Rooflight and skylight installation in Hatfield Peverel

Pre war property

Steep pitches, traditional cut roofs with rafters and purlins, and coverings of clay plain tile and slate. Good roofs to work on: the pitch does much of the weathering work, an opening can usually be formed without a structural trimmer, and the headroom gain from a roof window is generous.

Where a property is listed, listed building consent is required for a rooflight on any slope, front or rear, whether or not anyone can see it. The listing covers the whole building and there is no small works exception. In the conservation area, permitted development for rooflights on an unlisted house survives unless an Article 4 direction removes it, which is a short enquiry to the council.

The usual unknown on a roof of this age is what is underneath. A roof never stripped may have no underlay at all, in which case the weathering detail is built around the opening rather than lapped into a membrane. That is normal, it takes longer, and it belongs in the quotation rather than in a conversation on the day.

Post war and modern housing

Where most of our work here is. Concrete interlocking tiles, pitches around 30 to 35 degrees on the earlier properties and shallower on the newest, cut roofs up to the 1970s and trussed rafters after.

Cut against trussed decides more about the price than the choice of unit does. Rafters with a purlin and clear space between means a wide opening is ordinary carpentry and the loft is convertible. Triangular frames with diagonal webs joined by flat pressed steel plates means opening width is limited to the 600mm truss spacing unless a designed trimmer is installed by an engineer, and it means the loft is not convertible without replacing the structure.

A photograph looking up inside the loft answers it without a visit and is the most useful thing you can send.

Profiled interlocking tiles need a deep flashing kit rather than the flat kit used on slate. A flat kit leaves open voids under the tile channels, water gets under within a season, and it is the most common installation fault we find on other people’s work.

Loft conversions

Common in the pre war and early post war stock, and the measurement that decides viability is simple. Measure from the top of the existing ceiling joists to the underside of the ridge; you want comfortably over 2.4 metres before a floor, insulation and plasterboard eat into it.

In a habitable loft room the roof window usually carries the means of escape duty under Building Regulations as well as providing daylight. That brings a minimum clear openable area, minimum opening dimensions and a maximum sill height above the finished floor, and it rules out some designs. A centre pivot window is frequently unsuitable because the sash sits in the opening; a top hung unit that swings clear generally satisfies it.

Settle that at design stage rather than at order stage, because reversing it afterwards is expensive.

Extensions

Rear extensions are common across every band and flat roof skylights over them are steady work. The kerb decides whether the installation lasts: at least 150mm of upstand, the deck falling away from it so water cannot pond against the seal, and rigid insulation on the outer face of the kerb itself.

That last item appears on almost no quotation and matters more than the glass specification does, because an uninsulated timber kerb punches straight through the roof insulation around the whole perimeter of the opening.

On the newer housing, check the deeds as well. Modern developments frequently carry covenants restricting alterations to elevations facing the street, which are private, enforceable and easy to read before rather than after.

Access

Generally good on the post war and modern roads, with off street parking and space to stand a tower at the rear. Tighter around the older core, where frontages sit close to the road and scaffold may need a highway licence.

What an opening rooflight actually does

An opening at the highest point of a room lets warm moist air leave, and as it goes it draws drier air in through anything open lower down. That is stack ventilation and it clears a room in minutes where a wall window on its own takes hours.

In a kitchen or bathroom it is the single most effective thing you can do about persistent condensation, provided something is open at low level as well. A rooflight on its own in a sealed room moves very little air.

Building Regulations Part F sets purge ventilation requirements for habitable rooms and an opening rooflight contributes to that provision. It is worth confirming the free area figure for the specific model at design stage, because a top hung unit and a centre pivot of the same size do not offer the same open area.

How you will work it

A rooflight above easy reach that is difficult to open does not get opened. Manual with a pole is fine up to about two and a half metres and a chore above it. Mains electric gives a wall switch and a rain sensor, with the wiring rather than the unit being where the cost sits. Solar carries its own panel and battery, needs no connection at all, and is the usual answer for retrofit into a finished room.

If any work is being done, run a capped cable to the rooflight position even if you fit a manual unit. It costs almost nothing at first fix and turns a disruptive future job into a cheap one. Photograph where it is before the ceiling closes.