Raised Collar Roof

by | May 2, 2024 | Glossary | 0 comments

Understanding the Raised Collar Roof Structure

In the world of architecture and construction, the roof structure plays a pivotal role in the overall stability and aesthetics of a building. One such intriguing roof structure is the ‘raised collar roof’. This blog post aims to shed light on this unique roof structure and its implications for building compliance testing.

What is a Raised Collar Roof?

In properties with partially sloping ceilings, the flat ceiling joists that provide restraint are raised above the base of the rafter. This configuration makes the structure less effective at resisting certain types of movement. This specific roof structure is referred to as a ‘raised collar roof’.

The Mechanics of a Raised Collar Roof

The raised collar roof is a unique structure where the collar, or horizontal member, is raised above the level of the ceiling joists. This design allows for additional headroom in the loft or attic space, making it a popular choice for conversions or extensions.

However, the raised position of the collar means it is less effective at restraining the rafters from spreading and pushing the supporting walls outwards. This is because the collar’s restraining force is applied higher up the rafter, reducing its leverage.

Implications for Building Compliance

Thermal Bridging

Thermal bridging is a critical aspect to consider in the context of a raised collar roof. This phenomenon occurs when heat or cold bypasses the insulation material through a more conductive material, leading to energy loss. In a raised collar roof, thermal bridges can occur at the junctions between the rafters and the collar. To mitigate this, it’s essential to incorporate thermal break solutions in the design, such as using insulating sheathing or specialized thermal break materials.


Proper ventilation is vital in a raised collar roof to prevent the buildup of moisture, which can lead to issues like mold growth and timber decay. The design should ensure adequate air circulation in the roof space, especially around the raised collar area. This can be achieved through methods like ridge vents, soffit vents, or mechanical ventilation systems. During building compliance testing, the effectiveness of these ventilation solutions would be assessed.


Insulation in a raised collar roof can be challenging due to the increased roof volume and complex shape. However, it’s crucial for maintaining indoor thermal comfort and energy efficiency. Insulation materials should be carefully selected and installed to fit snugly between the rafters and around the collar, leaving no gaps. Special attention should be given to insulating the raised collar area to prevent heat loss. The insulation’s performance would be a key focus during the compliance testing.

In conclusion, a raised collar roof, while offering aesthetic and space benefits, requires careful consideration of factors like thermal bridging, ventilation, and insulation to meet building compliance standards. At Building Compliance Testing Limited, we’re committed to helping you navigate these complexities and ensure your building is safe, comfortable, and compliant. Feel free to reach out to us for any queries or assistance related to your building compliance needs.


The raised collar roof offers many benefits, including increased headroom and aesthetic appeal. However, its unique structure requires careful consideration during the design, construction, and compliance testing phases to ensure the building’s safety and longevity. As always, it’s recommended to work with experienced professionals when dealing with such complex structural elements.

Remember, at Building Compliance Testing Limited, we’re here to help you navigate these complexities and ensure your building meets all necessary compliance standards. Feel free to reach out to us for any queries or assistance related to your building compliance needs.