The Need for Roof Inspections - The Law

Before the mid-Sixties domestic timber roof structures were constructed by carpenters who had various levels of expertise and skill. There were some basic rules of construction (many of which were not officially documented) but most work comprised a four or six panel/bay "Howe" truss, depending on the span between external walls.

4 Bay Truss 

6 Bay Truss

 “HOWE” Trusses

Often internal walls were used as additional supports but, ironically, this practice often caused failure of the truss due to the introduction of local, high stresses.

Hip and Valley construction, which require the use of girders, (special trusses used to carry other trusses) were used indiscriminately and often irresponsibly as well as illegally because this type of construction required then, as it still does today, the services of engineer to ensure that the girders are capable of carrying the additional loads. The carpenters often ignored forces at the truss /girder joints concentrating only on the size of timber used and not on the number of bolts required to hold the timbers together. In fact, many older roof structures have such an inadequacy of construction that it is only due to the fact that most roofs in South Africa are never subjected to snow loads that we don't have many catastrophic failures.

For a roof to "fail" structurally doesn't require its total collapse. When members of the roof structure become deformed due to overstress or lack of bracing, inadequate joints or just plain, simple construction inadequacies, which contradict basic design assumptions, the roof will lose its ability to perform in the long term. Movement of the structure in turn means movement of the tiles and ridges which will invariably cause roof leaks adding further to the cost of remedial work.

Your insurance company may pay for the repair cost of consequential water damage but will not pay to repair the cause of the damage!!!  i.e. the faulty roof structure.

The shortage of skilled roof artisans eventually led to a shortage of experienced building inspectors and, in 1985 the new National Building Regulations (N.B.R.) made it clear that compliance with building codes was the responsibility of the building owner.


Now this may seem unfair…….. but it is THE LAW!

Many homeowners and even many builders still do not understand this and this has led to a proliferation of bad practices especially in the home building industry. Many consumers have had bad experiences with their most expensive life purchase being an unnecessary burden to them when their dream home started to sag, crack, leak etc. etc. and the builder was nowhere to be found or he just didn't care!

In 1999, the government introduced further legislation to protect consumers from the bad building practices which had gone unchecked due to the N.B.R. expecting the homeowner, who usually had engaged a builder to build to often vague and misunderstood specifications, to be the person directly responsible for compliance with N.B.R. (there are many levels of competence/incompetence within the industry and the cheapest building quote may turn out to be the most costly, not only financially but emotionally as well!)

This situation was also a result of homeowners not realising that if they had engaged an engineer to further look after their interests during construction they would have avoided much heartache (and expense) later on.

The Building Regulations have always required that engineered designs (known as "rational" designs) be checked on site and signed off by the responsible engineer by him/her issuing a formal "completion certificate". This is a requirement of all local authorities who believe in applying the laws which protect homeowners.  

Neither local authority building inspectors nor NHBRC inspectors are entitled to accept/sign-off any rational design such as a timber roof structure.  This duty must be performed by the engineer responsible for the design ... It's the law!!!!!

It is a serious case of false economy to believe, as a homeowner or as a builder, that you can "get away without having the roof inspected" as the consequences of bad workmanship can be extremely costly and, if your local authority is doing its job properly, as many of them now are, will prevent you from obtaining the "occupation certificate" for your house or extension.

A roof inspection and formal certification by a registered engineer that the roof structure is safe is probably the best money that a homeowner could ever spend!!

All rational designs carried out by Engineering Calculation must comply with the requirements of the National Building Regulations and in particular:-

SANS 10160 - The loadings and procedures to be adopted in the design of buildings; and

SANS 10163 - The structural use of timber.

Manufacturing and erection procedures for the trusses should be carried out in accordance with:-

SANS 10243 - The manufacture and erection of timber trusses.

The  configuration of a typical engineered/designed truss (“Fink” profile) is shown below and this configuration can easily replace a six-bay (site made) “Howe” truss whilst using only 60% of the volume of timber!  Today, it is a serious false economy to build roof trusses on site.  Factory made trusses are far more reliable and are designed by sophisticated computer software to achieve economy of materials.

Engineered “FINK” truss

In the mid-Sixties, when trusses manufactured with nail plate connectors were introduced into South Africa, these designs were all "rational" designs in order to achieve economy. However, in 1985, the new National Building Regulations demanded that all rational designs be signed off by the engineer responsible. For many years local authorities did not apply this rule but in 1995 the Ministry of Trade and Industry, which is in statutory charge of the Building Regulations, wrote to all of South Africa's provincial premiers insisting that all local authorities falling under their provincial jurisdiction apply the law forthwith, as the law existed, specifically, to ensure the homeowner’s safety.

It is taking some local authorities longer than others to fully implement this edict but, more and more, the law is being observed.

(it is interesting to note that homeowners often seem to be able to find the money for expensive tiles and gold taps in the bathrooms but resent paying just a few rands extra to ensure the long-term safety of their family by having an engineer’s certificate for the most vulnerable part of the structure i.e. the roof!)

Tel: (011) 658-1022  / Fax: (011) 658-1021
P.O.Box 675, Jukskei Park, 2153. South Africa