Conservation Rooflight Installation
Slim cast frames set flush, for stone slate, listed and conservation roofs.
the Cotswolds
Rooflight and skylight installation in Bibury, planned before anything is ordered.
Bibury, and the roofs around it: very high listed density, steep 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
- very high listed density, steep stone slateRecorded for Bibury specifically
In Bibury
Rooflights we fit around Bibury
VELUX Window Installation
VELUX fitted alongside Fakro, Keylite and Roto, chosen to suit the roof.
Electric and Opening Rooflights
Actuated openers, rain sensors and controls, wired and commissioned.
Energy Efficient Rooflights
Specified on U-value and g-value for the way the roof actually faces.
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.
The local detail
Fourteen things worth knowing about Bibury roofs, and what each one changes.
Bibury is a very small village that is looked at by a very large number of people, and that single fact governs everything about putting a rooflight into a roof here. William Morris called it the most beautiful village in England, the phrase stuck, and the village has spent the century since being photographed. Coaches come through on the B4425, the row of cottages by the water meadow appears on more postcards than any other building in Gloucestershire, and the roofscape of steep stone slate is not a backdrop to that but the substance of it. Severn Skylights Gloucester travels out to Bibury from the city, and the honest opening position is that appearance control here is tighter than anywhere else in the county, and that jobs still get done inside it.
A village photographed several thousand times a day
Most conservation area work involves a judgement about who can see a roof. In Bibury the answer is close to everybody. The village is compact, the buildings face the river and the road, the ground rises behind them, and there is no part of the built area that is not in somebody’s photograph on an ordinary afternoon.
That removes the argument that usually carries a Cotswold application. A rear slope, screened from the street, invisible from any public place: in Northleach or Fairford that describes a real condition, and in Bibury it frequently does not. The lanes and footpaths run behind as well as in front, the ground rises to give elevated views over roofs that would be private anywhere else, and the river frontage puts the backs of buildings on display. Establishing what is genuinely unseen takes a walk round the whole village with a camera, and the answer is sometimes that nothing on that particular building qualifies.
On Bibury roofs Conservation consent and matching the stone.
Arlington Row, the water meadow, and the buildings in the same view
The row of former weavers’ cottages by Rack Isle is in National Trust ownership and carries heavy designation. It is not going to be the subject of a domestic rooflight enquiry. Its relevance to this page is the setting.
Setting is a material planning consideration, and it extends well beyond the boundary of the designated building itself. A roof that appears in the same view as the row, or in the same view as the water meadow and the river frontage, is assessed with that in mind. In a village this size that catches a great many buildings that are otherwise perfectly ordinary houses. The way the two consent regimes work, and what setting means in practice, is on conservation areas and listed buildings in Gloucestershire.
Rack Isle, the Coln, and the wet ground through the middle of the village
The Coln runs through Bibury and the meadow beside it was where cloth was hung on racks to dry, which is where its name comes from and why it has never been built on. The water table across the low ground is high, the river is close to the buildings, and there is a trout farm drawing on the same water.
For a rooflight, the consequences are indirect but real. Roof voids on the low ground run damper than the county average, north facing slopes carry more moss and lichen, and timber gets checked with a moisture meter rather than by eye, because a soft wall plate in a humid void is a finding that changes a job. It also means the covering on a north facing Bibury slope is often heavily colonised, and any new or reclaimed stone laid into it takes years to catch up in appearance.
What appearance control means when the village is the view
Cotswold District Council are the planning authority and the officers who deal with Bibury have seen more rooflight proposals here than almost anywhere. The conditions that come back are consistent enough to be worth designing to from the start rather than revising afterwards.
- Unit type. A slim metal conservation frame with a single central glazing bar, named in the condition rather than left open.
- Finish. Black or a dark colour, matt rather than gloss, factory applied, because site painting is rarely accepted.
- Flushness. Set flush or as near flush as a 25mm slate allows, sometimes with a stated maximum projection.
- Size and number. A maximum size, or a cap on total glazed area on one slope. Two small units regularly land where one large one does not.
- Position. Aligned with the openings on the elevation below, and set a stated number of courses from ridge, eaves or verge.
- Making good. Matched reclaimed stone slate, and lead flashings formed on site rather than a moulded kit.
What each of those means for the order, and which products satisfy them, is on conservation rooflight installation.
Weavers’ cottages, low eaves and rooms already in the roof
The domestic stock in and around the village runs to small stone cottages with steeply pitched roofs, gabled dormers on some, and first floor rooms that are partly in the roof space already. Eaves are low, ceilings follow the rafter line, and the walls are 500mm or more of rubble limestone.
That geometry is why people want a rooflight here in the first place. The original windows are small, the reveals are deep, and a room with two modest windows in a thick wall receives far less daylight than its floor area suggests. It also constrains the answer. Where the ceiling follows the rafters, the reveal is short and the unit sits close to the finished surface, which is good for light. Where a collar crosses at head height, the usable slope above it may be very limited, and that gets measured rather than guessed.
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.
Steep Bibury pitches, and the diminishing gauge on a 50 degree slope
The stone slate roofs here are laid steeply, commonly in the high forties to low fifties in degrees. That pitch is not a style choice. A hand split limestone slate is irregular, the joints between them are open, and only a steep slope moves water off them fast enough.
The slates are graded and laid in diminishing courses, largest and thickest at the eaves and reducing continuously to the ridge, so the gauge changes on every course and no two courses are alike. An opening cannot be cut through that and closed around a frame. The courses above are stripped back up the slope, the frame set, and the courses re-laid downwards to re-establish the rhythm. On a steep slope the frame is also read face-on from the lane rather than obliquely, which is exactly why flushness is the condition officers care about most here. The covering treatment in full is on rooflights in natural slate roofs.
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 Bibury stone, and the wait that goes with it
Matched reclaimed stone slate is not a refinement on a Bibury job, it is normally a condition of the approval, and it is the item that most often sets the start date.
Matching means three things at once: thickness, because a 30mm eaves slate and a 15mm ridge slate are not interchangeable; size, because the slate has to fit the course it is going into and the gauge either side of it; and weathering colour, because freshly worked limestone reads pale and flat against a roof that has been oxidising and gathering lichen for two or three hundred years, and it stays visible for a decade. Reclamation yards hold what they hold. A sensible programme finds the stone first and books the scaffold second, and any date offered before the material is identified is a guess.
On a Bibury roof the reclaimed stone is sourced before a start date is agreed, not ordered once the scaffold is up.
Torching and riven battens, and the fabric that cannot go back
Under a large share of these roofs there is no underlay of any kind. The joints between the slates are sealed from below with a lime mortar torching, often mixed with animal hair, spread on the underside of the slates between riven oak or elm battens. Both the torching and the battens are historic fabric.
Neither can be taken off and reinstated as it was, which is why the replacement detail is agreed with the conservation officer in advance rather than settled on the boards. The usual answer around a new opening is a breather membrane on counter battens kept local to the work, with the surviving torching left undisturbed beyond the working area, and the surviving riven battens retained wherever they can carry a fixing. That goes into a written method statement with the application, and on a listed building it is frequently the part of the submission an officer reads first.
Two small units on one Bibury slope, and why the pair wins
The pattern across approvals in this village is that a pair of modest openings is accepted where one larger one is refused, and there are three separate reasons for it.
A cap on total glazed area is a common condition, and two small units can sit under a cap that one large one exceeds. A small unit stays inside a single rafter bay and a manageable run of coursing, so less historic fabric is disturbed and no structural design is needed. And two openings spread across a room deliver a more even wash of daylight than one in the middle, which is the outcome the homeowner actually wanted. Set the pair symmetrically about a feature on the elevation below, or aligned with the windows already there, because alignment is the condition that comes back most reliably.
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.
Sun tunnels in a Bibury cottage, and the smaller hole in the roof
Where the space that needs light is a landing, an internal bathroom or a back stair, a sun tunnel is frequently the stronger proposal in this village, and the argument is one of area.
A sun tunnel takes daylight through a small dome, commonly around 350mm across, and carries it down a highly reflective rigid or flexible tube through the roof void to a diffuser in the ceiling below. The aperture in the covering is a fraction of what a roof window needs, so a fraction of the coursing is disturbed and a fraction of the roof surface is visibly altered. On a slope where a conservation rooflight would be resisted, a small low profile dome sometimes will not be. It is not a substitute for a window where a view or ventilation is wanted, and it is a very good answer where the requirement is simply that a dark space stops being dark. The comparison is on sun tunnels and where they beat a rooflight.
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.
Coaches, the B4425 and getting scaffold into the village
Bibury’s traffic problem is well documented and it is a genuine constraint on a building job. The main road through the village carries coaches and cars in numbers the lane was never built for, parking is contested, and there is very little verge or hard standing to work from.
What follows for a rooflight installation: deliveries are timed early in the day, the scaffold footprint is kept as small as the work allows, material is landed in one visit rather than several, and where a licence is needed to stand scaffold on the highway the lead time goes into the programme. On some plots the only route to the rear is through the house or along a narrow passage, and tube and boards are carried in by hand. All of this is walked and measured at survey, which is the only way a fixed price holds. How far Severn travels across the county is set out on the areas pages.
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.
Working a job in a village full of visitors
There is a courtesy dimension here that is also a practical one. A crew working in Bibury is working in front of an audience for the whole day, with people walking within a metre of the base of the scaffold and stopping to photograph the building being worked on.
So the working area is fenced properly rather than coned, stone is stacked on the scaffold rather than on the pavement or the verge, cutting is done where the dust does not blow across a footpath, and the site is cleared each evening rather than at the end of the week. It costs a little more time and it avoids the complaint that turns a straightforward job into a conversation with the parish council.
The roof closed every evening, on a covering with nothing underneath it
Severn does not leave a roof open overnight anywhere, and on a torched stone slate roof with no membrane below the slates that rule sets the entire sequence. An opening is not started unless it can be closed and made watertight the same day. If the forecast turns during the morning, outside work stops at a point where the covering is whole.
On a listed Bibury roof it is also a heritage argument. Exposed torching or a stripped area of riven batten taking a night of rain is damage to protected fabric, and that is the sort of thing that ends up in an enforcement file rather than a snagging list. The work is planned in slope areas that open and close within a working day, from the top of the working area downwards.
What a Bibury enquiry needs to contain, and how the price is built
Send more than you would for an ordinary address. Photographs of the roof from every direction it can be seen from, including from any lane or footpath above the building. A photograph of the room inside. A note of what the covering is if you know. A marked-up photograph showing roughly where the light is wanted. And the address, because the designation position for a Bibury address is the fact that shapes everything.
An indicative range comes back by email within a day or two, with the designation position and an honest view on which slopes are worth proposing. Pre-application advice from the conservation officer, with a specific unit named and a section drawing showing its projection, is the highest value step available in this village and it comes before anything is ordered. A survey follows, and the fixed price after it is itemised: unit, labour, scaffold, reclaimed stone, lead, Building Control, and any pre-application work. The notification is submitted and closed out as part of the job, and the workmanship carries a ten year guarantee. Neighbouring Northleach and Cirencester have their own pages, and the costs page explains how a range becomes a figure that holds.
Also covered: the Cotswolds