Conservation Rooflight Installation
Slim cast frames set flush, for stone slate, listed and conservation roofs.
the Cotswolds
Rooflight and skylight installation in Cirencester, surveyed first, and fitted once.
Cirencester, and the roofs around it: market town, dense listed core, stone slate. Everything below is what that means once the covering comes off.
- Covered from Gloucester
- 15 years on Gloucestershire roofs
- 10 year workmanship guarantee
- From Gloucester by road
- 15 to 30 milesApproximate, and inside the 30 mile radius
- Dominant roof stock
- Cotswold stone slate in diminishing coursesWhat the covering is decides the detail
- The usual constraint
- Conservation consent and matching the stoneSettled at survey, before anything is ordered
- Local character
- market town, dense listed core, stone slateRecorded for Cirencester specifically
In Cirencester
What we fit on Cirencester roofs
Replacing a Failed or Misted Rooflight
Misted and tired units taken out, and the opening made good underneath.
Walk-On Rooflight Installation
Structural glass rated to stand on, over rooms below a terrace.
Sun Tunnel Installation
Daylight into landings and bathrooms with no roofline to work with.
Roof Lantern Installation
Flat roof glazing sized to the room and detailed into the kerb it stands on.
Flat Roof Rooflight Installation
Flush and kerb mounted units into felt, single ply and GRP flat roofs.
The local detail
Fifteen things worth knowing about Cirencester roofs, worth reading before the survey.
Cirencester is the largest town Severn Skylights Gloucester works in east of the city, and it is the one where the roof under discussion is hardest to guess from the address alone. A single postcode district here can cover a Georgian townhouse with a parapet and a hidden lead flat behind it, a Victorian brick terrace on one of the roads out, a stone cottage with diminishing courses of Cotswold slate, and a 1990s trussed estate house with concrete interlocking tiles. Those four roofs want four different units, four different flashing arrangements and, in two cases, a different consent route. Severn travels out from Gloucester to survey, and the survey exists because the town’s stock is too varied for a sensible answer over the phone. Coverage across the county sits on the areas pages.
Cirencester carries more kinds of roof than the rest of the wolds put together
Most Cotswold towns are one thing. Cirencester is four or five at once, because it kept growing after the wool trade stopped paying for the building. The historic core is stone with stone slate and, in places, later Welsh slate. Around it sits a ring of nineteenth century brick and slate built as the town spread along its approach roads. Beyond that are interwar and post-war houses with concrete tiles, and beyond those the modern estates.
The consequence for a rooflight is that the first useful question is never what unit you want. It is what covering you have, what pitch it sits at, and whether the roof structure is cut on site or made in a factory. Two houses a quarter of a mile apart in this town can need entirely different work at entirely different prices for the same room outcome.
The Georgian townhouse, and the roof behind the parapet
The better eighteenth and early nineteenth century houses in the town centre present a stone or rendered elevation with a coped parapet along the top, and the roof sits behind it out of sight from the pavement. Sometimes that is a shallow double pitch draining into a central valley gutter. Sometimes it is an M-shaped roof with a lead flat between the two ridges. Sometimes there is a genuine lead flat with a parapet gutter running to an outlet through the wall.
This geometry is the single most useful thing to establish before anyone talks about consent, because a unit on a slope that no member of the public can see is a different conversation from a unit on a visible face. It also changes the product. A parapet gutter and its outlets have to be left entirely alone, which usually means the unit sits toward the middle of the slope rather than where the room below would prefer, and on a very shallow upper slope the answer becomes a kerb-mounted rooflight rather than an in-plane roof window, because manufactured roof windows are rated from around 15 degrees.
Where the town’s stone slate gives way to Welsh slate
Not every old roof in Cirencester is stone. The town was on the rail network in the nineteenth century, and Welsh slate arrived cheaply enough that a good deal of Victorian building here, and a good deal of re-covering of older buildings, was done in Countess and Duchess sizes rather than in stone.
The two behave nothing alike at an opening. A Welsh slate is five to eight millimetres thick, takes a flat flashing kit, and gives the neatest rooflight detail available on any covering, with interleaved soakers that disappear. Cotswold stone slate is commonly 20 to 30mm, irregular in thickness, and takes lead formed on site because no moulded kit will bed onto it. The full method for each is set out on rooflights in natural slate roofs. Establishing which one you have is a five minute job at survey with a slate lifted at a verge, and it decides the order.
the Cotswolds
Diminishing courses mean the slate at the ridge and the slate at the eaves are different sizes. An opening has to be set out against that, not against a tape measure.
Attic floors above the shops in the town centre
The commercial core has a pattern that repeats: retail at ground level, storage or a flat on the first floor, and an attic above that under a stone or slate roof with dormers or nothing at all. Those attics are frequently the darkest usable space in the building and the obvious candidate for daylight from above.
Three constraints come with them. The roof structure is often hand-cut, with purlins, struts and collars in positions that were never drawn, so the clear rectangle available between them is measured rather than assumed. Access to the roof is from a street or a rear yard shared with a business, which shapes the scaffold. And the ceiling below the working area may be lath and plaster, which does not enjoy being walked over from the loft side. The sequence for that kind of building runs from outside wherever it can.
The covering
Cotswold stone slate laid in diminishing courses on torched battens, the covering that decides the whole detail.
Cotswold stone slate in diminishing courses, which is what the survey is looking at before it looks at the glass.
Victorian brick on the roads out of the town
Along the approach roads the building turns to brick with slate or clay tile, in terraces and semi-detached pairs, much of it with the same narrow two-storey rear addition found in Gloucester. That addition roof is where a large share of the enquiries in this part of Cirencester come from, because the kitchen underneath has one small window and faces a yard.
The catch is the run of slope, which on a rear addition is often only 1.8 to 2.4 metres from gutter to abutment. A standard roof window plus the head and cill laps it needs eats most of that. The workable answers are a smaller unit set high in the slope, two narrow units side by side, or a made-to-size flat roof rooflight on the flat area where the addition meets the back wall of the main house. Getting it wrong leaves a head flashing with nothing above it to lap under, which is where marks on a ceiling begin.
Chesterton, Stratton and the estate roofs on the edges
The twentieth and twenty-first century parts of the town are the easiest roofs in it and they carry their own rule. Post-war and later houses around the town’s outer edges are largely trussed rafter construction: factory-made triangulated frames at 600mm centres held with punched nail plates.
Nothing in a truss is spare. Cut a web to make room for a wider window and the load path changes, the truss deflects, and the result shows up months later as a line in the ceiling. So an opening either fits between two trusses, which gives roughly 550 to 570mm of clear width and suits the narrow units the manufacturers make precisely for it, or it needs a designed trimmer carrying the affected truss on a beam. That second version is a structural calculation and a Building Control submission before the tiles come off. Both are routine, and the difference is set out at survey rather than found on the day. The detail is on rooflights in a trussed roof.
Rear extensions behind the town houses, and the lantern that suits them
A large number of Cirencester houses, old and new, have gained a flat-roofed kitchen or garden room at the back. Those are the least constrained roofs in the town and the ones where the biggest change to a room is available, because a made-to-size rooflight or a roof lantern can be sized to the space rather than to a manufacturer’s list.
The technical work is in the kerb. The standard upstand is 150mm measured from the finished surface of the waterproofing at the high point of the fall, not from the deck, and the kerb is insulated on its outside face so it does not become a cold ring around the glass. The deck should fall at around 1:40 so that after deflection the finished fall is no shallower than 1:80. Where an existing flat roof already holds water against the position somebody wants, the honest answer is that the falls need correcting first, and that gets said before a price is given. See roof lantern installation and flat roof rooflight installation.
Conservation here is not a formality. It is the reason the stock still looks like this.
Setting out an opening on a coursed stone slope
On the stone slate roofs in and around the town, the setting out follows the coursing, not the room. Cotswold stone slate is graded and laid in diminishing courses, largest and thickest at the eaves, reducing up the slope, so the gauge changes continuously and there is no repeating module to work to.
The opening is marked from inside so the reveal lands where the room wants it, then the position is transferred outside by drilling at the corners, and then it is adjusted to the nearest sensible course boundary. The courses above are stripped back up the slope, the frame is set, and the courses are re-laid downwards, re-establishing the diminishing gauge so the finished slope reads correctly rather than showing a rectangle of uniform coursing around the window.
On a stone slate roof the coursing decides where the frame head can sit, so the setting out is agreed before the unit is ordered.
The covering
Cotswold stone slate laid in diminishing courses on torched battens, the covering that decides the whole detail.
Cotswold stone slate in diminishing courses, which is what the survey is looking at before it looks at the glass.
Reclaimed Cotswold stone, and how it sets the date
Stone slates break coming off. Some are already cracked, some are bedded in old mortar, and the thicker courses low down are heavy enough that a dropped one is finished. So a proportion of the covering around any new opening has to be made up from reclaimed material, matched for thickness, size and weathering colour.
New stone reads bright against a roof that has been weathering for two centuries, and it stays visible for a decade or more. Matched reclaimed slate is worth waiting for, and the waiting is real: sourcing the right sizes in the right thicknesses takes time, and on a heritage job the material is often a condition of the approval anyway. The programme therefore runs material first, date second. A date agreed before the stone is found is a date that moves.
Consent for a rooflight in a Cirencester conservation area
The historic core of the town is a conservation area with a large body of listed buildings inside it, and the district planning authority is Cotswold District Council. Two things are worth separating. Conservation area status controls what an application is judged against and can remove permitted development rights where an Article 4 direction applies. Listing creates a separate consent that is required for anything affecting the building’s character, inside and out, whether or not anyone can see it.
The pattern of what gets approved is fairly settled: a modest, dark, near-flush unit on a rear or concealed slope, aligned with the openings on the elevation below, with matched reclaimed stone for the making good and lead formed on site. Two small units frequently land better than one large one. The full consent landscape across the county, authority by authority, is on conservation areas and listed buildings in Gloucestershire.
Building Control on a town centre roof
Forming a new opening is notifiable work and so is replacing a unit in most circumstances. On the older buildings in the town three parts of the regulations come up more often than the rest.
Structure, because trimming a hand-cut rafter beside an existing purlin is not the same as trimming one in a clear bay, and where the span or the load needs it an engineer’s calculation goes in with the application. Fire safety, because where a roof window forms the escape opening from a room in the roof the clear openable area must be at least 0.33 square metres with a minimum of 450mm in both height and width, and the bottom of that opening between 800 and 1100mm above the floor. And conservation of fuel and power, where the limiting standard for a replacement roof window is 1.4 W/m2K, comfortably met by any current unit. The notification is submitted and closed out as part of the job, and the completion certificate comes back in the homeowner’s name.
Conservation here is not a formality. It is the reason the stock still looks like this.
Scaffold where the pavement is the only standing ground
Working on a frontage in the middle of Cirencester is a logistics problem before it is a roofing one. There is often no front garden, the pavement is narrow, the street may be one way, and a scaffold standing on the footway needs a licence from the highway authority with its own lead time and its own conditions about lighting and pedestrian routes.
Rear access is usually better and sometimes it is a shared yard or a passage barely a metre wide, which means the scaffold is hand-carried in and a made-to-size lantern’s glass may need extra hands or a mechanical lift. None of that is unusual and all of it is priced from what the survey sees rather than assumed, so the figure holds when the crew arrives.
Loft conversions in the larger houses
The bigger Victorian and Edwardian houses on the town’s approach roads have generous roof voids with cut structure, and they convert well. A conversion typically wants more glass than a single window, and the useful principle is that two or three smaller units spread along a slope light a room far more evenly than one large one in the middle, need no structural design if they sit in existing bays, and deliver more glass in total.
Position is worth thinking about in daylight terms rather than view terms. A unit set high in the slope throws light deep into the room. A unit set low gives a view of the garden from a bed and lights the floor immediately below it. Most conversions want one of each. Sizing guidance is on rooflights for a loft conversion.
Conservation unit or standard roof window on a Cirencester roof
The choice is decided by the covering thickness and by the designation, in that order.
| Situation | Usual answer | Why |
|---|---|---|
| Stone slate, listed or prominent slope | Conservation rooflight, slim steel frame, single glazing bar | Sits near flush in a 25mm covering rather than standing proud |
| Stone slate, concealed rear slope, not listed | Conservation unit still usual, occasionally a recessed roof window | Officers commonly condition a flush appearance regardless of visibility |
| Welsh slate, rear slope in the conservation area | Recessed manufactured roof window in a dark finish | A 6mm covering swallows the whole recess and the unit sets into the plane |
| Clay tile or concrete tile, outside the historic core | Standard manufactured roof window with the matching kit | Profile depth already hides the frame, and the kit is made for it |
| Flat rear extension anywhere in the town | Made-to-size rooflight or lantern on an insulated kerb | Size is chosen for the room instead of from a list |
Product detail for the heritage version is on conservation rooflight installation.
On Cirencester roofs Conservation consent and matching the stone.
How a Cirencester job gets from an enquiry to a fixed price
Send a photograph of the roof from the garden or the street, a photograph of the room from inside, the covering if you know it, and the address, to info@severnskylightsgloucester.co.uk. An indicative range comes back by email within a day or two, which exists so nobody spends an afternoon on a survey for a project that was never going to work financially.
A survey follows. On a Cirencester roof it records the covering and its measured gauge, the pitch off a digital level, the rafter or truss centres and their depth, the position of any purlin or binder, the condition of the underlay or the absence of one, the designation position for the address, and the practical questions of scaffold, licence and where glass can be lifted from. After that comes a fixed price, itemised so it is clear what is unit, labour, scaffold and Building Control. That figure holds unless the scope changes at the customer’s request. The route in more detail is on the costs page, and the written guides go further into individual questions.
Also covered: the Cotswolds