Skylights & rooflights in Tetbury Stone slate above, fresh air below

Tetbury has a conservation area covering much of the historic centre, and Cotswold District Council handles planning for it. Many houses in the middle of town are also listed, and the surrounding countryside carries its own landscape designation, so it pays to ask the council before you commit to a front slope. In a listed building, any new rooflight has to be agreed through the consent route. Whether you need permission at all, and what the council wants to see, is set out in our planning guide.

The usual answer for these roofs is a conservation rooflight. Slender metal forms the frame, with one bar of glass-holding steel or aluminium down the centre, made to sit low in the slope. Some open, and a sash on a winding crank lets a cold attic bedroom take in a proper lungful of air on a warm evening, and once it is shut it looks like the cast iron skylights that lit attics and workshops a century ago.

What the survey checks

Stone slate roofs are heavy, and the timbers under them were sized for that weight. Before proposing a unit we climb into the loft and study the underside, then go outside and judge the same roof from the lane. What matters is where the rafters run, how the slates are hung and whether a smaller opening, or a pair of narrow ones, suits the old timbers better than one wide window.

Fitting is only half of it. Removing a complete rooflight, frame and glazing, is notifiable work, and it is our job to notify Building Control. If you only need a failed sealed glass unit swapped inside a sound frame, that usually is not notifiable. The Building Regulations guide explains the difference.

Most old houses here work best with a split plan. The front slope, which faces the street, takes either nothing or one small fixed conservation unit that the council is happy with. The back slope, hidden above the yard or garden, takes the unit that opens widest. A vent bar along its top edge lets a trickle through overnight while the sash stays shut, which matters in a stone attic that has soaked up the day's sun.

Roof timbers in a stone house are rarely straight, and no two bays are the same. We allow time for that. A job on one of these roofs is planned slate by slate: which ones come off, where they go back, and how the new frame is flashed so water runs over it and not into it. That care is why the outside of the finished job looks as though it has always been there.

Stone houses also hold temperature differently from brick. Thick walls stay cool in a heatwave and slow to warm in spring, but the roof space above them has no such mass, and it is the stone slates and the loft air that heat up. An opening set high lets that layer go, and the rooms underneath stay as they were. Think of it as a chimney for the top of the house, one you can shut when it rains or when the evening turns cold.

Loft rooms in terraces and semis

In the terraces and semis, the problem is the loft bedroom or the top landing, where the day's heat from every floor ends up. A roof window set into the rear slope gives the room a view, daylight and a sash that tilts outward. In a bungalow or chalet room the same window may be the route out in a fire, with rules on how large it must be and how low its sill sits. The escape window guide explains the rules. Not so on a two-storey house, where a loft conversion needs a protected stair, and the window above it only supplies daylight and fresh air.

Glass roofs on extensions

Newer kitchens and garden rooms often are capped by a flat roof, a big fixed rooflight or a lantern. They are bright, and by mid-afternoon they can hold the sun's heat like a greenhouse. Put an opening flat rooflight in the roof, or choose a lantern with sashes that open, and the room can vent from the top. The fresh-air rooflights page explains how an opening unit and a low window work together.

For the nearby places we also cover, see Malmesbury, Nailsworth and Sherston. For what shapes the price of any of this, the costs page breaks it down.

Interwar and postwar houses on the town's outskirts follow a different pattern again. Their roofs are concrete or clay tile, laid on a simpler frame, and the slopes are easy to work with. A bathroom under the rear slope is a good candidate, because a window set above the shower gives steam a way up and out. A hall or landing without a window can borrow daylight from a sun tunnel, and a vent kit on some models lets it move a little air too.

Access in Tetbury takes planning. Some lanes are steep and some streets narrow, with parking at a premium on market days. We plan deliveries and scaffold with that in mind, protect floors inside and close the roof in before we leave each day, so the house is never left open overnight.

Whichever house you live in, the question we ask first is simple: which room is the stuffiest, and where does the warm air go? The answer usually points to the spot for the opening unit, and the type of unit follows from the roof beneath it.