Choosing a commercial roofing contractor is a procurement job rather than a shopping one. The building has to keep working, somebody else's insurer is watching, and the guarantee on the system you are buying usually depends on who installs it. Three things are checkable before anyone quotes, and they filter out most of the risk.
What you can verify before the first site visit
Whether the firm is registered on a competent person scheme, which you look up on the scheme's own register rather than on the contractor's site. Whether it is an approved installer for the system it is proposing, because most manufacturer guarantees on single ply and liquid systems depend on that approval and are worthless without it. And whether the company exists as a legal entity with accounts, which matters because a twenty year guarantee is only as good as the company standing behind it.
The questions that separate commercial from domestic
Ask how the roof will be made watertight at the end of each working period, because that is the difference between a bay-by-bay programme and a gamble on the weather. Ask what the access arrangement is and who provides the edge protection. Ask how deliveries and waste will move without blocking the yard. And ask what happens to the programme if it rains for a week, because the honest answer is a longer programme rather than a fixed date.
Guarantees, and what they actually promise
There are usually two: the contractor's workmanship guarantee, which lasts as long as the contractor does, and the manufacturer's product or system guarantee, which lasts longer and is conditional. Read what the conditions are. Most require an approved installer, correct detailing, and often a periodic inspection regime that somebody has to remember to book. A guarantee with an inspection condition nobody diarised is a guarantee that lapses quietly.
Questions people ask about commercial roofers
Do commercial roofers need a licence in the UK?
There is no single licence for roofing. What exists is competent person scheme registration, which is a government licensed route to self-certifying work against the Building Regulations, plus manufacturer approvals for specific systems.
How many quotes should we get for a commercial roof?
Three, against a written specification you provide rather than three specifications the contractors each wrote. Otherwise you are comparing different roofs.
Who signs off commercial roofing work?
Where the work is controlled under the Building Regulations, either building control or a contractor registered on a competent person scheme. The manufacturer's guarantee is a separate piece of paper with separate conditions.