Dereham Roofers provides commercial roofing for businesses, landlords and industrial premises in Barnham Broom, covering flat roofs, pitched roofs, cladding and guttering on every type of commercial building.
Whether you manage a retail unit, an agricultural barn, a workshop or a block of commercial premises, the roof is the single most important element protecting your investment. Dereham Roofers works across Barnham Broom and the surrounding villages, handling everything from routine maintenance and repairs through to full roof replacements on flat and pitched commercial buildings.
We work with landlords, business owners and farm operators who need reliable roofing work carried out with as little disruption to their operations as possible.
Commercial roofing is a broader category than most people realise. It includes flat roof systems on extensions, outbuildings and industrial units; pitched roofs on warehouses, barns and retail premises; cladding panels on steel-framed structures; and the full guttering and drainage systems that keep water moving away from the building. A problem in any one of these areas can cause damage far beyond the roof itself.
This is the part that catches many building owners and landlords out. Commercial roofs are designed to be largely out of sight, which means problems can develop for months or even years before they become obvious. By the time water is dripping through a ceiling or pooling on a warehouse floor, the underlying damage is usually far worse than the visible symptom suggests.
Knowing what to look for, and understanding what causes each warning sign, puts you in a much stronger position to act before a manageable repair becomes a full replacement.
A brown or yellow stain spreading across a ceiling is the most common sign that water has found a route through the roof. On flat-roofed commercial buildings, the entry point is rarely directly above the stain - water travels along joists and roof decking before dripping through. Chasing the stain directly often leads to the wrong area being repaired, which is why a thorough inspection of the whole roof surface, the flashings and all penetrations (pipes, vents, rooflights) is necessary rather than a spot repair.
On pitched roofs, internal staining often points to a slipped or broken tile or slate allowing rain in, or to failed mortar at a ridge, hip or valley. It can also indicate that the sarking felt beneath the tiles has split or perished, which means the whole tiling may need to come up to replace it properly.
A flat commercial roof should never truly be flat. Correctly laid flat roof systems are built with a fall of at least 1:80 (roughly 12mm per metre) so that water drains towards outlets. When water ponds and sits for more than 48 hours after rain, it indicates either that the falls were never adequate, or that the roof deck has deflected over time, or that outlets are blocked. Ponding water accelerates the deterioration of felt systems significantly. It adds weight, it keeps the surface membrane wet continuously rather than allowing it to dry out, and it concentrates freeze-thaw stress in winter.
A common problem with older commercial flat roofs is that multiple layers of felt have been applied over the original covering, adding weight and disguising underlying damage. When that is the case, the only lasting repair is to strip everything back to the deck, inspect the decking itself for rot or corrosion, and relay a new system correctly.
Blisters on a felt or membrane surface form when moisture trapped beneath the covering heats up and expands. Once a blister grows large enough to break, water enters directly. Cracking and splitting typically follow age-related brittleness, but can also result from thermal movement on large roof areas where expansion joints were not included in the original design. A small split in a membrane is cheap to repair. Left for a winter, it is rarely small any more.
EPDM rubber membranes are significantly more resistant to cracking and thermal movement than traditional torch-on felt, which is why they are increasingly used on commercial flat roofs where longevity matters. A well-laid EPDM system can remain serviceable for considerably longer than the 10-15 year typical lifespan of standard built-up felt, though any system requires periodic inspection to catch minor issues before they become serious.
Flashings are the metal or lead upstands and cover pieces that seal the junction between the roof surface and any vertical element: parapet walls, chimney stacks, dormer cheeks, pipe penetrations and rooflights. They are, statistically, the most likely point of failure on both flat and pitched commercial roofs. Lead flashings expand and contract with temperature change, and over years the mortar pointing that holds them into masonry joints cracks and falls away, letting water in behind.
On commercial buildings with parapet walls, failed parapet flashings are particularly damaging because water enters the wall cavity and can saturate insulation, cause masonry to spall, and eventually affect the structural integrity of the parapet itself. Checking and re-pointing flashings every few years is one of the most cost-effective things a building owner can do to extend roof life.
A flat roof that looks wavy or has obvious low spots when viewed from a high point is telling you that the deck beneath the covering has moved or deteriorated. On older commercial buildings, flat roof decking is often timber - either chipboard, plywood or older tongue-and-groove boarding - and prolonged damp causes it to swell, delaminate and eventually rot. Once decking has rotted, it cannot hold fixings and the membrane above it cannot be tensioned correctly. At that point, the only option is a full strip and re-deck.
On steel-framed agricultural and industrial buildings, the equivalent problem is corrugated metal cladding or metal decking that has begun to corrode through. Surface rust on cladding is cosmetic. Through-corrosion at fixings, at laps or at the foot of sheets (where debris and moisture collect) compromises the weather seal and, if left, the structural capacity of the sheet.
Guttering failure is consistently underestimated as a cause of commercial building damage. A blocked gutter on a large roof concentrates enormous volumes of water at the point of overflow. That water runs down external walls, saturates the base of the wall, and can undermine foundations if the pattern is repeated over years. On flat roofs, blocked internal outlets cause exactly the ponding problems described above.
Commercial guttering on larger buildings is often cast iron or pressed aluminium, both of which corrode at joints and at fixings if not maintained. uPVC guttering on commercial-scale roofs needs correctly sized and spaced brackets; undersized or poorly fixed guttering sags, pools water and eventually pulls away from the fascia. Gutter clearance twice a year is the minimum for buildings surrounded by trees.
In agricultural barns, workshops and outbuildings, a practical check is to walk inside on a bright day and look up. Pinpricks of light through the roof covering mean gaps that rain will find. This is especially telling in older corrugated-sheet agricultural buildings where washers have failed or sheets have shifted at the laps. A sheet that has moved just a few millimetres at its overlap is no longer weather-tight at that joint.
Not all moisture problems in commercial buildings come through the roof surface. Poor or absent roof insulation, or insulation that has become wet and compacted, can cause condensation on the underside of the roof structure as warm moist air inside meets a cold surface. This is a common problem on metal-clad industrial buildings that have been converted to heated uses without upgrading the insulation layer. The solution involves improving the cold bridge, not just repairing the surface. Confusing condensation damage with a membrane leak leads to wasted money on repairs that do not solve the problem.
Understanding the root cause of a roofing problem determines what the right fix is. The same symptom can have several different causes, and patching the surface without addressing the cause means the problem returns.
Standard built-up felt flat roof systems have a working life of roughly 10-20 years depending on specification and maintenance. Older properties with flat roofs that have never been fully replaced may be on their third or fourth layer of felt. Each additional layer adds weight and traps more moisture. At some point, stripping and starting again is cheaper over a 10-year horizon than repeated patching.
Pitched slate roofs on commercial buildings last much longer, but the nibs that hold slates on the battens eventually weaken with age, leading to slates sliding. The battens themselves and the sarking felt beneath them have a separate lifespan. A roof where individual slates keep slipping is often telling you that a full re-slate is approaching, even if the slates themselves could be reused.
A significant proportion of roofing call-outs relate to problems caused by the original installation rather than wear and tear. Common installation errors on commercial roofs include: insufficient falls on flat roofs; flashings bedded in mortar rather than properly soaked and dressed into the masonry; membrane laps that are too short or inadequately bonded; and insulation boards that were not laid to break joint, creating continuous cold bridges.
When these problems are discovered, a responsible approach is to tell the building owner what caused the issue, not simply to patch the visible damage. A repair that ignores the root cause is a short-term fix at best.
Commercial roofs that are never inspected, gutters that are never cleared, and flashings that are never re-pointed tend to fail faster and more expensively than those on maintained buildings. Annual or biennial inspections on commercial properties allow minor problems to be caught before they become costly. On larger commercial premises, a maintenance log is a straightforward way to keep track of what has been done and what is approaching end of life.
Flat roofs that are accessed for maintenance of plant, air conditioning units or solar panels are vulnerable to physical damage. Membrane systems can be punctured or creased by foot traffic if walk boards are not used. Outlets can be disturbed or blocked by contractors working in the area. Any flat roof that is regularly accessed should have proper access routes and walk boards as part of its design.
For commercial flat roofs, the two systems most commonly used today are torch-on felt and EPDM rubber membrane. Both are suitable for a range of commercial building types, but they differ in how they are installed, how long they last and how they behave under different conditions.
Torch-on felt (also called modified bitumen) is a familiar and cost-effective system for straightforward flat roofs. It is applied in layers using a propane torch, with the top layer typically incorporating a mineral surface finish. It is a proven system but is more susceptible to cracking from thermal movement on large uninterrupted roof areas than rubber membrane systems.
EPDM rubber membrane is a single-ply system bonded or mechanically fixed to the roof deck. It handles thermal movement better than felt, is lighter, and does not require open flame for installation. It is increasingly specified on commercial flat roofs where long-term performance and low maintenance are priorities. Commercial flat roof replacement in the UK typically costs in the region of £70-£120 per square metre depending on system, access, deck condition and existing covering removal. Larger roofs often benefit from economies of scale in material and labour cost per square metre.
Steel-framed agricultural and industrial buildings across this part of Norfolk rely on profiled metal cladding as their primary weather envelope. Cladding systems have a design life, and when they reach it, the options are re-cladding (replacing all sheets) or over-cladding (fixing new profiled sheets over the existing ones). Over-cladding avoids the cost of sheet removal and disposal, and can be done without taking the building out of use for long periods. It is not always appropriate, particularly where the existing sheets are structurally compromised or where insulation needs to be upgraded at the same time.
Colour-coated steel cladding sheets typically carry a manufacturer's coating warranty of 15-25 years, though actual service life depends on orientation and exposure. Signs that cladding is reaching end of life include surface chalking and fading, coating breakdown at cut edges, and visible corrosion at fixings and laps. Fixing replacement is often all that is needed on otherwise sound cladding to restore weather-tightness.
Commercial guttering is not simply a scaled-up version of domestic guttering. Rainfall run-off calculations for large roof areas require correctly sized gutters and downpipes. Undersized guttering on a large commercial roof will overflow in moderate rainfall regardless of how clean it is kept. When guttering is replaced on a commercial building, it is worth checking that the replacement is correctly sized for the roof area, not simply matched to whatever was there before.
For large commercial and agricultural buildings, half-round cast aluminium or pressed steel guttering is often the appropriate choice for its capacity and durability. Cast iron is the most durable but is now rarely used on new work due to weight and cost. uPVC is lighter and lower cost but requires more frequent bracket support on commercial spans to prevent sagging.
Before any roofing contractor starts work on a commercial building, there are some practical questions worth asking:
A contractor who can give clear, specific answers to these questions without hedging is one who has done the work properly before.
If you have noticed any of the warning signs described above, or if your commercial roof has not been inspected in the last two years, call Dereham Roofers to arrange a roof survey. We cover Barnham Broom and the surrounding area, including neighbouring towns and villages across this part of Norfolk and out towards Norwich. We will tell you honestly what we find, what it will cost, and what the options are before any work begins.
No obligation · We usually respond within 2 hours
Storm damage, active leak, damaged ridge - we aim to be on-site within 24 hours.
