Rooflight and skylight installation in Silver End

Flat roofs on a house, not an extension

Almost everywhere else, a flat roof means a rear extension. Here it means the main roof of the dwelling, which changes the job.

The construction is not modern. These roofs have been recovered several times over a century, and what is under the current covering varies from property to property: original construction, mid century repairs, and modern warm or cold roof build ups all occur. A survey establishes what is actually there rather than assuming, because the insulation position decides how the rooflight is detailed.

The kerb matters as much as anywhere and it is more constrained. A rooflight bedded straight onto a flat deck sits in whatever water the roof holds, and every flat roof holds some. At least 150mm of upstand, the deck falling away from it, and rigid insulation on the outer face of the kerb itself. On a listed modernist house, however, a kerb standing proud is exactly what the design does not want, so the balance between weathering and appearance has to be settled with the conservation officer rather than decided on site.

The listing question

Several Silver End houses are listed for their architectural significance rather than their age, which is a distinction worth understanding.

The consequence is the same as for any listed building: listed building consent is required for a rooflight on any part of the roof, whether or not it can be seen. There is no small works threshold. But the reasoning an officer applies is different. On a medieval cottage the concern is historic fabric. Here it is the integrity of a designed composition, so the questions are about proportion, position and whether the addition reads as part of the original intention or against it.

In practice that makes a flush or near flush unit far more likely to succeed than anything standing proud, and it makes position on the roof plane a design question rather than a convenience.

For unlisted houses in the conservation area, permitted development for rooflights survives unless an Article 4 direction removes it. In a village whose whole point is its coherence, a direction is entirely plausible, and it is a short enquiry to the council.

The conventional houses

Not everything in Silver End is flat roofed. The programme also built pitched roof cottages, and later development around the village is ordinary twentieth century construction.

On those, the usual questions apply. Cut roof or trussed rafters, which decides how wide an opening can be without a designed trimmer. Covering, which decides the flashing kit, with profiled tiles needing a deep kit rather than the flat kit used on slate. And access, which here is generally easy with off street parking and space to stand a tower.

Metal windows and matching

The original Crittall steel windows are part of the character of these houses and, on listed properties, part of what is protected.

Where a rooflight is being added to a house with steel windows, a slim framed unit in a dark finish generally sits better with them than a bulky white or timber one. That is an aesthetic judgement rather than a rule, and it is one a conservation officer is likely to have a view on, so it is worth raising in the application rather than leaving to chance.

What to send us

Photographs of the roof and the frontage, the address so we can check the listing and conservation position, and if you know it, whether the roof has been recovered and when.

Silver End needs a survey more than most places, because what is under a flat roof here genuinely varies from house to house. We would rather establish that before quoting than discover it on the day.

How much glass

On a flat roof over a habitable room, glazed area around 15 to 20 percent of floor area gives a bright room without turning it into a greenhouse. A rooflight in a flat roof faces straight up, which means it collects far more sun through the middle of the day than a pitched unit of the same size, so the temptation to go large should be resisted more firmly here than elsewhere.

Solar control glass is close to essential on any substantial flat roof unit, whatever direction the house faces, because a horizontal pane has no orientation to shelter behind. It costs a modest premium at the point of order and a great deal to change afterwards.

Getting heat out

An opening unit at the highest point lets accumulated heat leave and draws cooler air in through anything open lower down. On a flat roof that is the only high level opening available, which makes it more valuable than on a house with a pitched roof and eaves.

A rain sensor is worth more on a flat roof than a pitched one, because a horizontal opening left open in a shower admits considerably more water than a sloped one.

Drainage and standing water

The detail that decides everything on a flat roof, and it matters more here because these roofs have been recovered repeatedly over a century and the falls are not always what the original design intended.

Water must move away from the unit rather than sit against it. That means a fall built into the deck around the kerb and an outlet that actually works. A perfect fall discharging into a blocked gulley is a pond, and standing water against a seal is what kills a flat roof rooflight early.

Where the existing falls are poor, correcting them locally around the opening is part of the job rather than an optional extra, and it should appear in the quotation.

Maintenance

Keep the perimeter clear. Leaves and silt collect around a kerb, and on a flat roof there is nowhere for them to go on their own. Twice yearly on a plot with trees, annually otherwise.

Check the outlet at the same time. Clean the glass with water and a soft brush, and where the unit opens, clean the gasket, because grit on a compression seal stops the sash seating and gets reported as a leak.

An actuator on a motorised unit is the shortest lived component, ten to fifteen years against twenty five for the glazing, and it is a serviceable part that unbolts and is replaced rather than a reason to change the window.