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.
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. IT
IS, THEREFORE, NOT THE RESPONSIBILITY OF THE LOCAL AUTHORITY BUILDING
INSPECTOR TO ENSURE THAT YOUR HOUSE COMPLIES WITH BUILDING
REGULATIONS…… 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.
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!) CONTACT
INFORMATION:
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