skylights & rooflights in harman's cross

The loft above a bungalow hall is deeper than owners assume

A common belief about single-storey houses meets a tape measure.

Bungalows and chalet houses stand alongside the older stone cottages in Harman's Cross, along the A351 and the lanes off it. The typical layout puts a hallway or a landing at the middle of the plan, with the rooms around it taking daylight from outside walls. The hall is dark, the inner bathroom has no window at all, and a light stays on through the day.

Owners often tell us the loft above is too shallow for anything to be fitted. A few are. Many are not. A hipped bungalow roof usually leaves a clear void between the ceiling joists and the underside of the tiles, and a sun tunnel's tube or the boarded shaft of a window has to run through exactly that space. The only way to tell is to climb into the loft with a tape, then check the slope the opening would sit on. Rafter spacing, any purlin in the path and the height from joist to tile are all written down.

A second point is the room below. A hall with doors on both sides has no outside wall, so daylight has to arrive from above or not at all. A sun tunnel puts a round diffuser in the ceiling and can be placed over the part of the hall that needs it most. A window in the slope lights a wider area and can open for air. The choice follows the measurements, and the sheet lays both options out with the product, the size and the position marked.

The measuring that settles it is covered in our measured survey page.

The same reasoning holds for chalet houses, where the upper room already sits inside the roof and a window in the slope opens straight into it. No shaft is needed there, so the depth question falls away and the measurements that count are knee wall height, ceiling slope and sill position.

The regulation numbers behind a new window in the slope

National rules set the heat-loss limits, the escape window height and the size codes on a Harman's Cross roof as on any other in England.

Heat loss is the first regulation figure that touches a rooflight job. For a new rooflight the target is 2.2 W/m²K, while a new roof window is held to 1.4 W/m²K (or WER Band B). Each is a measure of heat escaping through the unit, so a lower number is better. Current energy-efficient glazing meets both comfortably, and your quote names the product so that its rating can be read off the data sheet.

Escape is the second. A roof window in a first-floor room can act as the escape route only for a storey no higher than 4.5 m above ground level. So a bungalow or chalet house can use a suitably sized window in the slope, while a two-storey house with a loft room above needs a protected stair. The sill height and the clear opening are both measured at the survey, since a window that is large on paper can still be too high to climb through.

The size code is the third. Reading a VELUX code is a matter of splitting it: width comes from the leading letter, height from the digits that follow. An MK04, for example, is 78 cm across and 98 cm high. Whether 78 cm sits between two rafters depends on how far apart they are, and where it does not, one rafter is trimmed and the opening framed around it. The size code guide lists the whole range.

Beyond these three, a rooflight on the Isle of Purbeck sits under the same national rules as one in Bournemouth. Where this village differs is in the records behind a particular address, which is why the sheet records them before the order.

Roof words a Harman's Cross survey sheet uses

Plain definitions for the terms that sit on the sheet you take away.

The sheet that follows every visit is written in plain language, with a few roof terms that cannot be avoided. They are the same for a bungalow beside the A351 and for a stone cottage near the station.

The sheet also records the narrow things that decide a fit: how much hall width the opening must light, whether a purlin runs through the path of a shaft, and what the loft floor will carry. A purlin is a horizontal beam under the rafters that sits where a boarded shaft might want to pass, and a sun tunnel may be nudged sideways to avoid one. Where nothing in the way needs adjusting, the sheet simply says so.

If any word on the sheet is unclear, ask at the visit. Walking round the loft with the person who wrote the sheet is quicker than reading about it. A sun tunnel gets its own set of measurements, since tube length and bends count more than frame size. Nearby, Langton Matravers and Corfe Castle have older stone roofs that raise their own questions.

One last note on the sheet. The room below is measured as carefully as the roof above: ceiling height, the position of the light switch, and the route a boarded shaft takes through a loft that may hold tanks or old insulation. Those details decide whether a trimmed rafter lands where it should, and they are the part of the sheet owners most often read twice.