Rooflight installation in Galleywood

Exposure on the Galleywood ridge

Every rooflight manufacturer publishes a minimum pitch. On an exposed site the practical minimum sits above the printed one, because the printed figure assumes rain falling roughly downwards onto the flashing.

On the ridge it does not. Wind pushes water horizontally across the slope and up under the tail of a lap, and it does so for hours at a time in a westerly. The consequences are rarely dramatic. A slow damp line appears on the plasterboard reveal two winters after the install, and it traces back to a flashing that was within specification for a sheltered plot and marginal for this one. Where a Galleywood roof is close to a manufacturer’s stated limit, the honest answer is that the pitch is the problem and the detail has to be built to compensate.

Deep profile concrete tiles on the postwar semis

The bulk of Galleywood is covered in deep profile concrete interlocking tile, the large single lap pantile pattern that went onto almost every English estate between about 1950 and 1980. It is a good roof to work on and it needs its own flashing kit.

The distinction matters. A deep profile kit has a pleated apron with enough travel to dress down into a 40mm or 50mm trough. A flat profile kit, made for plain tile or slate, sits proud of that trough and leaves an open channel straight into the roof. Both kits look similar in the box. Choosing between them is done on site off the actual covering, not from the drawing.

Age is the second factor. Concrete tiles of this vintage lose their surface coating and start to fret, and a fretted tile lifted from the roof often will not go back. Matching stock is set aside from a discreet area of the slope so the finished opening reads as original rather than as a modern square in a weathered field.

Chalet bungalows and the flat deck at the top

Chalet bungalows across the village very often have a small flat deck where the two main slopes would otherwise have met at a ridge. It is a few square metres, usually felt or single ply, and it is almost always the oldest covering on the house.

That deck is a genuine opportunity. A rooflight in it lands daylight straight down onto a landing that has none, and the structure below is a simple joisted deck rather than anything that needs designing around. The catch is that a deck of that size rarely has much fall, and the outlet is often at the awkward end. Setting glass into it is worth doing once the fall is right, and in that order.

The older fabric by the church on the common

St Michael and All Angels stands out on the common, and the older cottages and houses gathered near it are a different proposition from the estates. Plain clay tile, some weatherboard, low eaves, and a planning context that treats a visible roof slope as part of the setting.

Anything going into a slope that reads from the common wants a conservation rooflight: slim cast frame, central vertical glazing bar, and the unit sitting flush in the plane of the tiles. Rear slopes hidden from public view are usually treated with more latitude, though that is a question for the planning officer rather than an assumption to build on.

Condensation in a bungalow roof void

Bungalows have a large roof void over a small floor plan, and forming an opening through it interrupts the air path that keeps that void dry.

A cold roof of this type relies on continuous ventilation at the eaves, typically twenty five millimetres of free area, with a smaller high level opening at or near the ridge to drive the flow. Trimming an opening blocks a bay. The fix is to reinstate the cross flow around it, with counterbattens or proprietary vents, so no bay is left as a dead end. Below the opening the vapour control layer is lapped and taped to the frame, because warm moist air leaking upwards from a bathroom or kitchen does far more damage than anything arriving from outside.

Escape windows once a loft becomes a bedroom

If a Galleywood loft is being converted into a habitable room, at least one window in it usually has to serve as a means of escape, and that changes which unit can be specified.

The clear opening has to give an unobstructed area with no dimension too small to climb through, and the bottom of that opening has to sit within reach of the floor rather than up near the ridge. On a shallow bungalow or chalet slope those two requirements fight each other, because a low sill on a low pitch puts the head of the window barely above waist height. The workable answer is usually a top hung unit with a wide swing, chosen at design stage rather than discovered at second fix. There is more on the range and the operating options across the roof window installation page.

What a Galleywood survey records, and how a price is reached

A range comes back by email from photographs and a measurement. A fixed price comes after somebody has stood on the roof.

The survey records the covering and its condition, the pitch measured rather than estimated, what is holding the roof up, where the ceiling line sits, the orientation, and the route materials will take. The recurring finds in this village are a bungalow pitch below the printed minimum, a chalet deck with no usable fall, and a trussed loft where the plan assumed cut rafters. All three are cheaper to know about before a figure is agreed. Galleywood sits alongside the rest of the county on the areas we cover page, and the costs guide sets out what moves a job between the range and the fixed figure.