Rooflights and skylights in Melbourn

Clunch is the local name for a hard band of chalk that was cut and laid as building stone across this corner of Cambridgeshire. It is soft by the standards of brick or limestone, it dislikes being kept wet, and walls built from it were usually rendered or limewashed to protect the face. Cottages from before the railway age sit alongside Victorian and later brick houses along the older streets, and each carries its own roof: steep plain tiles, some slate, and here and there a roof that has been rebuilt more than once.

Beyond that core, much of the village was added in a single long burst of house building after the war. Those houses are brick, usually semi-detached or in short terraces, with a gently pitched roof in concrete tile and a loft that has spent fifty years holding a water tank and a box of decorations. Many have since gained a flat-roofed extension at the back, a garage conversion, or a loft room. Their owners come to us wanting the same thing a cottage owner wants, more daylight, but the route to it is quite different. Our wider rooflight and skylight installation across Cambridge works from the same principle in both: plan where the light will land, then fit the glass.

Next door, Meldreth runs into Melbourn with little more than a field between them, and much of what follows applies to the older cottages there too.

Prefabricated trussed rafters came into wide use on housing in the 1960s. Each truss is a triangle of slim timbers with diagonal webs running through the loft, set at close centres and held together by metal plates. They are efficient and they are strong as a system, but none of the members can be cut without redesigning the load path. A roof window that fits between two trusses needs no structural change. Anything wider needs trimming designed by an engineer, and that design forms part of the Building Regulations application.

Earlier houses on the estate may have a cut roof with purlins and a ridge board, which gives more freedom. Either way, a roof of this era is usually low in pitch compared with a cottage, and a shallow concrete tile roof can sit close to the minimum pitch a roof window manufacturer will accept. We measure the pitch at the survey instead of assuming it, because a unit fitted below its rated pitch will not shed water as it should.

Where a full-width opening would mean heavy structural work, there are gentler ways to bring in daylight. A sun tunnel passes between the trusses with no structural change and lights a landing or an internal bathroom, which in a lot of estate layouts sits in the middle of the plan with no outside wall. For a loft room, two narrower roof windows side by side between the trusses can light the space more evenly than one large unit, and they keep the roof intact.

Under Class C of the permitted development rules, a rooflight on a house can usually go ahead without a planning application if it projects no more than 150mm beyond the plane of the roof, sits no higher than the highest part of the roof, and, on a side-facing slope, is obscure glazed and fixed shut unless the opening part is more than 1.7m above the floor. On most 1960s and 1970s estate houses in Melbourn, a flush roof window on the rear slope will meet those limits comfortably.

Conservation areas do not remove Class C on their own. What can remove it is an Article 4 direction, and listed buildings always need listed building consent for changes that affect their character, however small the rooflight. South Cambridgeshire has many conservation areas, and parts of the historic core of a village like Melbourn may be covered. We do not assume either way. Before a survey on an older property we check the constraints map published by Greater Cambridge Shared Planning, and we would expect you to see that check written into the light plan. Flats and maisonettes have no permitted development rights for rooflights at all.

Planning and Building Regulations are separate. A new rooflight almost always needs Building Regulations approval, for the structure, the thermal performance of the glass and, near a boundary, fire spread. We handle that Building Control notification where the work is notifiable. Our pages on rooflight planning permission and rooflight Building Regulations set out both processes in detail.

We start inside, in the room you want to light. Where do you sit, cook or work, and at what time of day? Which part of the room feels gloomy, and when? Then we check the orientation with a compass, look at what stands to the south and west that might shade the roof, and go into the loft or look at the extension roof to see the structure. On a cottage we look at the rafters and the condition of the roof covering. On an estate house we look for trusses and measure the pitch.

Back at the desk, the light plan puts all of this together. It shows the proposed position of the rooflight, its size, the glass specification and any blind or shading, and it explains why each was chosen. The quote sits alongside it, so you can see what the money buys and why. Nothing is cut until you have agreed both in writing.

• A plan of the room showing where the sun patch falls at different times of year
• The structural approach, including any engineer input on trussed roofs
• The planning position, including the constraints check on older properties
• Whether the work needs a Building Control notification, which we then handle

Every installation carries our 10-year workmanship guarantee. If you would like us to look at your house, book a light survey or message us on WhatsApp.