How long does a commercial rooflight job take?

The roof work itself, unit by unit

Taken in isolation, the installation times are consistent enough to publish.

Those are working days on the roof, in usable weather, with access already in place. They do not include mobilisation, and they assume the deck underneath turns out to be what the survey said it was.

The weeks that pass before we arrive

This is where a commercial programme actually lives. Survey to quotation is a few days. Order to delivery on a stock unit is short, but a made-to-order unit with a specific glass build-up, a rated non-fragile assembly or a non-standard size runs into weeks, and a fabricated unit with a solar control coating and a colour-matched frame can run longer than that.

Alongside the unit sit the arrangements: access equipment booked, a permit to work issued if the estate uses them, method statement and risk assessment reviewed and accepted, the occupier notified, and where the roof covering is under a manufacturer warranty, confirmation of the method that keeps it intact. On a managed estate the document review alone can take longer than the installation.

Multiple units across one roof

Units after the first are much quicker than the first. The access is up, the set-up is done, the detail is established and the crew has the rhythm. A roof taking six identical kerb-mounted units does not take six times a single unit’s duration, it takes something closer to half that.

What breaks the rhythm is variation. Six units of the same size in the same covering run fast. Six units of different sizes across three different roof build-ups on two levels are effectively six separate jobs sharing one scaffold. When you are planning a scheme, standardising the sizes is the cheapest programme saving available.

What slows a commercial job and never slows a domestic one

Several things appear on a commercial site that simply do not exist on a house. Site induction, sometimes half a morning of it, before anyone touches the roof. A permit to work signed each day. An isolation of the fire alarm zone under the work and its reinstatement. Coordination with other trades on the same roof. A daily exclusion zone that has to be set and struck. Escorted access where the building is secure.

Individually each is small. Together they can take an hour and a half out of every working day, which on a five-day job is most of a day. We build that into the programme rather than discovering it, which is why we ask about induction and permits at survey.

Weather, and what actually stops the job

Two different limits apply. Rain stops the moment an opening is exposed, because you do not open a roof over an occupied building in weather. Wind stops work sooner and at a lower threshold, because access equipment and large glass panels both have wind limits, and at 12 metres the wind is stronger than the forecast at ground level suggests.

In practice a five-day commercial programme in November should be planned as seven. In June it will usually run to plan. We would rather quote a realistic window and beat it than quote the best case and spend the job explaining. Where the date is genuinely fixed by the occupier, a shutdown period in summer is worth more than any amount of optimism in the programme.

Working around an occupier stretches the calendar

The same physical work takes longer when the building is in use, and the multiplier depends on how much of the day is available. A warehouse that gives us the full day loses very little. A restaurant that gives us mornings only loses roughly half. A building where the space below can only be closed for two hours at a time turns a two-day job into a fortnight.

This is the single biggest variable in commercial programming, and it is the one clients most often underestimate. It is worth pricing a short full closure against a long phased run before assuming phasing is cheaper. Our page on programme and phasing on a commercial roof goes through the options.

What a single installation day actually looks like

Arrive and set out, protect the area below and cordon it, and confirm the permit. Set out the opening from inside and from above so the two agree, because a position that looks right on the roof can land 300mm off a purlin inside. Open the covering back to the line, form or trim the opening, build the kerb and insulate it.

Then the unit goes in, the covering is dressed up the kerb and terminated above the water line, the flashings are lapped and fixed, and the perimeter is sealed. Last hour is clearing down, striking the cordon and checking from inside. If the day is going to run over, the decision to close the roof rather than push on is taken with an hour of daylight still in hand.

Holding a date once we have given it

We give a start date when the units are ordered and the access is booked, not before, because a date given before those two things is not a date. Once given, we hold it unless weather or a client-side delay moves it, and if it moves we tell you the same day rather than on the morning.

For a job with a hard deadline, a school holiday or a shutdown, tell us the deadline at enquiry stage and we will work backwards from it and tell you the last date the order can be placed. If that date has already passed, we will say so. Call 01865 704245 or email info@heritageskylightsoxford.co.uk with your unit count, roof type and any fixed date you are working to. We install and replace rooflights only, with a ten-year workmanship guarantee and fifteen years in the trade behind it.