What are roof eaves and what is their function

Marley solar panels on a domestic house

What are eaves?

Eaves are found at the edges of a roof, where they extend beyond the wall of a building. In their simplest form, such as on a garden shed, that may be all there is to say about the eaves. But in most buildings, eaves are an important part of the complete roof system and they fulfil several roles, including:

  • Keeping rainwater away from the walls – Because the eaves extend beyond the external wall, they guide rainwater away so it can fall to the ground or be collected in the gutter. This helps ensure that precipitation does not pool near the top of the wall or get into the wall cavity.
  • Providing ventilation – Roof ventilation can be incorporated along the entire length of the eaves, providing low-level ventilation to the roof space and helping prevent condensation; a requirement of BS 5250:2021.
  • Supporting the guttering – Gutters run along the bottom of the eaves, gathering rainwater or melted snow, and guiding it away from the structure.
  • Supporting the roof membrane – To avoid a sagging roof membrane, special clips or trays can be installed at the eaves.
  • Keeping animals out of the roof – The eaves should be designed to keep birds, cats, squirrels, bats, insects and other animals or pests out of the roof space.
  • Shading – Sometimes, eaves may extend out from the rooftop far enough to provide a degree of shade, possibly reducing solar gains or glare inside the building.
  • Contributing to the building’s aesthetic – The eaves play a significant part in the roof’s overall look, giving the building an attractive, finished appearance.

What are the main types of roof eaves?

When planning a roof structure, there are four main types of eaves to consider. The right choice will depend on aesthetic preferences as well as the rest of the roof structure. The four main types are:

  • Exposed eaves – With exposed eaves, the rafters and underside of the roofing are visible from underneath. These exposed elements must be finished to protect them from weather and wear and tear.
  • Boxed-in eaves – These are similar to the exposed eaves, but the rafters have a cover that follows the roof pitch.
  • Soffited eaves – The soffit is a panel that runs horizontally under the eaves, creating a ceiling-like structure from the bottom edge of the eaves to the external wall of the building.
  • Abbreviated eaves – This is when the eaves end as close to the edge of the building as possible. There is almost no overhang at all with this type of eaves.

What does a roof eave comprise of?

The eaves of a roof comprise several elements, which all work together to give the finished eaves a professional and attractive appearance whilst protecting the roof and walls from weather and damp. The elements that make up a roof eave are:

  • Dry verge caps – An important part of a dry-fix roofing system, dry verge caps are specially formed roof tiles that wrap around the edge of the gabled end for a finished appearance.
  • Soffits – As described above, the soffit runs horizontally under the eaves. Soffits are often made from timber or PVC.
  • Fascia – The fascia runs vertically under the horizontal edges of a roofline. It is fixed directly to the roof trusses and supports the bottom row of tiles. It is also the fixing point for guttering.
  • Barge board – Similar to fascia, barge boards are used on the gable end, running diagonally along the side of the building.
  • Box ends – This is located on the corner of the eaves, connecting the fascia and soffits to the barge board.
  • Ventilation – Eaves vents allow fresh air into the roof void, preventing condensation. Options include soffit vents, as well as ventilation trays that run continuously along the bottom edge of the roofline.
  • Guttering – Gutting collects rainwater from the roof and carries it away efficiently, preventing water from collecting on the roof or running down the sides of the building. It is usually fixed to the fascia.
  • Membrane support trays – To prevent the underlying roof membrane from sagging, eaves can contain membrane supports. These usually lead into the gutter, so any rainwater that gets through the roof tiles and onto the underlay can be carried away.

Here at Marley, our complete roofing system includes everything you need to ensure that a roof’s eaves are both functional and aesthetically pleasing.

We offer a variety of eaves ventilation products, from soffit vents to continuous eaves ventilation products. Visit our 10mm eaves vent system page or our 25mm eaves vent system page to learn about those products in more detail. And if you need any technical specification advice, please get in touch to discuss your project with a member of our team. 

Category: Roofing Technical