Rooflights and skylights in Purley

Purley expanded rapidly as a suburb in the 1920s and 1930s, when rural estates became residential streets. That is a useful fact for anyone thinking about a rooflight, because it says when much of the housing arrived, even though it does not say what any one roof is made of.

The public record we hold for Purley does not name the roof coverings or describe how the roofs are framed, and we do not guess at them. A house from that period of growth may have clay or concrete tiles, slate, or a replacement covering laid in a later decade. Underneath may be cut rafters or factory trusses. Each choice changes the job. A tile needs one kind of flashing and a slate another, and the framing decides how wide an opening can be before the structure needs a trimmer or a new beam. We read all of that on the roof.

What the period does give us is a pattern of use. Streets built fast as family housing tend to hold lofts that were left as storage, and storage lofts are where a rooflight first does its work. A roof window turns an unused loft into a bedroom or a study, and a small unit over a dark landing can change a whole upper floor. Our guide to where to position a skylight in a room works through the choice of slope and height.

A loft that has already been converted raises the opposite question. If the room is in use and the existing window is tired, we are replacing, not adding. The opening is there, the plaster is finished, and the job is to fit a better unit without disturbing the room more than we must. The page on replacing an old skylight explains when like for like is enough and when a better unit earns its place.

In a pitched loft, a roof window brings daylight and fresh air to a bedroom or study. A centre-pivot unit opens wide enough to look out of while standing, and a top-hung unit swings further out and leaves more headroom at the sill. Size and position are settled together, and our guide to sizing a rooflight for the room shows how.

A landing often has no outside wall and little loft above it. A sun tunnel carries daylight down a short tube into such a space and fits where a full window would not.

Over a kitchen extension the choice lies between a flat rooflight and a lantern. A flat roof rooflight is the calmer of the two, with one large pane and no bars for rain to strike. A roof lantern lifts the ceiling and lets light in from several sides, but it has more bars and more edges, so the glazing build carries more weight. Both are installed to current Building Regulations, with the upstand insulated and the lining made good inside.

Inside a conservation area the shortlist narrows again. Low-profile, flush units on the rear slope come first, and the choice between a pivot and a fixed pane follows from what the council will accept at the address. The broader guide to choosing a rooflight for your home covers glass, frames and opening types.

A suburb that grew in the 1920s and 1930s has had a long time to accumulate rooflights of every age. Some were fitted in a loft conversion decades ago. Some came with a rear extension. A few may be original to the roof.

Age shows in several ways. The panes may have misted between the glass, which means the seal has gone and the cavity has let in moisture. The gasket may sit loose and let in cold air and sound. The frame may have warped, or the glass may be a single thin sheet that rings in rain. Our guide to the signs a rooflight has failed lists them, and the page on when to replace a rooflight helps you decide on timing.

Replacing is often simpler than adding, because the opening exists. We measure the old unit, check the upstand or kerb, and decide whether the same size will do or whether a change in size would improve the room. A modern unit brings better glass and tighter seals. It can also bring a quieter build than the old one, which is worth having in a bedroom. Where the old unit is on a flat roof, the same visit checks that the fall still clears water. The service page on misted and failed rooflight replacement sets out how the job is done.

A replacement can also be an upgrade in energy terms. Part L sets standards for heat loss, and a current unit is built to meet them. The energy efficient rooflights page explains the glazing choices, and the costs page sets out what moves a price, in general terms.