What am I likely to pay to replace a flat roof on a commercial building near Ely?

The cost of commercial flat roof replacement depends on the system used, the condition of the existing deck and the complexity of the roof layout. Torch-on felt and EPDM rubber are the two main options, and the price difference between them is often less significant than the deck condition - a rotten or waterlogged deck adds to the cost regardless of the membrane chosen. A site visit is the only reliable way to give you an accurate figure.

How do I know whether my commercial roof needs repairing or replacing?

The main indicators that point towards replacement rather than repair are widespread blistering or delamination across the membrane, a saturated or soft deck beneath, multiple previous repair patches that have not held, and water damage appearing in several different locations inside the building. Isolated damage to flashings, outlets or a single section of membrane can often be repaired cost-effectively if the rest of the roof is sound. We can inspect the roof and give you an honest assessment before you commit to anything.

Can you work on a commercial roof while the building is still in use?

Yes, in most cases. Work can be phased so that only one section of the building is affected at a time, and the exposed area should be made weathertight at the end of each day. For sensitive premises such as food units or schools, we discuss the programme and any specific requirements at the survey stage. Scaffolding, access and noise all need to be planned around the building's normal operation.

Lead Work in Mildenhall

Lead Work · Mildenhall

Expert Lead Work
in Mildenhall

Lead Work That Lasts - Choosing the Right Materials

Lead sheet is the traditional benchmark for roofing flashings, valleys and flat roof edges - and for good reason. When the correct grade is used and fixed properly, it is one of the most durable materials available for sealing roof junctions. But not all lead is the same, and not all alternatives behave the same way. Understanding what is available helps you have a more informed conversation with your roofer and spot when corners are being cut.

Lead Sheet - Codes and What They Mean

Lead sheet for roofing is graded by thickness, described as a "code" number. The higher the code, the thicker and heavier the sheet. The main codes used in domestic roofing are:

Code 3 (1.32 mm) - Too thin for most external flashing applications. It is sometimes used for soakers (the small individual pieces tucked under each tile at a step flashing), but not for exposed flashings or valleys. Any roofer proposing code 3 for a chimney flashing or valley lining should be asked why.
Code 4 (1.80 mm) - The standard minimum for most external flashings, including chimney aprons, step flashings, and parapet cappings. This is what British Standard BS EN 12588 recommends for the majority of domestic applications.
Code 5 (2.24 mm) - Recommended for back gutters behind chimney stacks, wide valley linings, and any location where water is likely to pond or where the sheet will carry significant weight. It is heavier, costs more per metre, but lasts longer in demanding positions.
Code 6 (2.65 mm) and above - Used on commercial buildings, historic properties and specialist applications. Rarely needed on a standard domestic roof but occasionally specified by conservation officers on listed buildings.

Typical lead sheet prices in the UK currently run from around £25 to £45 per square metre for the material alone, depending on the code. The labour and access costs sit on top of that.

Why Bay Length Matters

One of the most important but least visible aspects of a lead job is how the sheet is laid out in bays. Lead expands when it warms and contracts when it cools. A sheet dressed in a single run of more than roughly 1.5 metres will develop fatigue cracks over time as it repeatedly moves. British Standard practice requires flashings to be installed in individual bays with lapped joints between them to allow that movement freely.

A roofer who dresses a chimney back gutter in a single sheet without expansion joints is cutting a corner that will fail - it is just a question of when. Ask specifically about bay lengths before work starts.

Lead Alternatives - When Are They Used?

Several lead-alternative products exist on the market, most commonly aluminium-faced self-adhesive strips and roll-on lead-look membranes. These are cheaper to buy and quicker to install. The honest assessment is that they are not equivalent to properly fitted lead sheet, and most experienced roofers would not use them on a chimney or valley on a house they wanted to stand behind. They have shorter service lives, are more vulnerable to UV degradation, and some are not compatible with certain roof coatings or treated timbers.

That said, some self-adhesive flashing tapes have a legitimate use as a temporary patch while a full repair is arranged, or in very confined locations where lead cannot be dressed easily. They are not a permanent solution for a chimney stack or a full valley lining.

EPDM for Flat Roof Edges

Where lead has historically been used as a trim on flat roof edges, EPDM rubber sheet is a viable alternative that has grown in popularity. It is flexible, handles movement well, and resists frost without cracking. For flat roof perimeters and upstands, it performs well and is worth discussing with your roofer as an option alongside lead. For chimney flashings and roof valleys, lead remains the first choice.

The Honest Pros and Cons of Lead Sheet

Pro: Long service life - properly installed code 4 and code 5 lead can last several decades without needing replacement.
Pro: Highly malleable - it can be dressed to almost any profile, making it suitable for complex chimney geometries, curved surfaces and awkward junctions.
Pro: Self-healing to a limited extent - minor surface oxidation actually forms a stable patina that protects the metal beneath.
Con: Cost - lead is more expensive than alternatives, both in material and labour (dressing lead correctly takes more time than sticking down a tape product).
Con: Theft risk - lead is a valuable scrap metal, and flat roofs or low-pitched sections are vulnerable where accessible from ground level or neighbouring structures.
Con: Weight - on very large flat roof areas, the cumulative weight of lead sheet is a structural consideration, though on domestic flashing applications this is rarely a problem.
Con: Runoff from new lead - freshly installed lead sheet sheds a small amount of lead carbonate in rainwater runoff until the patina fully forms. This is a minor consideration for homes with water butts collecting from that roof section.

What Good Lead Work Actually Looks Like

A properly completed lead job has no visible gaps between the lead and the masonry, no exposed nail or screw heads in weathered positions, and lead tacks (clips) holding each bay in place so the sheet cannot lift in wind. The mortar pointing over the top edge of a flashing should be a neat, raked joint rather than a thick smear of mortar plastered across the face of the lead. Sloppy pointing traps water rather than shedding it.

At a chimney, the step flashings on each side should interleave with soakers - separate individual pieces tucked under each tile course - rather than being a single strip of lead folded over the tiles. Without soakers, a step flashing is only as watertight as the tiles allow, and that is not enough.

Typical Costs for Lead Work in the UK

Lead work pricing varies with access difficulty, the size of the area and the code of lead specified. As a rough guide, a straightforward chimney flashing repair - replacing a failed front apron or re-pointing loose step flashings - typically runs from around £200 to £500. A full chimney re-flash, replacing all components including step flashings, soakers, back gutter and front apron, commonly falls between £500 and £1,200 depending on stack size and access. A new valley lining on a typical semi-detached house is often in the £400 to £900 range. These figures are for the work itself; scaffold or tower hire adds to that if the pitch or height demands it.