Dimensions
Every Room Must be Fit for Purpose-Part C
The National Building Regulations (NBR) are not prescriptive when it comes to the dimensions or 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:
- Places of instruction (A3)
- Buildings used for worship (A4)
- Small shops (F2)
- Offices, as well as banks, consulting rooms and similar (G1)
- Dormitories where a groups of people are accommodated in one room (H2)
- Domestic residences with two or more dwelling units on a single plot (H3)
- 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:
- the underside of the ceiling,
- the underside of the roof covering (if there isn’t a ceiling), or
- 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
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).
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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https://sans10400.org.za/public-safety/
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.
what are the south African standards for door frames and window frames?
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
Hi Richard, I suggest you get hold of the Master Builders SA and ask them for a list of names of reputable builders in your area and get quotes directly from them. The MBASA website is here: http://www.mbsa.org.za/
What will it cost to build a 6 x 7m double garage in johanessburg
Louis this is usually specified in the zoning regs of each local authority. So check with them.
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.
I REALLY WANT TO KN HW TO MAKE GOOD SKETCH OF SITES PLAN
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.
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?
Morning, can you please tell me what the maximum height is for a single storey residential house?
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.
Hi,
Are there any minimum standards for office space ?
thanks
stewart
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.
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
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.
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?
Abel there is quite a lot of information about boundaries and building lines on this website, and on our sister website, Owner Building.
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.
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.
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?
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.
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
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.
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