Nov 172011
 

All buildings must have a strong, serviceable,

stable and durable design-Part B

Why do you suppose we need structural design professionals to be involved in every aspect of building processes? I’ve thought about this often, since we’ve done a load of DIY projects that involve building, and we have seldom had professionals help us. But the point is that any building or structural element, however simple it may be, must be built in accordance with accepted principles of structural design. For instance we don’t just pile bricks on top of one another without sandwiching suitably mixed mortar between them – although I have visited an amazing home in Johannesburg where an architect totally defied this principle and built an incredible home on Linksfield ridge out of bricks sans mortar! But this is not the norm. Similarly, we don’t balance poles together like pick-up-sticks in the hope that they will stay in place.
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The Role of the Regulations in Structural Design

As the national building regulations state:

“Any building and any structural element or component” must be designed to “provide strength, stability, serviceability and durability”.

It is also vital that buildings are designed so that if the structural system is in any way overloaded they won’t collapse with disastrous consequences.

The regulations also state that these design requirements shall be “deemed to be satisfied” when buildings are designed in accordance with this section of SANS 10400-Part B, namely Structural Design.

When I last accessed the SABS online to see if these section of the regs was available, it wasn’t. However, there is no doubt that it will ultimately list all the other standards that designers should refer to when undertaking structural design. UPDATE: This is now available from the SABS at a cost of R369.36

Structural Design must be in Accordance with National Standards

It is essential that all structural systems are designed and built by professionals. It is also essential that all materials used are suitable and SABS approved.

Some of the SANS that are used by structural designers are:

  • SANS 10100-1: The structural use of concrete (specifically Part 1: Design)
  • SANS 10162: The structural use of steel
  • SANS 10163: The structural use of timber
  • SANS 10164: The structural use of masonry

There are also various SANS that focus on the basis of structural design and actions for buildings and industrial structures. These relate to a variety of actions that are caused by self-weight and imposed loads, wind, seismic action, thermal elements, geotechnical elements, and even cranes and machinery.

Lastly, there are international standards that should also be followed, some of which are available from the SABS.

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Dimensions

  91 Responses to “Structural Design”

Comments (86) Pingbacks (5)
  1. Hi, could anyone please give me information relating to cob house building regulations in South Africa?

    • The regs are the same – i.e. you need to follow the National Building Regulations – but you also need an agrement certificate as per Part A of SANS 10400 – General Principles & Requirements

  2. Good Morning

    My neighbour built a structure out of steel and gavalnised zinc on the boundary wall without plans and my permission. We reside in the Northcliff area in Johannesburg. I had council out and they have indicated that the structure is fine and does not require plans. I measure the area and its above 10M2 about 11.8M2. I have now formally sent them an e-mail indicating such but have as yet not heard back from them. What i want to know is:

    1. How can i force the issue with regards plans?
    2. Would this structure be considered permanent as its concreted into the ground and has paving as a floor?
    3. My understadnign is that under the SANS 10400 is an engineering certificate not required?
    4. How can i sastify myself that these have been done and if not would i have a case to have this removed?

    Look forward to hearing from you.

    • Hi Dominique, If you have already had the council out to inspect and they say it is ok then there is not much more that you can do. Please have a look at our page that defines “minor building work” and you will see that the maximum size for a carport is 40 sq meters.

  3. I have just been registered as a Pr.Eng.Tech.
    Do I need to register with NHBRC?

    • Hi Charlie, It is only building contractors that must register with the NHBRC. The other professions must be registered (up to date) with their own organisations, these registration numbers/details are then used on all design submissions to councils and to the NHBRC.

  4. Subject:
    cracks

    Message:
    I just want to find out if is normal for a four months old houes to
    have cracks

    • Hi Moses, It depends on how many and how big the cracks are. It is “normal” for a house to “settle” after building and for a few minor cracks to appear. If they are quite big then it could be cause to worry. There are many factors that can contribute to this happening. Local council building inspectors are under a lot of pressure these days and I do not think that they would have time to come out and do an inspection. There are private companies that do house inspections for a fee. The NHBRC does cover any defect due to faulty building by one of the registered builders.

  5. Hi there

    Where would i find info on building codes relating to alternative building methods such as cobb, earthbag and straw bale

    Cheers

    • George there are no building codes as such that relate to alternative building methods. To build using one of the methods you need an agreement certificate, which is an official certificate that confirms fitness-for-purpose of a non-standardised product, material or component or the acceptability of the related non-standardised design and the conditions pertaining thereto (or both) issued by the Board of Agrément South Africa. There will, of course, be a number of standard techniques and products that you will use – e.g. plumbing, roofing etc and for these you will have to comply to the various parts of SANS 10400.
      In any event, you will also need a competent person to draw the plans and submit these to both Agrement SA and then your local authority for approval.

  6. I’m in the process of building a braairoom at my house – we’re about 2/3rds along the way – but a sticky point has now come to the fore between myself and the builder re some structural elements.

    We followed the correct procedure in getting plans drawn up, getting it approved by the local authorities etc. The builder then went ahead building strictly according to the plans.

    Unknowingly to me (I have no knowledge of the industry), the height of the ceiling specified on the plan (2.4m) does not allow for a minimum of 4 courses of brickwork above the sliding doors (3m). After the builder completed the brickwork and was about to start with the roof – a friend of mine (who is an architect) pointed out this structural issue when she saw photos of the “progress of the braairoom”.

    I pointed this out to the builder, who in turn dismissed the issue and decided to carry on – saying that his engineer will sign it off.

    Long story short – his engineer is now also not willing to sign it off; and the builder simply stands by his case that he “simply followed the approved plan”.

    My main question is: Is a builder not expected (by law) to follow the National Building Regulations above all else? Who is ultimately responsible for the problem I am now having?

    Your assistance would be greatly appreciated.

    Regards,

    Ruan

    • Ruan, Both the person who drew up your plans and the local authority are equally liable – probably more so that the builder. However, while he thinks he is safe using the approved plan as his “excuse”, the very fact that you drew his attention to the “error” prior to completion, PLUS the fact that he said his engineer would sign it off, increase his liability in my opinion.
      FYI: In the part of 10400 that deals with Roofing, it clearly states that four courses of brickwork are required below the trusses to accommodate the wire or strapping. See these drawings: four bricks
      There is also a comment that relates to this HERE.
      I believe it is the builder’s responsibility to get an engineer’s signature. If you haven’t already paid him in full, don’t do so until you have the signature. As it stands you might find yourself having to rectify the build. Having said this though, you should have comeback on the council for approving the plans. Make sure you keep all the documentation.

  7. What is the distance between the fence and a storm water drain?

  8. Hi all,

    I have just had a house built, on a gentle slope, clay soil, thick floating foundations. All to engineers specification. My question is, most houses have a concrete or tile apron around the house( a splash guard?) My foundations were backfilled, do i need one or does the law require one, as my builder says i do not, yet i feel that this is a pre requisite as severe highveld storms genersate a lot of water flow and i worry that this may erode under the foundations over time. Please help

    Greg

    • Greg, since your house was built (with approved plans – I presume) according to an engineer’s specification, unless this was part of the specification (which would, by law, have been included in the plans that were submitted to council), then your builder is correct. However, if you want some sort of protective “apron” around your house, that is your prerogative. In any event, if it was not specified in the approved plans, you can expect to be charged extra for the work and materials.

  9. Could you please tell me where I can find out what specific school building regulations entails? I need to know what the height of the windows should be drom the floor.

    • Hi Karin,
      There are no height restrictions regarding the window sill height above the floor. The only stipulation is that the glass below 500mm above floor level must be safety glass. Whoever designs a building does the design according to what the building is to be used for as well as the clients specifications.

  10. How do I find out the recommended spans of timber for building a deck structure?
    e.ge what could a 38 x 114 span between posts?

    • We are neither architects nor engineers Edward and the Building Regulations are not a design manual. They simply give very basic guidelines. Although the discussion of building with timber has been included in these latest building regulations, I am not aware of anything that deals with deck structures as such.
      We did a book on Decks & Patios some years ago, and one of the projects was a deck built on a slope next to a swimming pool. It was built by a professional who used 144 mm x 44 mm timber for beams and joists – and the span between posts was no more than 3 m. So if you are using less sturdy beams, you’ll have to reduce the span considerably. An engineer will be able to advise further.

  11. Good day Penny, Thank you for your replies to my earlier questions. I read in one of your posts that plans for open sided structures, like carports and verandas, are not necessary, although permission from your local authority is still a prerequisite. Can you confirm this or did I understand you wrong?
    Regards

    • Franco, the legislation (The National Building Regulations and Building Standards Act) defines minor building work – which does not require plans. Have a look at the link I have given you here. It doesn’t mention verandahs (these are usually part of the structure of the house), but “open-sided car, caravan or boat shelters or carports that do not exceed 40 square metres in size” are considered minor building work.
      The Act also says: “Any building control officer may in respect of the erection of a building defined in the national building regulations as a minor building work, in writing-
      (a) exempt the owner of such building from the obligation to submit a plan in terms of this Act to the local authority in question for approval;
      (b) grant authorization for the erection of such building in accordance with the conditions and directions specified in such authorization.”
      So you don’t need plans but you need “permission”.
      SANS 10400 is very clear that minor building work must comply with the NBR.
      There is commentary on minor building work in Part A of SANS 10400 (this has not been changed – so if you download the old SANS 10400 (1990) from our downloads page you can read all three paragraphs – pages 45-46). The first para says:
      “The term “minor building work” was intended to cover certain building work which, because of either its nature or magnitude (or both), was such that it would not be necessary to submit full plans or, in certain cases, where no plans or any other documents would be required. The implication is that where no plans are required, the building does not have to comply with the National Building Regulations since, without plans, there is no means of assessing an application. It is, however, necessary in all cases that an application be submitted to the local authority so that it is aware that the work is proposed and it can set conditions in those cases where it is considered necessary to invoke at least some of the National Building Regulations to control the proposed building work.”

  12. Hi Kryska,

    If the bedroom has direct access to the backyard, you will require a weatherstep in the order of 170mm. It may be less, if circumstances allow. You would then have to lower the yard level to suit.

    If the bedroom does not allow direct access to the backyard, the internal floor slab may be at the same level as the external yard (even lower), but there should be sound and proper waterproofing measures in place and the yard should be well drained in order to allow spontaneous storm water flows away from the structure. Best to contact a Professional Engineer to assist.

    Good luck

    Anton

  13. Hi, I would like to know if you could help me. We have moved into a
    new house but the addition to the house(4th bedroom) is not up to
    standard. It’s going to be corrected but there is a dispute about the
    floor level. The current floor level is on the same level as the
    backyard. Does it need to be raised or is it fine like that?

    Please help.

    Thank you Kryska

    • Hi Kryska,
      It’s impossible to tell just by this description. Your first step is to check the plans to see if the building was constructed according to the plans. Your local authority should be able to help in this regard (go to the planning department). The levels should be shown on the plans and these should relate to exactly where foundations for each level should be built. It sounds as if this is a sloping property?

  14. I bought a house from the developer, i gave the house plan but they
    didn’t build according to the approved plan, because the builder is
    not willing to solve the problem how can you help to solve this issue
    because am staying in the house that is not according to the approve
    plan . Please help.

    • Hi Sydney,
      You should contact the NHBRC, click this link >> “nhbrc.org” < < They might be able to help you IF the developer and builder are registered, which they should be by law. It seems to me that you have more of a contract problem than a building one. It all depends what was in the contract when you agreed to the contract terms. I suggest you read through this first.

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