A roof soffit is the underside of a projecting roof: the surface you see when you look up at the eaves overhang and the gutter from below. The Dutch language preserves an old, regional word for it — onderplezier — but in modern practice it is simply the soffit, the eaves lining or the overhang underside.
What it consists of
Where a roof has an overhang, the roof plane projects beyond the wall. The underside of that projection has to be finished, otherwise you look straight up at the rafter feet, the battens and the sarking. The finish generally comprises:
- Fascia board — the vertical board at the end of the overhang, usually carrying the gutter
- Soffit board — the horizontal or raking surface on the underside
- Bargeboard — the finish along the sloping edge at a gable
Why the overhang matters
A properly formed and finished overhang does more than look tidy:
- Protects the wall — an overhang of 300-600 mm keeps a significant part of driving rain off the wall and the windows, extending the redecoration cycle
- Shades in summer — on a south-facing elevation the overhang intercepts the high summer sun while letting the low winter sun in underneath
- Closes the roof — keeps birds, wasps and vermin out of the roof space
- Provides ventilation inlet — on a ventilated roof, air needs to enter here, through a vented soffit strip or a bird comb, not through a random gap
Soffit materials
- Painted timber or plywood — traditional, and needs maintaining on the same cycle as the rest of the joinery
- Fibre cement board — dimensionally stable and low maintenance
- uPVC or aluminium profiles — often with integral ventilation slots, effectively maintenance-free
> Never seal the soffit completely on a ventilated roof construction. Without an inlet at the eaves, ridge ventilation does not work and condensation can form under the sarking.
Related terms
- Roof overhang
- Fascia
- Bargeboard
- Eaves
- Gutter
- Bird comb
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