The short answer
A tile vent replaces a single tile with a hollow, matching fitting. Some let moist loft air escape, some are built to take a soil and vent pipe, and some end an extractor duct outside. Where it goes depends on its job: near the ridge for loft air, directly above the pipe or duct run for the others. Fitting one means lifting tiles and cutting the underlay, so it is a roofer's task.
What a tile vent is, and the three jobs it does
Stand across the road from a tiled house and you may notice one tile sitting slightly proud of the rest, or a short grey pipe poking through the slope. Those are tile vents. Each is a plastic or sometimes clay moulding shaped like the tiles around it, with an opening built in.
The first job is loft ventilation. Where the insulation lies along the loft floor, the space above stays cold and needs air moving through it so that damp from the house does not condense on the timbers. The second job is to carry a soil and vent pipe, the stack that lets drains breathe, up through the covering. The third is to give an extractor fan duct from a bathroom or kitchen somewhere to end outdoors.
Each type looks alike from the ground. The difference is inside: a loft vent is a ventilation grille with a baffle, a pipe vent has a collar that grips the stack, and a duct vent has a spigot to which flexible ducting connects.
How a loft tile vent actually ventilates
Moisture is the reason. Cooking, showers and breathing put water vapour into a house, and some of it drifts up into the loft. If it cannot leave, it condenses on cold rafters and the underside of the underlay, and over a few winters that means damp timber and mould.
BS 5250 deals with moisture control in buildings. Marley's guide to it describes ventilation at the eaves, with an extra continuous gap near the top once the pitch passes 35 degrees, where the span is more than 10 m, or where the roof is a lean-to. A line of tile vents beneath the ridge is one way to supply that upper opening when the ridge itself is not ventilated.
Air enters low, rises as it warms, and leaves high. A vent at the top works with the eaves gap, not on its own. Our guide to roof ventilation explains how the two ends of a loft balance each other.
Soil pipe and extractor vents
A soil and vent pipe rises inside the house from the drains and must finish above the roof so that gases are released safely away from windows. Where it goes through a tiled slope, a pipe vent tile gives the stack a proper opening and a flashing skirt that sheds water. Trying to fit the stack through an ordinary tile by cutting a hole and filling it with sealant does not last, because the sealant ages and the gap reopens.
Extractor ducts follow the same principle. A fan that blows warm, wet air into the loft only moves the problem, so the duct is carried through the roof and ended in a duct vent. The pipe or duct should run in the straightest line possible, because every bend gives condensation a place to settle.
Work on the stack itself is plumbing, not roofing. We deal with the covering around it.
Where roofers position them
For loft ventilation, vents usually go in a line a few courses below the ridge, spaced evenly along the slope so air moves along the whole loft rather than in one patch. Where the loft is divided by a party wall or a chimney, each section needs its own opening, since air does not pass through solid brickwork.
Pipe and duct vents go where the pipe or duct arrives, and then we work outwards. The vent needs to sit on the right batten so the tile courses either side keep their gauge, which is the spacing between rows that holds the roof watertight. If the pipe lands awkwardly between battens, an extra batten is fixed to carry the vent.
Where a vent has to be matched to the covering, we check the tile profile first. A vent made for a double Roman will not sit properly in a plain tile or pantile roof, and an ill-fitting one is a likely source of leaks.
Fitting a vent without opening up the roof more than needed
Fitting is a short job in principle. The tiles are lifted around the spot, the underlay is cut to match the opening, a short tray or sealed collar links the vent to the underlay so any water that gets in runs back out onto the tiles, and the covering is relaid around it. On older roofs the surrounding tiles are brittle, and a few often crack on the way off, so we allow replacements.
A vent set into a roof that is already failing is poor value. If tiles are slipping, battens are soft or the underlay is torn, the vent should wait for the repair, or go in as part of it. Our page on torn roof felt covers that last point. Sometimes a single vent really is all the roof needs, and in that case it is the only thing we will propose.
We also look at the insulation under the spot before cutting, because pushing a vent through packed loft insulation blocks the very airflow it exists to create.
What to check before asking for one
Before you book anyone, go up with a torch on a cold morning and look at the roof timbers. Condensation drops on the underside of the roof, blackened felt around the ridge or damp insulation near the eaves all point to a ventilation shortfall. A bathroom whose fan ends in the loft is a frequent culprit.
Then take a few photographs from the garden. After the survey you receive close-up pictures of the slope in question, then a written quote. If you are planning a conversion, vent positions matter even more, so read about loft conversion roofs before the design is fixed.
Our pitched roofing work is covered by a 10-year workmanship guarantee in writing, and the site is tidied away at the end. To book a visit, phone 01793 626096, use WhatsApp, or send the form on this site.