Eaves
/ iːvz /
Also known as: eaves overhang, eaves line
Definition
The eaves are the lowest edge of a pitched roof where it overhangs the top of the external wall. The eaves assembly includes the fascia board, soffit board, guttering, and the lowest courses of tiles or slates. Correctly detailed eaves protect the wall from rainfall, provide a fixing for the guttering, and ventilate the roof void to prevent condensation.
In practice
There are two main eaves types: closed eaves where a soffit board fills the gap between the fascia and wall (the most common modern form), and open eaves where the rafter feet are left exposed, more typical of traditional or rural buildings. On closed eaves, ventilation is provided by perforated soffit boards or slot vents.
The roofing underlay (felt or breathable membrane) must be dressed to fall into the gutter at the eaves rather than stopping short and allowing wind-driven rain behind the fascia. A correctly lapped eaves detail is one of the most common areas inspected during a roof survey. Gutter sizing must also be adequate for the roof area - undersized gutters overflow in heavy rain and cause damp at the base of the wall below.
Building Regulations
Approved Document F requires a minimum 25mm continuous clear airway at the eaves for cold pitched roof construction, to allow cross-ventilation with air outlets at the ridge or high level. Where insulation is laid between the rafters, a warm roof or hybrid construction approach must be used to maintain the ventilation path.
Full Building Regulations guidanceSee also