The short answer
A commercial re-roof takes from a few days for a small flat roof to several weeks for a large industrial building. There is no standard figure, because the programme depends on the roof area, the system being installed, how much has to be stripped, access, and whether the business keeps working underneath. Planning, ordering materials and surveys happen before the first day on site, so allow for that lead time as well as the building work.
What sets the length of the job
Four things do most of the work. The first is area: a roof is laid in sections, and twice the roof means roughly twice the labour. The second is the system. Fixing insulated composite panels to steel purlins moves faster than stripping a built-up felt roof, preparing the deck, laying tapered insulation and welding a new membrane. The third is what is already there. An old roof with several layers, wet insulation or a rotten deck takes longer to strip and repair than one that comes off cleanly. The fourth is access. Roofs reached by a single stair, with no space for a crane or a skip, take longer to supply and clear.
Weather is the wild card. Membranes cannot be laid onto a wet deck, liquid coatings need dry spells to cure, and high wind stops sheet and panel lifting. A programme should carry some slack for lost days, especially from autumn to spring.
The stages in order
The work before the roof starts is easy to forget. A survey establishes the condition of the covering, the deck and the structure. A specification is agreed, the insulation standard is checked with building control, and, on an older building, an asbestos check is made before anything is disturbed. Materials are ordered, and a long run of panels or a specialist membrane may take time to arrive. Scaffolding or edge protection goes up, and the working areas, the skips and the access route are agreed with whoever runs the site.
On the roof itself the sequence is strip, repair the deck, lay vapour control layer and insulation, fit the new covering, then detail the edges, penetrations and outlets, which are slow because every one is made by hand. Finally, the roof is checked, the site is cleared and the paperwork is handed over. Our guide to repair, overlay or replace helps decide how much of the stripping step you need.
Material choice moves the clock too. Lightweight sheeting goes on quickly once the purlins are checked, while a three-layer felt system needs each layer bonded and inspected before the next. Liquid-applied coatings are fast to roll out but depend on the weather for curing. Rooflights, smoke vents and plant curbs each add fiddly work at the edges. A roof with many penetrations will always take longer than a clean, open expanse of the same area.
Keeping the business open
If the building keeps trading, the work is usually phased. One section is stripped and made watertight each day, so the building is never open to the weather overnight, and noisy or dusty tasks are timed to suit the occupants. Phasing adds time but protects stock and staff. Our page on roof work while a business is trading explains how that works in practice.
An empty building can be done faster, since you can take the whole roof in larger bites. Shutdown periods such as bank holidays are used where the occupier can plan around them. Tell us about shift patterns, deliveries and any tenant requirements early. We try to fit the programme to the building, not the other way round.
How to keep a programme on track
Handover is part of the timeline. Before we leave, the roof is walked and checked at every outlet, upstand and edge, the gutters are cleared, and the site is swept and the waste taken away. If you need a written record for a lease, a lender or a landlord, tell us at the start, so the right photographs and documents are collected as the job runs and not chased afterwards.
Most delays are avoidable. A survey that finds the hidden problems, such as a wet deck or asbestos in the sheets, stops the surprise on day three. Early decisions on colour, rooflights and insulation thickness stop the supply chain from holding things up. A named person on your side who can approve changes keeps the work moving. Ask for a written programme with the start date, the phasing and the likely finish, and for a plan if the weather turns.
Cost is linked to time, because a longer job needs more scaffold hire and more supervision. Our page on commercial roof replacement cost shows what drives the price.
We begin with a free survey and photographs of your own roof, and we give a fixed written quote with a programme you can plan around. We will not promise a date before we have seen the roof. The full range of business work is on our commercial roofing in Basingstoke page.
Every roof is different. A free survey with photos settles it for yours.
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