New skylights and rooflights in Talbot Green

A garage turned into a workroom shares one trait with small extensions of all kinds: a flat roof, and wall space that has been given over to cupboards, a radiator or the neighbour's fence. Windows low in the front wall help a little. A rooflight puts light where the work actually happens.

Over a desk, a flat rooflight changes the quality of the working day. The lining around the opening shapes how daylight spreads into the room, so the shape of that opening is worth discussing at the survey, not leaving until the plastering. Daylight from above can fall on the keyboard and the papers rather than across a screen, so there can be less glare to fight than with a window behind you. A blind can still be wanted in high summer, and the question of how it will be worked belongs in the first conversation.

Heat deserves the same thought. A small glazed roof can warm a small room, so an opening unit that lets air out is worth weighing against a fixed one. Whether to choose fixed or opening glass is worked through on its own page.

For flat glass rooflights, Rainclear's installation guide advises a kerb sloping by at least 5 degrees so that rain does not pool on it. The roof shape matters here, because not every flat-looking roof is flat. VELUX gives the range for its flat roof dome as pitches from 0 up to 15 degrees, and the range for its low-pitch roof window as 10 up to 20 degrees. A garage roof with a gentle fall can therefore sit in either band, and the pitch is measured before anything is chosen. A roof that leans at 12 degrees, for example, falls inside both ranges, which is why the maker's details for each product are read side by side.

Energy guidance has a quirk worth knowing. Approved Document L (Wales) bases a rooflight's U-value on the whole developed surface area of the unit, which can be larger than the hole in the roof. Where the kerb arrives as one assembly with the rooflight, the 2.2 W/m²K figure covers the kerb too. The document is guidance, and it says a rooflight in an existing home should be no worse than 2.2.

At the end of the day the room feels different. With the lamp on and the sky dark, the glass overhead becomes a black panel with the desk reflected in it; a ceiling lining kept plain and a blind drawn across calm that down. The flat roof rooflights page shows the range.

Start from the room underneath. A ground-floor room beneath a flat roof or terrace may have no window at all, and a walk-on rooflight lets daylight down into it while the roof above stays usable. The glass is made to be walked across, and the room beneath receives the daylight that falls through it.

After dark the effect reverses. Lamps on in the room below show through the glass to anyone standing above, and the panel looks lit from beneath. With the room dark, the glass reads as a black rectangle in the roof surface. Neither is a problem, but both are worth picturing before the position is fixed, because a pane over a bed or a bath changes how private the room feels.

Choosing the glass is a conversation about loads and finish. Our pages on walk-on glass load ratings and on whether skylights can be walked on set out the terms. The rating depends on the product, and the maker's own data is the place to read it.

Cleaning is another matter to settle early. Pilkington's self-cleaning Activ range lists roof-lights and roof glazing among its uses. Whether it is offered on a walk-on unit is a question for the maker. Pilkington's wording is that the coating works by daylight and rain together.

On the energy side, building control confirms whether the Approved Document L (Wales) figure for a rooflight applies to a walk-on unit. Planning for the whole job is covered in the Welsh planning guide, and the pages on planning for walk-on rooflights and building regulations for walk-on rooflights go through it for this product.