International Building Regulations Archives » Building Regulations South Africa
Mar 052013
 

Regulations for Lightning Conductors on Thatch Roofs

Thatch house lightning Thatch Roofs and Lightning

Thatch roofs are most susceptible to be set alight by lightning than any other roof type. For the protection of the public and property the South African National Standard 62305-3 was introduced in 2011.

SANS 62305-3: Protection against Lightning (published in 2011) is drawn from an international standard, IEC 62305. Part 3 deals with “physical damage to structures and life hazard”.

Remember that anything related to electrics must be dealt with by a qualified and registered electrician.

Introduction to the Regulations for Thatch Roofs and Lightning

This part of IEC 62305 deals with the protection, in and around a structure, against physical damage and injury to living beings due to touch and step voltages.

The main and most effective measure for protection of thatch structures against physical damage is considered to be the lightning protection system (LPS). This usually consists of both external and internal lightning protection systems.

An external LPS is intended to:

  1. intercept a lightning flash to the structure (with an air-termination system),
  2. conduct the lightning current safely towards earth (using a down-conductor system),
  3. disperse the lightning current into the earth (using an earth-termination system).

An internal LPS prevents dangerous sparking within the structure using either equipotential bonding or a separation distance (and electrical insulation) between the external LPS components and other electrically conducting elements internal to the structure.

The main protection measures against injury to living beings due to touch and step voltages are intended to reduce the:

  1. dangerous current flowing through bodies by insulating exposed conductive parts, and/or by increasing the surface soil resistivity,
  2. occurrence of dangerous touch and step voltages by physical restrictions and/or warning notices.

The type and location of an LPS should be carefully considered in the initial design of a new structure, thereby enabling maximum advantage to be taken of the electrically conductive parts of the structure. By doing so, design and construction of an integrated installation is made easier, the overall aesthetic aspects can be improved, and the effectiveness of the LPS can be increased at minimum cost and effort.

Once construction work on a site has started, access to the ground and the proper use of foundation steelwork for the purpose of forming an effective earth-termination, may well be impossible. Therefore, soil resistivity and the nature of the earth should be considered at the earliest possible stage of a project. This information is fundamental to the design of an earth-termination system and may influence the foundation design work for the structure.

Regular consultation between LPS designers and installers, architects and builders is essential in order to achieve the best result at minimum cost.

If lightning protection is to be added to an existing structure, every effort should be made to ensure that it conforms to the principles of SANS 62305-3. The design of the type and location of an LPS should take into account the features of the existing structure.

Notations

NOTE 1

Specific requirements for an LPS in structures dangerous to their surroundings due to the risk of explosion are under consideration. Additional information is provided in Annex D for use in the interim.

NOTE 2

This part of IEC 62305 is not intended to provide protection against failures of electrical and electronic systems due to overvoltages. Specific requirements for such cases are provided in IEC 62305-4.

NOTE 3

Specific requirements for protection against lightning of wind turbines are reported in IEC 61400-24 [2].

References

The following referenced documents are indispensable for the application of this national standard. These references are listed in the standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

IEC 60079-10-1:2008, Explosive atmospheres – Part 10-1: Classification of areas – Explosive gas atmospheres

IEC 60079-10-2:2009, Explosive atmospheres – Part 10-2: Classification of areas – Combustible dust atmospheres

IEC 60079-14:2007, Explosive atmospheres – Part 14: Electrical installations design, selection and erection

IEC 61557-4, Electrical safety in low-voltage distribution systems up to 1 000 V a.c. and 1 500 V d.c. – Equipment for testing, measuring or monitoring of protective measures – Part 4: Resistance of earth connection and equipotential bonding

IEC 61643-1, Low-voltage surge protective devices – Part 1: Surge protective devices connected to low-voltage power distribution systems – Requirements and tests

IEC 61643-21, Low-voltage surge protective devices – Part 21: Surge protective devices connected to telecommunications and signalling networks – Performance requirements and testing methods

IEC 62305-1, Protection against lightning – Part 1: General principles IEC 62305-2, Protection against lightning – Part 2: Risk management

Jan 202012
 

Dozens of Residents Die When Building Collapses

AshrafiehCollapse 16012012 300x191 Building Collapses

Rescue workers pull bodies out of the rubble. Picture courtesy alakhbar http://english.al-akhbar.com/content/beirut-planning-slammed-building-collapse-kills-least-19

January 20, 2012: A badly maintained apartment block which was home to some 50 people, collapsed like a pack of cards in Beirut this week, killing at least 25 people.

A teenage girl and her grandmother, an elderly man (73), and several labourers from Sudan, Egypt, Jordan and the Philippines are known to have died instantly. At least 12 others survived, including the twin sister of the teenage girl. According to Lebanese officials, it was almost as though there had been a terrific earthquake when the six-storey building crashed to the ground. On Monday, General Raymond Khattar, who is head of Lebanon’s civil defence, told local reporters they hoped to find survivors in the rubble. But as rescue efforts continued through the week, only bodies were retrieved.

beirut building 4001 Building Collapses

A pile of broken concrete and twisted metal. Picture courtesy www.photoblog.msnbc.msn.com

Why the Building Collapsed

Former residents who were interviewed after the disaster claimed that the owner of the building had warned his tenants to leave the building, clearly because he realised it wasn’t safe. They said it was extremely run-down.

Speculation is that thunderstorms accompanied by heavy rain might have lead to the collapse. It is thought that nearby construction work might also have been a factor.

After the incident, it emerged that there are numerous buildings in the country that have been built illegally and/or have been extended without local authority or government permission. After President Michel Sleiman and Interior Minister Marwan Charbel had visited to site of the tragedy, it was announced that the government planned to survey buildings to pinpoint serious building irregularities.

The government has announced that the families of victims will each be paid $20,000 compensation, and those who survived will be given alternative housing which is safe.

The owner of the building, Michel Saadeh, has been arrested.

Could this Happen in South Africa?

While our National Building Regulations should prevent anything like this from happening, construction accidents do occur from time to time – and sometimes with fatal circumstances.

Not that long ago a concrete slab collapsed on a building site, killing a man and severely injuring several more. The incident made newspaper headlines.

According to Dr. Roderick Rankine, a South African engineer and expert in construction materials, who is also a highly qualified concrete technologist, the contractor did not follow engineering specifications.

The slab in question was suspended concrete, and it was constructed using a type of polystyrene shuttering (rather than traditional shuttering). The function of shuttering is, of course, to hold the concrete in place while it sets and strengthens. While the method has been tested to be safe, it is vital that the engineer’s specifications are followed to the last letter.  For instance, the concrete must:

  • be reinforced with steel
  • reach a strength of 25 MPa at 28 days (which can be checked by doing cube tests)

In this instance, the builder is understood to have mixed his own concrete on site and he didn’t bother with test cubes. It emerged after forensic investigators had inspected the site and completed their investigation, that because the builder didn’t know how strong his hardened concrete was, he simply left the props supporting the slab in for six weeks – hoping beyond hope that this action would increase the strength of the concrete to its maximum.

Then he removed the props – and like the building in Beirut, the slab collapsed.

The forensic investigators discovered that the strength of the concrete was less than 3 MPa!

Other South African Incidents that Have Made Headline News

Other than buildings collapsing because of fire, most (but not all) of this type of incident (where a building collapses) seems to happen on construction sites.

Buildings that have collapsed in South Africa in recent years include:

  • October 2011: A section of an historic building in Brakpan, built in 1905, collapsed during renovation.
  • October 2011: A building under construction at Rand Airport Park collapsed critically injuring at least four construction workers. In all about 14 men were injured.
  • October 2011: A woman was injured when the roof of a building collapsed in Rosebank, Johannesburg. It is thought that work on an adjacent construction site might have been the cause.
  • July 2010: A building under construction in Brakpan collapsed, seriously injuring several workers on site.
  • July 2009: The roof of a shopping mall in Newlands, Durban collapsed, injuring at least 11 people, seven seriously.
  • October 2008: At least two workers were killed and more than a dozen others injured when a half completed office block collapsed in Roodepoort.
  • 2004: according to the Engineering Council of SA, at least seven buildings collapsed in KZN.
  • November 2013: A mall in Tongaat, KZN collapses during construction reportedly killing one and injuring 29 others