Rear Extension Roof Structure with Velux Roof Windows

A well-designed roof structure is one of the most important elements of any house extension. Not only does it provide structural stability and weather protection, but it also plays a huge role in energy efficiency, natural light, and the overall appearance of the build.

The project shown here features a traditional pitched timber roof incorporating two roof windows, allowing plenty of daylight into the new extension while maintaining a clean and practical design.

Roof Structure Before Tiling

The first stage of construction involved installing the timber roof structure. Pressure-treated timber was used to form the rafters, which transfer the roof loads safely down to the supporting walls.

Key structural components included:

• Wall plates fixed to the masonry

• Timber rafters spanning from the existing property to the external wall

• Trimmers around the roof window openings

• Structural supports to distribute loads evenly

• Breathable membrane for weather protection

The roof windows were carefully positioned between the rafters and supported using additional trimming timbers to maintain the roof’s structural integrity.

Benefits of Roof Windows

Installing roof windows provides several advantages:

• Increased natural daylight

• Improved ventilation

• Reduced reliance on artificial lighting

• Enhanced feeling of space within the extension

• Modern architectural appearance

The roof windows shown were integrated directly into the timber structure before the roof covering was installed.

Timber Roof Framing

The timber framework forms the skeleton of the roof.

Structural Considerations

When designing a pitched extension roof, builders must consider:

Roof Pitch

The pitch affects:

• Drainage performance

• Tile selection

• Building regulations compliance

• Overall appearance

Load Calculations

The roof structure must support:

• Roof tiles

• Battens

• Membranes

• Insulation

• Snow loads

• Wind uplift forces

• Roof windows

Proper sizing of rafters is essential to prevent sagging and ensure long-term performance.

Installing the Roof Windows

The roof windows were fitted during the framing stage.

Each opening required:

• Double trimmers

• Additional structural support timbers

• Manufacturer-approved flashings

• Weatherproof detailing

Careful planning ensured the windows aligned with the room layout below while maintaining sufficient spacing between structural members.

Roof Covering Installation

Once the structure was complete, the roof was prepared for tiling.

The build-up included:

1. Breathable roofing membrane

2. Tile battens

3. Concrete roof tiles

4. Roof window flashings

5. Ridge and verge detailing

This layered system protects the extension from wind-driven rain while allowing moisture vapour to escape from within the roof construction.

Finished Tiled Roof

The completed roof blends seamlessly with the existing property.

Key features include:

• Matching roof tiles

• Integrated roof windows

• Weatherproof flashings

• Consistent roof pitch

• Clean roofline appearance

The finished installation provides both durability and visual appeal while maximising natural light into the extension below.

Insulation and Energy Efficiency

Modern extension roofs must meet strict thermal performance requirements.

Typical insulation measures include:

• High-performance PIR insulation between rafters

• Additional insulation beneath rafters

• Vapour control layers

• Airtight detailing around roof windows

These elements help reduce heat loss and improve the home’s energy efficiency.

Why a Timber Pitched Roof Remains Popular

Timber pitched roofs continue to be one of the most common choices for residential extensions because they offer:

• Excellent structural performance

• Long lifespan

• Cost-effective construction

• Compatibility with roof windows

• Traditional appearance

• Strong resale appeal

When built correctly, a timber roof structure can last for decades with minimal maintenance.

Project Summary

This rear extension demonstrates the complete process of constructing a pitched timber roof with integrated roof windows. From the initial framing stage through to the finished tiled roof, careful planning and quality workmanship ensure a durable, weatherproof, and energy-efficient result.

The addition of roof windows transforms the internal space by bringing natural light deep into the extension while maintaining a practical and attractive roof design.