Rooflights and skylights in Chesterton

That is worth settling first, because the name confuses people. Chesterton was once a village in its own right, with its own parish church of St Andrew and a medieval tower house, and older maps and deeds still treat it that way. Today the city boundary runs well beyond it to the north, so the policies that apply are Cambridge policies, the conservation areas are city conservation areas, and the Building Control notification for a new skylight goes through the same system as it would for a house on Mill Road.

What the area shares with the rest of central Cambridge is its housing pattern. The streets running off Chesterton Road and the High Street are lined with what look to be late Victorian and Edwardian terraces and small semis, a good number built in the pale gault brick the city is known for, set close together on long, narrow plots. Further north towards Milton Road, Arbury and the railway the housing gets later and more mixed. Newer homes near Cambridge North station are a different story again.

For the terraces, the pattern creates one very particular problem: a deep plan with daylight at the front and the back and very little in between. The right skylight for a house like this is the one that answers that problem. Our skylight and rooflight installation service for Cambridge is built around answering it with a written light plan before anything on the roof is touched.

Take two houses a short walk apart. One has a garden running south, so the back of the house faces the sun for much of the day. The other has a garden running north, so the rear wall is in shade from late morning, and the extension roof is the only surface that sees the southern sky. The same rooflight in the same position behaves very differently in each.

In the south-facing house, the extension already gets strong direct sun through its doors. A large clear roof pane above adds heat on a July afternoon, puts a hard, bright shape on the floor that moves across the room, and can make a screen on the kitchen wall hard to read. Here we lean towards solar control glass with a lower g-value, smaller or well-placed openings, and a position further back towards the old house where the doors do not reach.

In the north-facing house, the roof glazing is doing all the work. Sun from the south passes over the ridge of the main house for only part of the year, so for much of the winter the rooflight gives soft, even sky light without direct sun. That light is pleasant and glare-free, but there is less of it, so the unit can be larger and the glass can be clearer. East and west gardens bring low morning or evening sun straight in under the eaves, which is lovely at breakfast and harsh at dinner, and the blinds matter more than the glass.

The guide to which way a skylight should face sets out the principle. At a Chesterton survey we take a compass reading on the actual slope, look at the neighbours' walls and extensions, and mark where the sun patch will fall at different times of the year.

Cambridge City Council has designated a number of conservation areas across the city, each with its own appraisal describing what gives it character. Some cover parts of the older streets north of the river. We do not assume a particular road is in or out. Instead we look up the address on the council's constraints map before the survey, and we read the relevant appraisal for anything it says about roofs, rooflights or rear extensions.

Being in a conservation area does not remove the permitted development right to add rooflights on its own. It does mean the council has the power to restrict it through an Article 4 direction, and that any change visible from the street is looked at more closely. For a listed building, listed building consent is needed for any roof glazing, whatever its size or position.

Flats are a separate case. Some larger houses in the area have been divided, and permitted development rights for rooflights do not apply to flats or maisonettes, so a new skylight in a converted house normally needs a planning application whatever the conservation status. The same applies where a previous permission removed the rights by condition.

The rear slopes and flat extension roofs are usually the easier places to add glazing, because they are seen less from the public side. Our guide to planning permission for rooflights in Cambridge covers the rules in more depth. Where an application is needed, the light plan and the planning drawings are the same document, because a proposal that shows why the rooflight sits where it does, and how it will look from outside, is easier for an officer to assess.

Older flat roof domes and early double glazed units lose their seals with age. The first sign is a mist between the panes that never clears, followed by a drop in clarity and a cold spot on winter evenings. A dome may have turned yellow or brittle. Our misted and failed rooflight replacement service replaces the whole unit with a modern one rather than working on the old glass.

Replacement is also a chance to rethink the light. If the old unit was put in the wrong place for the room as it is used now, the new one can sometimes move, or the opening can be widened, especially if the roof covering is being renewed at the same time. We check the condition of the kerb and the timbers around the opening, because a new unit on a soft or uneven upstand will not perform well however good the glass is.

An older extension may also have been built with little insulation in its roof. Where the roof is being replaced, the new rooflight and the new build-up are designed together so the upstand is insulated and the light well lined to match.

Do I need planning permission for a rooflight in Chesterton?

Often not, if the house is a house rather than a flat, the unit projects no more than 150mm and it sits below the ridge. That can change if the property is in a conservation area with an Article 4 direction, is listed, or has had its rights removed by an earlier permission, so we check the address with the city council's records before the survey.

Can a skylight light the middle of a long terrace kitchen?

Yes, and that is usually where it helps most. A rooflight placed near the line of the old rear wall, rather than near the garden doors, sends daylight into the central part of the room that the doors and front windows cannot reach.

How do you get a large rooflight into a house with no rear access?

We measure the route through the house at the survey. If a single large unit will not pass, we choose a size that will, split the glazing into two units, or arrange for it to be lifted over, and we agree the method with you in writing before the work is booked.