Roofing Ventilation

Choosing the Right Roofing Ventilation Products

At County Building Supplies, we supply roofing ventilation products for professional roofers, builders, contractors and DIY customers. Correct roof ventilation helps manage moisture, reduce condensation risk and protect suitable roof structures from problems associated with trapped moisture.

Our range includes Timloc over-fascia vents, soffit vents and felt support trays for use in compatible pitched roof constructions.

Why Is Roof Ventilation Important?

Moisture can accumulate within roof spaces through water vapour moving from the building below. Without adequate moisture control, condensation may develop on cold surfaces, potentially contributing to damp insulation, mould and timber deterioration.

Roof ventilation allows air to circulate through designated spaces within suitable roof constructions, helping manage moisture and condensation risk.

The correct ventilation arrangement depends on the roof design, insulation position, roof pitch and underlay specification.

Over-Fascia Vents vs Soffit Vents

Both over-fascia vents and soffit vents can provide ventilation at the eaves, but they are installed in different positions.

• Over-fascia vents: Installed above the fascia board to provide a continuous ventilation opening into a compatible roof space.
• Soffit vents: Installed through suitable soffit boards to allow outside air into the roof space.

County stocks Timloc over-fascia ventilation strips and 70mm round push-in soffit vents in black, brown and white.

10mm vs 25mm Roof Ventilation

Roof ventilation products are available with different equivalent ventilation opening sizes to suit different roof specifications.

County stocks Timloc over-fascia vent strips providing nominal 10mm and 25mm continuous ventilation equivalents, both supplied in 1m lengths.

The correct ventilation provision depends on the roof construction and relevant technical guidance. A 25mm ventilation equivalent is not automatically required for every roof, and 10mm may not be sufficient for all designs.

What Is a Felt Support Tray Used For?

A felt support tray, sometimes called an eaves protector, supports roofing underlay at the eaves and helps direct water towards the guttering.

It also helps prevent unsupported underlay from sagging into the gutter or deteriorating at the roof edge.

County stocks the Timloc 1500mm Black Felt Support Tray for suitable pitched roof applications.

Felt support trays are not a substitute for roof ventilation and should be installed as part of the specified eaves detail.

Installing Roof Ventilation Correctly

Roof vents should be installed according to the manufacturer's instructions and the roof's ventilation design.

Ensure ventilation openings remain unobstructed by insulation, roofing underlay or other materials. Where necessary, suitable eaves ventilation trays or insulation retainers may be required to maintain airflow.

For roofs with breathable underlay, always check whether additional ventilation is required rather than assuming the membrane alone provides sufficient moisture control.

Need Advice?

Not sure which roofing ventilation products are suitable for your project? Visit your local County Building Supplies branch or contact our team for product information, quantities and availability.