Nov 152011
 

Regulations for Foundations-Part H
A Focus on Safety

Foundations, Part H, of any structure, large or small, must be built to safely transmit all loads of the building to the ground. If foundations are not correctly built, walls may crack and at worst, could even collapse.

While the National Building Regulations specify general requirements for foundations, it is the deemed-to-satisfy rules contained in SANS 10400 that give you more detailed information about how to ensure that your foundations comply.

Furthermore, the building regulations require you to have a competent person involved in the build of your home. You must also have plans drawn up according to the regulations AND the requirements of your local authority. This will ensure that the necessary controls are in place, and should guarantee that your structure will be safe and legal.

In addition to 10400, there are other South African National Standards (SANS) that deal with foundations. For example:

  • SANS 2001-CM2 covers construction works for a variety of foundation types (strip footings, pad footings and slab-on-the-ground foundations) for masonry walling.
  • SANS 10161 covers the design of foundations for buildings in general.
  • SANS 10746-2 relates to information technology, specifically open distributed processing. The reference model for this standard is foundations.
  • SANS 12575-2 which covers thermal insulation products, specifically exterior insulating systems for foundations. This is highly technical and really only for the professional use of commercial/industrial installers of foundations.

All these standards are available for a nominal fee from an SABS office or from the SABS online store.

The SABS also holds certain international standards, many of which were formulated by the International Standards Organisation (ISO). ISO standards relating to foundations refer to thermal insulation (ISO 12575-2:2007), thermal performance of building in cold weather, when there is frost (ISO 13793:2001), and information technology (ISO/IEC 10746-2:2009).

There is another IEC (International Electrotechnical Commission) standard available: IEC 61773: Overhead lines – Testing of foundations for structures.

How the Building Regulations Have Changed

The National Building Regulations and Building Standards Act, 1977 was amended substantially in 2008. In terms of  Part H of the regulations  the amendments amounted to an expansion rather than an alteration as such.

Previously H1 GENERAL REQUIREMENT (1) read:

“The foundation of any building shall be designed to safely transmit all the loads from such building to the ground.”

It now reads:

“The foundation of any building shall be designed and constructed to safely transmit all the actions which can reasonably be expected to occur from such building to the ground and in such a manner that any local damage (including cracking), deformation or vibration do not compromise the efficient use of a building or the functioning of any element of a building or equipment within a building.”

How to Ensure Your Foundations Comply
With the Regulations

Part H and Part B (which covers structural design) of the building regulations go hand in hand. So basically, if your foundation is designed and the concrete placed in accordance with the requirements of Part B, you’ll be safe.

Part B “establishes the representative actions and impacts applied to building elements and structural elements, and their structural response to these representative actions and impacts”. It “also establishes requirements for rational designs and rational assessments, Agrement certification and buildings on dolomite land”. This Part of SANS 10400 was only approved on August 31, 2012, four years after the legislation changed. It is available from the SABS for R369.36 incl. VAT.

Part H, (available from the SABS for R427.50) approved at the same time as Part B, “establishes the representative actions and impacts applied to foundations, and the response of structural elements to ground movements. Buildings that comply with the requirements of this part of SANS 10400 will also comply with the structural design performance parameters established in SANS 10400-B. It contains simple design and construction requirements for foundations for certain masonry buildings to accommodate a relatively small range of ground movements”.

In addition, there are a variety of other SANS available that relate to structural design, although most are intended for industrial and larger commercial structures, with a couple relating to the structural use of timber (SANS 10162-1 and 10163-2).

Empirical rules for foundations as specified in SANS 10400-1990 were relatively basic, following good building practice. For example:

  • The basic rules for foundations relate only to walls that are placed centrally on foundations – which ensures that they will safely transmit loads; AND are built on good quality ground soil – NOT heaving soil or shrinkable clay. So if there are ground issues on your site, or special foundations have to be designed by an engineer for some other reason, you cannot rely on the dimensions specified below.
  • Basic, uncomplicated foundations should be constructed with concrete that has a compressive strength of at least 10 MPa at 28 days, OR concrete that is mixed proportionately by volume in the ratio 1:4:5 cement:sand:stone. Mixing by volume involves carefully measuring out of the materials in a same sized container. A wheelbarrow may be used, but it is not a suitable method for large building projects.
  • Continuous strip foundations should be at least 200 mm thick, unless laid on solid rock.
  • The width of continuous strip foundations should be at least 600 mm if the foundation is for a load-bearing or free standing masonry wall, or a timber-framed wall that supports a tiled or thatched roof (which should, of course be constructed according to the building regulations), OR 400 mm if the wall is a non-load bearing internal wall or a timber framed wall that supports a metal sheet, fibre-cement sheet or light metal-tiled roof.
  • If a strip foundation is laid at more than one level, it is important for the higher portion of the foundation to extend over the lower portion for a distance that is equal at least to the thickness of the foundation. If there is a void between the top section and lower section, you will need to fill the void with concrete that is the same strength as the concrete used for the foundations.
  • Sometimes people thicken an existing concrete slab to form a foundation. In this instance, the TOTAL thickness (ie the concrete INCLUDING the original slab) must be at least the thickness that is usually required for continuous strip foundation (200 mm). The width of the thickened portion under the floor slab must be at least the thickness of a continuous strip foundation (see above).
  • The only time you won’t have to add additional thickening is when the walls are timber-framed and NOT load-bearing.
  • If a pier is built into the wall, or forms a part of the wall, the thickness of the foundation to the pier must be the same as the foundation required for the wall itself. The length and width of the foundation to a pier should project by 200 mm at any point on the perimeter of the pier (see drawing).
  • The thickness of the foundation to a supporting sleeper pier or sleeper wall must be at least 150 mm; the length of width of the foundation to the sleeper pier must be at least 450 mm; and the width of the foundation to the sleeper wall must be at least 300 mm.

If you are building a simple structure (a granny flat, a garage or perhaps a freestanding workshop) on flat ground or on a site that is easily levelled, you can rely on these dimensions and specifications. But don’t forget that the building regulations require you to draw up plans which a “competent person” must submit to your local authority for approval BEFORE you start construction of the foundations.

>

Floors

  110 Responses to “Foundations”

Comments (107) Pingbacks (3)
  1. I am enclosing a small bin room. I am trying to work out how much materials ill have to buy. The wall i am adding is 2.8metres and connects to existing house. I cant understand on our plans, but what are the foundation requirements for this small wall?

  2. Hi I’m designing a double story house. What foundations should I use and what should the dimmensions of the foundation be? The soil type is limestone rock and is by a lake. I wanted to use a Frankie pile with a depth of 3 meters.

    • Sorry we don’t do student assignments! And if it isn’t a student assignment (which it seems to be given your email address), only a competent person can design a house – and that person would know what to do!

  3. Morning
    Does the law allow under any circumstances for a person to just apply a slab on top of a ordinary loanhouse to make it double storey.Bank(LOAN HOUSES)are single lane and their foundations were never made for double storey.

  4. HAI
    ON the fencing wall i have it have small spaces in between to allow water access if it raining now the problem is im on top and my neighour is at the bottom and she is complaining about the water that coming from this access space and my neibhour is intending to close the water access with plaster sand without consultation

    Please help

  5. Hi im looking to purchase a property and I’ve noticed the grass has been laid all the way to the wall of the property is this good practice is it possible that this could cause damp? Should there be a small footpath around the perimeter of the house to prevent any problems?

    • There should be an underwall damp proof course … a footpath isn’t necessary

      • Hello,

        I am an engineer in a geotechnical company. I would like to know the following:
        – The standards considered for foundations design in South Africa (compared to Eurocodes)
        – The usual methods of soil characterization in place in the same country (SPT, CPT, Pressio …)
        – And what are the best known drilling companies

        Thank you very much

  6. Hi.

    I am building onto my original house and have been given various different answers.

    Our current foundations are 600 x 230 and I am making them 850 x 450.

    All I need to know is what size of reinforce steel in allowed to be used to pin existing foundations down and to insert into new casted foundation areas for a double storey?

    The foundations will be casted with 30-35Mpa strength.

    Some advised and said I need to use 16mm and others say 10mm reinforce steel is accepted.

    Your assistance would be appreciated.

    • Hi Domenico, If you are adding on to your house then by law you have to submit plans and have them approved by the local council BEFORE you start the additions. If you have done this then the “competent person” who drew up your plans would have specified the reinforcing size and this would have been approved by the council and that is what you must build. If you do not have plans approved then you are breaking the law and criminal charges can be laid against you. You will be found out eventually because when you sell your house the inspector will visit to endorse the sale and if your house is built differently to the plans on file you will be charged and fined.

      • I think the man is asking a reasonable question and your response is unnecessarily rude.. If you don’t know the answer then say so, don’t just throw approval regulations at him. Assume he knows the rules and just wants clarification on his actual question.

        • Hi Kim, I am sorry but I am not being rude with my reply in the slightest. As a writer yourself you should know that giving technical info without, in this case, a site inspection is fraught with possible repercussions. We have spent many years putting info on this site together and we find that people in general do not read before asking a question.

  7. We require the following books:
    1. Energy efficient – how up to date is the book in terms of technology?
    2. Concrete and Mortar
    3. All. sans regulations for building

    Where are your offices as I can collect the books and what is the total price?

    • The energy efficiency book was written after the new XA regs were published, so it’s as up to date as you’ll find. This and the concrete and mortar book are ebooks and can only be ordered online. If you want the SANS (National Building Regulations) you have to buy these from the SABS – either from one of their libraries or online.

  8. hi
    I’m about to build a granny flatlet. The plans are approved. I would like to know if an engineer is required for this simple project. If it’s required can I use an engineer who is not registered to the council of engineers but has a degree.

    Thank you

  9. hi I just board property and [ plot ] and I want to build thatches as guest house thatch lodges on turf how and what must I do please thank you Andre 0723573535

    • No idea what you are talking about Andre. In any case this isn’t something that is specified in the NBR – and if you don’t own the property you will need the owner’s permission to build anything.

  10. im here to request funding application forms from your institution so that so can able to submit my proposal. if you wish to contact me telephonically contact me @ 081 064 8881.
    thank you.

  11. Hi

    I would like to find out if it is possible to strengthen a single story foundation to a double if so what is the process

    Thanks

  12. I have received council approval for my house plans. Which includes a Geotechnical report that stipulates the specification required for the laying of the foundations. The building inspector has approved the trenches and the installed reinforcing. Do I need a Engineers certificate for the foundations and concrete slab?
    Council do provide a list of certificates and approvals that I need but nothing for the foundation and concrete slab.

    Kind Regards
    Brian

    • Double check with council; if they haven’t asked for one then you don’t need one. The forms etc are all in Part A of SANS 10400 and there isn’t anything there that I can find. If the foundations and slab were designed by an engineer, they might need something.

    • Hi Brain

      The engineer must supply drawings especially for the slab, then the contractor will carry out the work.

      Foundations can be stipulated verbally however paper os always recommended and engineer will inspect prior to pouring foundations.

      Don’t hesitate to contact me for any advice.

      Regards
      Daniel Ferreira
      082 962 5373

  13. I like this page. I will like you to help me explain how load is transmited from column to footing.

  14. Hi,I am in the process of putting up a tower to support my water tanks (2 X 2500 l ) next to my new borehole.I live on a plot which has an abundance of ou klip just under the top soil. The tower is constucted with four legs 9 m high,what should my concrete dimentions securing the legs be ?

    Kind regards
    George

  15. I would also like to find out the pros and cons with using the “Crush” mix for the foundation as opposed to the separate sand and stone?

 Leave a Reply

(required)

(required but will remain confidential and not be published)