Rooflight Installation in Jericho

Narrow roofs, and what fits

An artisan terrace is a narrow building by design. The plot was set out to get as many houses as possible along a street, and the roof was built to cover that plot and no more. What you end up with above a Jericho front room is a short, narrow plane bounded by a party wall on each side, the ridge above and the eaves below. Every one of those four edges is a hard limit on where an opening can go.

That matters because a rooflight is not only the glass. It is the frame, the flashing around the frame, and the run of covering that has to sit correctly on all four sides of it. You need sound courses of slate above the head to carry water past the unit, sound courses below to take it away, and enough covering left either side for the side flashings to be dressed into. On a wide roof none of that is a consideration. On a narrow terrace plane it can be the whole of the design problem.

Manufacturers make narrow units because roofs like these exist, and knowing which of them will land cleanly between the constraints in front of you is most of the skill. There is also more than one shape of answer. Two small units set in a row along the slope will sometimes fit where one larger one will not, spread light more evenly across a narrow room, and read better from outside than a single square panel.

Party walls and rafter runs

Terraces of this kind are built as a run of load-bearing masonry walls with roofs spanning between them, so the party wall is structure rather than partition. Chimney stacks generally sit on those walls, which puts masonry, flaunching and flue positions right where the roof plane ends. An opening cannot simply be pushed sideways to make it fit, because the space it would move into is occupied by the abutment detail that keeps water off the wall in the first place.

Inside the roof, the rafters were set out by the carpenter who built the house, using timber of the section then available, and they are not necessarily regular. Depth is usually shallow by current standards and spacing varies from house to house along the same terrace. That is how the roofs were made, and it means the position of an opening is decided by where the timbers actually are rather than where a drawing would like them to be.

Where an opening can be formed between two existing rafters without cutting either, the work is contained and the structure is untouched. Where the unit needs to be wider, a rafter is cut and the load carried by trimmers across the head and sill into the neighbouring rafters, which then take more than they were built for. That is a designed alteration, and in a narrow terrace it is the point at which a slightly smaller unit often becomes the better engineering decision as well as the cheaper one.

Work close to a party wall can also engage the Party Wall etc. Act, which is a matter between you and your neighbour, not something we determine. We will say when a proposal is heading that way, early enough for you to take advice.

Getting to the roof at all

Access in Jericho is a genuine part of the job and it deserves to be talked about honestly rather than discovered in week one. The streets are narrow, the houses come straight to the pavement, and there is generally no side passage, so there is no easy route from the road to the back of the property except through the house itself.

For work on a front slope, scaffold stands on the footway or the carriageway, which means a licence from the council and pedestrian protection that has to be designed rather than assumed. Parking is under pressure throughout the area, so deliveries of scaffold, timber and the unit itself are timed rather than left to chance, and permits take lead time that belongs in the programme.

For work on a rear slope the problem changes shape. The back gardens are small and reached through the hallway, so scaffold components, tools, spoil and the rooflight itself often travel through somebody’s living room. That can be done properly with floor protection, dust containment and a route agreed before anybody starts, but it has to be planned rather than discovered.

None of this makes a rooflight installation in Jericho risky. It makes it slower and more logistical than the same unit in the same roof on an open plot, and the price and programme should say so at the point of quotation rather than moving afterwards. A quotation that ignores access on a terraced street has not looked at the street.

Welsh slate and how it opens

Welsh slate is the covering across most of the original terraces here, laid in courses to a head lap and nailed to battens, with no felt beneath the older work so the underside of the slate is open to the roof void. Some houses now carry a later replacement covering instead, put on when the original reached the end of its life, and those behave differently enough that the covering is confirmed before a flashing is ordered.

Opening a slate roof properly is a stripping and re-dressing exercise, not a cutting exercise. Slates are lifted back from the area of the opening, the battens are cut, the structure is trimmed where the design calls for it, and an upstand is formed to the height the unit needs. Soakers and a flashing are then worked into the courses so that each piece of covering laps the one below in the way the original roof did. Put back correctly, the roof keeps the water out and the unit simply sits in it. Put back badly, a lap is short somewhere under the flashing and nothing announces itself for several winters.

Old slate is brittle and some will break on the way off, so sound slates are set aside for reuse and matched stock is allowed for. Matching matters more here than elsewhere, because a run of bright new slate around an opening reads clearly from the street on a terrace where every roof in the row is the same age and the same weathered grey. Where there is no felt beneath, the detailing at the opening is doing all the work on its own, which is why upstand height and the flashing laps get more attention on these roofs than the glass ever does.

The visible slope and consent

Jericho lies within a conservation area, and the planning authority is Oxford City Council. In practice that means the appearance of an alteration to a roof that can be seen from a public place becomes a material consideration, so what a rooflight looks like from the pavement is a real part of the specification rather than a matter of taste.

The specification that usually answers this is a conservation-style unit: set flush with the plane of the slate rather than proud of it, finished dark so it does not read as a bright rectangle in a grey roof, and often carrying a single vertical glazing bar so it reads as a traditional cast-iron light. Size, number and position sit inside the same judgement, and two modest units in line with the coursing tend to sit more quietly on an artisan terrace than one large panel.

Rear slopes are frequently less visible, but visibility is not a universal test. Some buildings are listed in their own right, in which case the designation covers the whole building rather than the front of it, and that is a matter of public record to check for a specific address. Article 4 directions, which remove particular permitted development rights, are a tool available to any authority, so their presence or absence at an address is a question to establish rather than assume in either direction.

We are installers, not the council, and we do not present ourselves as the people who decide. What we can tell you is the kind of position a building of that type in that setting is usually in, and which specification tends to satisfy it. Where an architect or heritage consultant is already involved, we specify to their drawings.

Building up and building back

Because the footprint of these houses is small, people extend upwards into the roof or backwards into the garden, and both bring rooflights with them.

A loft in a narrow terrace is constrained by head height along the ridge, so the usable floor area is only the band where the ceiling is high enough to stand up in, and anything eating into that band is expensive. Rooflights sit in the plane of the roof and take none of it, which is why they often do more for a small loft than a dormer would. Where the loft becomes a habitable room, the Building Regulations bring requirements for escape, and the size and opening arrangement of the roof window is bound up with that.

Rear additions bring a different roof. A single-storey kitchen or dining space at the back of a terrace usually has a flat or very shallow roof, so glazing there means flat-roof units or a lantern rather than a pitched roof window. The width available is again the governing figure, since the addition can only be as wide as the plot. On a flat roof the upstand, the fall and the direction water leaves in are the whole of the installation, and the build-up beneath needs to be a warm roof rather than an insulated void that collects condensation.

The light also does something particular in a narrow house. A terrace plan is deep front to back with windows only at the two ends, so the middle is dark whatever you do to the walls, and light from above is the only light reaching it. The rooms are small, too, which is why the glass matters: a slope taking the afternoon sun over a modest floor area warms it quickly, so a solar control coating goes on that side and clear glass on the other.

What we look at in Jericho

The order of work does not change, and on a Jericho terrace it starts with dimensions rather than product.

The plane, first. Which slope, how wide it is between the party walls, how far it runs from ridge to eaves, and where the stacks and abutments sit. This alone rules some units out.

The structure, second. Rafter depth and spacing as built, whether an opening can sit between existing timbers, and what trimming is needed if it cannot. With that, the covering: original Welsh slate or a later replacement, its condition, and whether there is any underlay.

Access, third. Front or back, what the scaffold stands on, what licence that needs, and how material gets in and spoil gets out. On a terraced street this is a design question, not an afterthought.

The consent position, fourth. What the building is, what designation attaches to it, and how visible the slope is from a public place. That decides whether the answer is a flush conservation unit or a standard one.

The specification, and then the price. Unit, glass, opening method and detailing, chosen for the roof and the room rather than from preference. We install VELUX, Fakro, Keylite and Roto units. A figure quoted before those four steps is a guess, and on a narrow terrace it is usually a low one that gets revised as soon as the scaffold is priced.

We handle the Building Control notification as part of the job. Our workmanship carries a ten-year guarantee, with coverage and exclusions on its own page rather than in small print. We have been installing rooflights for fifteen years, we do new installations and replacements only, and Jericho sits well inside the twenty five mile road radius we work from Oxford. Send the address and tell us which room is dark, and the rest of the conversation gets shorter.