Do I need tile vents on my roof?

A tile vent is a manufactured tile with an opening built in, designed to pass air while keeping rain out. It is fitted into the covering where an ordinary tile would go, usually high on the slope, and it links the roof space to the open air. Many are made to match the tiles around them, so the roof looks the same from the road.

The purpose is airflow. In a cold roof, where the insulation lies on the loft floor, the roof space stays close to the temperature outdoors, and moving air carries off moisture before it condenses on the timbers. Our guide to roof ventilation and condensation looks at that whole system, while this answer deals with the vents themselves.

Most pitched roofs take air in at the eaves, through a gap behind the fascia or a vent strip in the soffit. Warm air rises, so fresh air entering low can travel up the slope and leave near the top. A vent high on the roof or at the ridge gives it somewhere to exit, and that cross-flow is what clears moisture.

Marley's guidance on BS 5250 gives typical figures. With a non-breathable underlay, the guidance asks for a 25 mm strip along the eaves on pitches up to 15 degrees, falling to 10 mm on steeper roofs. A further 5 mm at high level comes in for pitches above 35 degrees, spans over 10 m and lean-to roofs. Tile vents are one way to make that high opening, and they only work if the eaves are open. Painted-over soffit vents, or insulation pushed hard into the eaves, stop the flow whatever sits at the top.

The answer depends on the roof you have. Condensation on the underside of the underlay, damp battens, mould on rafters or a musty loft all suggest that air is not moving. A steep roof, a wide span, a lean-to, or a roof laid on non-breathable underlay are the situations where high-level vents are most likely to be wanted under the guidance above.

Breathable underlay shifts the calculation. Marley adds that a tight ceiling and an air-permeable covering can get by on the 3 mm gap that normal eaves construction leaves, or on a 5 mm ridge opening. That is why we do not fit vents out of habit. When a new underlay is going on, the ventilation is rechecked, as in our note on patching or re-tiling a roof.

Roof tile vents suit a roof being re-covered or repaired, because a vent tile swaps in for a plain one. Position matters: too few, or fitted where insulation blocks them from inside, and they achieve nothing. They also carry pipes or extractor ducts through the covering, and a loft room or dormer with its own roof needs its ventilation thought through separately; the planning side is in dormers and permitted development.

On houses in a conservation area, or with a traditional covering, a visible vent can change the look of a slope, so ridge options or hidden eaves ventilation may deserve a look first. For a listed building, ask the council's conservation officers before altering the roof in any way.

Vent tiles are made to suit particular tile profiles, so the vent has to match the covering: a plain tile vent for plain tiles, an interlocking vent for an interlocking tile, and a pantile vent for pantiles. A mismatched vent sits proud of the slope and can let rain in at its laps.

Placement follows the airflow. Vents belong high up the slope, spread along the roof so that air crosses it instead of short-circuiting between two neighbours, and they must be clear of the insulation below them. A vent fitted over a loft that has been boarded across or packed with insulation can feel reassuring from outside while moving nothing. We check the underside of every vent we fit or find.

Fitting a tile vent will not fix a roof whose eaves are choked. We often meet lofts where insulation has been rolled out to the very edge, squashing the gap above the wall plate, or where a deep layer has been added over the years without a ventilation tray to hold it back. In those cases a ridge vent has nothing to draw, and the cure is clearing the eaves, not adding another tile.

Another trap is mixing systems. A breathable underlay with a well-sealed ceiling is judged differently from a non-breathable felt, and fitting vents suited to one onto the other can leave the roof over-ventilated, which is a waste, or under-ventilated, which is a risk. We record the underlay type and the eaves condition in the survey, so your quote adds vents only where they will do some work.

We look at the eaves from outside, then at the loft for blocked gaps, damp timber and any vents already there, and photograph what we find. A roof inspection runs to £150 to £500 on MyBuilder's 2026 price guide. In the written quote that follows, vent tiles are included and never left out.

Ventilation is checked whenever a roof is stripped, and our 10-year workmanship guarantee comes in writing. Until we have seen the roof, resist sealing a loft or stuffing an eaves gap to stop a draught. More tiled-roof questions are answered under pitched roofing.