Norwich Roofers installs, repairs, and maintains commercial roofs for businesses in Swaffham and across the surrounding Norfolk area.
Call any time. Calls are answered day and night and passed straight to our roofers.
Commercial roofing is a different discipline from domestic work. The roof areas are larger, the consequences of a leak are more disruptive, and the materials used are mostly flat or low-pitch systems rather than the pitched tiles you see on houses. We work on warehouses, retail units, office buildings, light industrial units, and schools - any commercial or non-domestic building that needs a roof installed, repaired, or properly maintained.
This page walks you through exactly what happens on a commercial roofing job, from the moment we arrive on site to the moment we leave it clean and signed off. If you are deciding whether to proceed with a project, or trying to understand what a contractor should actually be doing at each stage, this is the detail you need.
Flat roofing systems have different strengths, lifespans, and suitability depending on the building. A single-ply EPDM membrane is well suited to straightforward flat roof areas with good falls. Built-up felt systems use multiple layers of felt bonded together, typically with a mineral-finish cap sheet, and are still common on older commercial buildings. Metal sheet roofing - standing seam or profile sheet - is used on larger industrial and agricultural-style commercial buildings where span and weather resistance matter.
The right choice depends on the existing structure, the roof size, any roof penetrations such as rooflights, ventilation stacks or air handling units, and your budget. We will tell you what we think is most appropriate and why, rather than defaulting to whichever system carries the highest margin.
Before any work is quoted or planned, the roof needs to be properly inspected. For a larger building with complex detailing - parapet walls, internal gutters, multiple fall zones, roof penetrations - a survey could take considerably longer than for a straightforward unit.
A proper survey looks at the existing roof covering and its condition, the falls (the angle at which the roof drains), any areas of standing water or ponding, the condition of upstands and flashings around parapets and penetrations, the substrate beneath the covering, and the state of internal and external drainage. Many roofing problems on commercial buildings originate not from the membrane itself but from blocked or undersized outlets, failed flashings, or a substrate that has softened due to long-term moisture ingress.
We check whether the existing structure can support the proposed new system, particularly relevant where a heavier built-up system might be replacing a lighter single-ply. If there are doubts about the deck, we will flag them before any quote is issued, not after work begins.
Core samples - small circular cuts through the roof build-up - are sometimes taken on older roofs to check whether the insulation layer has taken on water. A saturated insulation board adds weight, has almost no thermal performance, and must be replaced rather than simply covered over. Any contractor who quotes for a flat roof overlay without checking the existing insulation condition is cutting a corner that will cost you later.
Once the survey is complete, the specification is drawn up. This sets out which system will be used, the thickness of any new insulation, how the edges and upstands will be detailed, how existing penetrations will be handled, and what the drainage arrangement will be.
For commercial buildings, insulation specification matters for two reasons. First, building regulations require minimum thermal performance for commercial roof replacements (not just new builds), so the U-value of the finished roof assembly needs to meet current standards. Second, adequate insulation protects the waterproofing layer itself - a cold, poorly insulated deck sees more thermal movement, which stresses the membrane and shortens its life.
Edge and upstand details are where many cheaper jobs fail. A membrane that is not properly dressed up and over a parapet wall, or that lacks a proper drip edge at the eaves, will allow water to track back under the system. Good commercial roofing specifications are specific about these details, not vague.
Commercial roofing almost always involves some form of access equipment. Scaffold, mobile elevated work platforms (MEWPs), or roof ladders depending on the height and configuration of the building. The access arrangement needs to be agreed before work starts, particularly on occupied premises where a scaffold over a car park or loading area affects the business below.
On occupied buildings, timing matters. Noisy work - breaking out old felt, using gas torches for torch-on systems - is often scheduled for early mornings or outside trading hours where possible. This is worth discussing at the planning stage rather than assuming it will sort itself out on site.
Material deliveries also need coordinating. Rolls of single-ply membrane, insulation boards, and sheet metal are bulky. A large commercial job might need several deliveries, and storing materials safely on or near the roof needs thought, particularly on older structures where concentrated point loads on an ageing deck can cause problems.
Most commercial re-roofing jobs involve removing the old system before laying the new one. An overlay - laying new material directly on top of the old - is sometimes possible, but only where the existing substrate is sound, dry, and level enough to work with. Overlaying a failing or wet roof simply encapsulates the problem and shortens the life of the new system.
Once the old felt or membrane is stripped, the deck is inspected closely. On timber decks, any boards that are soft, delaminated (on plywood), or structurally compromised are replaced before anything else is done. On concrete decks, any areas of spalling or friable surface are repaired and primed. On metal decks, the condition of the fixings and the deck profile is checked.
The deck must be clean, dry, and properly prepared before insulation or membrane goes down. Any contamination - grease, old bitumen adhesive residue, loose material - affects adhesion. This preparation stage is unglamorous, but skipping it is one of the most common causes of premature roof failure on commercial buildings.
Installation method depends on the system specified. EPDM single-ply membrane is typically adhered to the insulation layer using a compatible bonding adhesive, with the seams heat-welded or cold-adhesive bonded depending on the specific product. The membrane is then mechanically fixed or ballasted at the edges and upstands.
Built-up felt systems are installed in multiple layers, usually three, with each layer torched or cold-bonded to the one below. The cap sheet - the top layer - carries a mineral finish that reflects UV and provides some surface protection. Laps between rolls, and the way rolls are staggered to avoid continuous joints, matter for long-term waterproofing performance.
Metal sheet roofing involves fixing the sheets to the structural purlins below, with standing seam or profile sheets overlapping at the sides and ends. Flashings at ridges, verges, and any roof penetrations are formed in compatible metal - usually the same material to avoid electrolytic corrosion between dissimilar metals.
Throughout installation, falls need to be checked. A flat roof is never truly flat - it should drain at a minimum fall of 1:80 (about 1.25%, or 0.72 degrees), and ideally steeper. If the existing structure does not achieve this, tapered insulation boards can be used to create the fall within the new roof build-up.
This is the stage that separates a good commercial roofing job from a poor one. The field of the membrane - the large open area - is relatively straightforward to lay. The details are where leaks start.
Upstands at parapet walls should be taken up at least 150mm above the finished roof surface. Flashings over these upstands are typically formed in lead, aluminium, or zinc depending on the system and budget. Penetrations such as rooflights, pipe boots, and ventilation terminals each need individual waterproofing details, formed carefully to the shape of the penetration.
Outlets - the drain points where water leaves the roof - need to be set at the lowest point of each fall zone, clear of any upstands, and with a suitable sump or grate to prevent blockage. On a job where outlets are being replaced or repositioned, the pipework below needs to be traced to make sure it discharges correctly.
Internal gutters on commercial buildings are a particular weak point. They carry large volumes of water, they are usually lined with felt or lead that has a finite life, and when they fail the water goes directly inside the building. Internal gutter relining is a job in its own right, and it needs to be on the scope of works if the gutters are at or near the end of their serviceable life.
Once the roof is complete, it needs a thorough final inspection before the access equipment is removed. This means walking every square metre of the finished surface, checking all laps and seams, checking all upstand and flashing details, checking that all outlets are clear and correctly fitted, and checking that no debris has been left on the roof.
On single-ply systems, seams can be tested with a blunt probe to check they are fully bonded. On built-up felt systems, visual inspection of all laps and the cap sheet surface is carried out. Any defects found at this stage are addressed before the scaffold or access equipment comes down - not after, when getting back up to the roof involves mobilising equipment all over again.
You should receive a clear record of the work completed, the materials used, and any areas of the building that were noted as requiring attention in future (for example, brickwork to a parapet that is showing early signs of deterioration but is not yet a roofing problem). Good commercial roofing contractors leave you better informed about your building than you were before they arrived.
Commercial roofing generates considerable waste - old felt, insulation boards, packaging, off-cuts of membrane. All of this should be removed from site and disposed of correctly. Waste from commercial roofing work is classified as construction waste and needs to go to a licensed waste facility. If a contractor is offering to take your old flat roof away and you are not sure how it is being disposed of, it is worth asking.
The site around the building also needs to be reinstated. Scaffold boards protecting the ground, any temporary protection to doors or windows, and any materials stored on site all need to be cleared. The building should look the same at ground level as it did before work started, minus whatever was being protected.
A commercial roof that is inspected and maintained at regular intervals will significantly outlast one that is left alone until a leak appears. Maintenance visits involve clearing outlets and gutters, checking upstand and flashing details, identifying any areas of membrane damage or lap failure, and addressing minor defects before they become major ones.
For commercial flat roofs, autumn maintenance visits before the wetter winter months make particular sense. Blocked outlets and standing water through a wet winter accelerate deterioration of any flat roof system.
A planned maintenance programme also means you have a documented record of the roof's condition, which is useful for building management, lease negotiations, and future re-roofing budgeting.
If you manage or own a commercial building in or near Swaffham and need a roof surveyed, repaired, or replaced, call us to arrange a roof survey. We will tell you honestly what the roof needs and what your options are.
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Call any time. Calls are answered day and night and passed straight to our roofers.
