Nov 162011
 

Every Room Must be Fit for Purpose-Part C

The National Building Regulations (NBR) are not prescriptive when it comes to the size of rooms and buildings. However it is vital that the size of any room or space is fit for the purpose for which it was intended.

In the case of a really small house – or “dwelling unit” – the floor area of the entire building must be able to accommodate a “habitable” room as well as a separate room with toilet facilities. This is more for sanitary reasons than for comfort, and it makes perfect sense.

That’s about it, though the SANS deemed-to-satisfy requirements do give a little more guidance.

The updated requirements, published by the SABS in October 2010, were compiled with the assistance of the South African Institution of Civil Engineering. You can buy them from the SABS, either from one of their offices, or online.

What SANS 10400-C Covers

In essence the section on Part C, Dimensions in the Code of practice for the application of the National Building Regulations simply establishes the requirements for plan size dimensions as well as room heights and overall floor areas. It’s that simple.

Definitions

The National Building Regulations and Standards Act has a glossary of terms; however there are additional terms that are defined in the various parts of the SABS codes of practice.  In Part C, there is a new definition of category 1 buildings. These are specifically buildings that are classified as:

  1. Places of instruction (A3)
  2. Buildings used for worship (A4)
  3. Small shops (F2)
  4. Offices, as well as banks, consulting rooms and similar (G1)
  5. Dormitories where a groups of people are accommodated in one room (H2)
  6. Domestic residences with two or more dwelling units on a single plot (H3)
  7. Dwelling houses, which may or may not include a garage and/or outbuildings (H4)

But in addition to the classification there are several other parameters:

  • There must not be a basement in the building
  • The maximum length between walls or “members” that provide lateral support is 6 m
  • The floor area in the building may not exceed 80 square metres.

There are certain requirements and limitations that are imposed on category 1 buildings by other parts of SANS 10400. For instance, in terms of Part T, Fire Protection, they are restricted to one storey. The maximum number of people allowed in category 1 buildings is also regulated.

Supposedly this means that if a house, church, office, shop etc has a basement or is double storey, it is not classified category 1, and a different code of practice will apply.

Dimensions of Plans

When you see dimensions on plans, you will know that these are the horizontal dimensions between UNPLASTERED wall surfaces. Of course once you plaster a wall and re-measure it, the distance between the two walls will be slightly less, since there will usually be at least 10 mm of plaster on the wall (though no one coat should be thicker than 15 mm) – and up to 30 mm if three coats of 10 mm-thick plaster are applied.

The Height of Rooms

If you’re a keen camper, you may not mind bending down in your temporary canvas home. But homes and other buildings have to be able to accommodate people standing up! Very few people are taller than 1,8 m (most are shorter), and so room heights generally are set at between 2,1 m and 2,4 m. This doesn’t, however, prevent designers making ceilings higher than this, even though it does increase building costs.

Minimum heights specified relate to different rooms in homes and other buildings:

Bedrooms. 2,4 m above a floor area of at least 6 sq m with a clear
height of at least 1,8 m at any point that is more than
0,75 m from the edge of the floor space.
Any other habitable rooms in dwelling houses/units. 2,4 m above a minimum of 70% of the floor area, and
not less than 2,1 m above the remaining floor area.
All other habitable rooms. 2,4 m.
Passages and entrance halls. 2,1 m.
Bathrooms, shower rooms, laundries and toilets. 2,1 m above any area where a person would normally
stand upright.
Open mezzanine floor with an area no more than
25% of the area of floor immediately below it
2,1 m above and below the mezzanine floor.

Note that this specification has not changed since 1990 – so the existing table in the free downloadable version of SANS 10400 applies.

When ascertaining the height of a room, the minimum dimension allowed is measured from the top of the finished floor to either:

  1. the underside of the ceiling,
  2. the underside of the roof covering (if there isn’t a ceiling), or
  3. the underside of any structural element (member) that is below the ceiling or roof and is larger than 30% of the plan area of the room. In addition, if there is a structural element projecting below ceiling or roof covering level, the height of the projection may not be less than 2,1 m
dimensions

How to interpret the dimensions relating to minimum floor to ceiling height

In the top section of the drawing, two levels are indicated. Normally the height would be taken at level 2, but if the total plan size of the shaded areas in the bottom part of the drawing exceed 30% of the total area of the room, the ceiling height should be measured to the first level indicated.

Floor Areas for Buildings

Having said that the floor area of a small size home must be large enough to be habitable, plus must accommodate a separate toilet, there are other specifications in the regulations to consider. So while the minimum specifications are pretty tiny, they are not quite as small as you might be imagining.

For instance the regulations state that the floor of any permanent building that is used as a “dwelling house” must be no less than 30 m². Permanent category 1 building may be smaller, 27 m²; and temporary buildings can be as small as 15 m². So while a bedroom can legally be as small as 6 m² (providing no wall is shorter than 2 m) it won’t be sufficient to add on a bathroom and loo and claim that it is a house!

There are also minimum specifications in terms of the floor area allowed for a certain number of people using a room or building at any one time. This is based on the dimensions shown on the plans, but excluding the area that is taken by built-in cupboards, cabinets and so on (see drawings below).

dimensions

How to measure floor plan areas

These references are specifically in terms of change rooms and dining rooms, and so relate not only to private dwellings, but to hostels and other establishments. If one to 15 people are going to be using a dining room, the minimum allowable area is 0,8 m² per person, but the room must still be at least 6 m² in size.

Not much space to party!

Main Photograph top © Janek Szymanowski

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  125 Responses to “Dimensions”

Comments (124) Pingbacks (1)
  1. I recently purchase a 3 year old free standing house inside an Estate
    in Greestone. My question is what is the standard size of a Double
    garage? We are battling to park 2 cars, a small car and Suv with and
    be able to walk around cars with the garage door closed. I’m sure the
    buider short changed me. Branden

    • Generally a double garage will be 6.5 m wide. But the size will be on your plans. Measure what you have and compare the dimensions. You’ll soon see whether your builder scammed you!

  2. You seem competent. I see many garages built directly at boundary wall and not leaving 1.5m. Is it old rules? I would like to extend/move my existing garage to the boundary wall. Can I use it for other purposes, must the “garage” not have any windows and a maximum height or what regulations apply?

    • It varies and depends on the building line for the property. This should be indicated on the site plan for the property, and on the original drawing when the area was surveyed (which you can get from the Surveyor General’s office in Pretoria). But the local authority can give permission for a garage to be built on the boundary, though you would need to get permission from neighbours if the building line is changed. To extend or build a garage, you will need plans. All the NBR apply in terms of H4, which is a “dwelling house – occupancy consisting of a dwelling uni on its own site, including a garage and other domestic outbuildings, if any”. Plans will have to be drawn up by a “competent person” (CLICK HERE to read more about competency) who will advise what is required in terms of height, light and ventilation, fire walls etc. If the plans state that this is a garage, technically this is the only purpose it may be used for. However many garages are built either with additional space for storage, or are in fact used for storage. The two issues are “habitable rooms” and probably also rates payable to council. e.g. You cannot “live” in a garage, because it isn’t built for that purpose.

      • Thanks. Surely I won’t do it alone but knowing options beforehand helps alot. So a workshop, garage or hobby room would be allowed as long as you don’t live in them? I have just heard that those rules are going to change in March 2013. Do you know about that?

        • That’s not quite what I said. Basically plans include a description of “purpose” or function. And technically that is what the structure or room is for. Which rules have you heard are due to change? Let me know and I’ll find out. The NBR has only just been updated, and unless there are new parts, I doubt that there will be changes at this stage.

  3. We have people building a new house on the raised stand behind us. They have requested permission to build the double story house to less than a 1 meter from our boundry wall, behind the boundry wall is our small paved entertainement area that flows into our house. I am concerned about the rain water flowing off the roof into our patio and damaging our house. What is safe distance for the double story house to be built to prevent rain overflowing.

    • I would also be concerned that they would look straight onto your patio!
      But to answer your question… It is not so much a safe distance that you need to worry about, but an assurance that their drainage will be properly designed. We have recently been inundated with messages and queries from people whose neighbors blatantly build and alter boundary walls and then take zero responsibility for damage caused when they collapse or there isn’t proper runoff. Rain water needs to be channelled by gutters and downpipes into suitable storm water drains that run off to a municipal drain – and NOT onto your property.

  4. I would like to know if the municipality can insist that the dimensions of a toilet inside a house be at least 2m in lebght irrespectively of the width?

    • Adri they probably can, depending on the local authority’s interpretation. The NBR deemed-to-satisfy rules state that the minimum plan area of any “habitable” room must be at least 6 square metres and have no linear dimension that is less than 2 m. The only exceptions are kitchens, sculleries and laundries. But they don’t specify minimum size of toilet spaces.

      • I thank you for the response.
        Habitable room description does not include a toilet according to what I read.
        Does this then mean that the mun. can not actually do this.
        I await your responce.

        Thank you

        • You are right in terms of the definition of “habitable room”. The legislation defines this as “a room used or designed, erected, adapted or intended to be used by persons for sleeping in, living in, the preparation or consumption of food or drink, the transaction of business, the rendering of professional services, the manufacture, processing or sale of goods, the performance of work, the gathering together of persons or for recreational purposes”.
          And the legislation states only that, “The floor area of any dwelling unit shall not be less than that necessary to provide one habitable room and a separate room containing toilet facilities. So I think you have a strong argument.
          As a matter of interest, I just measured the guest loo in the house where I currently live and the room measure 1,7 m x 900 mm!

  5. I have built a prefab wooden room in my yard …… it is above the ground and not anchored or cemented in place. It is 3m x 3m and has a door and a window. My neighbour said i need plans for it and said he is going to get it pulled down ….. i was under the impression that if it was smaller than 10 sq meters and if it isnt a permanent structure (like a wendy shed), that I wouldnt need plans? Please help urgently as Ive spent a lot of money and Im very worried now 🙁

    • Minor building work [CLIK HERE to read more about this] does not required plans. BUT – and this is important – the National Building Regulations say that you must still notify your local authority that you are going to undertake minor building work.
      Like all other structures covered in the regulations, a “prefab wooden room” would have a purpose or function – and it needs to be built for this purpose. Minor building work does NOT cover living quarters. It does, though state that if a tool shed is smaller than ten square metres, it qualifies as “minor building work”. So you would be within your rights if you erected the “shed” IF it was under ten square AND you notified your local authority of your intention to erect it.
      There is another issue, and that involves “temporary buildings” which may be erected without plans and used for a specific period of time – agreed by the local authority. However in this instance the regulations say that you need to submit SITE PLANS and general LAYOUT DRAWINGS as well as state what it is for and how long it will be used. It doesn’t state how long you may have a temporary structure for – but builder’s sheds are precluded.
      My suggestion is that you submit a letter to your council to say that you have undertaken “minor building work” and have only now realized that you should have notified them of your intention to erect the shed. Specify what sort of structure it is – you will see what is allowed in the link above. If you are using the shed as a dwelling, it is very likely that your neighbour could have it pulled down. If you are using it as a tool shed (or garden shed) you shouldn’t have a problem. Good luck.

  6. Is there any scope for alternative building techniques in South Africa? For example earth bag, cob, strawbale etc.

    Also interested in the American “tiny house” movement. Looks like these buildings might be illegal in SA.

    • Yes Tim there is, and there are examples of all three you mention that have been built perfectly legally in this country. I think that half our problem – in SA that is – is that we can build with blocks and mortar very cheaply. We generally don’t bother with energy efficiency either.
      I also love the tiny house movement – some wonderful examples of minimalism… our minimum dimensions are rather tiny, so I wouldn’t assume illegal …

  7. Where can I find out how much of my property can be built on (R.O.C) is?

    • Cheryl there are building lines that the local authority will impose. For instance you can’t usually build less than 1.5 m from a boundary. This will determine the area on which you can build. There isn’t a set %.

  8. Hi Penny

    Trust all is well. We are looking at building a 36 square/m garage (double garage) next year. If possible could you please advise what the estimate cost of such a project is. Looking at using normal bricks or blocks and a normal roof. So plain-jane… We looking at just getting the structure up and we can modify as we continue to live on the property. At the moment we have a carport which is not working for our needs. It would really be appreciated if you could assist. We’ve been searching the net but most blogs are out dated. Your blog is the most recent I’ve come across.

    Many thanks for empowering us with knowledge.

    All the best.
    Regards
    Yolanda

    • Yolanda, there are so many factors that come into play – cost of bricks or blocks – cost of cement and sand (and crushed stone for foundations). Cost of timber. Type and cost of roof covering. Labour costs. Probably the cheapest route will be to use concrete blocks and corrugated iron sheeting (so that your trusses can be relatively lightweight). Remember that you are going to need professional plans to be passed by your local authority – and a “competent person” will need to submit these for you. A draughtsman is likely to be the least expensive option; and he/she would probably be able to give you a pretty accurate guesstimate of material and labour costs in your area. Here is a link to a story I wrote recently for an American website on small house building. It might be useful in terms of estimating. I also have a chapter on quantifying and costing in my updated book on Owner Building in South Africa.

      • Good Site -Penny, South Africans are getting ripped off by fly by night contractors. Building ventures must be well thought through your book will help many…
        Yolanda can enquire with a finanicial institute she uses for a estimate per
        sq metre pricing to build, tile roof or zink sheeting.

  9. The Home Owners in this estate require the height of my two lateral boundary walls on the excavation leading down to a marina to be measured from the “general height of the ground level, natural or engineered by the original developers, where the wall was built”.
    To alter the walls would cause me great expense as they are unfortunately already built. They say the relevant “Architectural Guidelines” for this development which state only “All heights measured from datum 3m above msl.” applies only to to houses. I think that “msl” is legally meaningless.
    If they are correct where can I find legal authority for the exact way the walls should be measured? My municipality is not prepared to lay out this information for me.
    Please help.

    • To be honest, I had never heard the term mean sea level (msl) until now. I presume this has been used because the development is right next to the sea. But what is the issue here? Is it the height of the walls (are they too high)? It also isn’t clear from what you say whether you or someone else built the wall, and when.
      If there are architectural guidelines for a development, this is the “legal authority”. It over-rides anything that the municipality might require from builders outside of the development. If there is nothing about walls other than those of houses, I would imagine that there could be some sort of precedent that relates to what other home owners have done/been allowed to do… unless of course this is a new development. My advice is to get a copy of the guidelines and track down the architects who compiled them. They should be able to help you.

  10. Hello

    What are the average building cost of a double garage ( double in lenght but not in width)

    Thanks 🙂

    • It depends what you use for building. e.g. concrete blocks, clay bricks etc – the pitch of the roof and materials used for the roof covering. It’s the old adage, “how long is a piece of string!”

  11. Hi

    I am in the process of buying a 550 square metre building site. What is the maximum size of house that I am permitted to build on this size stand?

    Thanks
    Jayce

    • It depends on the building lines attached to the plot. You will be allowed to build x metres from each boundary and can probably go up a storey. So let’s use the old adage again, “How long is a piece of string?”

  12. Hi there.
    What is the minimum size of windows and doors allowed for a room?
    Is there a calculation formula?

  13. Hi there

    What is the minimum width of a door way or door opening. And where can I find more detail in this regard ?

    • Hi. You found the right place on the site for dimensions, but the National Building Regulations and NHBRC guidelines do not give specs for doors and openings. Generally designers base their plans on standard door frame sizes. Based on this, an opening wouldn’t be less than about 700 mm wide, which is more or less the opening size from the inside members of a door frame.

  14. Hi

    i just recently purchased a new car (average – Hyundai sonata) and realized that it does not fit my garage (3m wide, 4.3 m long). As i am a tenant, i would like to know if there are any legal building regulations that regulates the minimum size of a space deemed fit for use as a garage? SANS 10400 does not give any minimum dimensions for garages.

    • That’s an interesting one Sylvie. Part C of the Building Regs gives minimum dimensions for rooms and buildings, but as you have probably realized, the focus here is on habitable spaces. The dimensions are small and intended to be guidelines for “affordable” housing – as well as “fit for purpose”. So if someone builds a “tiny” garage for their mini, I doubt that there is anything to stop them. Some local authorities may insist on a specific minimum size for a garage (you could check with yours); private housing developments might too. But anyone renting/leasing a property, does so knowing exactly what they are going to be renting. So I am going to stick my neck out and say you don’t have any recourse.

  15. Hi there

    I wonder if you could help me with a garage question. I’d like to build a double garage on my property, what would be the absolute minimum size we could build to? We have the length but width is a bit of a problem.

    Thanks
    Courtney

    • Hello Courtney,
      You should be guided by the size of the average car. You need to be able to park two cars side by side – and open doors without bashing the adjacent vehicle.
      A double garage may be built with two single doors, or with one double door. So you can also be guided by the size of standard garage doors. The length – or height – of both is generally 2130 (i.e. just over two metres). Single garage doors are 2440 or 2450 wide; and double doors, 3000 (roll-up) or 4880. Some double garage doors are as wide as five metros +.
      If you can’t accommodate a double garage width wise, perhaps you could build one that accommodates two cars tandem. It’s not ideal, but it might be a solution.

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