Roof Lantern Installation
Flat-roof glazing sized to the room and detailed into the kerb below it.
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Uttlesford
Rooflight installation in Thaxted
Guildhall town, very high listed density. What that means for getting glass into a roof here is the whole of this page.
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In Thaxted
What we install on Thaxted roofs
Flat Roof Rooflight Installation
Flush and kerb-mounted units into single-ply, felt and GRP flat roofs.
View this service →Roof Window Installation
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 Thaxted roofs
Thaxted is the hardest town in this part of Essex to put a rooflight into, and it is worth saying that at the top rather than three paragraphs down. The town has one of the densest concentrations of listed buildings in the county. The Guildhall, the almshouses under the church, and the runs of jettied and colourwashed frontage along Town Street, Newbiggen Street, Watling Lane and Stoney Lane are largely protected fabric, and on many of those buildings the roof structure itself is part of the listing.
None of which is a closed door. Conservation officers in Uttlesford deal with roof glazing constantly and there are well established answers. It does mean the order of the work is reversed compared with anywhere else: consent comes first, the roof survey second, and the glass is ordered last. Sunspire travels up to the town from Chelmsford, around twenty miles south, as one of the north western edges of the area covered across Essex.
- 01 Why the listing usually reaches the roof timbers
- 02 Cutting into a crownpost roof, and why it is different
- 03 Steep medieval pitches, and what they permit
- 04 Peg tiles on riven battens, and what that means at an opening
- 05 Thatch, and where the light comes from instead
- 06 Jettied frontages, and where a scaffold can stand
- 07 The roofscape seen from the church and the hill
- 08 What consent tends to allow, and what it tends not to
- 09 Almshouses and terraces under one continuous roof
- 10 Lime plaster ceilings, and the reveal below the glass
- 11 Ventilating an old roof once you open it
- 12 Timber frame, render and the wall a ladder leans on
- 13 The later Thaxted, and the roofs that behave normally
- 14 Flat roofs on the later rear additions
- 15 Permitted development, Article 4 and the two separate consents
- 16 What a Thaxted enquiry realistically looks like
Why the listing usually reaches the roof timbers
A listing covers the whole building, not the elevations. On a medieval Thaxted house that means the frame, and on many of them the roof carpentry is the most complete original element left, because floors get replaced and walls get replastered while a roof simply sits there.
What survives is crownpost construction: a central post standing on a tie beam, carrying a collar purlin that runs the length of the roof, with common rafters coupled in pairs above. Some have smoke blackening on the underside of the rafters from an open hall fire that stopped burning five hundred years ago. That soot is evidence, and it is the reason a conservation officer will look at a roof void before agreeing anything.
Cutting into a crownpost roof, and why it is different
A modern rafter is a repeatable component. Doubling the ones either side of an opening and putting trimmers above and below is routine carpentry. A crownpost roof is not that.
The rafters are irregular in size, jointed rather than nailed, and the collar purlin ties the whole assembly together longitudinally. Removing a rafter changes how the frame behaves along its length, not just across it. The usual outcome is that the opening is sized to fit between two existing rafters without touching either, which on a medieval roof at roughly four hundred millimetre centres is a narrow unit, and that narrowness is a genuine constraint rather than a negotiating position.
Steep medieval pitches, and what they permit
Thaxted roofs are steep. Fifty degrees is common on the older frames and some run steeper still, because the coverings originally available shed water by angle rather than by lap.
Steep is helpful. Most roof windows have a maximum working pitch well above that, water clears the glass instantly, and driven rain has less opportunity to sit on a horizontal surface because there is not one. The awkwardness is internal: a unit in a fifty degree slope sits high on the wall of the room below, so the head of the window is a long way up and the reveal has to be cut carefully to bring the light down into the space rather than throwing it at the ceiling.
Peg tiles on riven battens, and what that means at an opening
The older Thaxted roofs carry handmade clay plain tiles, hung by oak pegs or nibs on battens that on the oldest work are riven rather than sawn. Thickness varies by several millimetres across a single roof, the camber varies, and each tile has a slight twist.
That variation is what makes an old roof read correctly from the street, and it is why a flashing kit designed for a machine-pressed tile will not bed down onto one. Soakers are cut and dressed to the tiles actually present. A proportion of the tiles will break in handling, so matching salvage is put on site before the covering is opened rather than chased once the roof is stripped.
Thatch, and where the light comes from instead
There is thatch in and around the town, and thatch takes no rooflight. There is no dependable way to terminate a deep, flexible, breathing covering against a rigid frame, and the depth of the coat makes any flashing attempt a permanent weak point.
Daylight in a thatched cottage arrives elsewhere. An eyebrow dormer is a thatcher’s job. More often the useful work is on a later addition at the back with a tiled or flat roof over it, which is where the kitchen usually is and where a household actually spends the day. It also sits out of sight of the street, which shortens the consent conversation considerably.
Jettied frontages, and where a scaffold can stand
A jetty is an upper floor projecting beyond the one below, carried on the ends of the floor joists. Several Thaxted frontages have them, and they change the access problem completely.
A jetty will not take a scaffold tie and the projecting timbers will not take a load applied to their underside. On these buildings the platform is freestanding, built out from the street or the yard, and tied back only where there is genuinely solid masonry to tie to. Where the frontage sits directly on the footway with no verge, a highway licence from Essex County Council is needed, and that is a lead time rather than a formality.
The roofscape seen from the church and the hill
Most conservation judgements are about what can be seen from the street. Thaxted has an extra dimension, because the church sits high with a spire above it and the ground falls away, so the town’s roofs are read from above and from a distance in a way that flatter towns are not.
The practical effect is that a rear slope is not automatically invisible here. A roof plane hidden from the lane can still be prominent from the churchyard, from Margaret Street or from the approach past the windmill. Working out the real sightlines before an application goes in is worth doing, because it is the argument the case officer will make if it has not been anticipated.
What consent tends to allow, and what it tends not to
Patterns are consistent enough across Uttlesford to plan around. Small flush units in a cast frame with a central glazing bar, set into a rear or concealed slope, are the normal approved solution on a historic building. Large modern units with a wide white surround, on a plane visible from a public road, are not.
The specification that gets agreed is a conservation rooflight, sitting in the plane of the tiles rather than proud of them, with the frame in a dark finish so it reads as a lead-lined opening from the ground. These are made to size, so the lead time is measured in weeks and the order goes in after the decision notice, not before.
On a listed Thaxted roof the sequence is consent, then survey, then order, and reversing it is the one mistake that cannot be undone.
Almshouses and terraces under one continuous roof
The almshouses below the church and several runs of cottage along Town Street sit under a single unbroken roof plane covering more than one dwelling, with party walls rising to the underside of the covering.
That geometry matters twice. A party wall stack or upstand needs clearance for a flashing to be dressed properly, so a unit cannot be pushed tight to a boundary. And where the roof is shared structurally, the work touches a neighbour’s building whether or not it touches their property, which brings the Party Wall etc. Act into the conversation alongside the consent. Both are routine. Neither is quick if it is discovered late.
Lime plaster ceilings, and the reveal below the glass
Below the roof in an old Thaxted house you frequently find lath and lime plaster rather than plasterboard, sometimes following the line of the rafters, sometimes on a flat ceiling with a void above.
Lime plaster on riven lath is brittle at the edges and it does not cut cleanly. The lining around a new opening is formed back to a sound edge and made good in a compatible material, because modern gypsum run in against lime moves at a different rate and shows as a crack within a couple of winters. It also affects where the ceiling line actually is, which is not always where the drawing puts it.
Ventilating an old roof once you open it
Most medieval and Georgian roofs in the town were built cold and ventilated by accident, through gaps in the covering and around the eaves. Insulation added later, often at ceiling level or between the rafters, changes that.
Cutting a rooflight into an insulated slope creates a new junction where warm indoor air can reach a cold surface, and if there is no ventilation path above the insulation the moisture has nowhere to go. On these roofs the build-up around the opening is set out deliberately: an air gap maintained above the insulation, the ceiling line sealed properly at the reveal, and the ventilation route kept continuous past the new unit rather than blocked by it.
Timber frame, render and the wall a ladder leans on
The walls of the older town are timber frame with lime render or lath and plaster over it, often limewashed in the ochres and pinks the town is known for. They are soft and they are thin.
Neither a ladder foot nor a scaffold tie belongs against that surface. Render over lath is frequently twenty millimetres of material with a void behind and no masonry at all, and a dent in it is a lime plasterer’s visit rather than a touch-up. Establishing what the wall is made of at survey is how an elevation stays as it was found.
The later Thaxted, and the roofs that behave normally
Not everything in the town is medieval, and this is the part that gets overlooked. There is council housing off Walden Road and the Sampford Road side, interwar and post-war building on the edges, and a scatter of later infill.
These are ordinary roofs and they take ordinary work. Concrete interlocking tile or plain tile at a mid thirties pitch, purlin or trussed structure, plasterboard ceilings and a loft with headroom in the middle third. A roof window in this stock is a one day job with an off the shelf flashing kit, and outside the conservation area boundary it will often fall under permitted development.
Flat roofs on the later rear additions
A great many Thaxted properties, listed and otherwise, have gained a single storey rear addition since the war with a flat roof over it in felt, single ply or GRP. Where consent allows glass at all, this is very often where it goes.
The checks are the same as anywhere but they matter more here, because these decks were often added cheaply. The fall is measured, with 1:80 as the designed minimum that allows for deflection and construction tolerance. The deck is inspected, because chipboard under a covering laid over twice will not carry a kerb. A flat rooflight or a lantern goes into a roof that drains, or the drainage is sorted first.
Permitted development, Article 4 and the two separate consents
For an unlisted house outside a designated area, rooflights usually fall under permitted development provided the unit projects no more than one hundred and fifty millimetres beyond the plane of the existing slope and sits no higher than the highest part of the roof.
In Thaxted those rights are frequently constrained. The conservation area covers the historic town, an Article 4 direction can remove permitted development rights within it, and listed building consent is a separate matter again that runs alongside planning permission rather than instead of it. A building can need both. Checking which apply to a specific address is a short call to Uttlesford and it happens before anything is measured for.
What a Thaxted enquiry realistically looks like
Longer than elsewhere, and worth starting earlier. The first stage is establishing the designations, then a look at the roof void to see what the structure is and whether it is historic fabric. Only then is there a sensible conversation about size and position, and only after a decision is there an order.
Sunspire quotes in two stages, a range by email once the basics are known and a fixed written figure after a survey. For the range, a photograph of the roof from outside, one of the ceiling from inside and a rough room size is enough to start with, and the general ground on what moves the price is set out separately. Neighbouring work in Saffron Walden goes through the same district.
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