The Institute for Timber Construction (ITC-SA) offers some important information regarding regulations and nail-plated timber roofs.
- When placing your truss order confirm that the truss fabricator holds the current year’s ITC-SA Certificate of Competence. This should be displayed in the office premises.
- Ensure that the timber is stamped with the designed structural grade value (e.g. S5) together with the certification authority logo, either SABS or SATAS and the initials of the timber mill of source. These stamped marks should appear in red marking ink at approximately 1 metre intervals along the length of one face of each piece of timber. The truss fabricator’s trading name must also be marked on the trusses.
- Structural grade Pine imported from Zimbabwe is also fairly prevalent and is acceptable if it displays the ZSA logo and S5 grade mark.
- Joints in the timber trusses must be neat and close fitting. Not more than two slightly open joints are permitted per truss with the gap size in those 2 joints not exceeding 2mm. Openings on long joints (greater than 300mm) shall be less than 5mm tapering to zero.
- The nail plates are to be fully embedded in the timber, and should be placed usually symmetrically about each joint:
- Ensure that the nail plates bear the distinctive ITC-SA System members markings, ie.:
- The truss manufacturer must supply two complete sets of erection and bracing details; one set for the erector and one set for the inspector.
A roof plan showing truss layout and identification marks.
Truss to girder connection details.
Bracing and runner details.
Multi-member girder fixing requirements.
- Employ a reliable and knowledgeable roof erector, preferably an erector who holds a current ITC-SA Erector Certificate of Competence.
- Prior to the loading of the roof with the permanent cladding (tiles, sheeting, etc.) have the roof inspected by the design engineer or one of his appointed ITC-SA registered roof inspectors, or by an engineer registered with the Engineering Council of South Africa (ECSA) who is qualified to inspect a timber roof structure and who has access to all the necessary design and erection drawings.The roof trusses should be erected and braced in accordance with relative details as specified in the ITC-SA Vol. 1 and Vol. 2 Handbooks.This is in compliance with Regulation A19 of the National Building Regulations.
- The appointed responsible engineer will need to produce a Certificate of Completion for submission to the local authority as required by Regulation A19 as well as the necessary B1 and D1 certificates as called for by the National Home Builders Registration Council (NHBRC).For more information, visit www.itc-sa.org.
Intro image courtesy of BUCO KZN.
