Sheet Metal Works: price per linear metre 2026 and installation steps

A sheet metal worker, in many countries also called a tinsmith, works with thin metal sheet and the parts made from it. On a family house this mainly means gutters and downpipes, metal cappings on window sills, parapets and low walls, flashing around chimneys, roof windows and other penetrations, and metal roofing joined with seams. The roofer lays the roof covering itself: tiles, shingles or profiled metal sheet. The line between the two trades is thin. Chimney flashing and valleys are built together with the roof covering, and one simply does not work without the other.

So before work starts, agree who is responsible for which detail. In practice it often happens that the roofer lays the tiles and the sheet metal worker turns up a month later. By then the flashing can only be glued or siliconed onto the finished roof. That lasts a few seasons. Then the sealant hardens, comes away, and water finds its way under the covering. When one crew does both jobs, or both trades stick to a shared schedule, the flashing is slid under the covering and lapped the way the system manufacturer specifies.

The material you will meet most often is galvanised steel sheet, either bare or with a coloured coating, often sold as pre-painted or plastic-coated sheet. The coloured layer protects the zinc from the weather, but bending and cutting can damage it. Cut edges and scratches therefore need a coat of the touch-up paint the manufacturer recommends. Skip this, and corrosion slowly creeps from those spots under the coating.

Titanium zinc is a zinc alloy with small amounts of titanium and copper. It forms its own protective patina, and if you scratch it, the patina grows back over time. It is joined by soft soldering with tin, so even complicated shapes can have watertight joints. It has one quirk, though: it does not like the cold. Manufacturers usually say that if the material is below roughly 10 °C, it should be warmed before bending, otherwise it can crack at the bend.

Copper is mostly seen on historic and prestige buildings. After fitting, it first turns brown, and the familiar green patina comes slowly, usually only after many years, depending on the local air. Aluminium is light and does not rust, but it must not touch fresh mortar, concrete or lime render directly. Their alkaline moisture eats into it. Keep this in mind if your window sills are being fitted into external insulation or render.

When two different metals touch and there is moisture around, they form a galvanic cell. The less noble metal then corrodes faster. Compared with copper, zinc, galvanised sheet and aluminium are all the less noble ones. What few people know is that the metals do not even have to touch. Water running off a copper roof or copper flashing carries dissolved copper ions. When it lands in a galvanised gutter below, it gradually eats small pits into it.

The rule is simple: in the direction the water flows, copper may sit below zinc or aluminium, never above it. On older houses this rule is broken quite often. A cheaper galvanised gutter is connected to an original copper detail, the joint looks fine, and a few years later small holes appear in the bottom of the gutter. In a similar way, titanium zinc suffers under old bitumen felt, which can shed acidic water. Manufacturers recommend a protective coating or a different material in such places.

Gutter size and the number of downpipes depend on how much roof drains into the gutter and how heavy the rain gets in your area. The roof area is measured in plan, as seen from above, not along the slope. In shops, gutters are labelled by diameter or by the girth of the sheet, which is its width before forming, and downpipes by diameter. Every manufacturer publishes tables showing what roof area a given gutter and downpipe can reliably handle. On an ordinary roof, sizing by eye usually works out. On large areas, steep roofs and long eaves, it tends to end with water spilling over the edge in a summer storm.

Fall, brackets and expansion

The gutter has to slope towards the outlet, usually by a few millimetres per metre according to manufacturers. Got a long eaves line? Adding another downpipe is more sensible than increasing the fall. A steeply sloping gutter is visible on the facade and ends up sitting high above the eaves at the far end.

Bracket spacing is set by the manufacturer, usually up to one metre, and less in mountain areas with heavy snow. A metal gutter gets longer and shorter as the temperature changes. Long straight runs are therefore split with an expansion joint, or the downpipe is placed so the gutter can move freely in both directions. Depending on the material and manufacturer, expansion joints usually go in roughly every 10 to 15 metres.

Think about snow too. On a roof without snow guards, it slides off all at once and can tear away the gutter along with its brackets. Snow guards above the eaves protect not only the people below but also the gutters themselves.

An external window sill has one job: to carry water from the window as far from the facade as possible. For that it needs a fall outwards, a drip edge that projects beyond the face of the wall, and side end pieces that let the sheet expand. If the sheet is built rigidly into the reveal with no room to move, it buckles as the temperature changes. The render then cracks at the side ends, and water gets into the insulation through the cracks.

When a facade is insulated, the window sill is not a separate job for the end. It is part of the insulation system and goes in at the right point in the sequence: under the bottom window profile or into the connection strip, before the final render coat. Original short sills do not reach past the new insulation thickness, so water runs straight down the render. The typical result is dark streaks below the windows and insulation that slowly gets damp.

A chimney stands still, while the roof around it moves slightly. The flashing should therefore never be fixed rigidly to both the chimney and the roof covering at once. A two-part solution has proved itself. The flashing is turned up the side of the chimney and slid under the covering, and a separate cover flashing, set into a chase cut in the chimney, laps over it from above. Trade rules usually give the upstand above the covering as around 15 cm.

Behind a wider chimney, water from the roof collects, and snow and leaves get stuck there. For wider chimneys, a small saddle, often called a back gutter or cricket, is made behind it to send the water off to the sides. You cannot see this detail from the ground, and that is exactly why it tends to be left out on cheap jobs. The same principles apply to roof windows, vent pipes and solar panel penetrations. There, the manufacturer's own flashing kits are the preferred choice.

Parapet capping needs to fall towards the roof so water does not run down the facade. The sheet is held with clips or a continuous support profile, not with screws through the top surface. Every hole in that horizontal face is a place where water can get in. Depending on the material, joints are made with seams, with overlaps and a seal, or by soldering.

A standing-seam roof is joined by raised seams that are closed by hand or by machine. It is fixed to the deck with hidden clips, some fixed and some sliding, so the metal can expand. Many people think standing-seam roofing also suits a completely flat roof. It does not. Manufacturers set a minimum pitch, usually a few degrees, and at low pitches they ask for a double-lock seam, sealing tape and a suitable underlay. Under the metal you also need ventilation or a separating layer, otherwise condensation damages the sheet from below.

Replacing gutters and flashings like for like is usually treated as maintenance. The rules differ from country to country, though, and sometimes from one municipality to the next. Check your local building regulations and ask the local building authority before you start, rather than assuming nothing is needed. If the roof shape changes, or the house is listed or in a conservation area, agree the approach in advance with both the building authority and the heritage authority. In a block of flats, work on the roof and facade is decided by the building management or the owners' association.

On many houses, the metal gutter system is connected to the lightning protection, or the down conductors run right next to the downpipes. When gutters and downpipes are replaced, that conductive connection must not be broken and the clamps must not be removed. Any changes to the lightning protection and its inspection afterwards may only be done by a qualified electrician or lightning protection specialist.

If you want to connect downpipes to the drains, the conditions of the sewer operator and the municipality apply. You are usually not allowed to send rainwater into a foul sewer, and more and more often you are asked to hold the water back or let it soak away on your own plot. Find out these conditions before you reroute any downpipes. One more thing: work on a roof is work at height. The contractor must provide fall protection in line with health and safety rules.

If your house has a low eaves line, you can handle routine gutter cleaning yourself. For taller houses, steep roofs or any job that means climbing onto the roof, leave it to a company with proper equipment for work at height.

1. Stand the ladder on firm, level ground, secure it against slipping and ask someone to hold it.
2. Remove leaves, needles and silt from the gutter with a gloved hand or a plastic scoop, not a metal tool that scratches the surface.
3. Clean the strainer or leaf guard basket in the outlet above the downpipe.
4. Flush the gutter with a hose from the far end towards the outlet and watch that the water flows smoothly and does not stand anywhere.
5. Check that the downpipe is clear, and if it drains slowly, clear the blockage from below through the access fitting or the rainwater trap.
6. Clean the rainwater trap at ground level and remove settled tile grit and other dirt.
7. Inspect brackets, joints and pipe clips and note any spots with corrosion, looseness or dripping for a professional to repair.

Check the sheet metal details before the scaffolding comes down. Heavy rain is the ideal test, otherwise use water from a hose. At handover, go through these points:

• Water in the gutter runs to the outlets and does not stand in the gutter after rain
• Brackets are evenly spaced as the manufacturer specifies and the gutter does not sag under hand pressure
• Joints, corners and gutter ends do not drip and long runs have an expansion joint
• Downpipes are plumb, pipe clips are firm and downpipes discharge into a trap or away from the foundations
• The conductive connection to the lightning protection is intact and the contractor has pointed out the need for an inspection
• Window sills fall outwards, have a drip edge beyond the facade and side end pieces that allow expansion
• Chimney flashing is turned up above the covering and lapped by a cover flashing, not just sealed with mastic
• Parapet cappings fall towards the roof and no screws are visible in the top surface
• The coating is not peeling at cut edges of coloured sheet and copper is not fitted above zinc or aluminium
• The contractor has given you information on the material used, the system manufacturer and the warranty terms