Birdwell skylights and rooflights for tiled semis and their loft rooms

Lifting and relaying the tiles

Tiles are lifted around the opening in rows, starting from the top, and laid aside in the order they came off. Battens are shortened to the frame edge, and the underlay is cut and folded into the gutter that runs round it. A flashing set made for the tile profile fits over the top and sides, and the tiles are relaid over it so each course laps the one below. An interlocking tile has a shaped edge, and the flashing is shaped to match.

Putting a rooflight in an ordinary house normally falls under permitted development, and the exceptions are listed on our planning guide; the council to ask in Birdwell is Barnsley Council, and we tell Building Control about the fitting as well.

Choosing the size

A VELUX window's code gives its size, where the first letter is its width and the digits are its height, and other makes have their own systems. The size is limited by the rafter spacing and by the floor space the light has to cover. A snug fit between two rafters keeps the structural work to a minimum, while a wide unit means cutting and trimming more of the roof. Reading the codes is covered under VELUX window sizes and codes.

Headroom at the opening

In a loft bedroom, the lowest edge of the window should fall at a height where you can reach the handle from the floor. A window set too low shows the floor too much, and one set too high is hard to open. The sill is positioned relative to the bed and the sloping ceiling, with the furniture in mind.

Opening or fixed in a loft bedroom

A bedroom in the roof collects warm air, and an opening window lets it out through the roof as well as the room. A fixed unit is simpler to weather and has no moving parts, but a sleeping room usually gains from fresh air. Where the window sits above a bed, it should open without hitting the furniture, so the hinge position and the handle reach are worked out together.

The finish inside

The sides of the opening are lined with plasterboard and plastered into a splayed reveal, which spreads light into the room and removes a hard shadow line along the edge of the window.

Same size or larger

A replacement that matches the old window needs no change to the roof structure, because the opening is already there. The old frame comes out, the flashing is checked, and the new unit goes into the same gap. A larger window means widening the opening, and that alters the rafters and brings the work into the structural category. A bigger window also lights more of the floor, so for a loft bedroom with a single narrow gable window the extra width can be worth the added work. The steps are set out under swapping in a larger rooflight.

What is checked before the old unit comes out

We inspect the flashing and the neighbouring tiles first, because the old weathering may no longer suit the new frame. Rotten battens are replaced and the underlay is renewed at the edges. The old flashing set is removed, and a new one made for the tile profile is fitted, so the joint is rebuilt instead of relying on the old one.

The room after the swap

The room under a replacement window loses less warmth, and the inner pane runs warmer than the old glass did. The interior lining is checked and finished where the old frame left marks.

Fitting between the joists

Flat roof joists run in one direction, and the rooflight is placed to fall between two of them. If the unit needs a wider gap, a joist is cut and trimmed, which makes the job structural. On a small utility roof, a unit that fits between neighbouring joists is the simpler route, and it still lights the room well.

Meeting the house wall

A side extension has a wall of the house along one edge, and the roof covering turns up that wall in a step of flashing. The rooflight is kept clear of this junction, so water running down the house wall cannot reach the kerb. Placing it a little way out into the roof, away from the wall, gives both the junction and the kerb room to be weathered properly.

Privacy and security

A rooflight faces the sky and nobody can look into the room through it. Security is a question for the frame and its fixings on the kerb, which are chosen for the room beneath.

Fresh air in a utility room

Damp laundry produces moisture, and an opening rooflight clears it. An electric one is worked from a switch, which suits a ceiling that is hard to reach. Many models close by themselves when the first rain arrives. A fixed unit does the daylight job alone, and the extractor handles the air.

On fitting day the kerb goes down first, then the frame and glass.