Nov 152011
 

Walls Support the Roof and other Loads-Part K

Building walls

It is vital that walls are strong, stable, waterproof and fireproof. The way that the roof is affixed to the wall is also very important.

The fundamental structure of a house is formed by its external walls, which must support the roof and take any other load that is built above. The section of the National Building Regulations that deals with walls is SANS 10400-K  and it has several parts, each dealing with building walls, and the elements of how both internal and external walls should be correctly constructed.

Changes to the Legislation

Like much of SANS 10400, Part K: Walls has changed quite substantially, both in terms of the legislation and the section that deals with The application of the National Building Regulations, which is the document prepared by the SABS and published separately to the legislation.

(NOTE: Previously SABS 0400, which became SANS 10400, was published by the SABS in its entirety, with the legislation and a Code of Practice which took the form of “deemed-to-satisfy requirements”. When the legislation changed on May 30, 2008, this was gazetted. The SABS then progressively updated its guidelines and published them over a period of years, as a series of individual documents. These are available from offices of the SABS and from the Bureau’s webstore, HERE. The new version of Part K was published on 29-03-2011 and it costs R517.56 including VAT.)

This article deals primarily with the changes to the legislation, and how it applies to building walls, rather than the South African National Standards.

Structural Strength and Stability of Building Walls

Part K 1 of the regulations states that, “Any wall shall be designed and constructed to safely sustain any actions which can reasonably be expected to occur and in such a manner that any local damage (including cracking) or deformation do not compromise the opening and closing of doors and windows or the weather tightness of the wall and in the case of any structural wall, be capable of safely transferring such actions to the foundations supporting such wall.”

This has been substantially expanded. Previously the legislation simply said the walls should be capable of safely sustaining any loads to which they would be likely to be subjected. It also said that structural walls should be capable of safely transferring such loads to the foundation supporting a structural wall.

There are various walling materials available, made primarily from clay and cement-based products. You will need to decide which is the best material for your particular purposes. Walls can also be built with stone or timber, but each material has its own set of methods to satisfy the requirements.

Solid brick walls normally consist of two brick skins that are joined together and strengthened with brickforce or brick reinforcing and/or wall-ties (a mild steel wire laid between some of the courses to add strength). The interior and exterior surfaces are normally plastered but may be fairfaced (facebrick). Concrete block walls are a more economic option and are often used for garages and outbuildings.

Water Penetration of Walls

Whatever materials you choose to use when you build, the method used for building walls must comply with Part K 2 of the regulations. Primarily they must be built to prevent water penetrating into any part of the building. All cavity walls must be well drained by means of weep holes above a damp-proof course. All cement bricks and blocks are relatively porous and should be plastered or rendered on both sides for thorough waterproofing.

Basements and semi-basements are also referred to in the “new” legislation, and any room below ground must be adequately waterproofed.

The legislation reads: “Where a building includes a basement or semi-basement, the local authority may, if it considers that conditions on the site on which the building is to be erected necessitate integrated designs for the penetration of water into such basement or semi-basement applicable to all construction elements or components thereof, require the submission of such designs for approval. Construction shall be in accordance with the requirements of the approved design.”

In recent years, a variety of alternative construction methods have been developed, most notably in the sphere of cheaper housing. These include the building of walls with insulated fibrecement panels; with fibreglass panels; creating the basic structure with shuttered no-fines concrete; using polystyrene sprayed onto a basic framework; or piling up sausage-shaped bags of sand and cement. If you want to use any altrernative method it would be best to contact your local authority planning division, or building inspector, for guidance.

Roof Fixing

Part K 3 deals with the way in which the roof of any building is attached to the wall and states that this must be done securely and safely and must be able to withstand any natural forces such as high winds or rain and hail. Specifically, it states:

“Where any roof truss, rafter or beam is supported by any wall, provision shall be made to fix such truss, rafter or beam to such wall in a secure manner that will ensure than any actions to which the roof may normally be subjected will be transmitted to such wall.”

While this clause of the legislation is basically the same as it was previously – one word has changed with forces deleted and actions replacing it – there are substantial amendments to the so-called “deemed-to-satisfy requirements” published in SANS 10400, Part K Walls. Similarly there are many changes – more so in the form of additions – to SANS 10400, Part L Roofs.

The Ways Walls Behave in Fire

Part K 4 deals with Behaviour in Fire, and state simple that, “Any wall shall have combustibility and fire resistance characteristics appropriate to the location and use of such wall”.

Brick, block and stone walls are generally accepted as fire resistant. Timber frame with timber or fibrecement cladding need to be certified, and you should check with the supplier regarding these rules for their type of walling, before you decide which material you are going to use for building walls.

Deemed-to-Satisfy Requirements

Part K 5 of the legislation states that Parts K 1 to K 4 will have been deemed to be satisfied “where the structural strength and stability of any wall, the prevention of water penetration into or through such wall, the fixing of any roof to such wall, and the behavior in a fire of such wall” complies with the relevant part of SANS 10400. This standard, “Establishes deemed-to-satisfy solutions for rain penetration and damp-proofing and contains simple design and construction provisions for masonry walls in single-storey and double-storey buildings and framed buildings that do not exceed four storeys; masonry balustrade walls and masonry free-standing boundary, garden and retaining walls.”

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Roofs-Part L

  171 Responses to “Walls”

Comments (166) Pingbacks (5)
  1. HI Penny,

    I have a commercial property that has pillars and arches down the middle of it. I would like to brick it up to make a closed facade, the arches are currently closed of with “dry walling” and serves as a separation between two shops. Do I require building plans to brick up the arch? The height is about 3.6 to 4 m. Who should draw up the plans if so required. i would also like to build a brick wall inside the premises of 3 m high and take it further to the roof height of 6 m with dry walling. is this legal? and would i need plans?

  2. HI
    we are about to buy a house. the challenge that we are faced with are as follow
    1 roof leak – according to the seller his little bro has fixed the roof and we have asked for certificate of competency on working on the roof then the estate agent told us she will sue us if we pull out of the deal
    2 wall cracks – the same you brother was the one who fixed the walls.
    3 after they repair the walls they did not paint the house claiming they are out of cash.

    It sound like we are been force to accept the house even thought its incomplete and the young men who just completed matric was the one renovating and fixing the roof. So i need help regarding the matter, i havent sign the OPTC from the bank. what should i do

    • I think you have every right to pull out of the deal. If you tell the bank the story they will probably withdraw your bond! That would sort it all out.

  3. When we bought our house we knocked down an external BRICK WALL that strangely dissected the property
    It did not support any structures and was not on the boundary of the property
    Please let me know if we need to have plans passed to confirm this as a new buyer is querying the change

    • If it wasn’t structural there shouldn’t be any need for plans. However if your buyer requests the change, you might have to do it to ensure the sale goes through. Perhaps the best approach would be to ask your local authority if they need the change on your existing plans.

  4. Which mortar class and strength should you specify by cement face bricks at the coast?

    • There are SANS that specify mortar class and strength – but these are not part of SANS 10400 – The National Building Regulations. I have an info sheet on making concrete bricks and blocks that I can forward to you if you let me have your email address, however it doesn’t give this specific information – it is more general. But if you contact an SABS library they will be able to tell you which standard you need to look at.

  5. Hi Penny,

    We’ve recently built a house through a developer and there is a couple of things that bothers us.
    One of these is the strength of the bricks. We have a double storey and the lower level is build with bricks that average 6.3MPa. They had to break out quite a few bricks after we had a batch tested and it came out at 3MPa, but they left the 6.3 MPa bricks stating that NHBRC allows 10% variation. Is this true?

    Thanks in advance for your response.

    • The best thing is to contact the NHBRC and find out from them what they allow. You can also contact the SABS because there are other SANS that cover the strength of bricks… Or you could contact the Concrete Manufacturers Association. They would know.

  6. Hi there
    Long story, but a portion of my boundary wall between me and my neighbour was very badly built. Single brick, 2.4m high, no lateral support. Needless to say, it started collapsing 2 years ago. The enighbour refused to fix it, or to allow me to replace it. It finally collapsed completely a couple days ago.

    Now to my question: the builder he got (fortunately he has accepted responsibility), built a double layer foundation, but then used single brick above ground. He added piers projecting only to the neighbour’s side, in a hollow sort of design, every 3m or so. He intends building it to the original 2.4+m height.

    Is this ok? I’m only paying a part of it (again a long story), so I’m not sure if i can object if necessary? As you may have gathered, the guy isn’t very reasonable, and I would prefer not having any further confrontation with him.

    • All freestanding walls over 1.8 m require approved plans and they must be built according to the building regulations, which include where and how piers must be built. Table for wall piers Here’s the table for solid units (i.e. bricks vs hollow blocks).

  7. Hello

    I was told that it is illegal to build with concrete blocks,have to use bricks just like to confirm that.
    For the area of KZN

    • That’s absolute rubbish. Of course you can build with concrete blocks – they should though be specified on your plans.

  8. I came home during the course of last week to find that our neighbour has knocked down one column section of our adjoining vibracrete wall and had placed a thicker taller concrete pillar there…in a way it increases the security barrier, but does she not need plans to have to have this done? Also she has a garage and has recently, removed the garage roll gate and had a window frame fitted and converted it to a living space…does she not also need plans for this and our permission? What can be done in this regard?

    • If the wall column is hers she doesn’t need permission (presuming it is 1.8 m high or less). If it is yours or is common property she needs YOUR permission. It terms of the garage, she does need permission – not not necessarily yours. Alert the local authority in this regard.

  9. Hi there,
    I have to build a house soon and am pondering with the idea of casting the walls. Both external and internal. What are the implications and any recommendations please.

  10. We intend building an ensuite bathroom for our bedroom. We have a swimming pool and the bathroom will be build between our room and the swimming pool. Is there any restrictions on how close the outside wall of the bathroom may be to the swimming pool?

    • Swimming pools are not covered in the National Building Regulations Nelda. I have seen many swimming pools built right up to external house walls, so it shouldn’t be a problem providing all other specifications are met. You will of course need to have approved plans to build the bathroom and a qualified, registered plumber will need to do all the plumbing work.

  11. im about to build garden cottage.
    builders have submitted plan with 150mm maxibrick exterior walls
    An architect friend said max. length without lateral support is 3m (ie to closest internal/ external wall-as i understand it). The plan has a wall which is 5m (external) long-can it get passed?

  12. Hi
    I intend to do major changes to the interior of my house, eg a new passage and room size change.All interior walls broken down are not going to influence the roof structure.What is the regulation regarding the building of the new walls that will be to ceiling height?Thinking in terms of foundations.

    Thanking you
    Glen

    • Hi Glen, all the things you want to do might affect the roof structure and sounds as though the new walls that you want to erect will certainly have no supporting foundations if they are being moved from where they are at present. You will have to get an architect and or a structural engineer to draw up plans and give a report justifying the re-siting of the walls. I doubt that you will get approval if the proper foundations are not in place.

  13. Do you need plans if you want to brick up an outside opening to a servant’s room?

  14. Hi

    We are about to start with alterations and the building contractor has had common bricks, to be used for construction, delivered to our house. My concern is that the quality of the bricks seems to be sub-standard, as many of the bricks are partly broken, chipped and full of cracks. Is this reason for concern? Is there a certain minimum grade and/or requirement that bricks need to meet in order to be used for building internal and external walls? How would I be able to confirm whether the bricks are in fact sub-standard or not?

    Your advice would be greatly appreciated.

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