How is commercial roofing priced - per square metre or as a fixed project cost?

Most commercial roofing contractors price by the square metre for material and labour, then add a fixed allowance for access equipment, drainage work and any deck repairs found during stripping. For flat roof replacement in the Newmarket area, expect roughly £70 to £120 per square metre for torch-on felt and £80 to £140 per square metre for EPDM rubber, with larger roof areas typically attracting a lower per-metre rate. Always ask for the deck repair rate to be specified separately so you are not surprised if the boards beneath the old membrane need replacing.

How do I know if my commercial roof needs a full replacement or just a repair?

A repair is appropriate when the membrane or covering is broadly sound and the failure is localised to a specific area such as a flashing, a single split or a blocked outlet. Once a flat roof membrane shows widespread crazing, multiple blisters or perished laps across the whole surface, patching becomes uneconomical because new failures appear faster than old ones are fixed. A proper roof survey, which involves inspecting the membrane, drainage, flashings and any penetrations, will give you a clear picture of whether repair or replacement is the better investment.

Can commercial roofing work be carried out without closing my business?

In most cases, yes. Flat roof replacement on a commercial building is done from above, so the business beneath can usually continue operating normally. Work that involves cutting through the deck, removing rooflights or working near open edges above occupied areas requires more careful planning and may need to be phased or done outside business hours. Discuss this at the survey stage so the contractor can factor access requirements into the programme and the price.

Flat Roofing in Waterbeach

Flat Roofing · Waterbeach

Expert Flat Roofing
in Waterbeach

What Flat Roofs Are and Why They Fail

Flat roofs cover extensions, garages, porches, and outbuildings. They are built in layers: a structural deck, insulation, and a waterproof membrane. The most common systems are EPDM rubber and torch-on bitumen felt. Both are durable when properly installed, but all flat roofs are vulnerable at their edges, upstands, and any point where the membrane is penetrated by an outlet, pipe, or skylight.

Most leaks do not come through the open field of the membrane - they come from a failed edge trim, a lifted upstand, a cracked flashing, or a poorly sealed outlet. Water that enters the build-up at one of these points can travel a long way before it shows itself as a damp patch on the ceiling inside, so the visible wet patch is rarely directly beneath the actual entry point.

Spotting a Flat Roof Problem Early

A leak does not always announce itself with a drip. Early signs that something has failed include a damp or musty smell in the room below the roof, a faint tide mark on the ceiling that appears after heavy rain, or a ceiling that feels soft when pressed. By the time water is dripping, the deck or insulation is already saturated.

From a safe position - either from ground level or a stable ladder at the gutter - look for blistering or cracking on the membrane surface, any section of the perimeter trim that has lifted or pulled away, and upstands that are peeling away from the wall. Any of these warrant a roofer's attention promptly.

What to Do While You Wait for the Roofer

If the roof is actively leaking and a roofer cannot attend immediately, there are steps you can take inside and outside the property to reduce damage. Do these things rather than attempting to repair the roof yourself.

Inside the building: Place buckets or trays to catch drips. If water is pooling behind a ceiling and starting to push on a plasterboard panel, you can make a small hole with a nail or screwdriver at the lowest visible point to let the water drain in a controlled way. This relieves the pressure and prevents a much larger area of ceiling from collapsing. Put down towels or sheeting to protect flooring.
Move valuable items: If the room below is used for storage, move anything water-sensitive away from the area beneath the leak. Flat roof leaks are rarely emergency floods, but sustained slow ingress will damage anything left directly below.
Photograph the damage: Take photos of the damp area, the staining pattern, and any visible membrane damage from a safe position. A timestamp on the photo helps if there is any question later about when the problem started. These images are also useful for the roofer when they arrive.
A weighted tarpaulin: If you can safely reach the roof surface from a hatch or a very low edge, and if the membrane damage is visible and located, a tarpaulin can be laid over the problem area and weighted down at the edges with sandbags or bricks. The tarpaulin must extend past the damaged area and be secured at the edges - an unsecured sheet will lift in wind and can cause more damage than it prevents.

What Not to Do Yourself

There is a clear list of things that are tempting but genuinely counterproductive when a flat roof is failing.

Do not walk on the roof without knowing the deck condition. If the deck has been taking water for any length of time, the timber boarding may be soft and unable to take your weight safely. A section that appears sound can give way without warning, particularly if it is chipboard decking that has been wet repeatedly.
Do not apply roofing sealant, waterproofing paint, or bitumen repair products over a leaking area. These products are sold in DIY stores as temporary fixes, but they bond poorly to cold or damp surfaces, they rarely locate and seal the actual entry point, and they make a proper repair significantly harder afterwards. A roofer working over a patch of dried DIY sealant has to clean it off before laying a new membrane - that adds time and cost.
Do not use a pressure washer on the roof surface. High-pressure water will force itself under edge trims and seams and can strip the protective mineral surface from torch-on felt. If there is debris on the roof that you want to clear, use a soft brush from a safe position at the edge.
Do not delay getting a proper inspection. A flat roof that is showing signs of failure but is not yet actively leaking will eventually leak. Water in the insulation layer accelerates deck rot, and by the time a ceiling stain appears the structural timber underneath may already need replacing. Catching a problem at the membrane stage is far less expensive than catching it at the deck or joist stage.

What Happens When the Roofer Arrives

A proper flat roof inspection is carried out from roof level, not from a ladder at the edge. The roofer should check the full perimeter, all upstands, every penetration, and any area of visible surface damage. On a torch-on felt roof, they should press gently on any blisters to assess whether there is moisture underneath. On an EPDM roof, they should check seams and bonded edges.

The roofer should be able to tell you where the water is entering, what caused it, and whether the rest of the roof is in a condition that makes repair worthwhile or whether the system has reached the end of its life. You should expect a clear verbal explanation and, for any significant work, a written quote that specifies the material, the scope of work, and what is included in the price.

Repair or Replacement: a Quick Guide

A flat roof that has a single localised failure on a system that is otherwise sound - a lifted upstand, a failed outlet collar, a split near an edge trim - is generally worth repairing. Repair costs for localised flat roof work typically run from £150 to £600 depending on extent and access.

A roof that has multiple failure points, widespread blistering or cracking, or a deck that has been damaged by water ingress is usually better replaced. Full replacement costs in the UK typically range from £70 to £120 per square metre for a quality system. A 15 square metre garage roof might cost £1,200 to £2,000. These are realistic ranges rather than fixed prices - only an inspection and a written quote give you a reliable figure.