Rooflights and skylights for the stone terraces of Steeton

Reading a size code

A VELUX size code is a letter followed by digits. The letter gives the width of the window and the digits give its height, so in a code like MK04 the M is the width and the 04 is the height. Other makers use their own codes, and each one lists the sizes it makes. The code we pick is the one that fits the gap you have.

When the gap is narrow

If the window would be wider than the space between two rafters, a rafter has to be cut. The opening is then framed round the cut with timbers that carry its load, and the job is structural. A slightly narrower window can often avoid that, so we compare both and tell you what the difference would be.

Why the tape comes out first

A size is never chosen from the room below alone. A window that suits the bedroom beautifully but needs two rafters cut costs more and takes longer, so the roof gets its say before the catalogue does. Once the rafters are known, the choice among the sizes that fit is made on the room: how high the bed stands, how much floor needs the light and where the daylight should land.

Height up the slope

The height of the window matters as much as the width. A tall unit reaches farther up the slope, and that suits a bedroom where you want the light to arrive high. A short unit is better over a stair where the slope is short. The position is chosen with the room below in mind, so the light falls where the floor needs it.

Measuring from inside the roof

The rafters are measured from the attic, because that is where the true gaps show. Roof timbers in a village terrace can drift a little over the years, and one gap may differ from the next by more than you would expect. We measure the pair of rafters on either side of the planned position and take the tighter figure. Where the attic is boarded or filled with boxes, a clear area round the proposed spot is enough.

The stone beneath the slates

Where a terrace roof ends at a thick stone gable or a party wall, the frame has to stay clear of that masonry and its flashing. The position can be adjusted a little along the slope to do that.

The letters and what they stand for are listed in VELUX sizes and codes.

Houses in the village

A stone terrace or a semi in Steeton can normally take a roof window in a rear slope within permitted development. A front slope, a protected street or a direction removing those rights may change that, and the council can tell you which of them applies.

Conversions and flats

An older building that has been split into flats counts as flats for this purpose. Roof alterations to a flat are not covered by permitted development, so an application is the usual route and the council will advise. Any lease will name who has to consent to work on the roof.

Listed buildings

A house on the statutory list calls for listed building consent before a rooflight is added, which stands apart from the permitted development rules.

Roof lanterns on extensions

A lantern over a rear kitchen extension stands well above the roof surface. Whether it needs permission turns on the extension, and the council's planning team can say, or the extension's own approval may already include it.

Keeping the paperwork in step

Our written quote is made out for one room, one named unit and its dimensions. Where the law asks for it, we notify Building Control before the work starts. You then have the same details to hand if the council asks.

Rear and front slopes

The rear slope is the easier place for a rooflight, because it is hidden from the street. A front slope on a terrace tells a different story, since the whole row is seen together and one new window changes the line. If the stair or the front bedroom needs the light, we talk through both options.

Why it is worth asking early

An answer from the council arrives before any glass is ordered. If an application is needed, it names a definite unit and size, and it can be sent in without waiting for a visit to the roof.

Glass only

If the frame is sound, square and well sealed to the roof, fresh sealed glass can be fitted into it. This is the smaller job, and it leaves the flashing and the lining as they are. It also lets us choose better glass than the original, with a coating that cuts heat loss.

The whole rooflight

When the frame has warped, the paint has gone or the flashing has worn, a replacement of the whole rooflight is the better answer. It goes into the existing opening where the size still suits, and the flashing is renewed with it.

Changing the size

A bigger window is possible, but it needs a wider opening and new framing. For what that involves, read upsizing at replacement.

What the standard asks for

A replacement unit must reach the figures in Part L: 1.4 W/m²K for a roof window, or Window Energy Rating B, and 2.2 W/m²K for a rooflight. A single-pane unit from an older conversion falls well short of that, so the attic keeps more of its warmth after the change.

Condensation or a failed seal

Droplets on the room side of the pane are a different problem. They come from damp air indoors and clear with ventilation.

How to tell the two cases apart

Look at the glass from the room on a cool morning. A film that wipes away from the inside is condensation. A haze or a set of watermarks that stays put, however you rub the pane, sits inside the unit and means the seal has gone. If you are unsure, send us a photograph and we can say which it is.

The seal and the gas

A sealed unit holds two panes with a gap between them, often filled with argon, and a spacer round the edge keeps them apart. When the edge seal fails, damp air enters the gap and the coating can stain. Nothing can be done to the old unit, so the work is a swap.

Fitting the new unit

The old glass is lifted out, the frame is cleaned and checked, and the new sealed unit is set in and bedded. The flashing round the frame is looked at while the slates are lifted, since a tired flashing is better renewed while the roof is open.

What you can do beforehand

Clear the floor below the unit, and tell us whether the attic is boarded. A boarded floor needs lifting before the old frame is lifted out.