Skylight and rooflight installation and replacement in Stockport

Why people replace

Misting between the panes is the usual giveaway: the seal of the glazed unit has failed, so the mist sits where no cloth can reach. Others replace a window that is stiff, hard to reach or draughty, or a cloudy plastic dome on a flat roof, and some simply want a remote control where a pole used to be. Droplets on the room side of the glass are a different matter, since warm, damp air from a bathroom or kitchen meets cold glass and turns to water, as on a car windscreen. Opening the window or using the vent position often helps more than new glass would.

When it is not a straight swap

A new window with the same size code is made for the opening already there, so the existing lining and plaster can be left; another maker means checking the sizes line up, because the codes are not shared. Going bigger needs new trimming in the roof and new lining and plaster inside, so the job starts to look like a new opening. A change from manual to electric may need a power supply to the window, which a solar model avoids.

The rules for a replacement

For a replacement, these points apply:

• In England, a new or replacement roof window in an existing home should have a U-value no worse than 1.4 W/m²K, or a Window Energy Rating of Band B or better.
• Should the new unit be a rooflight, its U-value should come in no higher than 2.2 W/m²K, which is the figure for rooflights.
• A replacement element should also be no worse than the one it replaces.
• Ventilation is checked at the survey.
• Where a new house would need an escape window in that position and the existing window is big enough for escape, the replacement should give at least the same escape potential, though a window larger than needed can be reduced to the minimum escape size.
• Replacing only the glass, or a window in its existing frame, is not providing a controlled fitting, so the energy limits do not apply to that work.
• Table 4.2 of Approved Document L is the source of the energy figures.

Planning permission and Class C

In England, adding a rooflight or roof window to a house is usually permitted development under Class C, so it does not need a planning application, provided it meets the Class C limits and conditions. These are the limits and conditions:

• it must not stick out more than 150 mm beyond the plane of the original roof slope, measured at right angles to the roof surface, and the frame counts;
• no part of it may be higher than the highest part of the original roof;
• on a roof slope that forms a side elevation of the house, the whole window must be obscure-glazed, and non-opening unless the parts that open are more than 1.7 m above the floor of the room it is in;
• the house must not be one that became a home only through a change-of-use permitted development right, such as an office or farm building converted under Part 3, because those houses have no Class C rights.

For a house built before 1 July 1948, original means the roof as it stood on that date. A council can remove permitted development rights in all or part of its area with an Article 4 direction, and rights may also have been removed by a condition on the house's original or a later planning permission. Either way, a planning application is then needed, so we check with the council first. Flats and maisonettes have no householder permitted development rights; Class C applies to houses only. A rooflight on a flat needs planning permission (and usually the freeholder's consent).

Conservation areas, listed buildings and the Peak District

In England a conservation area leaves the Class C right in place; what removes it is an Article 4 direction, or else a restriction written into an earlier permission for the house. Class C has no listed-building exclusion in England, so a listed house still has Class C planning rights, but a new or altered rooflight on a listed building will almost always need listed building consent, and that consent decides the job. Inside the borough of Stockport the planning authority is Stockport Metropolitan Borough Council. National Park status does not by itself take Class C away either. Peak District National Park Authority is the local planning authority inside the park boundary. Outside the boundary, the local council is. If there is any doubt, a Lawful Development Certificate from the planning authority gives formal certainty.

A roof lantern added to an existing flat roof usually stands well over 150 mm proud of the roof, so it normally falls outside Class C and needs planning permission unless the council confirms otherwise. Where the roof is still to be built, the position differs. On a new extension, the lantern is assessed with the extension; we confirm the position with the council before work starts.

Building Regulations

• A new rooflight will generally need Building Regulations approval: the roof usually has to be cut and the opening trimmed, the roof has to carry the rooflight's weight or be strengthened, the rooflight has to be energy efficient, and near a boundary its fire performance comes into it.
• Replacing a roof window usually needs Building Regulations approval too, and the replacement answer above has the energy figures.
• Where the work is notifiable, we handle the Building Regulations notification with the council's building control team or a registered building control approver.
• A roof window counts as an escape route only on a storey no more than 4.5 m above ground, so a loft conversion on a two-storey house that creates a storey higher than that normally means addressing the full escape route down the stairs, rather than relying on a roof window.
• The Building Regulations in England set no daylight requirement for houses.

Our guides cover the planning limits in full and the Building Regulations.