Skylights and rooflights in Market Harborough

Planning questions about a rooflight here go to Harborough District Council, which runs the district from the Symington Building, a former corset factory in the middle of town. For an ordinary house, a rooflight is usually permitted development under Class C of the 2015 order. The glass may stand no more than 150mm proud of the roof slope, it may not rise above the highest part of the roof, and one on a side elevation has to be obscure-glazed and fixed shut with the one exception of an opening sash set more than 1.7m over the finished floor.

Two conservation areas matter in town. The Market Harborough conservation area covers the centre, and the planning register records 71 listed buildings inside it: two at Grade I, six at Grade II*, 62 at Grade II and one with no grade recorded. The Grand Union Canal conservation area passes less than a kilometre from the centre and holds another 25. Being inside a conservation area does not, on its own, take away the right to fit a rooflight under Class C. An Article 4 direction can, and that is a question for the council, property by property.

Planning and Building Regulations are separate questions, and a yes to the first says nothing about the second. Even where no application is needed, cutting a new opening in a roof is building work. If the work is notifiable, we make the Building Control notification ourselves, with the council or with a registered building control approver, so the paperwork follows the job rather than chasing it.

Stand in the Square and you can see why roofs here get looked at. The broach spire of St Dionysius rises straight from the street with no churchyard around it, the Old Grammar School of 1614 stands on timber posts beside it, and the buildings round about are of mixed styles and ages. A conservation rooflight sits low in the slates with a thin frame, which is the look most likely to settle into a slope with that kind of company.

Harborough became a brick town in the 18th century, when its timber, mud and thatch buildings were largely rebuilt. Later, rows of cottages were squeezed into the yards of the older houses, sharing water and drains, and the old town grew badly overcrowded. Many of those yards survive, cut down their length to give each piece a frontage on the High Street. For anyone after more daylight, the yard roof is the tight one: short slopes, neighbours close on both sides, and little room for a big opening. A small rooflight set between two rafters, or a sun tunnel taken down to an inner landing, is often the honest fit for a yard house.

The yard strips matter on the roof as much as on the street. Because each plot was cut lengthways, neighbouring windows look down on the same slopes from several angles, which is why a flush conservation rooflight with a low flashing tends to suit these roofs better than a standard unit with a deep frame. On the interwar council roads the issue is inside rather than out: a rear kitchen under a flat roof is usually bright at the garden end and dim at the worktops, and a rooflight on a kerb built to the right height (the raised timber frame the unit sits on) evens that out. In the post-war lofts, the difference between a purlin roof and a trussed one is the first thing we check, because it decides how wide the opening can be before any size is talked about.

The roads built to empty the yards

The council's answer was new housing for rent. Between 1918 and 1928 about 400 houses went up, 164 of them built by the council, starting with the Bowden Fields Estate north of the town. The land between Northampton Road and Farndon Road followed from 1930. After the Second World War some 600 people were waiting for a council home; Bowden Fields was extended by 1949 and the Southern Estate was planned. A private house and a council house from the same decade can look alike from the pavement and be framed quite differently in the loft, which is why we never size a roof window from a photo of the front.

When an old skylight is swapped out, the new one has to meet Part L, which asks a roof window to reach Window Energy Rating band B or 1.4 W/m²K, and a rooflight on a flat roof to reach 2.2 W/m²K.

If the roof window is part of a loft conversion on one of these two-storey houses, Approved Document B is plain that it is not the way out in a fire. An escape window only counts for storeys within 4.5m of the ground; a loft room above that needs a protected stair instead. So we size the roof window for daylight and fresh air, and leave the escape route to the stair, where the regulations put it.

Market Harborough is a market town close to the Northamptonshire border, 15.2 road miles south-east of Leicester and about 28 minutes away by van. The A4304, A508 and B6047 all pass within a kilometre of the centre, and the railway station is less than a kilometre from it, so a morning survey here still leaves the afternoon for the drawing.

The canal shaped the town as much as the market did. A canal from Leicester to the London to Birmingham line was planned, but it bypassed Harborough, so a branch was cut from Foxton with a wharf at Gallow Hill, where the British Glues and Chemicals works later grew up by the water. In 1950 the basin hosted a week-long National Festival of Boats, the first the Inland Waterways Association organised, and the start of the canal network's revival for leisure. Three miles from town, Foxton Locks lift the Grand Union through ten locks in two staircases of five.

The centre has been reworked more than once since then. The canal basin, restored as Union Wharf, now holds workshops, a restaurant, studios and flats. A rooflight over a flat there starts with a planning application, and the freeholder may need to agree as well, so it is worth asking them early.

A house near the water can fall inside the canal conservation area, and its back slope may be in plain view of the towpath. That changes what looks right on the roof more often than it changes what is allowed. A flat roof rooflight with a low upstand, or a lantern kept modest in height, reads more quietly from the water than a tall glazed ridge. Boaters are a patient audience, but they do look up.

Out at Gracelands Park and Blackberry Grange, or on the rising ground towards Burnmill Hill, the roofs are a different job from the yards in the centre, but the question is the same: where can the light get in without fighting the frame? A sun tunnel through the loft can reach a landing that no rooflight sits above, with a small dome outside and a ceiling diffuser below.