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Understanding your roof

More than just a cover over your house, the roof serves an important function for protecting and creating an energy efficient structure. Understanding terminology and good installation practices is important to ensure that your roof meets the latest industry standards.

 

 

 

STRUCTURAL REQUIREMENTS

Rafters/trusses - To comply with SANS 563 Softwood structural timber and engineer’s specifications.

Roofing Undertile Membrane - MONIER Roofing undertile membrane Agrément approved certificate 2004/304.

Battens - To comply with SANS 653 Softwood battens and brandering.

Batten nails - Non-corrodible nails 3,35mm Ø - long enough to penetrate the rafter to a depth of 55mm.

Tiles - To comply with SANS 542 for concrete roof tiles.

Fittings - To suit design criteria.

Tile nails - Non-corrodible clout nails long enough to penetrate the batten to 2/3 of its depth.

Tile clips - Non-corrodible “Storm clip”.

Flashings - Non-corrodible flashing materials should be used. To avoid the possibility of electrolytic corrosion, always ensure that flashings, which come into contact with one another, are compatible.

ROOF INSTALLATION

Preparation - All work on beam fillings, fascia boards, guttering, flashings and parapets, etc., should be completed before tiling commences.

Rafters/trusses - To comply with SABS 563 Softwood structural timber.

Undertile membrane - Must be laid for the full length of each valley ensuring that the opposing slopes overlap the edges. All undertile membrane is to be nailed to the rafters with a minimum of non-corrodible clout nails.

Battens - To comply with SABS 653 Softwood battens and brandering. Batten joints must meet halfway across the top face of a rafter.

Tiling - Tiles are to be laid “straight-bond” in even courses. The Clay Marseille profile and the Concrete Elite profile are the only exceptions to this rule and must be laid “broken-bond”.

Batten gauges - Concrete Tiles: >26° - not to exceed 345mm. <26° - not to exceed 320mm. Always ensure that the battens are spaced equidistant from each other by correctly setting out the roof prior to commencing the tiling.

Eaves - The bottom edge of the first course of tiles must overhang the fascia board sufficiently to allow rain water to discharge efficiently into the gutter, and must be elevated to bring the eaves course into the same plane as the following courses. Where eaves filler units are used, these should be fixed simultaneously.

Verges - Verges must have equal overhangs at each end of the roof and should be finished with purpose-made verge tiles.

Tile rows - In most instances rows can be laid without cutting tiles. When cut tiles are required to complete a row, always ensure that the surface area of each cut tile exceeds half the tile area. Two cut tiles containing the nail hole provide a superior finish to a row, rather than a single quarter tile at the end of a row without any provision for fixing. Tiles must be laid loose and not tight against each other to allow for thermal movement.

Valleys -

Open valley: a non-corrodible valley gutter at least 200mm wide should be constructed between two counter battens. The tiles on each side of the valley should be neatly cut to alignment to project over the side welt by at least 50mm. The cut tiles should be supported and well fixed to the timber.

Closed valley: as above, except that the tiles should be cut in a manner to allow a neat butt-joint at the valley centre.

Abutments - An adequate flashing material should be used to seal the junctions at the abutments. Where concealed gutters are necessary, the tiles should be neatly cut to approximately 40mm from the abutment. In all other instances, tiles should be cut to fit as close as is practical to abutments. An apron flashing must be used where the roof slope falls below the abutment. Conversely, where the slope falls above the abutment, back-gutters must be installed.

Mechanical fixing - Tiles are to be nailed and/or clipped to resist wind uplift in accordance with the existing SABS Codes of Practice and the manufacturer’s recommendations. At roof perimeters, abutments and intersections, the overhanging or abutting tiles plus two tiles in from that tile shall be fixed.

Mortar - Coverland recommends the Dry Ridge System for a neat solution to sealing ridges as opposed to traditional methods. These often show colour variations and result in a messy finish. The Coverland Dry Ridge System is the only ventilating ridge system that prevents leaks and is maintenance-free. All bedding mortar is to consist of 3 parts coarse graded sand to 1 part Portland cement, suitably pigmented to match the colour of the tiles. All butt-joints are to be solid bedded.

For more information visit the Coverland website.

 

Although Coverland has compiled the data in the technical sections of this website as accurately as possible, discrepancies may occur in construction methods due to flexibilities in the building industry. Information contained on this site is provided in an advisory capacity only and Coverland accepts no liability for work executed by contractors or private individuals.

 

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