A roof is an exceptionally important structure – it protects both the occupants and the contents of any home.
That aside, badly built roofs can be exceptionally dangerous – they are heavy structures, and if they fall down, they could pose serious physical danger to anybody who is in the house at the time. Yet, poorly constructed roofs have become a real problem in residential South Africa.
Antonella Dési offers some tips on how to ensure that your new home or extension gets a well-built roof structure.
The first and most important step to take with regards to investing in a good roof, is to choose reliable and well-qualified roof fabricators and engineers. Associations such as the Institute of Timber Construction South Africa (ITC-SA) for example, make this process a simple one – all homeowners needs to do is to contact the institute directly or visit its website (www.itc-sa.org). It has a comprehensive list of all the truss manufacturers on a national basis.
Using a roof fabricator or engineer that is registered with the ITC-SA might cost you a little extra when compared with hiring a tradesman off the side of the street, but you will be guaranteed of a professionally completed job and a well-constructed roof structure. Each and every ITC-SA-approved fabricator is audited on an annual basis with regards to quality, competence and compliance to the South African National Standards.
An annual Certificate of Competence is given to confirm that the fabricator is regulated and audited by the ITC-SA – so don’t take their word that they are registered, rather ask to see their certification for yourself.
The ITC-SA will send out an inspector to ensure that everything pertaining to the roof structure is as it should be and in accordance with the necessary regulations. If a consumer uses an ITC-SA-registered fabricator and/or engineer and the outcome is unsatisfactory, they will be able to take recourse through the institute.
Essential elements
The following elements are vital for any well-built roof truss system:
Only structural timber must be used, and it must comply with the design intent: Structural timber is marked on the face of the timber at 1 metre intervals. If it does not bear these structural markings, it will be condemned and is not suitable for structural purposes – so beware of unmarked timber or timber with black crosses on it.
An accurate cutting bill must be produced by the designer: The cutting bill will dictate the exact lengths and angles at which the timber must be cut for proper assembly.
The correct engineering systems must be utilised: There are four main engineering systems used in South Africa, namely MiTek, Alpine International South Africa, International Truss Systems, and Multinail. The metal connector plates used must be supplied by the specific engineering system that has been chosen. In addition, it is essential that they are the correct size, and positioned in the right locations as per the standard methods and tolerances.
All connections and bracing details must be in accordance with the design intent: Everything that holds the structure together, such as the number of nails, bolts, washers, brackets and cleats, must be in accordance with the engineering design. All necessary bracing accessories must be stipulated on the design plans.
Common mistakes made by consumers
Choosing price over quality: Many homeowners try to save on the roof construction, and often end up spending more remedying the issues that arise from using sub-standard materials and workmanship. In order to create a professional and sound end-result, a professional individual needs to be employed to get the job done properly – it will cost more initially than non-qualified individuals, but will save the homeowner a lot of money and stress down the line.
Choosing the right engineer: Use a qualified structural engineer to design and sign-off the roof.
Prefabricated roof trusses are the best: Prefabricated roof trusses are cut by specially designed machinery and are therefore more accurate than their hand-made counterparts. Prefabricated trusses also use less timber and are more likely to comply with NBR requirements.
Guarantee: Reputable fabricators offer peace of mind – these companies or individuals are regularly audited and monitored, and should something go wrong with their workmanship, you will have some kind of recourse.
Readers' Comments Have a comment about this article? Email us now.
This excellent article should be circulated to architects & estate agents. – Gunnar Strom
We are about to extend our house, but the roof has been our main concern. Mainly from a cost point of view. Thank you for clearly stating how important it is to have the roof design and built by the professionals.
Great article !! - Mary
