Skylights in post-war houses: what the New Town roof asks for

A house built between 1949 and 1975 was designed for a different set of rules and a different idea of daylight. Knowing the decade tells you what is probably above the ceiling before anyone climbs a ladder.

Crawley's neighbourhoods arrived in a sequence. West Green started in 1949, Northgate in 1951, Langley Green and Three Bridges in 1952, Pound Hill and Ifield in 1953, Tilgate and Southgate in 1955, Gossops Green in 1956, Furnace Green in 1960 and Broadfield in 1969. Bewbush began in 1974 and 1975. Each phase had its own developer mix, its own roof shapes and its own ideas about what a loft was for.

The earliest houses were generally built as compact family homes with a simple pitched roof and small bedrooms. Later phases brought in more terraces, more flats, more flat-roofed garages and porches, and more private estates next to council housing. By the time a homeowner today thinks about a rooflight, the original roof may well have been altered: a loft turned into a bedroom, a kitchen pushed out at the back, a garage absorbed into the house. Those alterations are usually where the skylight is wanted, and they are also where the surprises sit.

That is why we treat the year of construction as a starting question rather than a label. It does not decide the specification. It tells us where to look first, and it shapes the conversation about how much of the existing roof can be trusted to carry new glass. If you are still deciding between products, how to choose a rooflight covers the wider choices before you narrow to your own roof.

A survey on a post-war house starts from the roof and works inwards. The product comes last, once the structure has told us what it can take.

From inside the loft, the first thing to check is the rafters or trusses. Houses of this period were built with lighter timber sections than people expect today, sometimes as cut-and-pitched roofs and sometimes with early factory trusses. Where a truss web crosses the place you want an opening, the opening cannot simply be cut. The timber has to be trimmed and carried properly, and on trussed roofs that can change the position or the size of the unit. If a beam or a structural change is involved, the question of whether you need an engineer is answered before any glass is ordered. Whether a rooflight needs a structural engineer explains where that line usually falls.

Next comes the covering. Concrete interlocking tiles were widespread across the period, and so were clay plain tiles on the earlier brick houses. A porch or bay roof may be much shallower than the main slope. A shallow pitch narrows the choice of roof window, because each product has a minimum pitch and an upper limit for its flashing kit.

Then the underlay. A roof from these decades may have bitumen felt that has been in place for a very long time, sometimes without the breathing properties we now specify. Cutting an opening disturbs it, and a new flashing has to tie into whatever is there. We look at its condition, and we describe on the quote what will be renewed around the opening and what will be left alone.

• Timber sizes and spacing: decide how the opening is trimmed.
• Roof covering and pitch: decide which roof window or flashing kit fits.
• Felt or underlay condition: decides how much is renewed around the new unit.
• Ceiling and loft insulation: decide the lining and the light well.

A loft bedroom in a 1950s or 1960s semi is a natural home for a skylight. The ceiling is sloped, the floor area is tight, and a good roof window can make the room feel twice as large.

The rafters set the sizes available. Most roof windows are made to fit between rafters at standard centres, and on an older roof the centres are not always standard. Where they are close, a window may fit with no cutting of structural timber at all. Where they are wider or uneven, a trimmer goes in above and below. That is ordinary carpentry, but it changes the time on site and how we describe the job in writing.

Position matters as much as size. A window set too high lights the ceiling and leaves the floor dim. One set too low can look straight into a neighbour's upstairs window or leave no room for a wardrobe beneath. Where to position a skylight in a room goes through the trade-offs, and for this kind of loft the answer is usually set by the headroom line, the bed position and the ridge. If you are weighing two or three smaller windows against one large one, how many rooflights a room needs helps frame the decision.

A bedroom brings its own concern about morning light. Skylights catch the sun earlier than a wall window does, and a room that faces east can brighten before you want it to. Will a skylight in a bedroom wake me at dawn? deals with blinds, glass tint and orientation, so the room stays restful.

The detail that changes most between a semi and a modern loft is the insulation. A post-war roof may have little between the rafters, and the new opening will need a properly lined light well so there is no cold bridge at the reveal. Part L sets the standard for the unit's thermal performance, and we build the lining to match the insulation level you choose. Roof window installation sets out how that work is organised.

The flat roof is where post-war homes most often need a new rooflight, and where the original build is most likely to have aged. A kitchen extension from the 1960s or 1970s may have a flat deck, a bitumen felt covering and a fall that was never generous.

Before fitting a flat rooflight we want to know the fall. Water has to move across the deck toward the outlet, and a fall of 1:80 is a common design target for a finished flat roof. Older roofs may be flatter than that, and some have settled into shallow hollows. A new kerb can make a hollow worse, because the upstand holds water that would otherwise have run past. Where the deck is sound but too flat, we can build a tapered insulation layer or adjust the joists so the roof drains toward the outlet rather than toward the kerb.

The deck itself deserves a look from below. Boards that have been damp for years can be soft at the edges, and a kerb needs something firm to be fixed to. If the deck is sound, the new rooflight is built on a proper upstand and the new membrane is taken up and over it. If the deck is tired, a new roof covering belongs in the same job, because a new rooflight set in an old felt roof will outlast the felt only by luck.

The choice of unit follows the roof. A fixed flat rooflight, an opening one and a roof lantern each behave differently over a deck of this age, and flat roof rooflight installation explains how we match one to another. A lantern adds height and a visible frame, which suits a wider extension. A flat glass rooflight gives a cleaner look. On a small porch or a garage conversion, a flat glass unit is often the better proportion. Should I choose a skylight or a roof lantern? sets out the difference.

Older plastic domes are found on plenty of extensions, and they are often what the owner wants to change. Can I replace a plastic dome skylight with glass? covers the question of whether the upstand that carried the dome can carry glass, which is heavier.

Not every post-war roof is a standard timber semi. Crawley's own records include the unusual. Northgate has 142 concrete houses from 1955, described as unique in the town, and it has a higher share of flats than the other areas. Bewbush is roughly 90% terraces or flats, and Southgate West added low-rise blocks between 1968 and 1972.

A flat in a low-rise block may have a roof that is not yours to alter. Responsibility for the structure usually sits with a freeholder or management company, and a rooflight on a top-floor flat needs their consent as well as any planning or Building Regulations steps. The ownership of the roof is never a detail. It comes up at the first conversation.

Terraces have a different constraint. A roof shared along a run of houses is joined at the party walls, and an opening near the boundary affects the fire separation that Part B of the Building Regulations cares about. Distance from a boundary also influences what glass and frame are appropriate. On an end-of-terrace this is usually simple, and on a middle house it means being precise about where the opening sits relative to the party wall.

Concrete construction, where it exists, is a survey item in its own right. A precast or in-situ concrete roof or wall cannot be trimmed the way a timber roof can, and the route for any opening has to be worked out before a price is given. If your house is one of the unusual types, say so when you ask for a quote and we will plan the survey around it.

The same house can ask for different things depending on its neighbourhood and decade. This table puts the main patterns side by side, as a starting guide rather than a verdict on any one address.

Read the last column as a first instinct, not an instruction. The roof survey can overturn any row of it.

Houses from the 1960s deserve a special mention, because they are the ones people search for when they want rooflights for 1960s houses. They commonly combine a low-pitched main roof, a flat-roofed extension added later and a garage that has been turned into a room. That mix can ask for more than one product on one property. A roof window may suit the loft, a flat rooflight may suit the extension, and a sun tunnel may be the answer for a small landing or bathroom where an opening cannot be framed. Sun tunnel installation is worth reading if you have a dark central space with no outside wall.

A post-war roof is not always a quiet one. Thin tile and felt, light timbers and small loft spaces do little to deaden outside sound, and a new pane of glass can be the largest hard surface in the room.

Gatwick is part of Crawley borough, and the council's Local Plan treats the land between the town and the airport as heavily constrained by aircraft noise. One third-party flight-path site suggests that Langley Green and Northgate, on the northern edge of the town, get climb-out and ground noise, while the town centre and southern neighbourhoods sit outside the loudest band. That is indicative only, and it is not official contour data. What it does mean is that the noise your loft hears depends on where you are. Rooflights under the Gatwick flight paths sets out how we think about it, and can you hear planes through a skylight? answers the question directly.

Elsewhere the noise is different. The M23 and the Brighton Main Line run through the town, and neighbourhoods close to either hear a steadier, lower sound. Rain on a flat glass rooflight is a third kind of noise, and it is the one nearly every flat-roofed extension shares. The answer is in the build of the unit, not in the weather. How to reduce rain noise under a flat rooflight explains the options, and are skylights noisy in the rain? gives the short answer.

We choose the glazing for what the room hears. A laminated acoustic inner pane damps more than a toughened one of the same thickness, and a cavity of the right width helps. Seals that grip and an upstand that is insulated and solid add to the effect. None of this needs a number to be useful: the quiet spec we write with every quote names the panes, the cavity, the seals and the upstand. The quiet spec shows the format, and acoustic laminated glass explained goes into the glass.

Older roofs lose heat in ways modern ones do not, and a rooflight can make a cold loft feel colder if the detail is wrong. The job is to make the new opening better than the roof around it.

Current Building Regulations set thermal performance limits for new and replacement rooflights, in Approved Document L. We build to those limits, and we go beyond them where the room benefits. The glass matters, but the frame, the spacer and the lining matter just as much. A cold reveal is where condensation forms first, and a loft that was never ventilated for modern living can show mould on a plasterboard return long before the glass itself mists. Do rooflights cause condensation? covers where moisture really comes from.

Ventilation is part of the picture too. Post-war lofts were often ventilated by accident, through gaps in the eaves and in the felt. When a loft is converted and insulated, those gaps may be closed, and the moisture that used to escape stays in the room. A new opening with a trickle vent or an opening sash can help, and Approved Document F sets the ventilation requirement for habitable rooms. Building Regulations for rooflights explained covers the parts that apply to a typical job.

For anyone looking at energy performance specifically, energy efficient rooflights explains how the performance of a unit is achieved. Triple glazing is sometimes raised at this stage, and whether triple glazing makes a rooflight quieter may not give the answer you expect.

A post-war home may already have a skylight, put in when the loft was converted or the extension built. Replacing it is usually simpler than cutting a new opening, and it is the moment to upgrade.

A renewal starts with the opening you have. If the existing unit has failed, the glass is misted or the seals have gone, you will see it from the inside. Signs a rooflight has failed lists what to look for, and misted and failed rooflight replacement describes how we approach a unit that has reached the end of its life. Whether it is worth it is a fair question, and is it worth replacing an old skylight? gives a straight answer.

Replacing like for like keeps the original size and the original frame position. Upgrading may mean a larger unit, a different product or a different glazing. Replacing an old skylight: like for like or a better unit weighs the two. If the opening is to grow, can you put a bigger rooflight in the same opening? explains what has to change.

Replacement on a post-war house can reveal the condition of the roof around the unit. A failed seal on a 1960s extension can mean the kerb has been wet for years. We tell you what we find, and we write it into the quote before the work is agreed.

Most post-war houses sit outside the town's conservation areas, but a few do not. Crawley Borough Council lists 13 conservation areas, including Gossops Green Neighbourhood Centre, Southgate Neighbourhood Centre, and Forestfield and Shrublands in Furnace Green, and the position is checked for the address. That matters even when your house is ordinary brick, because a neighbourhood centre can sit close to surrounding streets.

Elsewhere, permitted development often covers a roof window that does not project far from the slope, but flats do not have the same rights as houses, and a flat roof has its own rules. Can I add a rooflight under permitted development? and planning permission for rooflights and skylights explain the rules and their limits, and does Crawley Borough Council need to approve a rooflight? deals with the local side.

Building Regulations are a separate question from planning. A new rooflight can be notifiable, and we handle the Building Control notification where the work is. Does a new rooflight need Building Control sign-off? and is replacing a rooflight notifiable under Building Regulations? set out which jobs fall where.

The quote for a house of this age should read like a description of your roof, not a generic product page. It should name the unit, the size in all three measurements, the glazing build and the work to the roof around it.

Ask for the lining, the flashing or upstand, the insulation level and the treatment of the old felt. Ask who is responsible for any boarding, plastering or decorating after the work. Ask what happens if the opening shows a problem we could not see from the loft. What should a quote for a new rooflight include? is a full checklist, and questions to ask a skylight installer is a useful list to take into any conversation.

Every quote from us comes with a written quiet spec and covers Crawley and 30 miles around. The work is installed to current Building Regulations and carries a 10-year workmanship guarantee, and you can read the terms at our guarantee. To ask for a survey, use the quote form or message us on WhatsApp. The price depends on the roof, and costs explains the drivers in general terms. This page belongs to the wider skylight and rooflight installation service for Crawley.

These questions come up when a house from the New Town decades is being looked at for its first or next rooflight.

Will my 1950s roof take the weight of a glass rooflight?

Often it will, but it is checked rather than assumed. Glass units weigh more than the plastic domes many extensions carry, and lantern frames add further load. We look at the joists, the span and the deck at survey, and we say in writing whether any strengthening is needed.

Can I put a skylight in a flat in a low-rise block?

Only with the agreement of whoever owns or manages the roof, which is usually the freeholder. Planning and Building Regulations are separate steps. Start by finding out who holds the roof, then contact us with that answer.

My extension roof ponds after rain. Is that a problem for a new rooflight?

It can be. Standing water on the deck puts load on the new upstand and speeds up ageing of the membrane. We measure the fall and propose a correction where it is needed, because a new unit should not sit in the wettest part of the roof.

Is one big rooflight better than two small ones in a 1960s house?

That depends on the structure and the room. Two smaller units spread light and suit rafter spacing, while one large unit gives a cleaner look and a single flashing to maintain. The survey decides which the roof can take.

If your question is not here, contact us and we will answer it for your roof.