What does a shop roof repair involve?

Many town-centre shops sit in a terrace with neighbours either side. The front slope may be pitched and tiled or slated, while the rear is a flat roof over a stock room, kitchen or store. Above the sales floor there might be a flat or a first-floor flat that is let separately. The roof therefore serves more than one party, and a leak in one place can show as a stain somewhere else.

Shop roofs also tend to collect extras over the years. Extract flues, aerials, signage brackets, air-conditioning pipework and rooflights are all penetrations through the covering, and each one is a point where water can get in. A modest roof area with a lot of details is often harder to keep watertight than a large plain one.

Access matters as well. Many units back onto service yards or alleys with no space for a scaffold, so a repair may rely on a tower, a ladder or work from a neighbouring roof, which needs permission.

Experience points to a short list of repeat faults, and we check them in order.

• The flat rear roof. Felt blisters, splits at laps and cracked upstands let water through. Ponding around outlets is a warning that the fall has gone or the outlet is partly blocked.
• Parapet and valley gutters. These hidden channels hold a lot of water and silt up with leaves, moss and rubbish. When they overflow, the water finds the wall.
• Flashings. Lead or mortar-fixed flashings where the roof meets a higher wall can lift or crack. A flashing is the lead or zinc trim that seals the join where a roof meets a wall.
• Slipped or broken tiles and slates. On the front slope, a few missing pieces can let wind-driven rain in during a storm.
• Rooflights. Seals dry out, glazing slips and condensation drips can look like leaks.

For flat roofs, the lifespans in our guide to commercial flat roofs help you decide whether a patch is worthwhile.

Water travels. It runs along a timber, drops at a joint, then marks a ceiling a metre or two from where it entered. Fixing the stain without finding the entry point only moves the problem. A proper investigation looks at the roof surface, the drainage, the details above the stain and the building fabric below, and it reads the pattern of damp rather than one spot.

On shop roofs, a good start is the last heavy rain. Note where the water showed first and how quickly, because a fast drip points at an open joint or blocked outlet and a slow stain points at a seep through the covering. Photographs of the ceiling, taken with a date, help us read the story. Then comes the roof itself, and the photographs we take there are yours to keep.

Blocked outlets and gutters are cheap to clear and are always worth ruling out first. If you have a shared drain, our page on siphonic drainage explains why large commercial outlets behave differently from domestic ones.

The answer turns on the extent of the failure. Isolated splits, a lifted flashing or a blocked gutter are repair jobs, and a repair that cures the fault beats a larger job nobody needed. Widespread cracking, soft or wet decking, repeated patches in the same area or a covering past the end of its life point towards replacement.

Metal sheeting on a small commercial building has its own questions, from corroded fixings to joints that have opened. If your unit is sheet-clad and noisy in the rain, our page on metal roof noise covers a related problem. For industrial-scale leaks, see industrial roof leaks.

Where replacement is the sound advice, the photographs make the case. Where a repair will do, the quote prices a repair. Either way, the larger picture of commercial work lives on our commercial roofing page, and the question of old coverings failing in clusters is a good one to ask on the day, since two or three patches in one area often mean the surrounding covering is tired too.

A retail unit cannot always close, and a repair that takes the shop out of action costs more than the roofing itself. We plan the visit to suit you. Early starts, quiet days and short phases keep disruption low, and we make the roof watertight before we leave each day. Customers should never walk beneath live work, so we agree entrances and routes in advance. For bigger programmes, our page on commercial roof design sets out how a roof is planned as a system.

If you rent the unit, check your lease before ordering work. Many leases make the landlord responsible for the structure and the tenant for the interior, with repairing obligations written in between. Photographs and a written quote make that conversation easier.

Start with a few photographs of the ceiling stains and, if it is safe to take them, the roof from the street or an upstairs window. Add a line about the timing: after heavy rain, after any rain, or only with a particular wind direction. Please do not climb up to look yourself, as flat shop roofs often hide fragile rooflights and soft decking.

Stopping water entry comes first, with leaks and storm damage prioritised. The survey then produces pictures of the roof above your unit and a written quote. The workmanship guarantee runs for 10 years in writing, and the yard or alley is left clear when we go. Our number is 01793 626096, and the form on this page or a WhatsApp message will also reach us.