Answered · Skylight & Rooflight Installation & Replacement Chelmsford

How long does a skylight replacement take?

The short answer

One working day for a straightforward like for like swap into a sound existing opening. One to two where the kerb has to be rebuilt. Two to four where the opening is being widened and structure is involved. Those are the honest figures for the work itself, and they hold for most Essex housing.

The longer wait is almost always before the day rather than on it. Ordering a unit takes weeks, and a made to measure size takes more. People plan around the installation and are then surprised by the lead time, when it is the other way round.

The ordinary durations, by what you have

The unit type and the covering set the duration more than the size does.

Job	Time on site	What governs it
Roof window, like for like, tiled slope	One day	Stripping and resetting courses of tile
Flat rooflight into a sound kerb	One day	Local covering reinstatement
Flat rooflight, kerb rebuilt	One to two days	Carpentry and covering dressed up new faces
Dome swapped for a flush unit	One to two days	Kerb height and new frame seating
Opening widened	Two to four days	Structure, then everything else
Roof lantern onto an existing opening	Two to three days	Frame assembly and individual glazing

Where the hours actually go on a one day job

The glass is on the roof for a fraction of the day, which surprises people watching from the kitchen.

Roughly an hour goes on protection inside and setting up access. An hour to an hour and a half strips the covering back and releases the old unit. Half an hour lifts it out and gets it down. Two hours prepare the kerb or the opening, check it for square and level, and set and mechanically fix the new frame. Two to three hours weather it: flashing kit or membrane, laps, terminations. The last hour is the internal reveal and clearing up. Nothing in that list can be usefully hurried.

What adds half a day

Several things regularly extend a one day job into a long one, and all of them are visible at survey.

A kerb that needs rebuilding at the deck junction, which is carpentry plus covering dressed up new faces.
An opening that is out of square by more than the frame tolerance, needing packing and re-lining.
Handmade clay tiles, which come off one at a time and go back the same way.
A tower or scaffold that has to be moved partway through to reach a second elevation.
An electrical supply run for an actuator where the void is accessible.

What turns one day into three

Three findings change the shape of the job rather than adding hours to it, and each is worth knowing about in advance.

Soft deck around the opening means the boarding comes up and goes back before anything else can proceed, and the extent is rarely obvious until the covering is off. Structure, where an opening is being widened across the span, brings a calculation, a bearing detail and often a steel. And suspect material on a pre-2000 roof stops the programme entirely until it is sampled and, where confirmed, handled by a specialist holding the licence for that work. None of the three is unusual. All three are found at survey rather than at eleven o’clock on a Tuesday.

The lead time before anybody arrives

This is the part of the calendar people underestimate, and it is where the real waiting sits.

A standard size unit from a mainstream range is commonly two to three weeks from order. A non stock glazing specification, meaning solar control, laminated inner and outer, or an unusual cavity, moves that to three to five. A made to measure unit built to a surveyed dimension runs four to eight weeks and occasionally longer through the winter. An electric unit with a controller sometimes arrives in two deliveries. The date on site is set once the unit is confirmed, not when the order is placed.

Bespoke sizes, and the weeks they buy you

Openings formed before the mid nineteen seventies were set out in feet and inches, and a great many Essex roofs still carry two by three, three by four and four by four foot holes. Metric ranges do not land on those numbers.

A bespoke unit adds weeks to the calendar and removes days from the site programme, because the structure is left completely alone. On a trussed roof at South Woodham Ferrers or Great Notley, where easing an opening is exactly what a truss will not tolerate, that trade is usually worth making. Waiting six weeks and installing in one day beats waiting two and installing in four.

Plaster, paint and the days after the roofers leave

The rooflight is finished on the day. The room is not, and it is fairer to say so.

A replacement almost always disturbs the reveal, because frame depths and flange widths have moved between generations and a new unit rarely lands on exactly the old line. Making good is a small area of plaster, but it wants a day to firm and several days to dry properly before paint. Where the old reveal was square and the plaster is coming back anyway, splaying it so the lining opens towards the room spreads light across the ceiling and costs almost nothing at that moment. Budget roughly a week between the installation and the final coat.

What actually makes a job overrun

Overruns come from three sources and only one of them is weather.

The commonest is a unit that arrives incorrect, which is why nothing is stripped until the new unit is on site, unwrapped and checked against the measured opening. The second is a survey that did not get onto the roof, so the kerb condition was assumed rather than tested with a bradawl at the deck junction. The third is genuinely the weather, and in winter that moves a start date rather than extending a job. Where several units are being done, taking them on one visit compresses the total considerably, which is covered on doing them all at once. The full sequence sits on the skylight replacement page.

Tell us about your roof

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.

Surveyed before it is priced
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Building Control notification handled
New installations and replacements