventilation, and usable space into your home.

Whether you’re upgrading a loft conversion or opening up a dark attic, adding a roof window can transform the feel of your home.

If you’re looking for roof or dormer window installation in Sunbury-on-thames, Checkatrade can help you find installers to bring your project to life with care and attention to detail.

What are roof windows and dormer windows?

Roof windows

Roof windows are installed directly into the slope of the roof and are designed to bring in light and fresh air.

They’re widely used in lofts, converted attics, upstairs bathrooms, and even solid-roof conservatories.

Roof windows are sometimes confused with skylights or rooflights, but there are differences:

• Skylights typically don’t open
• Rooflights are often fixed flat to the roof
• Roof windows are usually larger and designed to open for ventilation

Types of roof windows

You’ll find a wide variety of options depending on roof type and room layout:

• Centre pivot windows
• Top-hung roof windows
• Balcony roof windows
• VELUX-style pitched roof windows
• Flat-roof domes
• Roof lanterns and skylights
• Walk-on rooflights for terraces

Dormer windows

Dormer windows extend outward from the roof, creating extra headroom and floor space. They can make a loft feel like a full-height room.

Types of dormer windows

Dormer windows come in different shapes and styles, each shaping the look of your loft:

• Gabled dormers
• Flat roof dormers
• Hipped dormers
• Shed dormers
• Eyebrow dormers
• Segmental arched dormers

Your installer can help you understand which design suits your roof structure and planning rules.

Benefits of adding dormer or roof windows

• More natural light, reducing the need for artificial lighting
• Improved ventilation for fresher, healthier rooms
• Better use of previously dark attic spaces
• Potential to increase usable floor space (dormers)
• Increased property value
• Suitable for loft conversions, bathrooms, stairwells, and extensions

Do you need planning permission to install roof or dormer windows?

Roof windows: Usually fall under permitted development, meaning planning permission is not required unless the window protrudes significantly or the property is in a conservation area.

Dormer windows: May require planning permission if the dormer extends above the existing roof height or alters the roof shape.

Building Regulations approval is often required for structural work, roof alterations, and glazing.

How long does installation take?

• Roof windows: Typically half a day to 1 day
• Flat rooflights or lanterns: Often 1 day
• Dormer windows: Depending on size, usually 2–5 days, with structural work taking longer

Timelines vary depending on access, internal finishes, and weather conditions.

Popular dormer and roof window installation jobs

• Adding roof windows to brighten loft spaces
• Installing skylights in flat-roof extensions
• Upgrading old or leaking roof windows
• Fitting dormer windows as part of a loft conversion
• Replacing existing units with larger, energy-efficient glazing
• Adding balcony-style roof windows to create feature spaces

How much do roof windows and dormer windows cost?

The cost of roof or dormer windows vary depending on size, glazing, installation complexity, and roof structure.

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What might affect the cost?

• Window size and glazing type
• Roof access and height
• Structural modifications needed
• Insulation, flashing kits, and finishing
• Internal plastering and decoration
• Property location

For a tailored estimate use our Job Value Estimator, and see our roof and dormer window cost guides for detailed pricing.

What should be included in your quote?

When comparing quotes from installers in Sunbury-on-thames, check for:

• Exact window type and size
• Supply and installation costs
• Flashing kit and insulation details
• Structural work (if needed)
• Making good internally (plastering, finishing)
• Scaffolding or access equipment
• Waste removal
• Estimated timescales
• Planning or Building Regulations guidance

An itemised quote helps you compare options clearly.

Dormer & roof windows vs other ways of adding light

Roof windows

- Pros: quick to install, excellent light/ventilation, great for lofts

- Cons: limited effect on increasing space

Dormer windows

- Pros: adds height, light and usable floor area

- Cons: higher cost, may require planning approval

Roof lanterns

- Pros: ideal for flat-roof extensions, dramatic natural light

- Cons: not suitable for pitched roofs or lofts

How long do dormer and roof windows last?

Good-quality roof windows and dormer windows typically last 20–30 years, depending on glazing, seals, and exposure to the elements.

Longevity depends on:

• Glazing quality
• External weather exposure
• Correct installation
• Routine maintenance

Maintenance tips for dormer and roof windows

• Keep frames and glass clean to maintain transparency
• Check seals annually for wear
• Ensure flashing is intact to prevent leaks
• Clear nearby moss or debris
• Lubricate hinges on opening roof windows
• Inspect internal plasterwork for damp spots

Tips for hiring a roof or dormer window installer in your area

Before choosing a roof or dormer window installer near you:

• Read customer reviews on Checkatrade
• Ask what window brands they install (e.g., VELUX)
• Request to see examples of recent installations
• Confirm whether internal finishing is included
• Check if scaffolding is needed and included
• Compare several quotes to ensure good value
• Ask about planning and Building Regulations advice

To find installers committed to quality and a job done right, search for dormer and roof window installation in Sunbury-on-thames with Checkatrade.