How much does it cost to reline a box gutter?

What relining a box gutter involves

A box gutter is a trough that takes water from the meeting of two roof slopes, or from a slope against a wall, and gathers it and carries it to an outlet. A parapet gutter follows the same idea but sits behind a parapet wall. Both are lined with a waterproof sheet, traditionally lead, laid over a timber deck that is cut to falls so that water runs along the channel to the outlet.

Relining means stripping the old lining out and laying a new one. In practice that is a sequence of tasks: setting up access, taking up the old lead, inspecting and repairing the boards and falls underneath, laying a separating layer, forming the new lining with its drips and upstands, dressing flashings at the sides, fitting the outlet and tidying the finish.

It is rarely only the lining. A gutter that has leaked for a time has often soaked the timber below. The boards can be rotten, the falls can have sagged, and the outlet or hopper can be blocked or broken. That is why a figure over the phone rarely holds once the old lining is up, and why we survey first. Our page on box gutters explains how they are built.

Typical UK ranges for the lining

Typical UK ranges, as reported by MyBuilder's flat roof cost guide (2026), are shown below per square metre of finished roof. No figure here is an Empire price.

The same guide puts bitumen felt at £70 to £100 per square metre. For flat roof replacement overall it reports a typical total of £2,800 to £7,500, averaging about £75 per square metre.

Two cautions apply. First, these are rates for roofs, and a gutter is a narrow strip. The area is small, so the rate per square metre often understates the real cost of the labour in tight, awkward places, where most of the effort goes into detail and access. Second, lead costs most because the metal is expensive and the work is skilled, but it is also the covering associated with the longest life when correctly laid, as covered in our answer on how long lead lasts. The quote you receive is fixed and written, and it comes after the survey.

What pushes the price up or down

These are the factors that matter most on a box or parapet gutter.

• Length and width of the channel. Area drives material and time. Long gutters also need more drips, which means more bays and more joints.
• The lead code. Heavier sheet costs more. Parapet and box gutters are normally associated with code 5 and above, a code being the thickness grade of the sheet, from 1.32 mm at code 3 to 3.55 mm at code 8. Our page on lead codes lists them.
• Access. A gutter behind a Georgian parapet may only be reachable from scaffold, a tower or a platform. MyBuilder puts scaffolding for a whole roof at about £1,125 as a general guide, and on a terraced street the scaffold can be the largest single item after the metal.
• Condition of the deck. Replacing rotten boards, adding firring pieces to restore the fall or treating timber adds cost. BS 6229:2018 best practice, as quoted by Rockwool, is to design gutter beds to a fall of 1:40 so the finished fall reaches 1:80. We find out when the old lining comes off, and we tell you before going further.
• Detailing. Drips, upstands, returns at corners, a secret gutter or an awkward junction with a chimney each add labour.
• Outlets and hoppers. A new outlet, hopper head or length of cast downpipe adds cost, and the old fittings are sometimes the cause of the problem.
• Waste and clearance. Old lead has scrap value, but boards, felt and debris need removing and the site cleared.
• Constraints on a listed building. Replacement is expected to match the original, and listed building consent comes from B&NES.

Lead, EPDM or GRP in a gutter

The cheaper linings are real options on some roofs, and the choice is not simply about price. Lead has the best long record on historic buildings. It can be dressed into complex shapes and its patina matches period stone and slate. Where a listed building or a conservation area is involved, like-for-like material is usually expected, so speak to B&NES before any change.

EPDM is a rubber membrane that is simple to lay in a single piece, which suits a long, straight gutter with few details. GRP is glass-reinforced plastic that is laid wet and sets hard in place. We cover that option in our answer on GRP box gutters. Both can leave a different look at the edges and are less adaptable around complex junctions. Their life depends on the product and the workmanship. Typical published lives, which vary with exposure and workmanship: GreenSpec gives EPDM 20 to 30 years and Less gives GRP 25 to 40 years, while Less puts a properly laid lead flat roof at 50 to 100 years.

On an unlisted house a lighter lining may make sense, especially if lead theft is a worry, as stolen lead and insurance explains. We say what each option gives you and what it gives up. Repair comes first where it will hold, and older roofs get matching materials.

Getting a quote you can compare

When you collect quotes for relining, ask each roofer to set out the same things. Without them, two prices will not mean the same thing.

• The material and, for lead, the code.
• The length and width of the gutter and the number of drips.
• Whether the boards and falls are included or are an extra if found to be bad.
• The outlet and any new hopper or pipe.
• Scaffold or access, and who arranges it.
• Waste removal and clearing the site.
• The guarantee, and what it covers.

A low price that leaves out scaffold, or that covers the lining but not the boards, is not low. A price that rises when the old lining comes off is a sign the survey was not thorough.

The survey is free, and pictures of your own roof show the condition of the lining before any price is agreed. Your fixed price is in writing and does not move on the day, and the work carries a written 10-year workmanship guarantee. Where the existing lead can be welded or lapped rather than renewed, we explain that too, as covered in our answer on lead welding. For the whole range of lead work, see lead roofing.