Do you need vented soffits?
Yes, unless the eaves are ventilated another way. A pitched roof needs a continuous air path at the eaves. A vented soffit, over-fascia vent or tile vent can provide it. Roofs at 15 degrees or more with a loft usually need a 10 mm continuous opening.
How much ventilation does the roof need?
| Roof type | Eaves opening |
|---|---|
| Pitched, 15 degrees or more, loft void | 10 mm continuous (10,000 mm2 per metre) |
| Under 15 degrees, flat, or room in roof | 25 mm continuous (25,000 mm2 per metre) |
What are the options for providing it?
- Vented soffit board or soffit vent strip
- Over-fascia vent fixed to the top of the fascia
- Push-in round soffit vents (these suit the 10 mm level only)
What else should installers check?
Keep a ventilation channel at least 25 mm deep above insulation on pitched roofs, and 50 mm on flat roofs. Ventilation needs to run along the eaves on both sides for cross-flow, and slots should keep insects out (maker slots are 3.5 to 4 mm, in line with BS 5250). A warm roof can differ, so follow the roof designer’s specification.
MLI Building Products stocks vented soffit and eaves ventilation for trade buyers in Worthing.
Need a trade price? Call the trade counter on 01903 262 636 or visit us at Unit 1, Friar Walk, Worthing. We offer free delivery within 30 miles.
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