Roof Lantern Installation
Flat-roof glazing sized to the room and detailed into the kerb below it.
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Hertfordshire
Rooflight installation in Sawbridgeworth
Maltings conversions, listed core. What that means for getting glass into a roof here is the whole of this page.
We travel to Sawbridgeworth
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SawbridgeworthTown covered
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30Mile radius by road
10Year workmanship guarantee
In Sawbridgeworth
What we install on Sawbridgeworth roofs
Flat Roof Rooflight Installation
Flush and kerb-mounted units into single-ply, felt and GRP flat roofs.
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Roof windows trimmed into slate, clay and concrete tile without proud flashing.
View this service →VELUX Window Installation
We install VELUX alongside Fakro, Keylite and Roto roof windows.
View this service →Electric and Opening Rooflights
Actuated opening units, rain sensors and controls, wired and commissioned.
View this service →Energy Efficient Rooflights
Specified on U-value and g-value, not on the brochure photograph.
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The local detail
16 things worth knowing about Sawbridgeworth roofs
Sawbridgeworth is small and it is heavily protected, and those two facts together decide most rooflight enquiries from the town. For its size it carries a remarkable amount of listed fabric, concentrated along Bell Street, Knight Street, The Square and Fair Green, and the conservation designation reaches out from there across streets that owners would not necessarily think of as historic.
The other half of the town is industrial and it is the more interesting half technically. The maltings on the Stort were built for a process rather than for people, and the flats made out of them behave nothing like a house. Sunspire travels across from Chelmsford, around twenty five miles by road, and the town sits at the western reach of the area covered. Like Bishops Stortford four miles north, this is Hertfordshire, so the application and the notification go to East Herts.
- 01 Listing at a density most towns do not carry
- 02 The maltings, and roofs built for a process
- 03 Kilns, cowls and the shapes on the river side
- 04 A flat in a converted building, and who has to agree
- 05 Deep floor plates, and light that can only arrive from above
- 06 Bell Street and Knight Street, and the room a scaffold needs
- 07 Slate on the industrial roofs, and taking it off cleanly
- 08 King posts, iron and the structure over a mill floor
- 09 Fair Green, and the older houses around it
- 10 The Stort Navigation, and the wet side of a plot
- 11 Rivers’ nursery ground, and what it left west of the town
- 12 Twentieth century Sawbridgeworth, off West Road and Bullfields
- 13 Flat roofs behind the High Street frontages
- 14 Upstands on a low lying riverside deck
- 15 Which way a Sawbridgeworth roof faces
- 16 Consent, notification and the order they run in
Listing at a density most towns do not carry
The old town is compact and almost all of it is designated. Bell Street and Knight Street run north from The Square with near continuous frontages of timber framed and later brick buildings, many of them listed individually, and the group value of the run is part of what is being protected.
Listed building consent is a separate matter from planning permission and covers alterations affecting character, inside as well as outside. A building can need both, and on the oldest buildings here the roof carpentry is itself part of what is listed. None of that is a closed door. It does mean the decision notice comes before the order rather than after it, because a conservation unit is made to a size and has no second use if the approved dimension turns out to be different.
The maltings, and roofs built for a process
The Stort Navigation carried barley and the maltings that grew up along it are the largest buildings in the town. What survives has been converted, and the roofs on them are unlike anything domestic.
A malting floor is a long, low, wide space with a roof spanning further than any house roof, carried on trusses at wide centres rather than on rafters at four hundred. The covering is usually slate over close boarding, occasionally over sarking. There is no loft. The underside of the roof structure is the ceiling of the top flat, so a rooflight in one of these buildings is not trimmed between rafters, it is fitted into a structural bay and the timber it lands beside is doing real work.
Kilns, cowls and the shapes on the river side
The kiln is the tall element with the pyramidal roof and the cowl on top, and it is the part of a maltings that reads most strongly from the towpath. Where kilns survive in a conversion they are usually the feature the consent was granted around.
That makes them the last place glass gets added. The workable roof planes in a converted maltings are the long, plain slated slopes over the former floors, away from the kiln, away from the gable ends and away from the elevation the designation cares about. Establishing which planes are considered neutral before drawing anything saves a refusal, and a case officer will usually say so informally if asked early.
A flat in a converted building, and who has to agree
Permitted development rights apply to houses. They do not apply to flats or maisonettes, so a rooflight in a converted maltings apartment needs a planning application in every case, and listed building consent as well where the building is designated.
On a leasehold flat the roof is very often demised to the freeholder, so the lease is read before the roof is measured.
Alongside the public consents there is a private one. The lease will say who owns the roof structure and the external fabric, and in nearly every converted block that is the freeholder or a management company acting for them. Their written consent is a separate document with its own timescale, and it usually asks for the specification and the installer’s insurance position in advance.
Deep floor plates, and light that can only arrive from above
This is why the enquiries come in the first place. A malting floor is wide and it has windows only at the ends and along the sides, so the middle of a converted apartment can be a long way from any glass. Vertical windows in a thick masonry wall throw light a limited distance into a deep plan.
A rooflight collects from the whole dome of the sky rather than from roughly half of it, and it is not shaded by the building opposite. The working figure used in daylight design is that glass in a roof delivers something in the order of two to three times the illuminance of a vertical window of the same area. In a deep plan top floor flat that is the difference between a room that needs the lights on at two in the afternoon and one that does not.
Bell Street and Knight Street, and the room a scaffold needs
The old streets are narrow, the buildings meet the pavement, and Bell Street carries traffic. There is no working space in front of these buildings at all.
Two consequences follow. Where a rear elevation and a garden exist, that is where the platform goes, even if it means a longer carry and a hoist. Where it does not, the work needs a highway licence from the county, a footway closure and a working day arranged around the town rather than around the roof. Neither is unusual and both take time to arrange, which is why access is one of the first things a survey records rather than one of the last.
Slate on the industrial roofs, and taking it off cleanly
Welsh slate covers most of the nineteenth century fabric in Sawbridgeworth, domestic and industrial, laid at pitches in the low thirties.
Slate is thin, flat and brittle, and it is held by nails rather than hung on battens, so it comes off in whole courses with a ripper rather than being levered out singly. Re-laying wants new copper nails and a run of matching salvage held ready before the covering is opened, because breakage in handling is normal and a modern slate beside a weathered original is visible from the ground. The flashing for slate is a low profile kit dressed tight, which is a different component from anything used on a profiled tile.
King posts, iron and the structure over a mill floor
Older industrial roofs in the Stort valley are carried on trusses, sometimes entirely in timber with a king post or queen posts, sometimes composite with wrought iron tension members and timber in compression.
The distinction matters at an opening. A composite truss has its tie and its struts sized to work together, and neither the iron nor the timber tolerates being notched or drilled to suit a kerb. The practical answer is the same as it is in a trussed house roof, only at a larger scale: the opening is set out to sit within a structural bay so that no member is touched, and where the required size will not fit a bay, an engineer designs the trimming and the calculation goes in with the application.
Fair Green, and the older houses around it
Away from the High Street the town has a quieter historic edge around Fair Green and towards the church, with cottages under handmade clay plain tile at steep pitches and rafters that vary in size along their length.
Handmade tile is uneven by nature, the colour ranges from orange to a dark red within one roof, and no two tiles are the same thickness. The flashing works with soakers dressed between the courses rather than an apron bridging a profile, and on an uneven roof those soakers are cut to the tiles that are actually there. A flashing sitting proud on this sort of covering is obvious from the pavement, which is the test that matters here.
Rivers’ nursery ground, and what it left west of the town
Sawbridgeworth was a nursery town before it was a commuter one. The Rivers family raised fruit trees here on a large scale for well over a century, and the land they used runs west and north of the centre.
Two things survive that touch a roof job. The first is mature standing trees, some of them protected, which shade plots that look open on a map and which change the daylight calculation for a room considerably. The second is that the nursery land has been developed in phases, so a run of houses along one road can span four decades of construction, four different roof structures and four different coverings. On this side of town nothing is assumed from the address.
Twentieth century Sawbridgeworth, off West Road and Bullfields
Beyond the designation there is a good deal of ordinary town: interwar semis, post-war housing and estates built from the nineteen seventies onward.
These are straightforward roofs and the work runs quickly on them. Concrete interlocking tile or clay plain tile at a pitch in the mid thirties, an off the shelf flashing kit for the profile, plasterboard ceilings and a loft with usable headroom. Anything from the mid sixties onward is likely to be trussed, which caps a single opening at roughly five hundred and fifty millimetres between trusses at six hundred centres unless an engineer designs a trimmed opening. Two units in adjacent bays usually gives a better spread of light anyway.
Flat roofs behind the High Street frontages
The burgage plots behind the main street are long and narrow and almost all of them have been built on. The roofs over those rear additions are flat, in felt, single ply or GRP, and they are where most of the new glass in the town actually goes.
Two measurements come before any product conversation. The fall, designed at a minimum of 1:80 to allow for deflection and construction tolerance, which plenty of older decks never achieved. And the deck itself, since a chipboard deck under a covering laid over twice will not carry a kerb. Where water still stands more than a couple of days after rain, the fall is sorted first and the glass goes into a roof that drains.
Upstands on a low lying riverside deck
One hundred and fifty millimetres from the finished surface to the top of the kerb is the industry figure, derived from the depth of water that can lie on a flat roof combined with how far wind driven rain can be pushed up a vertical face.
On the valley floor that number is a floor rather than a target. These decks are large, level and slow to drain, and a rooflight kerb sitting in standing water finds any weakness in the detail within a couple of winters. Four things around the edge decide whether it stays dry in a decade: the upstand height, the fall of the roof around it, the laps of the flashing, and where the covering terminates. None of the four is visible afterwards, which is precisely why the workmanship carries a ten year guarantee.
Which way a Sawbridgeworth roof faces
Orientation gets settled before size does. A north facing plane gives steady, cool, shadowless light with almost no heat gain, and it will carry a generous area of fairly neutral glass. A south or west facing plane collects the afternoon sun at a high angle in summer.
The two numbers that describe a unit pull against each other. The U-value measures heat loss and lower is better. The g-value measures the fraction of solar energy that passes through, and lower means less gain and slightly less light. In a converted maltings the point is sharper than in a house, because a large uninsulated masonry volume with a big area of roof glass overhead heats up slowly and then holds it. Solar control glass is the default on anything facing south here.
Consent, notification and the order they run in
On a designated Sawbridgeworth building the sequence is fixed: establish the designation, agree the position and the unit in principle, apply for planning permission and listed building consent where they are needed, obtain any freeholder consent, then order to the approved size. Reversing any two of those costs money.
The Building Regulations notification is separate again and Sunspire handles it as part of the job. It engages Part L for thermal performance, Part K where there is a risk of falling, and Part B where a room in the roof depends on the opening for escape. For a first figure a photograph of the roof, one of the ceiling below and a rough room size is enough, and the general ground on what drives the price is set out separately.
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