Rooflight Installation in Eynsham

A house built in campaigns

Eynsham has grown steadily, and it has grown by adding rather than by clearing. The consequence for anybody putting glass in a roof here is that one property often carries the work of several building campaigns, each built with the materials and to the standards of its own moment. An original range at the front. A rear addition put on when the household needed another room. A wider extension across the back when kitchens moved rearwards. A recent single-storey addition sitting against, or partly over, all of it.

Each campaign brought its own roof, and those roofs are not versions of one another. They run at different heights, they are framed by different methods, and they answer to different expectations about what a roof had to do. One property can offer a hand-cut roof of rafters and purlins over the oldest part, a prefabricated trussed roof over a later section, and a flat or near-flat roof over the newest, all under one address and each wanting a different approach where a unit goes in.

None of that is a fault. But it does mean the ordinary opening question, which slope faces the room you want lit, is only the second question here. The first is which building campaign you are proposing to cut into, because the answer changes the structure, the covering, the flashing detail, the insulation build-up and the price.

Where two roofs meet

Junctions are where water goes wrong on an extended house, and they deserve understanding before a unit goes near one. Where a lower roof runs into the wall of an older range, the covering is turned up and a cover flashing worked into a joint or a chase in the stonework above. Where two slopes of different pitch meet, there is a valley or a concealed gutter doing work nothing else on the roof does. Every one of those details has a defined route for water to leave by.

A rooflight near one of those junctions is a genuine specification question rather than a matter of preference. Two things change. First, the unit sheds water, and whatever it sheds arrives at the junction below in a narrower stream than the open slope would. Second, a unit needs a clear run of covering to each side so its own flashings can be laid into the courses properly, and close to an abutment that clear run may not exist. Manufacturers set out minimum clearances between a unit and an obstruction for exactly this reason.

On a house altered several times there is a further wrinkle. The junction between the oldest range and the first addition may have been formed with a mortar fillet rather than lead, because that was normal then. The junction between a later extension and the same wall may be detailed differently again. Two abutments, a few paces apart, behaving differently. Establishing which is which comes before deciding where the glass sits.

Coverings that already disagree

Owners of extended houses often open by asking that a new unit match the existing roof. On a house built in one go that is a straightforward promise. Here it needs defining first, because there is usually more than one existing roof and they do not match each other already.

Each campaign used what was available and affordable at the time. The oldest part of a village house may carry stone slate. A later range may be in Welsh slate, which arrived once it could be carried cheaply. Plain clay tile turns up on additions of one period and concrete interlocking tile on another. The most recent flat section is likely to be felt or a single-ply membrane. Four coverings, one house, and no two of them wanting the same detail at the perimeter of a rooflight.

So the honest version of matching is this: which of your roofs is the reference. If the unit goes into the newest section, matching that section is easy and the oldest is not the question. If it goes into the original range, we are working into a covering laid in courses set out long before anybody considered an opening, and the material has weathered a long time. New stock beside old reads differently at first whatever is done, so salvaged material is worth using where it can be. Flashing kits are made for specific profiles, and a kit forced over the wrong covering leaves a channel where water tracks sideways under wind.

What is above the ceiling

Structure on a re-extended house is genuinely unpredictable, and no amount of experience turns that into a guess worth quoting from. What sits above the ceiling of a later extension is not what sits above the original range, and the ceiling tells you little, because a re-plastered one looks the same whatever holds it up.

The oldest part tends to be a cut roof: rafters and purlins of uneven section, often at irregular spacing, sometimes with a slope altered during the building’s life. Trimming an opening in that is ordinary work, but the setting out follows the timbers present. A later section is more likely to be prefabricated trusses at consistent centres, tidy and predictable, except that the diagonal webs inside a truss are structural and cannot be cut through without a designed alteration. A flat section may be a warm build-up with insulation above the deck, or a cold one with insulation between joists.

The only way to settle it is to look. Where there is a hatch and a reachable roof space, a proper look answers most of it in one visit. Where a later extension has no access at all, either something is opened up or the specification carries an assumption, and an assumption is what turns a firm price into a revised one. We would rather spend an hour establishing the structure than write a number we have to move. Where an assumption cannot be avoided, we say what it is and what would change if it proves wrong.

Insulation varies across one house

Thermal performance on an extended house is not a single property of the building. It varies from room to room, and it varies most sharply at roof level.

The original range may have nothing at the rafter line, with insulation laid at ceiling level over a cold void. A middle-period extension may have a modest layer put in when it was built. The newest section will have been built to a later standard with a designed build-up, a vapour control layer and a defined ventilation path. Building Regulations apply to the work being carried out, so making a room habitable under the old part frequently draws in an insulation upgrade at the rafter line, and the depth above and below those rafters governs how that is achieved. In the newest section the build-up may already be close to what is wanted.

This is why a unit in the old part and a unit in the new part of the same house are not the same job and do not carry the same price, even where the glass is identical. The reveal differs too. A deep insulated rafter line produces a deep reveal that has to be lined and insulated around its full perimeter, or the corner becomes the coldest surface in the room and collects moisture. A shallower modern build-up gives a shorter reveal and an easier detail. Continuity of the vapour control layer through the opening matters in both, and most where an old cold roof is made warm.

Choosing which roof takes glass

On many Eynsham houses the real decision is not the unit at all. It is which era of roof to put it into, and that decision is usually available, because several roofs offer several routes to the same daylight.

The newest section is frequently the easiest and the least sensitive. The structure is regular and known, there is a modern underlay to turn into the opening, and the covering has a flashing kit made for it, or a flat roof takes a kerb the membrane dresses onto. The build-up is already insulated. It is also usually the least conspicuous part of the house from anywhere the public can stand.

Where the room you want lit sits under the original range, that is worth doing properly. Sometimes it is worth reconsidering the room instead, because on open-plan rear layouts light entering a newer section reaches a good way back into the older one. We will say which applies, including when the awkward roof is the only one that solves the problem.

The old stone centre

The historic core of the village is a conservation area, and the buildings there are largely of local limestone. Inside that designation the appearance of an alteration becomes a material consideration, which is why the flush conservation unit exists as a category: set into the plane of the roof rather than standing proud of it, finished dark, and traditionally carrying a single vertical glazing bar. Where a building is listed, listed building consent is separate from planning permission and neither substitutes for the other.

Two points matter on an extended house in the core. Listing covers the whole of a listed building, generally including later additions attached to it, so the assumption that a modern rear extension falls outside the designation is not one to make from the pavement. And conservation area boundaries follow lines on a map rather than the character of a street, so a house that looks modern can sit inside one. Both are matters of public record, worth establishing at the start.

Eynsham sits in West Oxfordshire, and the planning authority is West Oxfordshire District Council rather than the city. We are installers, not the authority, and we do not present ourselves as the people who decide. What we will tell you is the kind of position your building is likely to be in and which specification usually satisfies it. Where a determination is needed, we say so plainly, and where you are working with an architect we specify to their drawings.

Before we quote in Eynsham

The address and its designations, first. On the newer housing around the edges this takes minutes. In the older core it is the whole of the early work and can change the answer.

The building campaigns, second. We walk the outside and establish how many roofs the house has, where they meet, and which one the room you want lit sits under.

The roof space, third. Structure, spacing, depth, covering, underlay, and the insulation build-up the room requires. On a replacement, the state of the existing opening and upstand, because a new unit on an unsound upstand inherits every fault beneath it.

The specification, fourth, and the price last. Flush conservation detailing where the building calls for it, a standard unit where it does not, glass chosen for the orientation of the slope, and an opening method chosen for the room. We install VELUX, Fakro, Keylite and Roto units, and specify what the roof requires.

On those newer roofs the work is straightforward: concrete interlocking tile, trusses at regular centres, a proprietary kit. Older units on that stock are reaching the end of their working lives and are replaced with new flashings and a sound upstand.

We handle the Building Control notification as part of the job, our workmanship carries a ten-year guarantee, and we have installed rooflights for fifteen years. Eynsham sits inside the twenty five mile road radius we work from Oxford. If you are considering rooflight installation in Eynsham, tell us how many times the house has been added to before you tell us which unit you like.