Slate roofs on Gomersal's stone cottages and terraces, lit by skylights and rooflights

What the address can change

• Listed status adds a separate step: listed building consent has to be in place before a rooflight goes in, whatever Class C says.
• A conservation area may carry an Article 4 direction, which takes the permitted right away and sends the question to the council.
• Flats sit outside Class C for roof alterations, so planning permission is normally the route and the council can confirm.

Road side or garden side

Terraced roofs in stone country run in long, unbroken lines, so one rooflight set to line up with the windows below looks tidier than two placed at random. A rear slope is also out of sight from the road, which leaves the street elevation as it was. If a stair can take its light from either side of the roof, we look at the rear slope first.

Cottages that share a roof line

Where a row of cottages runs under one ridge, a rooflight goes in your own slope and nobody else's. The frame is set clear of the neighbouring flashing and the line of the next house's chimney, so the new work stays inside your side of the roof.

Gomersal's newer streets

Twentieth-century houses away from the old centre keep the usual permitted development right unless a check says otherwise. The checks above still run, and once they come back clear the work moves straight to choosing a unit for the room.

Swapping a unit that is already there

Reusing an opening leaves most of the roof untouched, where a new cut opens a fresh hole. A listed house can still need consent for a like-for-like swap, so the check comes first either way.

Putting the unit on paper

Should an application be needed, it names one unit in one position. Our fixed quote is written for one room and one unit, with its size stated, so what the council sees is what is later built.

Lifting the covering around the opening

Stone slates are heavy, and each one is worth keeping. We lift them by hand, stack them as they come off and lay them back in their own courses around the frame. A slate that breaks is matched as closely as the existing roof allows. Blue slate is lighter and brittle at the edges, so it is lifted with care and cut to run over the top of the flashing.

Weight and rafters

A stone-slate roof is built with timbers strong enough for the covering, and we look at the rafters before the opening is marked. Their spacing sets how wide a unit can go without extra framing, and a thick stone roof leaves less room for error when slates are lifted than a thin blue one.

Terraces re-roofed in sections

On a terrace that has been re-roofed house by house, the covering can change at the party wall. We read the slope where your opening will sit, not the one next door, and order the flashing for that.

Framing the opening

The gap is trimmed between the rafters, so the load of any cut timber is carried round the new frame. That makes it notifiable work. (We notify Building Control of the work.) Inside, the frame is lined and plastered, and the finished reveal is ready for paint.

Flashing for a thick, uneven covering

A flat kit designed for thin slate does not seal against a thick stone one. The gaps down each side are wider and less regular, so the flashing is dressed to the surface it meets, often in lead. Blue slate takes a standard slate kit. We note which you have so the right one arrives on the day.

Glass for the new opening

Part L allows a roof window up to 1.4 W/m²K, with Window Energy Rating band B as the alternative route, and a rooflight up to 2.2. Both are a clear step up from the single glazing found in the oldest cottage roofs.

Condensation or a failed seal

Moisture on the room side of a pane is condensation, which comes and goes with the weather inside the house, and the full explanation sits in rooflight condensation. Moisture sealed between the panes does not move or clear, and that is the sign of a failed seal.

Glass first, or the whole unit

If the frame is straight and tight, only the sealed glazed unit needs to change. If the frame has warped, rotted or lost its coating, a new seal in an old frame would not last, and the whole rooflight comes out. A look at the frame from inside and out settles which it is.

Old timber frames

A timber frame that has stood in a stone roof for decades often shows its age at the bottom rail, where water collects. Soft or flaking wood there points to a whole new rooflight, however clear the glass still is. Pressing a thumb into the lower rail from inside is the quickest test, and we do the same during the visit before any glass is ordered.

Measuring for the swap

A like-for-like replacement keeps the opening, the flashing and the plaster lining, so there is far less to disturb than with a new cut. Check which edge of the kerb a maker's size refers to; we measure the opening as it stands and match the replacement to it, using the steps set out in swapping one roof window for another.

Taking the chance to improve the glass

A modern unit pairs double glazing and a low-emissivity coating with a warm-edge spacer, and some are gas-filled. Better glazing loses less heat through the same opening, and the numbers are explained in the guide to rooflight U-values and Part L.