Two figures: an indicative range by email, then a fixed written price after a survey. This page explains what moves the number in this county, and gives you a way to check any quotation you are holding, ours included.
From four answers: which town, what the roof is covered with, roughly which way the relevant slope faces, and the approximate size of the room below. It comes back as a range rather than a number, because nobody has been on the roof yet. Anybody giving you a single firm figure at this stage is guessing, and the guess is later described as an unforeseen extra.
Itemised and firm. It names the unit, the glazing, the structural work, the access and who is making good inside. If the survey turns something up in the roof, which on an older Gloucestershire roof it sometimes does, you hear about it before anybody proceeds rather than on the final invoice.
Why there are no figures on this page. We do not publish a price list, a range or a "from" figure, because the honest version of that number depends on the covering, the structure, the access and the consent position, and those four things vary more across this county than the rooflight itself costs. Instead, everything below tells you exactly what we will be looking at, so that when the number does arrive you can see what is in it. Send the four answers and you get the range the same way everybody else does.
In rough order of how much each one swings a job in Gloucestershire. Size is the obvious one and it is not the biggest. Two of these do not apply anywhere outside the Cotswolds and the valleys, which is why the same rooflight is a different job in Painswick and in Longlevens.
| Driver | Effect | Why it moves |
|---|---|---|
| Access and scaffold | Large | A rear extension off a level Quedgeley garden is a tower and a couple of days. A third storey slope on a Chalford lane with no vehicle access, or a Stroud valley site where the scaffold has to be founded on a bank, is priced by the week and by how hard it is to get material to it. This swings a job further than anything else on the list. |
| Re-laying a stone slate covering | Large | Cotswold stone slate is laid in diminishing courses, so an opening cannot be cut and patched. The covering comes back above and below it and is re-laid in sequence, with reclaimed slates matched by length making up the shortfall. It is skilled and slow, and on a Painswick, Bibury or Chipping Campden roof it is usually the largest single line on the quotation. |
| Structure | Large | Past roughly 1.5m the load has to go somewhere. On the trussed estate roofs at Ashchurch, Quedgeley and Yate a designed trimmer or a steel is not optional, and it brings an engineer's calculation, a longer programme and a different conversation with Building Control. |
| Size | Large, and not linear | Past about 1.5m in either direction the glass stops being a stock size and becomes a special. The step is a jump rather than a slope, so a slightly smaller unit is sometimes very much better value than a slightly larger one. |
| Listed status and conservation consent | Moderate to large | Consent affects the programme more than the labour, and weeks matter. A listed building, a conservation area or an Article 4 direction usually decides the unit as well: a conservation rooflight sitting flush in the plane with a central glazing bar is a different product from a standard one, and it is specified before anything is ordered. |
| Glazing specification | Moderate | Solar control, triple glazing, laminated or acoustic panes each add. Specified for the orientation of the slope rather than for the brochure, which is why the orientation tool sits on this site at all. |
| Making good inside | Moderate | A splayed reveal takes a little more plastering than a square one and roughly doubles the apparent size of the opening. It is the commonest difference between two quotations that otherwise look identical. |
| Waste and disposal | Smaller | On a replacement the old unit and the covering around it have to leave site. On a stone roof the sound slates do not: they are worth considerably more back on the roof than in a skip, and a quotation that assumes otherwise is telling you something. |
| Opening or fixed | Smaller | An actuator, a rain sensor and the wiring, or a manual opener on a pole. Real, but rarely the thing that decides a job. |
Put in the room and what the roof is covered with. This applies the same rules a survey starts from: glazing area against floor area, then the glass specified for the way the slope faces. It returns areas and specifications, never a price, because a price needs somebody on the roof.
| Floor area | Glazing at 15% | Glazing at 20% | Glazing at 25% |
|---|---|---|---|
| 12 m² | 1.8 m² | 2.4 m² | 3.0 m² |
| 16 m² | 2.4 m² | 3.2 m² | 4.0 m² |
| 20 m² | 3.0 m² | 4.0 m² | 5.0 m² |
| 25 m² | 3.8 m² | 5.0 m² | 6.3 m² |
| 30 m² | 4.5 m² | 6.0 m² | 7.5 m² |
The share moves up towards a quarter for a deep room with one external wall, and down towards a tenth for a small bright room where the same area would only overheat it. Direction decides the glass: a north slope takes neutral glazing, south and west want solar control.
The bearing of the plane is the most under-discussed input in this whole subject, and it decides the glass before size does. Pick a direction.
| Plane faces | Character of the light | Solar gain | Usual glazing call |
|---|---|---|---|
| North | Even, cool, shadowless all day | Low | Neutral glass, larger area viable |
| East | Bright early, calm by afternoon | Moderate | Neutral, or light solar control |
| South | Strong from midday onward | High | Solar control, area disciplined |
| West | Low, hot, late in the day | High | Solar control, consider shading |
| Flat | The whole dome of sky | Peaks in summer | Solar control almost always |
Tick what your quotation actually names. Anything left unticked is either included and unstated, or not included at all, and those two things cost very different amounts. Nothing is sent anywhere: the ticks stay in your browser.
The unit is the small half of the job. That surprises people who have spent a fortnight comparing manufacturers, but the glass and the frame arrive in a crate and go in over the course of an hour or two. The rest is labour: forming and trimming an opening in a structure that was never designed to have one, terminating a roof covering correctly against a frame, building and weathering a kerb, restoring insulation and vapour control around the perimeter, and rebuilding the ceiling and reveal so the finished thing looks like it was always there. Alongside that sit the constants of any job, which are safe access to the work, the Building Control notification and inspections, waste away from site, and design work where the structure needs it. Two quotations for the identical unit can differ substantially and both be honest, because they describe different amounts of that labour.
Size moves the price in steps rather than smoothly. Manufactured roof windows come in coded sizes, made in volume and supplied with a matching flashing kit, and while a unit stays inside that range it is a catalogue item. Go past roughly a metre and a half in either direction and the glass becomes a special: made to order, longer to arrive, heavier, and often needing more than two people on the scaffold to place it. So a slightly smaller unit is sometimes very much better value than a slightly larger one, and two modest units in adjacent structural bays can give more glass and more even light for less structural work than one wide one.
Specification then sits on top of size. Low-emissivity coatings are standard now; solar control on the outer pane, laminated inner panes, acoustic interlayers, triple glazing and self-cleaning surfaces are each specified individually. The mechanism does the same: a fixed unit is the least involved, a manual opener is little more, and a motorised one brings an actuator, a rain sensor, a control and mains wiring that has to be run and certified. This is the part of the price that is entirely a choice, and it is best decided by the orientation of the slope and what the room has to do rather than by a brochure.
In most of the country the covering is a modest line on a quotation. In Gloucestershire it is frequently the largest one. Cotswold stone slate is graded and laid in diminishing courses, thick and heavy, on riven battens, commonly torched from below with lime mortar. An opening cannot be cut through it and closed around a frame: the courses are taken back up the slope, the frame is set, and the courses re-laid downwards with the diminishing gauge re-established so the roof reads correctly. Slates break on the way, and reclaimed stone is sourced and matched for thickness and weathering colour.
At the other end, concrete interlocking tile is the most straightforward covering there is: tiles unclipped, standard flashing kit, tiles re-laid. Welsh slate, clay plain tile and pantile sit between the two, each with its own soaker detail and its own habit of breaking at the nail holes or the nibs. The same unit in the same size of opening spans a wide range of labour depending on nothing but what is on the roof.
Pitch is not a line on a quotation but it governs several that are. Below the rated minimum for an in-plane roof window the job becomes a kerb-mounted one, which means building and insulating an upstand and dressing the waterproofing up and over it, and that is more work than fitting a flashing kit. At the steep end, a Forest of Dean or Cotswold roof at forty-five degrees or more changes the working conditions on the scaffold, the height of the reveal inside, and often the mechanism, because the opener ends up out of reach from the floor. Very shallow roofs bring the opposite question: where an existing deck already holds water against the proposed position, the falls are corrected before a kerb goes anywhere near it.
Across this county, access swings a job further than anything except the covering. A single-storey rear extension off a level garden is a tower and a short carry. A third-storey slope on a Chalford lane with no vehicle access, or a Stroud valley site where scaffold has to be founded on a bank and hand-carried in, is a different order of work before a single tile is lifted. The variables are storey height, whether a lorry can reach the elevation, whether there is anywhere flat and firm to found a scaffold, whether a neighbour’s land is involved, and how far glass has to travel from where it can be unloaded. On a lantern, that last one alone can decide the programme.
An opening that fits within existing structure is the straightforward case: a head and cill trimmer between two rafters or two trusses, and no calculation beyond the standard notification. Past that, load has to be redistributed. On a cut roof, trimming across two or three rafter bays means doubled trimmers, sometimes a flitch plate, sometimes a small steel, and the rafters either side then carry more than they were designed for. On a trussed roof, any opening wider than the clear space between two trusses means part of a triangulated frame is carried on a beam spanning to its neighbours, which is an engineer’s calculation without exception. That brings design work, a heavier member, a longer programme and a fuller conversation with Building Control. It is entirely achievable and regularly the right thing to do for a loft room. It is simply a bigger job, and the survey says so before anything is ordered.
The perimeter is where the job either lasts or does not, and it is the part least visible on a quotation. A kerb is built in treated timber, insulated on its outside face so it does not become a cold ring around the glass, with the waterproofing dressed up it and over the top. On a pitched roof the equivalent work is the flashing set: apron, soakers or side flashing, and a head flashing dressed under the course above, laps run in the direction of flow and every piece fixed at the head only so it can move. Underneath both, the underlay is dressed around the frame rather than slit. None of that can be inspected once the job is finished, which is exactly why it is the first thing to vanish from a keen price, and why the workmanship here carries a ten-year guarantee written against those buried details.
The internal reveal is the commonest reason two quotations for the same unit differ. A square-sided lining is quicker. A reveal with a vertical head lining, a horizontal cill and splayed sides throws far more daylight into the room and lets warm air wash up the face of the glass, which is the cheapest condensation control there is, and it takes another half day of carpentry and plastering. How far the finish is taken is a legitimate choice: board and skim ready for your own decorator, or a finished and decorated reveal. Fitted furniture, a finished loft room or a ceiling that has to be opened up all add to it.
Rooflight work does not scale in a straight line, and it works in the customer’s favour. Scaffold, access, the notification and the visits are largely the same for one unit as for three on the same elevation. Where a roof carries several units of the same age, doing them together means one scaffold, one submission, and glass and frames that match across the elevation instead of drifting through three product generations. That matters most on replacement, because where one sealed unit has misted, the others glazed on the same day are usually within a couple of years of the same fate.
The first thing Severn sends is a range, not a number, and it arrives by email without anybody visiting. It rests on four answers: which town, what the roof is covered with, roughly which way the relevant slope faces, and the approximate size of the room below. Photographs of the roof from outside and the room from inside make it considerably tighter. A range is the honest shape for that information, because nobody has been on the roof, in the loft or up the lane. It exists to establish quickly whether a project is in the right territory, so neither side spends an afternoon on a survey for something that was never going to work. Anybody giving a single firm number at this stage is guessing, and a guess of that kind tends to reappear later described as an unforeseen extra.
After the survey comes a fixed written price, itemised so it is clear what is unit, what is labour, what is access, what is structural work, what is making good and what is Building Control. It is the figure the job is done for. It can only be fixed at that point because until then several of the largest drivers are simply unknown. Nobody can tell from a photograph what the rafter centres and depths are, whether a purlin crosses the proposed position, what the falls on a flat deck are doing, whether the underlay is a modern breather membrane or brittle bitumen felt, or whether an existing opening was trimmed properly. Each of those changes the work. A fixed price given before they are known is either padded against the worst case or exposed to it, and both are paid for by the customer in the end.
A survey takes around forty minutes for a single roof window and longer for a lantern. Inside, the rafter or joist centres and depths are recorded, the pitch taken off a digital level, and any purlin, binder, strut or collar located, along with anything routed through the void. Outside, the covering is identified properly, head laps and batten gauge measured, and the underlay checked at the eaves and at any existing opening. Then the practical part: how scaffold reaches the elevation, whether a lorry can turn in the lane, and where glass can be lifted from. Everything on that list can move a price, which is precisely why the price comes after it.
The fixed price holds. Two things can change it, and both are visible before they happen. The first is a change of scope at your request: a larger opening once the room is seen with light in it, an upgrade to solar control glass, a motorised opener added, a decorated finish instead of a skimmed one. Those are re-priced and agreed in writing beforehand.
The second is something structural uncovered in the roof that could not be seen at survey. On older Gloucestershire stock that occasionally happens: a rafter cut thirty years ago with nothing trimming it, timber gone soft under a historical water run, a kerb in untreated softwood. Where the survey identifies that as a possibility it is documented as a risk in advance, with a note of what correcting it would involve, so it is a known contingency rather than a surprise. Either way the finding goes in writing, with a price, before anybody proceeds.
To start, email info@severnskylightsgloucester.co.uk with those four answers and a photograph or two. The range comes back by email, the survey follows at a time that suits, and the fixed price follows the survey. The services pages describe what each type of work involves, and the areas pages explain why the roof at your address behaves the way it does.
Which town, what the roof is covered with, roughly which way the slope faces, and the approximate size of the room below. That is enough for a sensible range by email, and it takes about a minute to write.
We will come and look at it, and tell you honestly what it needs.
Fill in what you can. It opens WhatsApp with the message ready to send.