The short answer
Duration depends on roof area, the covering, how the roof is reached and the weather, so no single figure fits every building. A small flat roof over a shop is a matter of days, while a large industrial unit with new insulation, rooflights and drainage runs into weeks. The survey leads to a programme written for your building and its trading hours.
What sets the length of a re-roof programme?
Area is the obvious factor, but it is rarely the biggest one. Access, the type of roof and what lies beneath it usually matter more. A flat roof with a simple membrane over an existing deck moves quickly. A pitched metal roof with new purlins, insulation and rooflights has more trades, more materials to lift and more places where work has to pause.
Roof height changes the pace as well. Materials are lifted by crane, hoist or telehandler, and every lift takes time. Plant, pipework and rooflights each add detail work. A tidy, empty roof goes far faster than one crowded with extract fans, services and walkways.
The covering matters too. A single-ply membrane on a flat roof can be laid in a few days on a small area, whereas profiled sheets on a large portal frame must be set out, lapped and fixed row by row. Each system has a natural pace.
Compare programmes on a like-for-like basis: the same area, covering and working hours, since a shorter duration quoted for a smaller scope tells you nothing.
How does the weather change the timetable?
Weather decides which days are working days. Rain stops membrane laying and sheet fixing, high wind stops crane lifts and makes large sheets unsafe to handle, and frost or damp can upset adhesives. A sensible programme allows for some lost days and sequences the work so the building is weathertight at the end of each shift, not left open overnight.
Our page on commercial roofing in winter explains what changes in the colder months and why some systems cope better than others. Booking a re-roof for the drier part of the year helps, though a leaking roof does not always leave a choice of season.
Cold, wet spells can pause glued or torched systems for days, while mechanically fixed systems are more forgiving. Ask which suits the time of year you are booking.
Wind limits apply to crane lifts and sheet handling alike, and a gusty day can lose a full shift even when no rain falls.
Which stages take the time on a typical job?
A re-roof moves through stages, each with its own length. Setup comes first: scaffolding, edge protection, a welfare area and a route for materials. Strip-out follows, which can mean removing the old covering and sometimes the insulation below. The deck and structure are then checked and repaired, because a soaked deck or corroded support must be dealt with before anything goes back.
Insulation, vapour control and the new waterproof layer come next, with detailing at every upstand, outlet and penetration. Flashings, gutters and a final clean finish the job. Our commercial roof insulation page covers how the thermal layer affects the build-up and the timetable. Adding insulation to meet Part L can lengthen the programme, and building control sign-off may follow if the work is notifiable.
Disposal runs alongside. Skips fill quickly on a large strip-out and need swapping on a schedule, or the site stalls waiting for them.
Can the business keep trading during the job?
Often it can, with planning. Work in phases, covering one section at a time so each part of the roof is weathertight before the next opens. Noisy tasks such as cutting and fixing sheets can be timed around opening hours, and loading areas, fire exits and entrances need protected routes.
Some buildings cannot tolerate disruption at all. Cold stores, food production and sites with sensitive stock may need extra protection beneath the roof or a programme built around shutdowns. Tell us about those limits at the survey, because they shape the order of work more than any other factor. The total price in the quote covers the whole programme, so a change of plan does not arrive as a surprise add-on.
Noise is worth discussing with neighbours as well as staff. Cutting metal sheet and running compressors can be loud, and a short notice letter to adjoining units avoids complaints.
What should be agreed before the first day on site?
Start with dates that suit the business, a named site contact and clear access for deliveries. Agree where skips and storage will go, and who moves vehicles and stock. If the building is leased, check whether the landlord needs notice or consent, and whether the roof falls under the tenant's repairing obligations.
Then ask each firm for a written programme alongside the price, and check that VAT, scaffold, disposal and making good appear in each total. When we hand over, the site is left clear and the waste has gone. Our composite roof panels page shows how a panel system can shorten the programme, because insulation and weather skin go on in one pass.
Lead times matter before the first day. Specialist panels, rooflights and large sheets can take weeks to arrive, so ordering early prevents a roof standing open while materials are awaited.
What happens when the roof hides surprises?
Hidden problems are the usual reason a programme grows. A saturated deck, a corroded rail or old asbestos cement sheets can add days, and sometimes the scope changes altogether. Our page on church roof repairs shows how consent and heritage rules can stretch a timetable in the same way. For the full list of services, start from commercial roofing.
Ask for a revised programme in writing whenever the scope changes, so you can brief the people who rely on the building.