Roof Lantern Installation
Flat-roof glazing sized to the room and detailed into the kerb below it.
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West Essex
Rooflight installation in Ongar
Small market town, listed high street. What that means for getting glass into a roof here is the whole of this page.
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OngarTown covered
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In Ongar
What we install on Ongar 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 Ongar roofs
Ongar divides cleanly in two and the line runs along the High Street. On one side sit timber framed and Georgian buildings inside a conservation area, where a rooflight is a consent question before it is ever a product question. On the other side are the interwar semis strung along the roads out of town and the post-war estates behind them, where the same unit goes in with a Building Regulations notification and nothing more.
Knowing which half a house belongs to settles the programme, the unit type and the price band within about a minute of looking at it. Sunspire travels out to Ongar from Chelmsford as part of its normal working radius, and the drive is the easy part of the job.
- 01 Burgage plots, and why access is the first question in Ongar
- 02 Georgian fronts over older frames
- 03 Hand-made peg tile at a steep Ongar pitch
- 04 Rear outshots, catslides and the low-pitch limit
- 05 Article 4, and the Ongar conservation area boundary
- 06 Listed building consent above an Ongar shopfront
- 07 Ribbon development along the roads out towards Brentwood and Harlow
- 08 Trussed roofs on the estates behind Marden Ash
- 09 Cripsey Brook, damp ground and a warmer inner pane
- 10 Flat roofs on Ongar garages and rear additions
- 11 Setting an opening out from timbers that were never regular
- 12 Sun tunnels where the roofline sits away from the room
- 13 Programme, and what consent does to it
- 14 Insulation depth in a historic Ongar rafter
- 15 What an Ongar survey records
- 16 Where an Ongar enquiry starts
Burgage plots, and why access is the first question in Ongar
The medieval plot pattern is still legible in Ongar. Narrow frontages onto the High Street, long thin plots running back behind them, and buildings that grew backwards down the plot rather than sideways. It is why the town looks the way it does and it is also why the roof is rarely the hard part of a job here.
A rear roof forty metres back from the street with no vehicle access is a materials problem before it is a glazing problem. Scaffold components, a sealed unit weighing a couple of hundred kilos and the waste from a stripped covering all have to travel that distance by hand, through a house or along a shared entry. That gets measured and priced at survey rather than discovered on the first morning.
Georgian fronts over older frames
A good many Ongar buildings that present a flat Georgian brick face to the street are timber framed behind it. Refronting was fashionable and cheap: a brick skin, sash windows and a parapet or a raised eaves line, applied to a structure that was already two hundred years old.
The roof usually tells the truth. Behind the front wall the pitch is steeper than a Georgian roof would be, the ridge sits off-centre relative to the frontage, and the timbers in the loft are oak, pegged and irregular. That matters because the age of the structure, not the age of the facade, decides how an opening is formed and what a conservation officer is protecting.
On a refronted building the loft is the honest document, not the elevation.
Hand-made peg tile at a steep Ongar pitch
The older Ongar roofs are hand-made clay peg tile laid at 45 degrees or better, sometimes over riven battens, occasionally with the remains of torching still sitting on the underside. The tiles are small, the gauge wanders and no two courses line through exactly.
A factory flashing kit is designed around a consistent covering, so on this stock the weathering is built rather than unpacked. Lead soakers are cut and dressed between courses, an apron is formed to the actual tile profile, and the tiles around the opening are lifted, sorted and relaid. Where breakages have to be made good, reclaimed tile of the right make and colour is worth the wait. New machine-made tile beside 200-year-old hand-made tile is visible from the far end of the street.
Rear outshots, catslides and the low-pitch limit
Ongar houses of any age tend to have something stuck on the back: a scullery outshot, a catslide continuing the main slope down over a rear range, or a lean-to added at some point in the last century. Those are the rooms people most want daylight in, because they are the deepest and the darkest.
The pitch is the constraint. A catslide often flattens to 20 degrees or less at its foot, and a lean-to may sit at 12 or 15. Most roof windows are rated from 15 degrees, some from 10 with a specific underlay detail below the unit, and beneath that the manufacturer will not stand behind the weathering. Measuring the actual pitch with a level rather than accepting the drawing decides which of those three answers applies.
Article 4, and the Ongar conservation area boundary
The conservation area covers the High Street, Castle Street and a good deal of the fabric behind them. Inside that boundary permitted development rights for rooflights are commonly withdrawn by an Article 4 direction, which means the unit that needs no application at all on an estate two streets away needs a full one here.
That is a sequencing issue rather than a refusal. The designation map is public, it takes a minute to read, and establishing what the district council will accept before anything is ordered is the difference between a six week job and a five month one. The conservation rooflight page covers what those units look like and why the frame profile matters to an officer.
Listed building consent above an Ongar shopfront
Listed building consent is a separate approval from planning permission and it applies to alterations affecting the character of the building, internally as well as externally. On the High Street that catches a lot of work that looks invisible from the pavement.
Forming an opening in a historic roof structure engages consent because the roof timbers are themselves listed fabric, even where the finished glass cannot be seen from public ground. The design response is straightforward: place the opening between existing common rafters so no principal member, purlin or tie is cut, and record the timbers photographically before anything moves. An application supported by that evidence is a far shorter conversation than one without it.
Ribbon development along the roads out towards Brentwood and Harlow
Beyond the old core, Ongar has the standard interwar ribbon: bay fronted semis and detached houses lining the main roads, built between roughly 1925 and 1939, with hipped roofs at 35 to 40 degrees in plain clay or early concrete tile.
These are among the easiest roofs in Essex to work on. The structure is a traditional cut roof with rafters at 400 or 450 centres and a purlin on each slope, so an opening is trimmed with doubled rafters and timber trimmers above and below, and the load redistributes without a calculation. The one thing worth checking is the purlin position, because an opening that wants to land across it needs either moving up the slope or designing around.
Trussed roofs on the estates behind Marden Ash
The post-war and later housing around Marden Ash and the estates off the through roads use trussed rafter roofs, and a truss is an engineered component rather than a piece of carpentry.
The webs and the bottom chord carry load in tension and compression, so cutting one is a different act from cutting a rafter. In practice a roof window on this stock is sized to sit between trusses rather than through them, which usually caps the width at around 550mm unless a structural engineer designs a trimming solution. Two narrow units spaced along the slope is very often the honest answer where somebody arrived wanting one wide one, and the light distribution is generally better anyway.
Cripsey Brook, damp ground and a warmer inner pane
Cripsey Brook runs through the low ground south and west of the town and the land around it holds moisture. Older buildings on damp ground carry more humidity in their fabric than a modern house does, and that changes the condensation arithmetic on any new glass.
Surface condensation forms when warm moist air meets a cold surface. It is physics rather than a fault, and there are two levers. The first is a warmer inner pane, which means attending to the U-value rather than taking whatever is cheapest in the range. The second is giving the moist air a route out, which an opening unit at the highest point of a room does better than any amount of wiping. The energy efficient rooflights page goes into the glazing side of that.
Flat roofs on Ongar garages and rear additions
Almost every Ongar property of any period has a flat roof somewhere: a garage, a rear addition, a shop store behind the High Street, a 1970s extension with a felt or single ply deck.
Those decks take a flat rooflight, and the detail that decides the outcome is the kerb underneath. The upstand is built off the roof structure, the covering is dressed up its sides, and the unit lands on top of that. The figure quoted across the trade is 150mm from the finished surface to the top of the kerb, and it is derived from the depth of water that can stand on a deck plus the height driven rain climbs a vertical face. Where the roof has a genuine fall, some manufacturers will warrant less. Where it does not, 150 is the floor.
Setting an opening out from timbers that were never regular
On any pre-Victorian Ongar roof the rafter spacing is whatever the carpenter did on the day. Bays of 350mm and 480mm turn up in the same slope, and a bay can taper across its length.
That irregularity is a design input rather than an obstacle. The opening gets set out from what is physically there, measured in the loft with a tape before anything is ordered, and the unit is chosen to suit the bay rather than the bay being cut to suit the unit. It is also why standard sizes are more useful on historic stock than made to measure: the constraint is the gap between two old timbers, not a line on a drawing.
Sun tunnels where the roofline sits away from the room
Deep plan Ongar buildings frequently have a room with no roof above it at all. A middle bedroom on a first floor with a second storey over it, a windowless bathroom carved out of a landing, a hallway in the middle of a long rear range.
A sun tunnel answers those. It is a reflective duct running from a dome or a flush unit on the roof surface, through the void, to a diffuser in the ceiling below, and a rigid tube of 350mm diameter delivers usable daylight over a run of several metres. The external unit is small, which is also why it is the least contentious thing to put on a slope in a conservation area.
Programme, and what consent does to it
The three approvals that can apply in Ongar run on different clocks, and only one of them is handled by the installer.
| Approval | When it applies in Ongar | Typical effect on programme |
|---|---|---|
| None beyond notification | Estates and ribbon housing outside the boundary | Order lead time only |
| Planning permission | Inside the conservation area where Article 4 applies | Adds a determination period before ordering |
| Listed building consent | Any alteration to listed fabric, roof timbers included | Runs alongside planning, needs supporting photographs |
| Building Regulations | Every new or replacement rooflight | Notified by Sunspire as part of the job |
Insulation depth in a historic Ongar rafter
Old rafters are shallow. A 100mm or 125mm oak or softwood rafter is common in the town’s older roofs, and Part L expects a thermal line around a new opening that a rafter of that depth cannot accommodate with mineral wool alone.
The usual answer is a high performance rigid board between and under the rafters, which buys the thermal value in less depth, with a ventilated void kept above it where the construction is a cold roof. That decision has a visible consequence: every millimetre added below the rafter line deepens the reveal, and a deep reveal on a small opening throws a narrow shaft of light instead of a spread. Splaying the lining outwards towards the room recovers most of it, and costs nothing but plaster.
What an Ongar survey records
A survey on the historic stock takes longer than one on an estate house and gathers more. The covering and its condition, the pitch taken with a level at more than one point, the actual rafter centres and timber sections measured in the loft, where the ceiling line will land relative to the opening, the orientation of the slope, and the route materials will take up and waste will take down.
On a listed or conservation building it also gathers the evidence a consent application will want: photographs of the slope, a note of what is visible from public ground, and the proposed projection of the frame above the tile surface. Collecting that once, at survey, saves a second visit and a fortnight.
Where an Ongar enquiry starts
Send a photograph of the roof slope from outside, one of the ceiling from inside, a rough room size, and say whether the building is listed or sits inside the conservation area. If that last point is uncertain, the district council’s designation map settles it quickly.
What comes back is a range by email with a note of whether consent looks likely and roughly what it adds to the programme, followed by a fixed written figure after the survey. The costs page explains what moves a number between those two stages. Ongar sits alongside Epping and the rest of West Essex on the areas we cover page, and the guides section goes further into how conservation units differ from standard roof windows.
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We start with the building, the covering and the slope. Then we tell you what will suit it, and what it will cost, as a fixed written number.
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