Rooflight and skylight installation in Greenstead

What that means in practice

It does not mean you cannot have a rooflight. It means the width of the opening is decided by the truss spacing rather than by what you would like.

Trusses are typically at 600mm centres. A roof window that fits between two trusses without touching either goes in with no structural work at all, and that is a straightforward job. It also limits you to a fairly narrow unit, which is why so many Greenstead roof windows are tall rather than wide.

Anything wider means removing part of a truss and installing a structural trimmer designed to carry the load around the opening. That is entirely possible, it is done routinely, and it needs a structural engineer to specify it rather than a fitter to judge it. It is also the point at which the price changes noticeably, and it is the single most common reason a Greenstead quotation comes back higher than the customer expected.

The other consequence is loft conversions. A trussed rafter loft has webs running through the middle of the space, so a conversion means replacing the roof structure rather than boarding it out. That is a much bigger project than a conversion in a Victorian cut roof, and it is why loft conversions are less common here than in the older parts of town despite the houses being a similar size.

The covering

Concrete interlocking tiles, overwhelmingly, and often the original ones. They are heavy, they are profiled, and both facts matter.

Profiled means a deep flashing kit rather than the flat kit used for slate. It is a different part with a different price, and using the wrong one is the most common installation fault we find on this kind of roof. A flat kit on a profiled tile leaves gaps under the tile profile that water finds within a season.

The tiles themselves are usually robust and lift cleanly, which makes the work quicker than on a fragile clay roof. Where they have been on since the 1950s, some will be at the end of their life and a few will break on removal, so an allowance for replacements is sensible. Matching a sixty year old concrete tile is easier than matching a handmade clay one but it is not always possible, and where it is not, the answer is usually to take sound tiles from a less visible slope.

Pitch

Generally between 30 and 35 degrees, sometimes lower on the later blocks. That is within range for a roof window but it is at the shallower end, and two things follow.

Every roof window has a minimum pitch stated by the manufacturer, commonly 15 degrees, so the roofs here are fine. But the shallower the pitch, the less water sheds naturally and the more the flashing detail has to work, so the installation quality matters more here than on a steep slate roof where gravity is doing half the job.

The second is headroom. A shallow pitch means a roof window gives less usable height gain than the same unit in a steep roof, and it means the reveal is longer. A splayed reveal, cut back at an angle rather than square, makes a large difference to how much light actually reaches the room, and it is worth specifying.

Flat roof work

A lot of Greenstead properties have gained rear extensions with flat or near flat roofs, and that is where most of the skylight work here happens. A flat roof rooflight on a properly built kerb is a good, cheap way to light a kitchen or a utility room.

The thing we check first is the kerb, because on a self built or older extension there frequently is not one. A rooflight bedded straight onto a flat deck sits in whatever water the roof holds, and a flat roof always holds some. A kerb of at least 150mm with a fall built into the deck around it is what makes the difference between a twenty five year installation and a leak in three winters.

Access and parking

Mostly straightforward. The estate roads are wide, the properties have front gardens and there is usually somewhere to stand a tower. Where houses are in terraces or short blocks, scaffold for a rear slope sometimes needs to come through a neighbour’s side access, which is worth arranging before the day rather than on it.

What to send us

A photograph of the roof from outside and, if you can get into the loft safely, one looking up at the structure. That second picture tells us whether you have trusses or a cut roof, which is the question that decides the price, and it saves a visit.

What an opening rooflight actually does

An opening at the highest point of a room lets warm moist air leave, and as it leaves 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 a bathroom in one of these houses 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.

Where the unit is above easy reach, a motorised opener with a rain sensor is worth the premium, because a window that closes itself when it starts raining is a window that actually gets left open. Where running mains cable through a finished ceiling would mean lifting flooring and chasing walls, a solar powered opener needs no connection at all and fits in a couple of hours.

Sun tunnels for the internal rooms

A lot of Greenstead layouts put a bathroom or a WC in the middle of the plan with no external wall. There is no rooflight solution for a room with no roof above it, but there is a tunnel solution for one with a loft above.

A rigid mirrored tube brings real daylight down from the roof for a fraction of the cost of any other option, and the roof component is small enough to be effectively invisible from the street. In a windowless bathroom it is the difference between reaching for the switch and not.

Two things decide whether it works. Diameter, because output goes with area rather than width, so a 350mm tube passes roughly twice the light of a 250mm one. And whether the tube is rigid or flexible, because a flexible foil concertina scatters light at every fold and delivers perhaps a third of what a rigid tube of the same size gives. We fit rigid wherever the route through the loft allows it.

What a job day looks like

Floors covered and a dust barrier at the door first, because the making good is where the mess comes from. Then the strip out, the frame set and checked square, the underlay collar dressed and lapped, the flashing kit fitted, the covering reinstated over it, the insulation collar in, and the lining made good.

That sequence is the entire job. Nearly every roof window that leaks leaks because one step of it was done out of order, and none of it is visible when the work is finished.

We do not leave an opening uncovered overnight and we will not start a strip out if the forecast will not let us close it the same day. In this part of the country that occasionally costs a day and it has never cost a customer a ceiling.