What Is the Difference Between Commercial and Domestic Roofing?

The roof itself

A typical house has a pitched roof of clay or concrete tiles or slate, over battens and underlay (the secondary waterproof layer under the tiles), on timber rafters. Water runs off quickly and the covering is made of many small units. A commercial building is more varied. A warehouse or factory often has profiled metal sheets or insulated composite panels on steel purlins. A shop, office or school block tends to have a flat or low-slope roof of single-ply, built-up felt or liquid-applied membrane on concrete or metal decking. A long, shallow roof depends on its seams, laps and outlets, rather than on the angle.

The long spans also change the failure pattern. Leaks on large roofs commonly start at fixings, rooflights, gutters and parapets, and the water can travel a long way inside before it shows. Our guide to the best roof for a commercial building goes through the options by building type.

Materials and repairs

Repair methods follow the roof type. On a tiled house, a slipped tile or a failed hip mortar joint is fixed by hand, and the fix is small. On a commercial roof, a repair might be a patch on a single-ply seam, a new sealant bead along a sheet lap, a replaced rooflight or a coating over a worn section. Materials are bought differently as well, with sheets and panels cut to length, insulation boards ordered by the pallet and membranes delivered on rolls. Lead times can be longer, so a job on a large roof needs planning earlier.

Access, safety and regulations

The risks are different too. A house roof is reached by ladder or scaffold. A commercial roof may be several storeys up, with a fragile surface, no edge protection and rooflights that can give way under a person. The Work at Height Regulations 2005 apply to every job, and on large roofs this means planned access, edge protection, netting and a proper rescue plan. Read our pages on fragile roofs and rooflights and roof edge protection.

On the regulatory side, a business premises falls under the non-domestic part of Approved Document L, and its roof is a thermal element, so renewing a covering usually means considering the insulation. Fire performance carries more weight when the building is large or sits close to others. A commercial lease may also decide who pays, which we cover in our page on who repairs the roof. On a house, the main questions are the Building Regulations thresholds for re-roofing and, in some areas, planning rules. Your council's planning team and your building control body can confirm what applies to your own building.

Disruption and programme

A homeowner can usually stay in the house or go away for a few days. A business often cannot stop. Stock, machinery, staff, customers and insurance requirements all shape the plan, so the work may be phased in sections, done at weekends, or arranged around deliveries. Noise, dust and the position of the scaffold and skips matter more than on a driveway. Our page on roof work while a business is trading shows how that is handled.

Procurement is different as well. A facilities manager or landlord may need a written specification, a programme, an asbestos survey result and a fixed price before approving works. A homeowner more often wants a clear quote and a start date. Both need to see what is wrong before spending, which is why every job we take starts with a free survey and photos.

Upkeep and what stays the same

Roof drainage deserves a special mention. On a house, a blocked gutter drips down a wall. On a flat commercial roof, a blocked outlet lets water pile up on the surface, which loads the structure and finds every weak seam. Parapet gutters and box gutters on commercial buildings need regular clearing, and the outlets need to be visible and reachable.

Commercial roofs should be inspected on a schedule, because a slow leak in a large roof can damage stock and equipment well before it is noticed. Domestic roofs are normally checked after storms or when a problem appears. Underneath it all, the basics are the same: sound decking, good falls, clear drainage, well-made joints and flashings, and a covering suited to the building.

We work on both house and business roofs, and the approach does not change: we show you the fault in photographs, repair where repair works, and give a fixed written quote. Our commercial roofing in Basingstoke page explains the business side of our work in more detail.