MATERIAL & INSTALLATION
The coastline of South Africa is a particularly harsh environment which carries chlorides. In urban areas, corrosion is accelerated by the presence of sulphur emissions from industry and traffic. The choice of the correct steel substrate is therefore important to avoid high replacement costs and losses in rentals, etc. Please request additional information from Safintra in this regard.
Severe corrosive conditions
If this product is to be used in marine, severe industrial, or unusually corrosive environments, consult the technical staff at your nearest Safintra branch for guidance.
ATMOSPHERIC CORROSION REGIONS
The above map provides a general indication of corrosion rates throughout the subcontinent. Microclimatic conditions can vary substantially from one local site to another depending on factors such as wind direction, land contours, height above sea level and industrial pollution.
WIND TERRAIN CATEGORIES
Areas where structures are exposed include canopies, walkways, exposed lean-to roofs, loading bays, gate entrances or aesthetic structures such as wings or buttresses. Overhangs are prone to a buildup of wind pressure below the sheet surface and are considered a weaker point in the roof structure.
To ensure the correct specification of purlin spacing and roof sheet gauge, it is important to consult an engineer at design stage. Steel products can be affected by some environmental conditions such as industrial, agricultural, marine, intensive animal farming, swimming pools or other aggressive conditions. If any of our products are to be used in these conditions, or unusually corrosive environments, seek advice from your local Safintra branch.
The terrain category would determine the fixing method and purlin spacing. All materials and fixings have been designed to accommodate terrain category C.
Terrain Category A
Exposed smooth terrain with virtually no obstructions and in which the height of any obstructions is less than 1.5m. The category includes open sea shores, lake shores and flat, treeless plains with little vegetation other than short grass.
Terrain Category C
Terrain having numerous closely spaced obstructions generally having the size of domestic houses. This category includes the wooded areas and suburbs, towns and industrial areas, fully or substantially developed.
Terrain Category B
Open terrain with widely spaced obstructions (more than 100m apart) having heights and plan dimensions generally between 1.5m and 10m. This category includes large airfields, open parklands or farmlands and undeveloped outskirts of towns and suburbs, with few trees, hillside or other exposed areas.
Terrain Category D
Terrain with numerous large, tall, closely-spaced obstructions. This category includes large city centres.
Overhangs of 600mm and greater are classified as exposed.
MATERIAL COMPATIBILITY – DIRECT CONTACT
MATERIAL COMPATIBILITY – DRAINAGE FROM UPPER ONTO LOWER
Optimum product life will be achieved if all external surfaces are washed regularly. Areas not cleaned by natural rainfall (such as the underside of sheeting at the eaves of the building should be washed down every six months. Regular maintenance and inspections, especially after severe storms, are essential.
Care should be taken to ensure that none of the debris arising from the fixing of a steel roof remains on the sheets after completion of work. If nails, swarf, etc. are allowed to remain on roof sheets, unsightly spots will soon appear. Initially, these rust spots will merely be stains from rapidly rusting fine particles of steel, if allowed to develop further, a loss of Zinc coating in the stained areas will appear. Sheets are often subject to wet cement splashes that create an area that is subject to alkali attack. Cement splashes should, therefore, be cleaned off immediately.
Cut materials over the ground and not over other materials. Sweep all metallic swarf and other debris from roof areas and gutters at the end of each day and at the completion of the installation. Failure to do so can lead to surface staining when the metal particles rust.
EDGE WAVE AND OIL CANNING
Various factors may contribute to a phenomenon described as oil canning. These include material, manufacturing and structural alignment criteria. The effect is aesthetic in nature and bears no influence on the structural integrity of the roofing system. Edge wave will manifest on the sides of roof sheeting where the overlap is likely to conceal the issue.
REQUIRED STRUCTURAL TOLERANCES
– Maximum purlin twist 1.5°
– Purlin plane alignment a maximum of purlin centres/360. In a case of varying purlin centres the deviation is to be restricted to the lessor of this calculation
– Adjacent purlin alignment at the rafter connection point should be ≤2mm
– Clip/cleat alignment within 1° referenced to the sheeting longitudinal axis. Lateral deflection of purlins (sagging) between rafter should be limited to a maximum of 20mm.
- Touch up paint is not recommended.
- Never use abrasive or solvent type cleaners.
- Clean with soft cloths and avoid wire brushes/steel wool to clean roof.
- A fine automotive polish can be used to remove swarf.