Foundations

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.

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110 comments

  1. I need the specifications for foundations for a granny flat – Cape Town area

  2. Hello Daniel, we have added information about foundations which should help you. Go to National Building Regulations, Building Regs Part 1 – Foundations; or follow this link
    http://sans10400.co.za/foundations/
    You might also find an article on casting a slab, that is on one of our sister sites, useful. This particular slab was in fact constructed for a factory-manufactured timber “granny flat”.
    The site is http://www.howtoinfo.co.za
    Cast a Concrete Slab … which you will find under Building & DIY
    or follow this link
    http://www.howtoinfo.co.za/cast-concrete-slab/
    If you require more info let us know.
    Kind regards
    Penny
    Follow this link

  3. Hi Penny,
    Thanks for the reply. Could you also send me info on the manufacturing of roof trusses, please. I would also appreciate drawings of trusses and specifically how to join into an existing roof.

    Thanks

    Danie

  4. Hello Danie, I have added a section on roofs and roof trusses relating to the National Building Regulations. http://sans10400.co.za/roofs/
    I have also included a drawing of different roof trusses from our book, The Complete Book of Owner Building in South Africa.
    I cannot advise specifically how to join your two roofs, as I have no idea of the design of the existing roof. The simplest option – which will work if the extension continues in a straight line from the existing house – will be to continue the line of the rafters, and to construct them in the same way as those that were originally used. For example, if they roof was designed using six bay Howe trusses, then you continue the extension with these. Obviously the pitch will then need to be identical as well.
    I will add some more information relating to the manufacture of roof trusses at the beginning of the week. In the meantime, I hope this is helpful.
    Kind regards
    Penny
    PS We totally revised Owner Building last year, and an all-new edition will be published soon.

  5. Mrs. A. Balaam

    Hi Penny,

    Can you please tell me when do you need plans for an open carport? Its got a corrorated iron roof with 4 tube steel pillars supporting it and open on the sides. But its built on a concrete slab thats about 1 meter high and is raised. I don’t know what’s inside it. The land is sloping so the house is built at the bottom about 6 meters down. There were no plans submitted to town planning and it’s not on the sectional title plan. Thanks. I can email a photo if it would help.

  6. Any structure that has a solid roof should have a plan. Generally a carport with steel posts would be constructed with the posts embedded in a concrete footing. If you can get hold of a copy of our book Build Your Own Carport & Pergola (Struik Publishers 1994), you will see that these should be approx. 600 mm x 600 mm x 600 mm. I am presuming that the concrete slab is simply a surface for parking, rather than a foundation. If it is raised, it might have been filled with soil or rubble. Do email a pic, it will give us a clearer picture.

  7. Hi Penny, thanks. How do I attach a picture? I don’t see a button for it?

  8. Hi Penny

    Is strip foundation specifications for a double storey with concrete first floor and chromadek roof the same as for a single storey?

    Thanks very much.

  9. The specification given in the Building Regulations and SANS 10400 are MINIMUM specification for building. The greater the load, the more substantial the foundations will need to be. It is the local authority’s responsibility to check that the dimensions and other specs – e.g. reinforcement – are sufficient for the plans that are submitted. So in a word: “No”.

  10. I was wondering if i need to put reinforcement into my foundations for a double garage/ store room/ accomodation?

  11. Probably – it certainly won’t do any harm. It depends largely on the soil conditions.

  12. hi i just want 2 know the size of foundation of a 3 story. And the types of foundation and why there differ

  13. I cover the different types of foundations in my book, Owner Building in South Africa. IT is available as an ebook and with a hard cover, from most good bookshops and from Kalahari. Foundations are also covered in detail in the NHBRC building manuals, see http://sans10400.co.za/national-home-builders-registration-council/

  14. Hi Penny,
    I just wanted to know,what is the procedure if I want to make my existing house into a double storey?

  15. Sudhir, It depends on the existing foundations.So your first step should be to access the original plans. If you don’t have them, your local authority should have them on file. If the foundations are not adequate to support a second storey built with bricks/blocks and mortar, your best bet will be to look at timber frame using relatively lightweight materials. Either way you are going to need a qualified person to draw up plans for you to submit to council.
    Another option might be to go into the roof – if it is pitched.

  16. For a project I need to discuss foundations on the Vaal river. Where can I find info on the type of foundation required near a river? Surely we need to know what kind of soil is present.

  17. I discuss problem soils in my book, Owner Building in South Africa. But you are correct in saying that you need to know what type of soil is present on site. So it is the Vaal River area rather than just generally a river, that you need to worry about. Areas in and around Jhb, Pta, Welkom and Bloem commonly have sand that moves a lot and collapsing sand is common. Much of the Free State has heaving clay. You should be able to find this information on the Internet.

  18. hi Penny
    im about the to build a dinning and covered patio area to my house(waiting for plans from council) both of which will have ibr sheeting for my roof The ground in the area is very rocky, can you please give me the depth and width for the foundations and do i require re-inforcing (re-bar)
    thanks

  19. Marcus, that information should be on your plans. Depth, width and reinforcing will depend, not only on the condition of the ground, but also on the structure itself.

  20. Lionel Kinsey

    Hi there Penny I am planning to build a house from vibracrete panels what type of foundation would be required as I know the posts go 600mm down but not sure of floor.

  21. Lionel, minimum foundations should be no less than 200 mm deep and no less than 600 mm wide – but of course that is for bricks and mortar. If posts are to buried 600 mm deep, the footings should be at least 200 mm below these. BUT – if your are using these posts and panels for a “house” you DO need plans. And the plans will state what foundations you need. AND THEN, the local authority will still have to approve these. A “jimmy” house could have a dirt floor. A slab though should be at least 200 mm deep. My book on Owner Building might help you.

  22. hi Penny
    i intend to build a lounge and garage /patio as an extension to the existing house, however i would like the foundation of the new lounge and garage to be strong so that in future it must allow me to add rooms on top of the garage and lounge (double storey) how deep must the foundation be?thickness of the walls and any other information that i will require.

    thanks in advance
    Desmond

  23. Desmond, if you are building an extension then you will need a competent person to draw the plans. This person will be able to advise you in terms of exactly what it is you plan to do in terms of foundations. My book on Owner Building has some very useful info, and you can also read what the NBR say. I have already given a fair bit of detail on this subject on the web site. There are too many variables for me to be able to give you a simple answer here.

  24. i bought a plot and plan house in a area, i stay about months in the
    house and in and out side it start to crack, my nr are 083xxxxxxx for
    more information

  25. HI,We built a house on a newly established estate. Part of the
    problems we have encountered was that the 1st 3 months of moving in
    our patio tiles have collapsed, our doors in the house do not close
    properly – even though the builder has “shaved” them a few times. and
    finally, after being in the house for just over a year, we noticed
    that our courtyard gate was rotting. The builder “fixed” this by
    painting over the rot. There are a few gates on the estate with the
    same problem. We have now been told by the developer that according to
    the NHBRC court yard gates are not covered and they are not liable to
    replace them. Please advise.

  26. Susan van Rensburg

    Goeiedag
    Ons huis is nou vier jaar vandat dit opgerig is deur ‘n bouer wat
    geregistreer was by NHBRC, ons het ‘n verbandlening aangegaan. Die
    vloerteels aan die binnekant van die skuifdeur lig nou op a.g.v.
    klammigheid. Het ons nou enige eis vir die herstel daarvan. Watter
    inligting benodig u nog om ons hierin behulpsaam te wees?

    JJJ van Rensburg
    Wistariastraat 13
    Blue Horizon Bay
    Port Elizabeth

    Sel 0842998977

  27. Hi Susan,
    Ek sal probeer in Afrikaans te andwoord, verskoon enige taal foute 🙂
    Dit lyk vir my dat dit hang af wat die inhoud van die kontrak is tussen U en die bouer.
    Jy moet dit weer deurlees en kyk vir enige “exclusions” of tyd beperkings.
    Die NHBRC het hulle eie tydperke waarbinne U ‘n eis kan maak binne hulle waarborg, hier is die “link”: http://www.nhbrc.org.za/index.php?option=com_content&view=article&id=71&Itemid=88
    Vra vir hulle of U ‘n prokureur moet kry.

  28. Hi Mark,
    I am sorry but we do not make phone calls. You will need to supply us with more information if you want us to give you some advice. It sounds as if you have a claim if the cracks are serious and not just normal “settling” cracks. Contact the agent who sold you the house and point out the problem to them. If you got a bond from a bank on the house they will need to send an inspector to check the house because the house is the security the bank holds and must be solid and not cracking up.

  29. Hi Kim,
    I think that as far as the gate is concerned, he is right. But that sounds like the least of your problems.
    You need to establish why the tiles have “collapsed” and why the doors in the house do not close. You say that the doors are inside the house so I assume that they have not got wet and swollen. If so, then you have to look if there are any cracks starting to appear above your doors or anywhere along your walls. If there are, then these could be settling cracks. BUT not being able to close the doors suggests that the problem could be more serious. Ask the builder for a meeting to explain why there is so much movement in the building so that the doors cannot close, if he tells you that it is because of the clay content, then he should have put extra reinforcing in the foundations if he knew this. You do have recourse to the NHBRC who cover these things. Have a look on our NHBRC Q&A page. There is also a link at the bottom of that page for their contact numbers.

  30. Kim I don’t believe you should be relying only on recourse to the NHBRC. Their warranty is limited (usually 5 years for structural defects) and very specific, and since this is happening within such a short period of time, the developer must surely be held liable. Check your agreement with the developer very carefully – if need be get a lawyer involved. You probably also have recourse in terms of the Consumer Protection Act. I’d be interested to know which developer this is. There are several major players in the building industry that continue to deliver shoddy workmanship and get away with it.

  31. We are looking at building a rock (natural stone) cottage on an incline (hill side) (rocky soil).
    At the bottom of the slope the site will have retaining walls (rock) of about 1m high, ontop of which the house walls (single storey) will be built.
    Natural stone is quite heavy. How deep and wide do the foundations have to be and will 10MPA strength be strong enough or do we need to consider re-bar? The resultant wall will then be 1m (footing) + 2.4m wall = 3.4m. We’re planning light roof (corrigated iron).

  32. Hi We have a lot of water draining in the area where the foundation was dug. An engineer is coming out as we’ve been pumping the water out for four days, but it keeps filling up. What to do?

  33. Hi Janine,
    I am not sure what area you are in or what your soil conditions are as some areas have a high water table during the wet season. This happened to me on one of the houses that I was having built on a sloping site and we discovered that it was an underground stream. The solution was to install a drainage system to divert and channel the water away from the foundations which was quite a mission. The engineer that you have called will certainly be able to advise you on the best solution.

  34. Hi Aletta,
    I would love to help you but any advice would be thumb-suck. The law requires that you have a “competent person” draw up plans and by the sounds of what you are wanting to do you will probably need an engineers report before starting construction. I know it might seem a bit “over the top” but that is what the regulations require.

  35. I am looking to build a home but want to use one of these standard roof structure they use mostly for stores and so on 20 x 9x 3.6 (h). They will supply me with full engineering drawing. Now my question is I still have to do the walls and foundation separate from the roof do I need a separate plan or do I still need a plan at all not sure of the complete process to follow. Do I need land surveyors. If f someone can help me with a general Idea of my steps to follow for my plans and before building starts I would highly appreciate it I am in the Pretoria area

    Regards

  36. Dirk I suggest you buy a copy of our book Owner Building in South Africa. It takes you through the whole process from buying land, getting plans drawn (including the role of land surveyors), building, finishing and landscaping. Alternatively take the time to read through this entire site – and our sister site. You will glean quite a bit from what we have written and posted.
    To briefly answer your questions: You need a full set of plans as described in Part A of SANS 10400 (see General Principles & Requirements on this site). The engineering drawing for the roof will then be submitted with your other plans – you need a competent person to do this. The link I have given you is to our other site where the concept of a competent person is described. This is required BY LAW!
    If your boundaries are not accurately demarcated you will need a land surveyor to check these.
    Contact your local authority (Tshwane) for further information – e.g. any bylaws you need to be aware of. You can also download the Tshwane Town Planning Scheme from this site. I have given you the link.

  37. I am looking at building a 3 line double brick wall with square pillars every 3000mm (4 brick pillar, 18 lines up). Total length will be 20 meters. These openings will have palisade panels in. My question is this, will a 200mm deep foundation be sufficient for this, 400mm wide?

  38. Werner, rule of thumb when building foundations is to ensure that the width of the foundation is equal to (or greater than) the thickness of the wall plus twice the thickness of the concrete. This in turn ensures that the concrete forms a 45 degree angle between the base of the wall and the bottom edge of the foundation. Since you are building pillars, you need to use the dimensions of the pillar – not the wall. And BTW we call them courses, not lines 🙂 Another good rule of thumb is that strip foundations should never be less than 200 mm deep or 600 mm wide. Standard bricks measure 222 mm x 106 mm and your mortar joint will be about 10 mm = 338 mm + 400 mm = 738 mm (if the foundation is 200 mm deep). So you should make the width about 750 mm.

  39. Hi I bought your book but can’t find any details on a double foundation We don’t intend to build double storey but we want to do a hight pitched light steel frame roof with chromodek & have the option to go up & use the loft space should we later want to. Can we do single foundation reinforced or must it be double foundation or must it be double and must every double foundation also be reinforced. What are the specification (formular) for double foundation? Thank you

  40. Charlie, if you are building you need plans drawn up by a competent person. That person is qualified and will know what to specify for the foundation, depending not only on your roof structure, but also on the design of your house, including the walls.
    Also, I think you are confusing terms here. You don’t have a “double foundation” because you are building a double storey building. The size of the foundation is determined by the weight it has to carry. Most foundations should be reinforced, but that reinforcing also needs to be specified by a competent person. The rule of thumb to use is explained on page 99 of my book (on page 101 of the old edition). Essentially the width should be the width of the wall plus twice the thickness of the concrete. But you would increase the dimensions to improve the load bearing capacity of a double storey. If you decide to use the loft space at a later stage you will need to submit a rider plan that indicates the class of occupancy according those given in Part A, General Principles and Requirements of SNAS 10400.

  41. Who can certify foundation and floor with a certificate?

  42. At what stage Liezl? I’m not sure about certificates, but both the NHBRC and the local authority check foundations and floor.

  43. The NHBRC are more worried about what they can get out of the deal. They are also very incompetent and do not assist at any stage if a problem occurs.

  44. I’ll second that one!

  45. Raymond Robertson

    Hi
    Our builder has recently poured the slab for our new house and then discovered the dimensions where incorrect (to small) He has subsequently added on the extra +- 300mm onto the existing slab which was poured over a week ago –
    Should the additional slab be “tied” in some how to the existing slab to avoid cracking etc? or is it ok to simply add on?
    thanks so much
    R Robertson

  46. HI.
    I have a huge school project that i have to do and i was wondering if you could help me.

    i have to design and a school pavilion which can be at and maximum 30m by 100m but im planning on making it smaller. and i want it 3 stories high. I’m try to figure out the thickness off the concrete foundation that i should use and the type of concrete i should use to keep my building standing with all the correct laws and regulations in place.
    please help.
    thanks.

  47. maret du plessis

    what is the minimum time recommended for any foundation to cure before building can be started?

  48. Hi,How deep must the foundation be for a boundary wall? Build with standard 190 x 190 building blocks.

  49. Hi Wynand, The size of the foundation does not only depend on what bricks or blocks are used but how high the wall is going to be so that the foundations can bear the weight safely. Here is the standard formula for walls:
    Footings
    You can read up more on our other site:
    http://www.ownerbuilding.co.za/concrete-foundations/

  50. Hi Maret, Soil, atmospheric and weather conditions as well as altitude all affect the drying and curing time of concrete foundations, but usually a day or so of drying should be OK. Just take care in very hot and dry conditions to keep the concrete damp (not wet) and let it cure properly.

  51. Freddie adoons

    Hi i wuld like to know,what happens if i just casted a slab then it started to rain imediatly afta casting?does this mean i mst demolish the slab and redo it again or can i just do screting on top?please reply,i thank u in advance!

  52. You should be OK so long as it was not a flood that washed away a lot of the cement. The longer the slab is kept damp while it cures the better it is for the slab. So lond as it is not too wet you can screed on top but just try to let it dry slowly as fast drying can cause cracking.

  53. We are busy building our first house via a contractor.

    We are now at foundation level for a while now with work not really continuing, due to a number of reasons the contractor mentioned. Someone mentioned to me, that as far as they are aware the foundation had to be done on one day. Our contractor did it over two days though. Is it true that there is a problem if it was done over more than one day?

    Kind regards.

  54. Ideally foundations and slabs should be placed in one go. These “emergency joints” are fairly common. It should not be a problem so long as the “construction joint” is done correctly. There should be a sloped edge (not smooth but rough)so that the fresh concrete can overlap the older concrete and make a good bond. It is recommended to brush the older edge with a wire brush before placing the new batch.

  55. Hi there
    I am wanting to build a double storey house in a rural site, please advise as to how thick and wide the foundation and the top floor slab. I intend to put the grass roof.
    I assume your book can be assisting also for me to know more about building, how can I get a copy ?

  56. Please read our post on foundations where you will get all the info you need: foundations There is a picture of our book on every page of the site you just have to click on that and you can buy it online.

  57. I want to build a Three Storey building with a Lift, Pls adive whats the minimum depth of the foundation is to be.

  58. Whats the depth of a three storey building with a proposed lift

  59. 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?

  60. Hi Janek
    I am in the process of doing extensions on my house and I need a book that will explain to me what process the builders should go threw from digging to completing the foundation at floor level. Can u assist?

  61. Morne, we have done the most comprehensive and best selling book in SA detailing all the steps on building a house, extensions go through all the same processes. This can be ordered through Kalahari. Look at our website and click on the link on the left “Get this best-selling book today”

  62. 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

  63. I wish I could help with concrete footings for supporting 5 tons of water plus the tower, I suggest possibly the tank suppliers, or possibly contact PPC cement technical department or then a structural engineer.

  64. Thanx , will contact them.

  65. You need an engineer to design your foundation for you.

  66. You need the assistance of an engineer.

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

  68. 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

  69. 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.

  70. I am not sure if you are talking about the foundation slab or the floor slab. If it is the floor slab, this should be resting on the foundations, and if made bigger it won’t. if it is the foundation slab, this should have been approved by the local authority before the concrete was placed. I think it is more important to be sure that the groundwork (i.e. the trenches) were prepared correctly. You shouldn’t have a problem placing concrete in batches – it happens all the time when there is a big area.

  71. Good luck with your project

  72. How deep below ground level should the foundation be?

  73. I have a question.my company is mandated to build a 1800m x2.1 m boundary self standing wall and I don’t know how deep the foundation must be

  74. Hi there!i live in carletonville west of jhb and I would like know if I am allowed to build about 8 small cottages in a 1000sqm stand to rent it out?

  75. Hi Wynand/ Janek

    This formula is a basic guide only and should not be used to construct any load bearing walls. The footing size is dependant on a few more factors other than those mentioned. The first step in foundation design is to know the existing soil conditions and to determine the load bearing capacity. This can be done by taking a standard DYNAMIC CONE
    PENETROMETER (DCP) TEST.
    The second step is to determine the load (self load + imposed load) which should preferably be determined by an structural engineer.
    The third step is to take the ultimate load and calculate the foundation width and depth accordingly.
    If the calculated foundation size is smaller than what is shown on the above image, then it is recommended to use the image as a nominal foundation size.

    Hope it helps.

  76. Hi Arno, Thanks for the added info, you are right there are always other factors that have to be considered that is why Architects and Engineers study for so many years to be able to work out all these calculations.

  77. 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

  78. You can underpin a foundation, but you will need input from an engineer.

  79. 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.

  80. 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

  81. 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

  82. Your local authority will have to answer that question, but it’s not likely.

  83. 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.

  84. Nobody will be contacting you because we are not a financial institution! Sorry about that.

  85. 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?

  86. 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.

  87. 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.

  88. 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.

  89. Daniel Ferreira

    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

  90. Daniel Ferreira

    Hi Lifa

    I highly doubt you can.

    Regards
    Daniel

  91. Daniel Ferreira

    And yes you do need a certificate.

  92. Steven Jennings

    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?

  93. Well put, sir, well put. I’ll cetlainry make note of that.

  94. 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

  95. Hi Muzi, Please read our article on this here: http://sans10400.co.za/stormwater-disposal-2/ You will see that you are not allowed to drain your stormwater or any other water run off on to your neighbours property.

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

  97. 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.

  98. 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

  99. 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.

  100. 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?

  101. 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!

  102. As I don’t have access to your plans I am unable to do this calculation.

  103. No – the foundations would need to be underpinned

  104. 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.

  105. Good afternoon. I have a 1970s single skin double garage with 600×150 foundations and wish to go double story with a granny flat above.

    I know i will need to add a a further skin to my walls to take the load and tie that in with brick force and butterflies but am uncertain what to do with my foundations and how to strengthen them up to take the load.

    The other thought is to make it self supporting and do a steel structure with columns on a suitable plinth but not sure that wont cost more.

    Your advise would be most welcome. Thank you

  106. Hi Warren, With additions like this you will need to submit plans done by a competent person and they need to do an inspection and advise you if your foundations will take the extra weight before drawing the plans. It is not only the size of the foundations but the type and quality of the soil under the foundations that is equally important.

  107. 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.

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