What happens on installation day

The week before, and the three things confirmed in writing

Before the day exists there is a short exchange that removes most of what goes wrong on it.

The unit is confirmed as delivered and checked, because the single most common cause of a wasted day is glass that arrived damaged and was not unwrapped until the morning. Access is confirmed: where the van can stand, whether the scaffold is already up, whether a gate needs unlocking, whether a neighbour’s permission is needed to stand a tower. And the internal scope is confirmed, meaning whether the day finishes at a weathered opening with a temporary lining or runs on to plaster on a second visit.

You will also be asked to clear the room below and, on a pitched roof job, the loft above it. That is not politeness. Anything under the opening is going to have dust and grit fall on it, and anything in the loft directly under the working area is in the way of the person putting their weight on the ceiling joists.

Scaffold, which usually goes up first and not on the day

On anything above a single storey, or anywhere the working position is more than about three metres up, an independent scaffold with a working lift at the right height goes up before installation day rather than on it. That is a separate visit, often a day or two earlier, and it means the crew arrives to a platform rather than spending the morning building one.

On a single-storey rear extension a mobile tower is frequently enough and it goes up on the morning, which takes half an hour. On a valley site in Stroud, Chalford or Nailsworth, where the tube and boards are hand-carried in from a lane, the scaffold visit is its own day and it is planned as one. Access in detail is on do you need scaffolding to fit a rooflight.

Arrival, and the ten minutes on the doorstep

The van arrives between about half seven and eight. Before anything is unloaded there is a short conversation that is worth having properly rather than through a doorway.

What gets covered: which room, and a walk into it. Where the water and the electric consumer unit are. Whether anyone in the house is working from home, sleeping after a night shift, or has a baby asleep upstairs. Whether the neighbours need warning. Where the crew can make tea and use a toilet if that has been agreed. Where the waste is going to stand. And the plan for the day in three sentences, including the time the roof will be open and the time it will be closed.

Then the position of the opening gets confirmed on the ceiling, in person, before a single tile is touched. It was agreed at survey and marked on the notes, and it still gets confirmed, because the room is a different place with furniture out of it and people occasionally change their mind by 300mm once they can see the space.

Where the van goes, and where the waste goes

Parking sounds trivial and on a Gloucester terrace it is not. Where there is no driveway the van needs a position close enough to carry a two-metre sealed unit from, and permit-only streets in Tredworth, Barton and central Cheltenham need that sorted before the morning rather than during it.

Waste is stacked rather than scattered. Old covering that is being re-used is stacked carefully on the scaffold or on boards on the ground, because a broken slate is a slate that has to be replaced. Material that is finished with goes into a dumpy bag or a van, not onto a lawn, and it leaves with the crew rather than sitting in the garden until somebody remembers it. On a stone slate roof the sorting is part of the work: sound slates one stack, broken ones another, and the count of what needs making up is taken there and then.

Protecting the room below, and the loft above it

Nothing gets cut until the inside is covered. Floors go under boards or heavy sheeting, taped at the edges so it does not walk about. Remaining furniture is sheeted. Doorways into the rest of the house get a dust screen with a zip, and any carpeted route from the front door to the room gets a runner.

On a pitched roof job the loft matters as much as the room. The hatch is sealed while cutting happens, because loft insulation and eighty years of dust will otherwise find their way down the stairwell into every room in the house. A crawl board goes across the joists in the working area so nobody puts a boot through a ceiling. Any cabling, a water tank, a soil vent pipe or a flue in the working zone is identified and, where it needs moving, that is a conversation before the saw comes out rather than a surprise afterwards.

Setting out from inside, so the reveal lands where the room wants it

The opening is set out from the inside first. That is the opposite of what people expect and it is the right way round, because the reveal is what you look at for the next thirty years and the rafters are what nobody sees.

A line is marked on the ceiling for the finished internal opening. The rafter or joist positions are found with a detector and confirmed by a small inspection hole, and the marked opening is adjusted to sit sensibly against them. Where the room wants the glass centred on a wall and the timbers want it 150mm to the left, that gets discussed rather than decided silently. Then the corners of the structural opening are drilled through so the position appears on the outside face of the roof.

On a loft conversion this is where the finished floor level, knee wall height and escape cill dimension all get checked against the drawing, because a cill measured from the joists rather than the finished floor is one of the more expensive mistakes available. The conversion sequence is on rooflights for a loft conversion.

The weather call, made before the covering comes off

The forecast is checked the evening before and again on the morning, and the decision to open the roof is made deliberately.

The test is not whether it is raining now. It is whether there is a clear enough window to strip, form, set, flash and re-lay before the weather arrives. On a straightforward roof window in concrete tile that window is a few hours. On Cotswold stone slate, where courses come back a long way up the slope, it is most of a day, so the threshold for starting is higher.

Where the call is no, the outside work does not start and the day either becomes internal preparation or gets moved. That is a frustrating phone call to receive and it is a great deal less frustrating than the alternative. Where the forecast turns during the morning, the outside work stops at a point where the roof is whole, which is why the sequence is arranged in closeable stages rather than as one continuous operation.

Wind matters as much as rain. Handling a large sealed unit on a scaffold in a gusting south-westerly is the point at which glass gets dropped, and in the Forest of Dean and on the wolds tops that is a real limit rather than a cautious one.

Stripping the covering, and stacking it for re-use

The covering comes off from the drilled corners outward, and further than people expect. A double-lap plain tile roof has to be opened a long way up the slope because of the lap. A stone slate roof opens further still.

Tiles and slates are lifted rather than levered where possible, and they are stacked in the order they will go back on any roof where the courses vary. Nibs snap on old clay tiles and slates split at the nail hole, so a proportion is always lost and the count of what needs making up is taken at this point. Battens in the opening zone come off, the underlay is cut back cleanly rather than torn, and what is underneath gets looked at properly. Brittle 1930s bitumen felt, a batten split where the original fixings went in, or timber with historical staining all get photographed and mentioned.

On a flat roof this stage is the membrane being cut back and the deck exposed, and the equivalent findings are a soft board, an uninsulated kerb from a previous unit, or a fall that is flatter than the survey could see from above.

Forming the opening, and trimming it

The structural opening is cut. On a cut pitched roof, one or more rafters come out and doubled trimmers go across the head and cill, fixed so the load from the cut rafter transfers into the trimmers and then into the rafters either side. On a trussed roof, nothing is cut: the opening sits between two trusses with head and cill trimmers, or a designed member is already on site and goes in as drawn. On a flat roof the joists are trimmed the same way against a design sized for the span.

This is the loudest part of the day and the shortest. It is also the one decision that cannot be undone, which is why the design happened weeks earlier and the setting out happened an hour earlier. Where an engineer’s calculation is part of the job, the member goes in exactly as specified and it is photographed for the Building Control file before anything covers it. Trimming detail is on trimming rafters for a pitched roof rooflight.

Setting the unit, and the checks made before it is fixed

The frame goes in dry first and gets checked before a single fixing is driven.

Four things get confirmed. It is square, measured on the diagonals rather than judged by eye. It is level across the head and consistent down both sides. It sits at the correct height relative to the batten line, which is a specific dimension in the manufacturer’s instructions and is the one that gets fudged by people in a hurry, particularly where an over-rafter insulation system has raised the battens. And the sash operates properly through its full travel, opens, closes and latches, before the frame is fixed rather than after.

Then it is fixed with the manufacturer’s own brackets in the specified positions. On a kerb-mounted rooflight the equivalent checks are the kerb’s four corners at the right heights, the top edge raked where the roof falls, and the unit seated on its gasket or bonded as the system requires.

Weathering, which takes longer than setting the unit

The unit going in takes half an hour. Making it watertight takes the rest of the afternoon, and it is the half that decides the next twenty years.

On a pitched roof the underlay comes first: a tongue of membrane taken up over the head of the frame and stapled to the batten above, side pieces dressed into the frame’s own drainage channel, so anything crossing the covering lands on the membrane and runs down outside the frame. Then the insulation collar where the unit has one. Then the flashing set, apron at the cill, side soakers or a continuous side flashing, head flashing dressed under the course above, every lap in the direction of flow, every piece of lead fixed at the head only so it can move along its length. Then the battens back, then the covering re-laid into the flashings.

On a flat roof it is the membrane dressed up the kerb face and over the top edge, the angle fillet at the base, and the laps welded, bonded or torched according to the system. Then the unit set down and clamped.

The full method is on how is a rooflight made watertight.

Closing the roof before anyone leaves

The roof is never left open overnight. That governs the sequence rather than the other way round: an opening is not started unless it can be closed and made watertight the same day.

In practice the crew starts winding down the outside work in the middle of the afternoon rather than at five, so the covering is back, the flashings are dressed and there is time to check the whole perimeter in daylight. Where several units are going in, the sequence runs from the top of the slope downwards so that every evening ends with a closed roof rather than a half-finished slope. Where a job is genuinely too large for one day, for instance a lantern needing structural work, the deck is sheeted and weathered at the end of each day and that is planned into the programme rather than improvised at dusk.

Before anyone leaves, the outside is checked with a hose if there is any doubt, the scaffold is cleared of loose material, the room below is swept, and the dust screen either stays up for the second visit or comes down.

Noise, dust and staying put for the day

Most single rooflight jobs are perfectly liveable through. It is worth knowing what to expect.

There is a loud hour, sometimes two, while the opening is cut. Circular saws, a reciprocating saw and a hammer drill into the rafters, and it is audible through the whole house. Dust is controlled but not eliminated: a sealed loft hatch and a zipped screen deal with most of it and a fine film still appears in the room. There will be people walking on the roof above your head for several hours, which sounds far more alarming from inside than it is. Water and power stay on. The room below is out of use for the day and, where plaster follows, for a couple of days after.

The one thing worth arranging is a plan for pets. A cat that gets out through an open patio door and a dog that reacts to the saw are both more disruptive than anything else on the list.

The second visit: insulation, vapour layer, reveal and plaster

On a typical job the outside is one day and the inside follows on a second, either the next day or shortly after. This is where the finish comes from and it is quieter work.

Insulation is packed continuously around the frame, tight to it with no voids, because a 20mm gap of nothing behind the plasterboard at the head of a roof window is a cold bridge and cold bridges are where black spotting appears in February. The vapour control layer is taped to the frame rather than trimmed short of it. Then the reveal is framed: vertical lining above the window to throw light deeper into the room, horizontal at the cill so warm air from a radiator rises up the face of the glass, and the two sides splayed where the design allows. Then plasterboard, scrim, skim and a wipe down.

Where the reveal splay was priced as an option, this is the point at which it either happens or does not, so it is confirmed at the start of the day rather than assumed. Reveal geometry is on rooflight reveals and why splaying them matters.

Building Control, and where the inspection falls

The notification is submitted and closed out as part of the job. Two inspection stages usually matter and both fall inside the working days described above.

The structural stage wants the trimmed opening visible before it is covered, so where an engineer’s design is involved the inspector either attends or accepts dated photographs against the calculation. The insulation stage wants continuity around the frame visible before boarding. Both get flagged to the inspector in advance so nothing is boarded over the day before a visit, and where Severn is fitting into a larger project run by somebody else, the stages are flagged to whoever holds the application.

The completion certificate comes back in the homeowner’s name afterwards. Keep it, because it is the paperwork a buyer’s solicitor asks for. The regulatory picture is on rooflight planning permission and building regulations.

Making good, and what finished is agreed to mean

“Making good” means different things to different trades, so it is defined in the quotation and it is worth reading that line before the day rather than after.

What is normally included: the reveal formed, boarded, skimmed and left ready for decoration; the covering re-laid and any broken pieces made up; the scaffold struck; waste removed; floors swept and the sheeting taken up. What is normally a separate line: painting the reveal, because plaster needs to dry before it takes paint properly; carpet refitting; and any decoration to the wider room. Where a fitted wardrobe or a kitchen unit had to be moved, who puts it back is written down at survey.

Blinds are the one item that catches people. An external awning needs its fixings before the covering goes back, so it is decided at order stage. Internal blinds fit afterwards and can be added at any point, and on a unit that is out of reach the wiring for an electric blind is far cheaper run on the day than retrofitted later.

Handover, and what gets left behind

The last twenty minutes are a walk round, and they are worth giving your attention to rather than doing from the kitchen.

What is demonstrated: opening and closing the sash and locking it; the ventilation flap and where the filter is behind it; on a centre pivot, rotating the sash through 180 degrees and engaging the barrel bolt so you can clean the outer face from inside; on an electric unit, the wall switch, the handset, pairing, the manual override and what the rain sensor does. Then what to look at once a year and what a normal amount of condensation on a cold morning looks like, so that ordinary physics does not get mistaken for a defect.

What gets left: the manufacturer’s documents with the size code and glazing specification, which matter enormously if a unit ever needs matching; the warranty paperwork for the glass and frame, which is separate from the workmanship guarantee; a note of what was found when the covering came off, with photographs of the trimming and the flashings before they were buried; and the ten-year workmanship guarantee itself, written against the four perimeter details that no one can inspect once the job is finished. The maintenance routine from there is on cleaning and maintaining a rooflight.

Days that run differently in this county

Four Gloucestershire situations change the shape of the day enough to be worth describing.

On Cotswold stone slate at Painswick, Bibury or Northleach, the covering sets the timetable. Courses are stripped back up the slope and re-laid downwards to re-establish the diminishing gauge, reclaimed slates are worked in to match, and the day is largely a roofing day with a window in the middle of it. Torching that has been disturbed is reinstated to whatever detail was agreed with the conservation officer, not decided on the scaffold.

In the Stroud valleys, everything moves by hand. Material comes in from a lane or up steps, the glass goes up with extra hands, and the working day includes carrying that most jobs do not. It is slower and it is priced that way from the survey rather than discovered on the morning.

On a Gloucester terrace with no side access, tube, boards, the unit and the waste all travel through the house, so the protected route from the front door matters more than usual and the neighbours get told the day before.

In central Cheltenham, work on a mansard behind a parapet often means working off a lead flat with a shared parapet gutter running through it. The gutter falls and the outlets are protected for the duration, because a blocked shared outlet on a terrace is next door’s problem as well as yours.

Whatever the roof, the shape of the day is the same: confirmed before it starts, closed before it ends. The full technical picture of the work sits on the skylight and rooflight installation hub, and the route from a first email through a range and a survey to a date is on costs.