Conservation Rooflight Installation
Slim cast frames set flush, for stone slate, listed and conservation roofs.
the Cotswolds
Rooflight and skylight installation in Blockley, surveyed first, and fitted once.
Around Blockley you are mostly dealing with former silk village, steep stone roofs, and that decides more about a rooflight than the rooflight does.
- 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
- former silk village, steep stone roofsRecorded for Blockley specifically
In Blockley
The work we do here, and where to read about it.
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.
Roof Window Installation
Roof windows trimmed into slate, clay and concrete tile without proud flashing.
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.
The local detail
Fifteen things worth knowing about Blockley roofs, worth reading before the survey.
Blockley is an industrial village that happens to be built of Cotswold stone, and that distinction changes almost every practical answer about putting a rooflight into a roof here. The brook running down the valley powered a run of mills through the eighteenth and nineteenth centuries, silk throwing being the trade the village is remembered for, and the buildings those mills left behind are unlike anything in the showpiece wolds villages a few miles away. Large mill roofs with long spans. Terraces of workers’ cottages stepping up a steep valley side. Ponds, leats and springs. Severn Skylights Gloucester travels out to Blockley from the city, and the survey here spends as much time on water and on ground levels as it does on the covering.
A brook, a run of silk mills, and the buildings they left behind
Blockley Brook drops enough height through the village to have carried a series of water powered mills, and at the trade’s peak the village was throwing silk for the ribbon industry rather than farming the wolds above it. The mills closed, and through the twentieth century most of the surviving buildings were converted to houses.
What that gives a rooflight installer is a housing stock with several distinct roof types in a village of modest size. Mill buildings with wide roofs over long spans. Mill owners’ houses, larger and better detailed than the village average. Terraces of small cottages built for the workforce. Later infill from every decade since. A single specification does not cover them, and the first job at survey is deciding which of those buildings you are standing in.
Converted mill roofs, and the structure that was never domestic
A mill roof was designed to cover a working floor, not a bedroom. The spans are long, so the structure is a king post or queen post arrangement, or on later work a composite truss with iron tie rods and cast connections, carrying purlins that in turn carry common rafters. The timbers are big and they are doing a lot.
You cannot trim through a principal rafter or a tie beam. An opening in a mill roof goes between the principals, in the zone of the common rafters, and the head or cill has to clear the purlin rather than sit on it. That usually decides the size of the unit before anybody discusses what the room would like. Where a wider opening is genuinely needed, the load is taken on a new member spanning between the principals, which is a structural engineer’s calculation and a Building Control submission before any covering comes off. Where the truss is an iron and timber composite, the connections are recorded and left entirely alone.
In a converted Blockley mill the purlin position, not the room layout, usually sets the height of the opening on the slope.
Blockley Brook, springs, and the survey question that comes first
Water is the background condition in this village. There is the brook itself, there are the leats and pond remnants that fed the mills, and the valley sides carry springs where the permeable limestone meets a less permeable band. Properties on the valley floor sit low against all of it.
None of that is a reason to avoid a rooflight, and a roof opening is a long way above the problem. It matters for two indirect reasons. First, homeowners here are alert to water and are entitled to be sceptical of anybody cheerful about putting a hole in a roof, so the perimeter detail gets explained properly rather than glossed over. Second, a damp loft in Blockley is not always the roof. A high water table and rising damp in a thick rubble wall produce moisture in the roof space through the wall head, and a survey that assumes the covering is at fault will get the diagnosis wrong. Moisture readings are taken at the wall plate as well as around any existing opening.
Steep valley sides, and the roof the lane above looks straight down on
Blockley is built on a slope steep enough that a lane can run past first floor level. Terraces step up the hillside, gardens are terraced behind retaining walls, and one house’s roof is another house’s view.
That weakens the idea of a hidden rear slope considerably. In a flat town the back of the house faces an enclosed garden and nobody sees it. In Blockley the back of the house may be the elevation most visible in the village, looked down on from the road above and looked up at from the valley floor. Conservation officers here judge a proposal on what is visible from the whole valley, and the assessment of which slope is discreet has to be made by walking the village rather than by looking at a plan. The broader picture across the county’s designated areas is on conservation areas and listed buildings in Gloucestershire.
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.
Silk workers’ cottages, deep plans and the dark middle
The cottage terraces are the buildings where a rooflight does the most good in Blockley. They are stone, they are small in frontage, the original window openings are modest because glass and heat both cost money, and the walls are 500mm or more of rubble, so a window opening admits less light than its size suggests.
Many of them have been extended back or knocked through internally, which produces a deep plan with a middle zone that no external wall reaches. That middle is where a rooflight earns its place, and it is often a stair landing, a bathroom or a kitchen rather than a bedroom. The unit does not need to be large to change it. Where the room below is a landing or an internal bathroom with no roof directly over it, a sun tunnel running a reflective tube from a small dome through the roof void is frequently the better answer, described on sun tunnel installation.
Getting scaffold into Blockley, and what the lanes will take
The village layout is medieval and industrial by turns: narrow lanes, sharp changes of level, footpaths and steps between the terraces, and retaining walls hard up against the backs of houses. A scaffold lorry can reach a good many addresses and cannot reach a fair number of others.
Where it cannot, tube and boards are carried in by hand, sometimes up a flight of steps, and glass for a larger unit may need extra hands or a mechanical lift standing further away than anybody would like. That is time and it is cost, and it is priced from the survey with the route actually walked rather than estimated from an aerial photograph. Saying it before the crew arrives is the only honest way to make a fixed price hold. The same problem in a more extreme form runs through the Stroud valleys, covered on the areas pages.
On Blockley roofs Conservation consent and matching the stone.
Blockley pitches, and what a steep slope gives you
The stone slate roofs here are laid steeply, commonly in the mid forties to low fifties in degrees, which is what a covering of this kind needs to shed water when the individual slates are irregular and the joints are open.
A steep pitch has two consequences worth planning for. Outside, more of any unit is seen from below, because on a 50 degree slope you are looking at the face of the roof rather than across it, so the flushness of the frame matters more here than it would on a 30 degree suburban roof. Inside, the geometry of the reveal changes: the plastered box between the frame and the room is taller, the head of the frame sits a long way above floor level, and reaching a manual opening handle from standing height stops being realistic. A rod operator or an electric unit with a rain sensor is a genuine specification decision rather than an upsell, and the options are on electric rooflight installation.
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.
Diminishing courses on a Blockley roof, and the reclaimed stone question
The covering is Cotswold stone slate, graded by size and laid in diminishing courses with the largest and thickest slates at the eaves, reducing continuously to the ridge. It sits on riven battens and it is commonly torched underneath with lime mortar rather than laid over any membrane.
So an opening is formed by stripping the courses back up the slope, setting the frame, and re-laying downwards to the original gauge. Breakage during that is a real number rather than an optimistic zero, and the replacements need to match thickness, size and weathering colour, which means reclaimed material and a sourcing lead time before a date is agreed. The full method for a covering of this type is on rooflights in natural slate roofs.
The parish that sat in Worcestershire until 1931
Blockley was a detached part of Worcestershire for centuries and only transferred into Gloucestershire in 1931, which is a piece of trivia with one practical edge to it: older records, older deeds and older maps for the village may be filed under the wrong county, and anybody researching a listing or a historic consent for a Blockley address should expect to look in both places.
For everything current, the planning authority is Cotswold District Council and the village sits within the Cotswolds National Landscape. There is nothing unusual about the modern position. It is only the paper trail that is split.
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.
Where a rooflight belongs on a building that steps down the slope
A great many Blockley houses are not one rectangle with one roof. They are a main range with a lower rear wing, an outshot, a lean-to and sometimes a former workshop attached, each with its own roof at its own level because the ground fell away as the building grew.
That is an advantage. A lower rear roof set behind the main ridge is screened by the main range from anybody standing uphill, and it is often the roof over the very rooms that need light. Setting the unit on a subsidiary roof rather than on the principal slope is usually the strongest proposal available in this village, and it is worth surveying every roof plane on the property before deciding, including the ones the homeowner has stopped thinking of as roofs.
Flat roofs on a Blockley plot, and the fall before anything else
Twentieth century rear extensions in the village frequently carry a flat roof, and on sloping ground with a retaining wall behind, those decks often drain in an awkward direction. Before any rooflight goes onto one, the falls get checked.
The standard is a designed fall of around 1:40 so that after deflection and timber movement the finished fall is still no shallower than 1:80. Flatter than that and water stands. A kerb is built in treated timber, insulated on its outer face so it does not form a cold ring around the glass, and the waterproofing is dressed up and over it, with the upstand a full 150mm measured from the finished surface at the high point of the fall. Where the existing deck already ponds against the position somebody wants, the honest answer is that the falls come first, and that gets said at survey rather than discovered later. The detail is on flat roof rooflight installation.
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.
Consent in Blockley, and the argument that works on a mill building
The village is a conservation area with a substantial body of listed buildings in it, including a number of the mill structures and mill houses. On a listed building, consent is needed for the alteration whether or not anybody can see it, and the internal work counts as much as the external.
Where a converted mill has an advantage is in the character argument. A mill roof was a functional industrial surface, and many of them carried glazing from the start because the working floors needed light. Where there is evidence of historic openings, a proposal for a slim conservation unit in that tradition is a much easier case than the same unit on a domestic cottage roof that has never had a break in it. That evidence is worth gathering: old photographs, the pattern of the surviving structure, and any surviving frames elsewhere on the building. Whether the frame itself is the conservation type, and what the officer will name in the condition, is on conservation rooflight installation.
Loft rooms in a converted mill, and the rules that follow
Where a rooflight is going into a room in the roof rather than a loft void, several parts of the Building Regulations engage at once and they are handled as part of the job rather than left with the homeowner.
- Structure. Any trimming near a truss, purlin or principal, with a calculation where the span needs it.
- Fire. Where the unit forms the escape opening, a clear openable area of at least 0.33 square metres, minimum 450mm in both directions, with the bottom of the opening between 800 and 1100mm above the floor.
- Thermal. The unit inside the current limiting standard, and insulation continuous around the reveal with no cold bridge at the head.
- Ventilation. Purge ventilation of at least one twentieth of the floor area, plus background ventilation from the unit’s vent flap.
- Glazing. Toughened outer and laminated inner over any habitable space, stair or bath.
The notification is submitted, the inspections booked, and the completion certificate issued in the homeowner’s name. Keep it, because a buyer’s solicitor will ask for it.
Torched battens are the reason a stone slate roof is opened carefully and closed properly.
Condensation in a stone cottage, and the reveal that prevents it
A small stone cottage with thick walls, a wood burner and a family in it generates a lot of moisture, and the coldest surface in the room is going to be the new glass overhead. Water on the room side of the glass on a February morning is not water getting in.
Three things control it, and two of them are built rather than bought. A vent flap in the head of the unit gives continuous background ventilation. A horizontal lining under the cill, rather than a splay, lets warm air from a radiator rise straight up the face of the glass instead of trapping a pocket of still cold air against it. And a vertical lining above the head throws light deeper into the room while keeping the insulation continuous. Insulation is taken tight to the frame with no voids and the vapour control layer is taped to it rather than trimmed short. A 20mm gap of nothing behind the plasterboard at the head is where black spotting appears. More on condensation, ventilation and rooflights.
How a Blockley job is sequenced, and how the price is built
The roof is never left open overnight, which on a torched stone slate roof with no membrane under it is not a slogan but the thing that decides the programme. Work is planned in areas that can be opened and closed inside a day, from the top of the working area down, with stone sorted and stacked before anything comes off.
The price follows a survey rather than a phone call. What moves it here: whether the building is a mill, a mill house or a cottage, what the structure over the opening is, how far scaffold has to be carried, whether reclaimed stone is needed and how long it takes to find, whether a structural calculation is required, and how far the internal finish is taken. Send photographs of the roof from the lane above and from the valley floor, a photograph of the room, and the address to info@severnskylightsgloucester.co.uk. An indicative range comes back by email, a survey follows, and the fixed price after it is itemised. The workmanship carries a ten year guarantee, and the costs page sets out how the two figures work.
Also covered: the Cotswolds