Standing seam is a way of joining sheet metal rather than a material. Panels run from ridge to eaves and are folded together at raised upstands, so the joints sit above the water rather than in it. That is why it works at pitches a tile cannot and why it appears on modern extensions, dormers and low slopes where nothing traditional would keep water out.
The metals, and what each is chosen for
Zinc is the common British choice on domestic work and weathers to a matt grey that most planning officers accept. Aluminium is lighter and comes pre finished in a colour range, which suits an extension meant to look deliberate rather than traditional. Copper is the longest lived and the most expensive and turns green over decades. Coated steel is the commercial default and the cheapest per square metre. All four are formed the same way, and the price difference is the metal and the fabricator's time rather than the technique.
Where standing seam actually earns its price
Low pitches are the honest case: a covering that would need twenty five or thirty degrees to shed water safely is replaced by one that works at three or five, which is what makes a flat looking extension roof possible without a membrane. Curved and tapered roofs are the second case, because sheet can be rolled to a shape a tile cannot follow. On an ordinary steep gable roof it is an aesthetic choice, and it is a dear one.
What separates a good installation from a leaking one
Movement is the whole problem. Metal expands and contracts far more than the deck under it, so the clips have to allow the panel to move while holding it down, and the fixings at the head and foot have to be detailed for it. Underneath, a separating layer stops the metal sitting on a substrate that will hold moisture against it. Most standing seam failures are movement restrained by a well meant extra fixing, or condensation from a build up nobody ventilated.
Questions people ask about standing seam metal roof
Does a standing seam roof need planning permission?
On a house, changing the roof covering material can take the work outside permitted development, and in a conservation area or on a listed building it almost certainly will. It is worth a call to the local planning authority before ordering metal.
How noisy is a metal roof in rain?
Far less than people expect on a warm deck build up, because the insulation and the boarding underneath damp the sound. It is noticeable on an uninsulated outbuilding, where the sheet is fixed to purlins with air behind it.
How long does a standing seam roof last?
Longer than most owners will need, when it is detailed for movement and ventilated correctly. The failures that shorten it are almost always workmanship at the clips, the upstands and the perimeter rather than the metal itself.