Installing standing seam roofing: single or double lock seam, fixed and sliding clips

Standing seam roofing is installed on roof boarding, over a separation mat, and is fixed with concealed clips: the sheet is not drilled. The panels are closed to one another by a seam, a double lock seam at low pitches and a single lock seam at pitches of at least 25°. Installation runs from the eaves towards the ridge and from right to left. Below are the BELPROFILE installation principles, one by one.

What is the seam, and when is it made single or double?

The seam is the raised joint between two adjacent panels: their edges are folded over one another and pressed tight. In a single lock seam the fold is made once, in a double lock seam twice. This is also where the name double lock standing seam roofing comes from.

• The double lock seam is used on roofs with a low pitch: the installation principles require it from 5°. It makes the roof covering watertight.
• The single lock seam is used on roofs with a pitch of at least 25°.

The seams of pre-profiled panels are closed with special pliers or with a seaming machine.

What is standing seam roofing installed on?

• The roof boarding. Dry boards 24 mm thick, 80 to 140 mm wide.
• The separation mat with a breather membrane. It is laid on the roof boarding and over the eaves flashing. It is a 180 g/m² breather membrane with a mat of polypropylene filaments, 7–8 mm thick. It keeps the sheet from touching the membrane, which can be damp because of condensation, evens out the surface and reduces the noise of the rain.

Fixed clips and sliding clips

The clips fix the panels to the roof boarding and stay concealed in the seam. Fixed clips stop the panels from sliding. Sliding clips have a fixed base on which the upper part slides, so the panel can expand and contract freely along its length.

• On short panels, under 2 m, only fixed clips are used.
• On long panels sliding clips are used as well, according to the installation diagram of each roof; the technical data sheet requires them for sheets over 3 m.

Why it matters: a steel panel changes its length by about 1.2 mm for every metre, at a temperature difference of 100°C, and an aluminium one by about 2.4 mm. On a 10 m panel that means 12 mm and 24 mm respectively.

The order of installation

1. The gutters and the eaves flashing. The components that collect the water are installed before the panels.
2. The separation mat, on the roof boarding and over the eaves flashing.
3. The valley, at the junction of two roof slopes. It is fixed with clips; drilling it is forbidden.
4. The panels. The geometry of the roof is checked beforehand. Installation starts from the eaves towards the ridge, from right to left.
5. The seaming, single or double lock, depending on the pitch.
6. The high hook-in profile, on either side of the ridge. It is fixed to the panels with pop rivets, over double-sided adhesive butyl tape, which takes the place of a gasket.
7. The straight ridge, over the high hook-in profile: it is fixed into the profile, without piercing the panel.
8. The gable flashing, where the roof is closed at the side.

How is the roof ventilated?

Through the perforated “Z” and “C” profiles. The “Z” profile is installed on the panels with pop rivets and butyl tape and holds the ridge; it is recommended on roofs with a pitch of at least 15°. The “C” profile is used for installation on double roof boarding and keeps wasps and bees from nesting in the ventilated area.

What sizes are the panels?

BELPROFILE standing seam roofing is made to order: widths from 260 to 730 mm and lengths from 1 to 12 m, in 0.50, 0.55 or 0.60 mm steel or in 0.70 mm aluminium. The panels can also be profiled with a taper, for round surfaces.

What is it cut with and how is it stored?

The sheet is cut with metal shears, electric or hand; cutting with an angle grinder is strictly forbidden. The filings are removed with a soft brush, and the cut edges are protected with touch-up paint. The panels are stored only in their original packaging, on rigid, dry platforms.

In short

24 mm roof boarding, a separation mat, concealed fixed and sliding clips, a double lock seam at low pitches and a single lock seam from 25°, a ridge fixed without drilling the panels. For a roof that is simpler to install, with the same look, there are click roofing sheets, from pitches of 12°. For your project, request a quote: the BELPROFILE team offers technical advice from design to installation.