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 Wimblington

Lead Work · Wimblington

Expert Lead Work
in Wimblington

Why Lead Work Fails - and What to Look For

Lead flashing is the sealing layer between your roof covering and any vertical surface it meets - a chimney stack, a parapet wall, a dormer, or a roof valley. When it fails, water finds a path into the roof structure and from there into ceilings and walls. The damage that follows is rarely limited to one spot, because water travels before it shows itself.

Knowing the warning signs early saves you from a much larger repair bill. Below is what to look for from the ground and inside the property.

Warning Signs You Can See from the Ground

You do not need to get on a roof to spot most lead work problems. A pair of binoculars and a dry day is enough for a useful first look.

Flashing that has lifted or rolled back. Lead is a soft metal and it moves with temperature. If it was not fixed correctly or the mortar joints holding it have crumbled, sections can peel away from the wall entirely, leaving a gap behind.
Cracked or missing mortar in the step or cover flashing joints. The top edge of most flashings is tucked into a raked mortar joint (called a chase) in the brickwork. When this mortar cracks or falls out, the flashing is held only by its own weight and wind can lift it.
Lead that has split or cracked. Over many years, lead work-hardens through repeated heating and cooling. Cracks appear first in areas that flex most - typically the corners of chimney flashings and the points in valley gutters. A cracked flashing cannot seal water.
Patches of sealant or mastic. Black mastic applied over a flashing joint is a sign of a previous repair that has failed or was only ever temporary. Mastic shrinks and cracks; it is not a long-term solution for lead.
Staining on brickwork below the flashing line. Dark tide marks or efflorescence (white salt deposits) running down brickwork below a chimney or parapet often trace back to water entering behind or under the flashing.
Slipped lead soakers in a tiled valley. Soakers sit under each course of tiles at a roof junction. If tiles have been lifted and re-laid without replacing soakers, or if soakers were never there, the valley will leak in heavy rain.

Warning Signs Inside the Property

Internal signs are often the first thing homeowners notice, but they rarely point directly at the source. Water entering through a flashing at the ridge can travel several metres along rafters or sarking felt before dropping onto a ceiling.

Brown or yellow staining on ceilings or upper walls. A tidemark that grows after rain is almost always a roof leak. Staining that appears in dry weather is more likely condensation or a plumbing fault.
Damp patches near a chimney breast. A chimney breast that feels damp in winter is a strong indicator of flashing failure, particularly if the chimney is no longer in use and has been capped but the stack is still exposed to rain.
Peeling plaster or wallpaper on a top-floor exterior wall. Parapet flashings and gutter linings on flat sections of roof often shed water onto the inside face of a wall when they fail. The plaster carries the moisture evidence long before the structural damage is obvious.
A musty smell in the loft. Timber roof members can absorb moisture from a slow leak for months before visible staining appears on ceilings below. A damp, musty loft with no obvious condensation source points to water ingress through the roof covering or its flashings.

What Causes Lead Work to Fail

Lead flashing that was correctly installed to British Standard and in the right code weight can last several decades without needing attention. Most of the failed lead work we see has one or more of the following root causes.

Underweight lead. Lead sheet is graded by code number, which reflects its thickness and weight per square metre. Code 4 (1.8mm) and code 5 (2.24mm) are the standard weights for most residential flashings. Code 3 is sometimes used by price-cutting roofers because it is cheaper, but it work-hardens and cracks much sooner than it should, particularly in exposed positions around chimneys.

Overlong sections. Lead expands and contracts with temperature changes. Individual sections of flashing must not exceed 1.5 metres in length, or the movement causes the metal to buckle and eventually split. A common fault in poor-quality work is one long continuous strip across a chimney rather than correctly jointed, shorter pieces.

No lead dressings or clips. The front apron and side flashings on a chimney must be clipped or secured with lead wedges dressed into the brickwork chase. Without fixings, thermal movement works the flashing loose over time, even if the mortar initially holds it.

Failed chase mortar. The mortar bed that holds the top edge of the flashing into the brick joint is exposed to frost and driving rain. Older lime mortars can erode; hard cement mortars can crack as the brickwork moves. Once the chase opens up, water runs directly behind the flashing.

Bodged repairs. Silicone and mastic do not bond permanently to lead in exposed conditions. A previous roofer who sealed a gap with mastic rather than re-dressing the lead properly has only delayed the leak. When the sealant eventually fails - and it always does - water enters through the original fault plus any new gaps the thermal movement has opened since.

What a Proper Lead Work Repair Involves

Good lead work is not simply slapping new material over old. On a chimney, this means stripping all existing flashing back to the brick, cutting fresh chases into sound mortar joints, cutting and dressing new code 4 or code 5 lead sheet to profile, fitting lead wedges to lock the top edge, and pointing over the chase with a mortar suited to the existing brickwork. The lead at the front (the apron) is dressed down over the tiles or slates; the step and cover flashings are dressed up the face of the chimney.

Valley liners and soakers need to be the correct width for the roof pitch. A steeper pitch sheds water faster, so soaker dimensions can differ from one roof to the next. Getting this wrong means the valley holds water at the edges and leaks under the tiles on either side.