Skylight Installation in Shenfield
Skylight and rooflight installation in Shenfield: large detached interwar housing on generous plots, and what that means for specifying a rooflight here.
Shenfield is a suburb of big roofs. The interwar building boom that made the place put detached houses on wide plots, and it gave almost all of them the same thing overhead: a tall hipped roof, cut by carpenters on site, with more volume under it than anyone downstairs has ever properly used. Ninety years later that volume is the most valuable floor area in the building, which is why so many roofs here have already been opened once and are about to be opened again. Putting glass into one is less a question about the unit than about two things the house decided long before you bought it: the shape of the roof, and the angle it sits at.
The roofs Shenfield built between the wars
Take a walk round the residential streets and the dominant stock reads as one period. Large detached houses, set well back behind deep front gardens, standing clear of their neighbours on plots wide enough that no roof plane is crowded by anything. That is a very particular kind of building to work on and it comes with a very particular roof.
Pitches are steep. Interwar builders worked at something in the region of forty to forty-five degrees because that is what plain clay tiles want, and a lot of these roofs went on as plain tiles or handmade-look clay from the start. Plenty have since been stripped and recovered in concrete interlocking tiles, which is worth knowing before anyone orders a flashing kit, because what is on the roof today is often not what the drawings would have said in 1934.
Underneath, the structure is a cut roof. Common rafters at close centres, purlins running the length of the building to carry them, and struts propping those purlins down onto load-bearing internal walls or a spine wall. Nothing is standardised. The carpenter put the purlin where the span needed it, so two houses that look like a matched pair from the pavement can have their timbers in different places. There is usually a substantial chimney stack, sometimes two, and stacks take up roof plane and throw shade across it.
Then there is everything that arrived afterwards. Shenfield has had decades of extension work and it shows on the roofs. Two-storey side additions built over an original garage. Single-storey rear additions with flat roofs, some of them now sitting behind a second flat-roofed addition. Rooms built into the loft in the eighties and nineties with dormers on the back. Newer detached houses squeezed into the gaps and the long back gardens of the old plots, and those come with factory trussed rafters rather than a cut roof, which is a completely different structural argument. On a single street you can have a 1930s purlin roof, a 1990s trussed one and a flat deck from last decade, all needing different treatment.
None of it carries salt. The estuary is around twenty-three miles away by road and there is no marine air working on external finishes here, so the corrosion pressure that shapes specifications on the seafront simply is not part of the conversation in Brentwood borough. What replaces it is age, geometry and the sun.
Hips, and what the roof shape does to your plans
The hipped roof is the signature of this housing and it is also the thing that quietly limits what you can do with it.
A gabled roof gives you a rectangle of usable space with full headroom running right to both end walls. A hipped roof does not. The ends slope inwards, so the space narrows towards each end of the house and the ridge itself is shorter than the building below. Stand in an unconverted Shenfield loft and the floor area looks enormous. Measure the part where you could stand up without ducking, and it has shrunk considerably at both ends.
That has two consequences for glazing. The first is that the useful slope, the one with real head height behind it, is narrower than the roof appears from outside, so the window position is set by where a person can actually stand rather than by where the roof looks empty. The second is clearance. Every unit needs a run of whole tiles or slates around it for its flashing to shed water properly, and a hip rafter running diagonally down to a corner eats that space fast. On a hipped end you can easily find there is no legitimate position for the size of unit somebody had in mind, even though the plane looks big enough.
The standard answer round here is the hip-to-gable conversion, where the hipped end is rebuilt as a vertical gable wall and the roof plane is extended out to meet it. That buys back the headroom and it also creates a fresh, uninterrupted slope with no hip rafter in it, which is usually the best surface on the whole building for a pair of roof windows. If you are already having that work done, decide the glazing at the same time. Cutting an opening into a slope while it is being built is a different and simpler job from cutting into one that is finished.
Watch for the L-shaped plan too. A good number of these houses have a rear outrigger or a later two-storey addition set at right angles, and where two pitched roofs meet you get a valley. Valleys need the same respect as hips: a unit crowded up against one is a leak waiting for the right storm, and there is no flashing kit that makes that acceptable.
Front slopes are their own decision. On a house set back behind a deep front garden, a roof window on the front plane is visible from the road in a way it would not be on a tight urban frontage, and the planning position on front-facing roof extensions is stricter than for the rear. The back of the house is the usual answer, for both reasons.
Pitch angle against sun height: two surfaces, opposite problems
This is where a Shenfield house gets interesting, because a heavily extended one has two roof surfaces behaving in completely opposite ways, and treating them as one specification is how people end up unhappy in July.
Start with the sun. At this latitude it climbs to roughly sixty-two degrees above the horizon at midday in late June, and to roughly fifteen degrees at midday in late December. Those two numbers govern everything that follows.
Now take the steep interwar main roof at forty-five degrees, facing south. Glass on that slope is presenting itself almost square on to a sixty-two degree summer sun. That is close to the worst geometry available: very little is being reflected away and nearly all of it is arriving. The consolation is the other end of the year, because that same slope also faces a fifteen degree December sun at a productive angle, so it collects genuinely useful free heat in winter. A steep south-facing pitch is a solar collector, and it is a good one in both directions.
Now take the flat roof on the rear extension. It has no aspect at all. It faces straight up, so it takes light and heat from every part of the sky, from first light to last, and across a whole summer day it collects more total energy than any pitched surface on the property. Come December, with the sun sitting at fifteen degrees, it barely collects anything, so it gives you very little back in winter. All cost, no dividend.
The newer trussed roofs on infill houses sit somewhere between the two, typically shallower than the interwar stock, which pulls their behaviour a little towards the flat-roof pattern.
So the honest answer on a house with both is that the flat extension roof needs solar control without any argument at all, and the steep south or west main slope needs it too, for a different reason. West is the orientation that catches people out on these plots, because late sun comes in under everything and there is nothing standing in the way on a wide plot with a long garden. A room that was fine at two o’clock is unpleasant at seven.
North-facing slopes are the exception worth remembering. Steady, even daylight, very little heat behind it, and on a big detached house you often have a north plane available that a terraced property would never offer. For a study or a landing, that surface is a gift, and clear glass on it is the right call.
| Surface on a Shenfield property | Specification we would start from | Typical U-value (W/m²K) | Typical G-value |
|---|---|---|---|
| Steep interwar slope facing north | Clear double glazing | around 1.6 | around 0.6 |
| Steep interwar slope facing south, east or west | Solar-control double glazing | around 1.4 | around 0.3 |
| Loft bedroom on a new hip-to-gable slope | Solar-control triple glazing | around 1.0 to 0.8 | around 0.3 |
| Flat-roofed rear addition, glass lying near level | Solar-control with a laminated inner pane | around 1.2 | around 0.3 |
| Flank-facing unit under 1.7 metres, neighbour close | Obscure solar-control, restricted opening | around 1.4 | around 0.3 |
The U-value describes how quickly warmth leaves through the unit on a cold night, in watts per square metre per kelvin, and smaller is better. Part L of the Building Regulations sets the level a new rooflight has to reach. The G-value scores how much of the sun’s energy the glass allows past, on a scale from nought to one. A plain double-glazed pane sits near 0.6. Put a solar-control coating in and you are down around 0.3, which is roughly half the summer heat through the same hole in the roof. Those figures are industry-typical and they shift with manufacturer and unit size, so read them as the shape of the decision rather than a quotation. The trade-off between the two numbers is worked through in our guide to energy-efficient skylight installation.
Blinds have their place, particularly blackout in a loft bedroom taking early eastern sun. They are also a control somebody has to remember to operate before the room heats up rather than after. Coated glass is doing its work at two in the afternoon whether anyone is home or not.
Opening up a ninety-year-old roof
Cutting into interwar timber is straightforward work done properly and messy work done casually. A few things about this stock are worth saying out loud before anyone starts.
What is under the tiles
Expect brittle bitumen underlay laid over the rafters, or on the earliest examples nothing at all beneath the battens. Ninety years of heat and cold turn old felt to something that tears if you look at it. Around a new opening that torn material has to be cut back cleanly and dressed properly into the new unit’s collar and flashing, so that water running down the underlay is delivered out over the tiles rather than in behind them. It is invisible once the tiles are back on and it is the part that decides whether the ceiling below stays dry in a decade’s time.
What the structure is doing
Trimming a cut roof means doubling the rafters either side of the opening and putting trimmers across the top and bottom, and interwar timbers usually take that comfortably. The complication in Shenfield is the strut. Purlin struts land on internal walls, and a great many of these houses have had those walls taken out at some point to open up the ground floor. If the load path a 1930s carpenter relied on has been altered since, that gets checked before anything is cut, not afterwards.
The other thing to check is weight. Where a plain clay tile roof has been recovered in concrete interlocking tiles, the roof is carrying more than it was built for, and a spreading or sagging ridge is a sign to look harder before adding an opening to it.
Coverings and flashings
Plain tiles, interlocking concrete tiles and slate all need their own flashing kit, made for that profile and that gauge. A house with an original main roof and two later additions can carry three different coverings, so the specification gets written per surface. Persuading a kit designed for one profile to sit in another is how a sound unit ends up letting water past the head years later.
Units already in the roof
Loft conversions done twenty-five or thirty years ago are common here, and the windows in them are now well past their working life. Misted panes, seals that have given up, frames that have gone chalky and yellow. Taking the old unit out and installing a properly specified modern one in the existing opening is our work, and it moves quicker than people expect, because the hole and the structural trimming already exist. If the actual trouble is with the tiling or the flashings rather than the glazing, that is a roofer’s job and we will tell you so straight.
Brentwood Borough Council, and what needs permission
Planning and Building Control for Shenfield are both handled by Brentwood Borough Council. Advice picked up about the coast does not carry across. The Article 4 Directions that restrict roofing and window changes in parts of Leigh belong to another authority’s designations entirely and have no bearing on a Shenfield address.
The general position on a house is that a rooflight is permitted development. The unit must not stand more than 150 millimetres proud of the plane it sits in, no part of it may rise above the highest point of the existing roof, and a unit in a side elevation with the floor less than 1.7 metres below it needs obscure glazing and an opening restricted at the bottom. Meet all of that and no application is required. Most straightforward glazing on these detached houses falls inside it.
Loft conversions are a separate calculation and it catches people out. Where a conversion adds volume, by way of a dormer or a hip-to-gable rebuild, permitted development allows an additional 50 cubic metres on a detached house and 40 cubic metres on a semi-detached or terraced one, measured against the original roof rather than against whatever is standing now. Extensions to the roof slope facing a highway are outside those rights. On a Shenfield house that has already had a dormer added by a previous owner, some of that allowance has been spent, and what remains has to be established before a design is drawn.
Three exceptions apply regardless. Flats and maisonettes never held rooflight permitted development rights, which matters near the station where there is apartment accommodation. Listed buildings need listed building consent whatever the rules say about roofs. And conservation areas restrict the automatic rights, with boundaries drawn as lines on a map that do not follow street names in any pattern you could guess from the pavement. Brentwood Borough Council holds the designations and the mapping, so the reliable move is an address check with the council rather than a rule of thumb from a neighbour. We will always tell you to confirm it before anything is ordered, and nobody working on a roof can promise you a consent.
Building Regulations are separate again and apply whether or not planning is involved. A rooflight that is new, or an existing opening being enlarged, has to be notified. Part L governs the thermal performance the unit must reach, which is why the glass specification is not an open choice, and Part K governs safety glazing and guarding, which is why the pane above your head is laminated rather than relying on toughened glass alone. That notification goes to Brentwood Borough Council and we submit it for you. There is nothing for you to fill in and nothing to chase.
Tall roofs, deep setbacks and mature trees
Access on these plots is comfortable in the ways that matter and awkward in ways people do not anticipate.
The comfortable part is space. A detached house with a genuine gap on both sides means scaffold can be stood where the work is rather than wherever it will squeeze, and there is off-street parking for a van and materials. No shared alleys, no negotiating with a neighbour for a foothold.
The awkward part is height. A forty-five degree pitch on a two-storey house puts the ridge a long way up, considerably higher than the shallower roof of a modern house of the same footprint. Scaffold goes up further, gets tied or buttressed properly, and takes longer to erect. Steep plain tile is also serious to work on: roof ladders, proper staging and a sensible working platform, not somebody improvising. That is time on the schedule before a single tile comes off, and it is better in a quotation than as a surprise.
Then the trees. This is a leafy part of Essex and many of these gardens hold mature specimens that were standing before the houses were, often on old field boundaries. Branches overhang roofs. Where a limb needs cutting back to bring scaffold in, check whether the tree is protected first, because a Tree Preservation Order is the borough’s to grant or refuse and it is not a decision to make with a saw. Canopy also matters after the job: overhanging trees drop leaf litter and blossom onto glass and into valleys, and a shaded, damp slope grows moss faster than an open one. That argues for keeping a new unit clear of the worst of an overhang where the roof gives you the option, and for gutters and valleys being cleared regularly whatever we install.
Deep front gardens add a last wrinkle. Where the house sits well back from the road, materials travel further than on a typical street, and a long gated side route past planting has to be measured before delivery day rather than discovered on it. Glazing units are heavy and unforgiving of being turned on a tight corner.
What we typically install on Shenfield roofs
Matching the unit to the surface is most of the craft. This is roughly how it falls here.
| What you have | What usually goes in | Why |
|---|---|---|
| Interwar detached, cut roof, loft being converted | Paired roof windows on the rear pitch, solar-control double or triple | Real headroom under a steep ridge means real glass area, so the heat has to be specified for rather than shaded afterwards |
| New slope created by a hip-to-gable rebuild | Two units side by side, positioned while the slope is being built | No hip rafter through the plane and no finished roof to cut into, so the position is free and the work is cleaner |
| Hipped end left in place | A single smaller unit set clear of the hip rafter, or nothing on that plane | Flashing clearances decide it, and a crowded hip is not worth the risk of getting it wrong |
| Flat-roofed rear addition | Non-opening flat glass on an insulated kerb, or a roof lantern where the ceiling height carries it | Daylight into the deep middle of an extended plan, with solar control doing the work a level surface demands |
| Room over a converted garage or a link between house and garage | A run of two smaller units rather than one wide one | These spaces usually have one window and a party wall, so the roof is the only daylight left, and smaller openings avoid structural work |
| Modern infill house with trussed rafters | A unit sized to sit between two trusses, or a designed structural opening first | Trusses are engineered as a whole and cannot be cut without replacing the job the removed member was doing |
| Twenty-five year old roof windows that have misted or dropped | Full replacement into the existing opening | The trimming and the hole are already there, so the disruption is much shorter than a first installation |
On the pitched work in particular, the detail that separates a good installation from an average one is how the unit sits down into the covering rather than perched on it, which is covered in more depth on our pitched roof skylight page. Indicative figures by unit type are on the costs page, and the quote form takes about a minute if you would rather go straight to a number for your own roof.
Shenfield skylight questions
Which council do I deal with for a Shenfield property?
Brentwood Borough Council, for planning and for Building Control. It is not the coastal authority, and its designations are its own. We make the Building Regulations notification to Brentwood as part of the installation, so that side is handled for you.
My loft has already had a dormer added. Does that limit what I can do now?
It can. The permitted development volume allowance for roof extensions, 50 cubic metres on a detached house, is measured against the roof as it was originally built, not as it stands today. Anything a previous owner added has come out of that figure. A plain rooflight sitting within 150 millimetres of the roof plane does not add volume in the same way, which is often why glazing goes ahead where a second dormer would not.
We are a long way from the sea. Does solar-control glass still matter?
Yes. Distance from the estuary changes the salt in the air, not the sun in the sky. A steep south-facing interwar slope presents itself almost square on to a high June sun, and a level extension roof collects from the whole sky all day. Both of those want glazing near a 0.3 G-value. What twenty-three miles inland does drop out of the specification is marine corrosion on external finishes.
Can a rooflight go on my hipped end?
Sometimes, and it depends on the hip rafter rather than on the size of the plane. Every unit needs whole tiles around it for its flashing to work, and a diagonal hip cuts into that clearance quickly. The rear main pitch is usually the better surface, and if a hip-to-gable conversion is on the cards then that new slope is better still.
Do I need to worry about the trees over the roof?
Only for two reasons. If a branch has to be cut back for scaffold access, establish whether the tree carries a preservation order before anyone touches it. And a slope under heavy canopy stays damp and collects leaf litter, so keep the unit clear of the worst of an overhang where the roof gives you the choice.
The windows from our nineties loft conversion have gone misty. Is that a whole job?
No, and it is one of the quicker installations there is. The structural opening was formed decades ago and it stays. The old unit comes out, the covering and underlay around it are made good, and a modern unit with a proper U-value and a solar-control coating goes into the same hole. The performance difference between a 1990s roof window and a current one is considerable.
How long does the work take?
One roof window in a sound cut roof is generally a day. A pair in a converted loft can run into a second. A lantern or a run of level glass on a rear addition depends on the kerb and the size of the opening. On a tall, steep roof, add time for the scaffold rather than for the glazing itself.
We install right across Shenfield and the wider spread of Essex towns we cover, from the big interwar detached stock to the newer houses filling the gaps behind them. Our workmanship guarantee runs for ten years on everything we put in, and we have been fitting rooflights for over fifteen. Start with the shape of the roof and the angle it sits at, and the rest of the specification follows on from there.
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