For every roof...

Seamline standing seam roofing on a private building in the Jizera Mountains.

The standing seam roofing is a high-quality and time-tested way of roofing buildings. The material for the standing seam roofing Lindab Seamline is sheet metal designated as PLX. This is a special type of cold-rolled steel sheet with a fine-grained structure, hot-dip galvanized. Due to this grain size, the material is significantly more formable than standard galvanized metal, despite the sheet having a thickness of 0.6 mm. The sheet is also coated with a paint finish available in 15 different colors. The 50 µm thick polyester paint layer provides additional protection to the steel core alongside the galvanization and allows the material to achieve a lifespan of up to sixty years. Additionally, a protective film is applied at the factory, which helps to eliminate minor surface damage during installation. This film is removed after the roof is completed.

The principle of the standing seam roofing is based on strips of sheet metal with an open standing seam – the fold, laid from the eave to the ridge of the roof. The strips are joined laterally by closing the aforementioned double standing seam. The seam is approximately 3 cm high and consists of a double-turned edge of the metal strip. Clips are inserted into the fold to secure the roofing to the substrate, typically consisting of wooden boarding. The boards can be replaced by OSB sheets. The substrate must provide sufficient support for the fastening of the clips. The resistance against the tearing out of the screws must be greater than the anticipated suction force of wind on the building, which acts on the surface of the roofing. The longitudinal spacing of the clips is max. 45 cm. The lateral distances are dictated by the width of the strip, namely 60 cm. To allow the metal sheet to expand in the longitudinal direction, so-called sliding clips are installed on part of the roof, allowing the movement of the strips caused by thermal expansion. If a large roof is equipped only with sliding clips, there is a risk of wave formation in the sheet or gradual loosening of the clips. It is recommended to insert an additional waterproofing layer between the roofing and the substrate made of a diffusion membrane or non-sanded bitumen. Diffusion membranes equipped with a wire mesh are very suitable, as they define a gap between the sheet and the substrate. This allows for partial ventilation of the roofing and smooth drainage of possible condensate. If condensation is expected to occur in larger quantities, the roof assembly should be designed to ensure ventilation in the space under the boarding (ventilated ridge, etc.).

Lindab Seamline roofing is anchored using sliding clips that allow the movement of whole strips due to temperature changes

After closing the seam, the roofing forms a solid unit that cannot be disassembled, therefore care must be taken in processing every detail. Due to the compactness of the standing seam roofing, it can be installed on slopes starting from 3.6º. It is often also a complement to roofs with tiled roofing, which cannot be used on mansard roofs and dormers with a small slope. A curved roof is also not a problem for this roofing, although the strips need to be curved. However, the minimum radius should not be less than 15 m.
In the case of smaller areas, standing seams can be built and closed manually. For larger areas, it is better to use machinery, which significantly improves the quality of the work and speeds up the installation process. Lindab is one of the few companies on the Czech market that provides a set of tools for folding with its material. The first step in preparing the folds is carried out by a profiling machine – a folder. Once installed on the roof, it is time to use the folding machine, which smoothly closes the fold into its final shape thanks to a series of shaping wheels. If the slope of the structure falls below 7º, it is recommended to insert an additional sealing component into the fold. This can be double-sided adhesive tape, folding oil, or regular silicone sealant. All these elements ensure the filling of the fold and prevent water infiltration into the roofing assembly. Capillary action through the fold poses a risk, particularly when melting snow remains on shallow slopes.

Clips for anchoring standing seam roofing

The wide range of color shades of Lindab Seamline roofing satisfies the aesthetic demands of customers and gives architects and design offices a broad field for creating various types of buildings. The processing and installation of this type of roofing are subject to strict quality requirements and correct roof assembly design. If these aspects are met, one can expect maintenance-free roofing for many years.

In connection with the recommendation of standing seam roofing for use especially in mountainous areas and places with harsh weather conditions, questions arise, which are answered by Štěpán Lášek, product manager of Lindab Seamline, Coverline, Lindab s.r.o.

What can be the effect of snow cover on the surface of the Lindab Seamline metal roofing?
The presence of snow does not have a direct negative effect on the surface or core of the Lindab Seamline roofing. Essentially, it is a coated steel sheet. The paint is hardened, and snow or ice cannot scratch it. This can, however, happen during movement on the roof or when removing snow with metal tools, so caution is warranted during these activities.

What measures are needed when the building is in extreme weather conditions?

Seamline roofing is suitable for slopes from 3.6° and for curved roofs. In the picture, the roof is equipped with snow guards.

The term extreme weather condition is hard to define due to current instability and unpredictability of weather. Conditions that we were used to in mountainous regions may now appear in cities and lowlands, just as spring temperatures can unexpectedly surprise us in the mountains. Therefore, it is advisable to always use a higher degree of safety than is common for the region (or used to be common). In standing seam roofing, it is customary to increase the safety of the roofing by sealing the seams. Also, safe overlaps and necessary openings and penetrations should not be underestimated. Sealing of the seams is today most commonly done with self-adhesive EPDM tape inserted into the open seams. A special oil or sealant (more of an emergency solution) can also be used. After closing, the tape is pressed down and fills small leaks that may occur on the seam, particularly during manual processing. Such micro-gaps are susceptible to so-called "pulling" water into the structure – capillary action through leaks. The rules for its application are provided in the Lindab assembly manual (slope less than 7° always). However, the judgment of the roofer is paramount, as they can evaluate the roof or a specific detail as risky and apply tape even outside of prescribed situations. When designing details, attention is also given to the windward side of the building, where details are carried out with greater caution and safety. Powdery snow and rising water can penetrate even into areas that were assumed to be sealed, secured with a mesh, etc.

What are possible defects and problems associated with installation at low temperatures?
A low temperature can be referred to when the temperature during material handling is below 10° C. If metal with a PLX core is used, which is made of fine-grained steel with high ductility, no additional measures are required for processing the rolled steel sheet. In general, mechanical processing is gentler on the sheet and can therefore be carried out down to -5° C. For manual work – hammering and forming with blows, the safe boundary is +5° C. The Lindab Seamline roofing is anchored using sliding clips that ensure the movement of whole strips due to temperature changes. In case of installation at a temperature of around 0°C, one must account for a higher increase in temperature than decrease. Conversely, when installing in summer at a temperature of around 30° C, the situation will be reversed and temperatures will tend to go down. Accordingly, the slider of the sliding clip is adjusted. The low thermal expansion of steel can be an advantage – dimensional changes are smaller than with other materials used.

What to consider when designing a roof assembly with Lindab Seamline roofing
When designing an assembly with Lindab Seamline roofing, one must count on 100% impermeability of the roofing to external water, but especially for water vapor that rises with warm air through the assembly to the roofing. It is undesirable for these vapors to condense anywhere in the roofing structure. A quality sealed vapor barrier, sufficient insulation thickness, and functional active ventilation are therefore absolute necessities. Diffusion membranes also serve a necessary safety function. Another danger is surface icing of the roofing, in cases where the roofing is warmed from below by warm air from the interior. Here, again, the thickness of the insulation is important, but more importantly, the solution for draining vapors and heat from the space beneath the roofing. More specific details can again be found in the Lindab assembly manual.

How to protect the adjacent area from uncontrolled snow sliding?
The smooth surface of the roofing helps with snow sliding, which can be an advantage but also a problem if the snow is to slide into a parking area, entrance, or, for example, a sidewalk. Here, the system of safety elements on roofs called Protectline comes into play. By applying special clamping elements to individual seams, we obtain attachment points for snow guards as well as roof walkways, ladders, etc. These clamping elements are attached to the seam by tightening screws without the need to drill through the seam or the roofing itself. This way, no potential future problems are created. The Lindab snow guards consist of three tubes forming a grid. Systems with fewer tubes are less effective.