Nov 162011
 

Every room must be fit for purpose

DimenPic1 s Dimensions

Photograph © Janek Szymanowski

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
Part C floor to ceiling dimensions1 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).

Part C floor areas 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!

  76 Responses to “Dimensions”

Comments (76)
  1. what are the south African standards for door frames and window frames?

    • Kevin, The SABS will be able to tell you which standards (SANS) are relevant. The SABS webstore is temporarily unavailable, so I can’t do a search for you, but there are probably several depending on the materials used – e.g. wood, steel, aluminum etc.

  2. Hi,

    Referring to G1 offices, I would like to find out when should a workplace need an emergency exit door (excluding the entrance door). Is it required or do we work on the size of the workplace?. Your assistance and guidance will be highly appreciated.

    Regards
    Louis

    • Louis you probably need to access Part T, Fire Protection of SANS 10400. This is where emergency exits are covered. viz.
      4.16 Provision of escape routes
      This relates to the size of the building as well as the number of people occupying it. e.g. “Any building of a height of more than three storeys shall be provided with not less than two escape routes and”

  3. What will it cost to build a 6 x 7m double garage in johanessburg

  4. When calculating the maximum size of a double storey house on a plot, do you consider the sizes of both the ground floor and the 1st floor, or only one of these? Comparing the size of a single storey and a double storey house on the same plot size how do these differ?

    • Jean in terms of the allowed area on which you are permitted to build, it is only the ground floor area that is taken into account. I think though that the local authority takes the full floor space into account when assessing rates and taxes.

    • I REALLY WANT TO KN HW TO MAKE GOOD SKETCH OF SITES PLAN

      • Hi, I am not sure what you mean, but if you want to copy the plans that your architect has supplied then there are photocopy stores in most cities that can do large plan copies.

  5. Morning, can you please tell me what the maximum height is for a single storey residential house?

  6. Hi,
    Are there any minimum standards for office space ?
    thanks
    stewart

    • Stewart this is covered in Part A of SANS 10400. A20 covers Classification and Designation of “Occupancies” and specifies how different functional areas are defined. G1 = Offices
      “Occupancy comprising offices, banks, consulting rooms and other similar usage.”
      This also specifies “design population”, and for G1 the requirements are “1 person per 15 m2″
      I hope this helps.

  7. Hi there, is there a spec / standards that depicts the minimum entrance width for a single garage entrance? About to build again and want to check

    • Hi Scott,
      The minimum size is more a practical one than a legislated one. So long as you can safely drive your car into the garage and get out comfortably then that will dictate the size. I would look at standard door sizes that are available so that you have a choice and will be reasonably priced. There the recommended size is: Opening – 2440mm wide X 2135mm high with brickwork of 220mm on the sides and 400mm above the opening. Measure your car and see if this will do. The average width of a medium size car or bakkie is no more than 2000mm.

  8. Hi
    Could you please tell me, what percentage of the overall plot area maybe constructed on? In other words, the floor area of a house should occupy no more than what percent of the land/plot area?

    • Cassim this is governed by the local authority by-laws and not the building regulations. So it depends where you live. I suggest you contact your local authority and ask them.

  9. Need to know where one could get information on the various height regulations for taps that are wall mounted above a hand or wash basin?
    Are there standards for shower head heights ect?

    • Ben I am not sure. These are not specified in the National Building Regulations but might be within other SANS. Since you are required to use a qualified and registered plumber for all work, he/she will be able to answer that question.

  10. Hi Penny. Please can you tell me what percentage of the area of a residential plot is one allowed to build on. Thanks

    • Mika it depends on the local authority by-laws and zoning of the property. Usually it’s about 60%, but I suggest you check with your local council.

    • Thank you. Great website!

    • It also depends on the building lines for that particular local authority or locality. Hope you understand wat we mean by building lines, that is the space or distance where you are not supposed to put any dwelling structure from the boundary wall or stand boundary and is usually stated in metres or feet with differences between front, back and sides.

  11. Hi
    What is the definision of floor area? Would the patio of a flat in a sectional title unit be considered floor area? The patio has no outer wall or rail and is on ground floor level. The roof of the patio is the floor of the 1st floor Unit?
    Jurgens

    • The “floor area” is defined in Part A of SANS 10400 as the “total area of a building, or a storey thereof, enclosed within its external walls, exclusive of the area occupied by any lift shaft”.

      • Thanks got that floor are definision.

        Am i correct, that the dimentions is taken on the inside of the unplastered walls to calculate floor area?
        Is the minumum size of a sectional titel unit 30m?

        Regards
        Jurgens

        • Yes Jurgens it would be the inside measurement. I am not an expert regarding Sectional Title but can’t find anything in the Act that specifies size. I imagine it would either be the local authority and/or the body corporate that decides on minimum sizes.

          • Hi Penny
            Thanks for the help. I would imagine the minumum size for a flat must be defined. Does not matter if it is part of a complex or sectional title units. Does the min size of 30M apply to alone standings dwelings only?
            Regards

          • Jurgens I assume that the minimum size would be exactly the same as the minimum size for any other dwelling. The regulations state that the floor of any permanent building that is used as a “dwelling house” must be no less than 30 m². Sorry I got hooked on sectional title – and then just thought it’s pretty obvious that the National Building Regulations apply to ALL buildings irrespective.
            See more HERE.

  12. Hi

    What is the minimum room size for accommodation?

    * For one labourer
    * For two labourers

    Thanks
    Charmaine

    • Charmaine the minimum sizes for rooms is given in SANS 10400, Part C Dimensions, which is explained on this page. But your question is a bit strange. Are you wanting to provide temporary accommodation for laborers? If so you will have to get permission from the local authority. If you are going to accommodate a labourer in a servant’s quarter or similar on your property, the minimum size is no different to the minimum size required for you!

      • Hi Penny

        Thanks for the reply. We have built accomodation (approved drawings etc). But an inspection done by our client says the room sizes are too small. The rooms are 12 square metres for 2 people.
        They ablutions, entertainment, dining etc are in separate buildings.

        • Your client? Surely if you build for someone else you know what they want you to build? And then he/she would also have approved the plans prior to them being submitted to council for approval. Or am I missing something? If your plans have been approved, I have to assume that they comply with NBR otherwise they wouldn’t have been approved.
          The regulations (Part C) say that the minimum plan area for any habitable room other than a kitchen, scullery or laundry (and this applies to ALL occupancies) is “6 m2 with no linear dimension less than 2 m”.
          Floor area of any “dwelling house” may not be less that 30 m2 in the case of any permanent building other than Category 1 building which must be at least 27 m2 in size.
          Part A, General principles and requirements, gives a table of different classes of occupancy. I assume this will be either H2 Dormitory Occupancy where groups of people are accommodated in one room.
          H3 Domestic residence Occupancy consisting of two or more dwelling units on a single site.
          H4 Dwelling house Occupancy consisting of a dwelling unit on its own site, including a garage and other domestic outbuildings, if any.
          Part A also specifies maximum “design population” for rooms. i.e. It can’t be smaller than this.
          H2 = 1 person per 5 sq m
          H3 and H4 = “2 persons per bedroom” … obviously this is read with the 30 or 27 sq m minimum for the house, and min 6 sq m for any habitable room. While not ideal by any means, you could fit a double bed into the min size – (if the room was square) with 1 m x 3 m along one side – and 800 mm on either side of the bed! So legally the rooms you have built are not “too small”.
          But then in Part P, Drainage, there are additional regulations that relate to the provision of sanitary fixtures. There are exceptions for shops in terms of these not needing to be in the same building, but I am not sure about exemptions for H2, H3 and H4.
          H2 depends on the number of people using the dormitories. H3 and H4 must have at least 1 toilet, 1 bath or shower and one basin. But again, if you have approved plans, I don’t see the problem.

  13. Hi there Penny

    I’m planning a new build and was thinking of having a flat concrete roof. My question is would the municipality charge for that concrete roof as living space? I realize that the municipality calculates the rates based on the square meterage of a dwelling, so would the flat concrete roof be included?

    Thanks for a brilliant site!
    Lance

    • Lance, A concrete roof would only be defined as “living space” if the roof became a floor. i.e. If you were to use it as an elevated patio, they could include the area as “living space”. If you are concerned, give their planning department a call and double-check.

  14. Hi, I need to know what the dimensions of the first floor should be in thickness… considering that all the rooms in the house of the ground floor are 220mm thick , and not exceeding a room area of 60m^2?

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