Apr 032013

Stormwater Disposal-Part R, What the Regulations Say

a street totally flooded.

When the heavens open up and flood gardens and roads, you rely on storm water drains to deal with the excess water.

A flooded street overflows into a residential property

The house on the far side of the road was totally flooded during a major downpour. The question is, whether the house was built with sufficient drainage to be able cope with all the storm water.

Property owners are responsible for the removal of storm water from their property. They may NOT simply discharge excess water onto adjacent land or into the street unless this is permitted by neighbors and/or the local council or municipality.

SANS 10400: Part R Stormwater Disposal

The law is very clear on the issue of stormwater disposal, although sites used exclusively for “dwelling houses” and dwelling units (defined as “one or more habitable rooms and provided with sanitary and cooking facilities”) are not as carefully controlled as larger buildings.

Note that a dwelling house is (in terms of the legislation) a single dwelling unit and any garage and other domestic outbuildings that are situated on the site. A dwelling unit contains one or more habitable rooms and it provided with both cooking facilities and adequate sanitary facilities.

Part R of the Act states: “The owner of any site shall provide suitable means for the control and disposal of accumulated stormwater which may run off from any earthworks, building or paving.”

The legislation also states that the “means of stormwater disposal” used may be addition to, or in combination with any drainage that may be required in terms of F4(2). SANS 10400: Part F Site Operations is described in more detail in the section on site operations on this website. The relevant section – 4(2) – is also discussed below.

These legal requirements will be “deemed to be satisfied” if the stormwater is provided in accordance with SANS 10400-R (the SANS drawn up by the SABS for “The application of the National Building Relations”, Part R), which is available from the SABS online store  for R174.42 incl. VAT.

SANS 10400, Part R deals with all types of stormwater disposal, including rain water from gutters, downpipes, roofs, and paving, and any other excess water that may accumulate on the property. It refers readers to Part H, Foundations stating that it is essential to have good, effective drainage of areas that are in close proximity to buildings, to ensure that ground movement is minimized.

Scope of Part R, Stormwater Disposal

The focus of Part R is on the disposal of stormwater on individual sites, but also included interconnected complexes that have multiple dwelling units, including both cluster homes and retirement, village-type properties where management of common property is often controlled by a management body of some sort.

Two types of stormwater system are defined in the regulations:

  1. Major stormwater systems that cater for severe, infrequent storm events
  2. Minor stormwater systems that cater for frequent storms of a minor nature

The rational design of these systems – if required – must be undertaken by “a competent person involving a process of reasoning and calculation and which may include a design based on the use of a standard or other suitable document.” The concept of a competent person is discussed in some detail in another article. However Part R states that a competent person required for stormwater system designs must be a civil engineer who is registered in terms of the Engineering Profession Act 2000 as a professional engineer or professional engineering technologist. Alternatively this person must have a tertiary qualification (a degree or a diploma) in civil engineering.

The legislation (the Act itself rather than the deemed to satisfy rules compiled by the SABS) states that it is the right of the local authority to demand that storm water disposal is provided in accordance with “an acceptable rational design prepared by an approved competent person” So if your local authority is of the opinion that a qualified person should design a stormwater disposal system for your property they must notify you (or the owner of the property) and explain their reasons in writing, and demand that plans and particulars of “a complete stormwater control and disposal installation” for the site and any buildings on it, are submitted for approval.

Stormwater Control and Disposal

The legislation states that the regulations should not be interpreted specifically as requiring roof gutters and downpipes if another suitable means of drainage has been provided to remove or disperse rainwater from the roof of the building. There are alternatives that architects sometimes prefer.

As always, the deemed to satisfy rules take this further. These state that any stormwater that emanates (or flows) from the roof, paving or any area that is in the immediate vicinity of a building shall not cause damage to the interior of the building, its structure or its structural elements. Steps must be taken to ensure that water does not accumulate in a way that “unduly inconveniences” the occupants of any building.

Part R also specifies other requirements of stormwater disposal arrangements. The system:

  • must not undercut foundations by erosion or flooding
  • must drain away from all buildings
  • must not allow water to accumulate against or close to external walls
  • must make provision for the drainage of any sites on the property that become waterlogged at any time
  • must be capable of being easily maintained and cleaned

Part R also specifies some of the disposal arrangements that need to be addressed, specifically:

  • those that allow rainwater to flow off the roof and away from the building, including roof valleys, gutters, and downpipes
  • those that channel surface water into stormwater drains that are either on the surface or below-ground, or channels – depending was is needed to remove stormwater from the site or to another part of the site where it will not affect the buildings

Ultimately, all drainage must  be shown on plans submitted to the local authority, and it is up to the local authority to decide whether these are suitable and adequate for each individual site. Also, it is the decision of the local authority whether stormwater may discharge into a stormwater system that is provided for a public road, or any servitude, or onto the street.

One of the major issues is people simply discharging their stormwater onto neighboring properties.  While the Building Regulations do not state that this may not be done, the Building Regulations do give very clear guidelines for stormwater control and disposal, and these DO NOT include the discharge of water into your neighbour’s garden! 

Stormwater Disposal in Interconnected Complexes

While the regulations and deemed to satisfy requirements described above apply to all properties, including complexes that are interconnected, there are additional requirements for the latter. For instance it is essential that stormwater is “controlled, safely routed and discharged from interconnected complexes without unduly eroding land, unsurfaced roads or water courses, contamination water resources or compromising environmentally sensitive areas identified in environmental impact assessment reports.”

In addition, both major and minor systems must be designed to cope with design flood recurrence intervals of both 50 and two years. At present there is legislation that requires flood lines for “townships” to be determined for 100-year recurrence intervals. This is because the storm water flow from 100-year floods is typically 25 percent greater than for 50-year floods. Part R states that major storm systems can be designed for a 50-year flood provided that the certified 100-year flood lines remain unchanged. This is very important.

Other requirements include:

  • the creation of terraces for dwelling units, where needed, that will allow the water to drain by gravity
  • the avoidance of erosion caused by too much water
  • specifications for the velocity of stormwater flow in road-edge channels constructed as part of a minor stormwater system
  • the need for channels built in soil that is susceptible to erosion to be lined
  • a specification that pipes in servitudes must have a diameter of no less than 300 mm

There is also a table that specifies minimum stormwater pipe gradient in relation to the diameter of the pipe. So if the minimum 300 mm pipe is used the desirable minimum gradient is 1 in 80, and the absolute minimum gradient is 1 in 230. If the maximum 1 200 mm diameter pipe is used, then the desirable minimum gradient is 1 in 520, and the absolute minimum gradient is 1 in 1500.

Gutters and Downpipes

There are some important specifications that relate to gutters and downpipes, including a table that gives roof, eaves and valley gutter sizes. In summer rainfall regions, the internal cross-sectional area of a valley or gutter per square metre of the roof plan area served (per square mm) is 140; in winter rainfall regions this is 80; and in areas where it rains all year round, the figure is 115.

In addition, the internal cross-sectional area of downpipes shall be not less than 100 square mm/square m of roof plan area served by such downpipe, or 4 400 square mm.

SANS 10400: Part F Site Operations F4(2)

Part F4 deals with preparation of a site that is to be built on. Point (2) states that when a building is to be erected on a site that is waterlogged or saturated with water, or where any building is going to be situated so that water will drain naturally towards it, drainage must be provided to direct the water away from the site or building, to a storm water drain, or somewhere that it can be disposed of in some other safe and approved manner.

Note that these requirement are in addition to Part R.

SANS 10400: Part L Roofs

This part of SANS 10400 is dealt with elsewhere on this site in the section on Roofs.

Waterproofing and runoff are dealt with in some detail in the relevant SANS for The application of the National Building Regulations.

Other SANS that deal with Stormwater Drainage

Additional SANS that deal with storm water drains and gullies are intended for the use of civil engineering construction and include:

  • SANS 1200 LE – Standardized specification for civil engineering construction Section LE: Stormwater drainage.

This is a drawing from the above SANS that shows how a precast concrete manhole for storm water should be built.stormwater disposalstormwater disposal

  • SANS 10120 – A Code of practice for use with the above, including:
  1. Part 2: Project specification Section LE: Stormwater drainage
  2. Part 3: Guidance for design Section LE: Stormwater drainage
  3. Part 4: Typical schedule of quantities Section LE: Stormwater drainage
  4. Part 5: Contract administration Section LE: Stormwater drainage


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  128 Responses to “Stormwater Disposal”

Comments (127) Pingbacks (1)
  1. Hi Penny, in terms of the building regulations, does my building have to have gutters and down pipes? If so, would a Cape Dutch manor house with a thatched roof would then need to have gutters? I’m constucting a farm building with concrete aprons and stormwater channels that collect the rainwater discharged off the roof. these channels then discharge into a farm dam.

    kind regards

    • Simon, gutters are just one way of discharging water. Not all building have gutter and downpipes – but they must then have an alternative method … e.g. I have seen architects use chains instead of downpipes. As long as it does the job you are covered.

  2. Hi Penny,

    I live in a small complex with 5 units. At the back of the complex are 3 semi attached units, with mine on the one end. All the water from the other 2 units flow into our property (we are the lowest), into a submerged sump under our paving that cannot handle the amount of water. The water then flow up through the nearest drain, which is ours, and our courtyard floods within minutes. Is this legal? Can the other units storm water flow into our property like this? If the Body Corporate does not want to solve this, legally do I have a leg to stand on?

    • Rory no it isn’t legal and yes you do have a leg to stand on. Sounds to me like the plumbing is inadequate. also you are not under any obligation to accept the water from other properties. Perhaps a good starting point would be the plumbing institute of SA, IOPSA. The law is very clear: “The owner of any site shall provide suitable means for the control and disposal of accumulated stormwater which may run off from any earthworks, building or paving.” Part R (Stormwater Disposal) of SANS 10400 give guidelines on how to ensure this is done.

  3. Hi

    Would you know when the new legislation regarding residential retention of storm water is coming into effect.

    • If soil has been filled in against the wall this makes it a retaining wall, which is illegal. If the roots from their trees are causing damage, they are liable. Simple. And you are correct – insurance isn’t liable.

  4. Please help, need some advice on what legal steps I may take. My neighbour has 3 dogs on his front property which is only paved, no grass, and in the boundary wall (normal pre cast wall) at the bottom he has made drainage holes onto my driveway, so for the past 8 years, once a week, he hoses down his paving and forces all the dog poop onto my driveway. I’m not sure that he has approved building plans, if he did then surely he would have had to see to correct drainage on his property, as every rainfall his house floods. Now my question, can I close the holes in the wall. I am not his lower property as we both reside on a slope and our back neighbours are below our properties, so as to my knowledge I am not responsible for his storm water drainage

    • You are correct, you are not responsible for his stormwater drainage. He is not allowed to drain anything onto your property.

  5. Help Please Penny.

    We have experienced a lot of damage over the years from two drainage pipes in a boundary wall. This is flowing from a higher property our new neighbours garden into our garden and sometimes into our house. We want to move the pipes further down the wall to direct the flow past the house. Can you pls advise what is required. They have also just built a pool and a cottage without plans? And I am rather worried about the pools back wash? We don’t want to block the flow just move it further up the wall to still accommodate them?

    Thanks for assisting.

    Kind regards.

    • Tanya I have added info to this page since you sent in your query – so have a look. You need a proper stormwater system in place – or rather they do. You do not have to accommodate their stormwater or their pool water. It is their responsibility to ensures it is disposed of in a way that complies with the National Building Regulations. They are not permitted to simply divert the water onto neighboring properties. And if they have built without plans you have every right to report them to the local authority.

  6. Dear Penny
    The property of my neighbour behind me is higher than mine and last year on two occasions stormwater came through the wall between our properties, flooded my property and the muddy stormwater cascaded into my pool. I spoke to him about this and he undertook to take corrective steps to ensure it wont happen again. This past weekend, with a heavy downpour we had, the same thing happened.

    I am aware that he must ensure run-off of his stormwater off his property but is there a regulation or section of the regulation that states he must ensure run-off into the street below my property.


    • All stormwater installations must be approved by the local authority. These installations must also be undertaken by a registered and qualified plumber. Apart from the regulations and SANS 10400 that relate to the NBR, there are several other regulations that govern plumbing. The Institute of Plumbing SA will probably be able to give you some helpful advice.

  7. Hi there. My neighbour replaced his garage and carport roof a few months back, the structures are right on our boundary wall. When the galvanised sheeting was going up I noticed that it was sloping towards our property & questioned this. I was told that they would be putting a gutter in with the downpipe on the neighbour’s side. They did put the gutter up but it is inadequate for the volume of water (Cape Town winter rains) and is causing a waterfall on our side. Very heavy rains will cause an accumulation of water that will result in our back garden and possibly the braai room flooding. A couple of questions : Is it legal for the roof to slope towards us? If not, what recourse do I have to get him to change the roof? If so, how do I get him to get proper gutters & drainage so that we aren’t flooded? Thank you.

    • Karen, firstly if the garage structure was replaced, your neighbour should have had new plans passed, and these should have included a drainage system that would adequately get rid of all stormwater without it flooding your property. As far as I know, the slope of the roof is not the issue, the issue is that it is his responsibility to ensure the water drains. Note that the City of Cape Town no longer requires a neighbour’s consent for buildings constructed up to the boundary, but approved plans are still required. So first check with the council that plans were submitted – then report the fact that your property is compromised. You must do this in writing – a telephone call is not sufficient.

      • Hi Penny, thanks for your feedback, will start with the council check and take it from there.

  8. Hi, I’m about to start building my house. The issue I have is the following. I Have the lowest level property. The guy next door made a hole in his wall for his drainage that goes into my property. The thing is, the stormwater of the two properties next to him goes into his property. Effectively my property would carry stormwater of all 3 properties next to me. I Bough a stand next to the boundary wall of the estate, the other issue is that the road on the other side of the boundary is higher than my stand so I can’t even drain all this water out there. According to my knowledge I must carry my neighbors stormwater, but only his. Not all three properties. I have no idea what to do. Please help

    • Xander – if you read all the responses to questions on this page you will get the information you need. It is NOT for you to be responsible for your neighbour’s or neighbours’ (plural) stormwater. It is their responsibility to drain it off their property – and NOT into yours. There needs to be a stormwater drainage plan that the local authority approves. So check with them.

  9. The land adjacent to mine (residential) was re-zoned to religious site. I had given the owners (Trust) permission to build on the boundry line in terms of the approved plans. However they have built thus far not in accordance with the approved plans. The approved plans showed an open basement parking. However, they have deviated in that they built boundary walls with windows and converted this into a hall. My home is affeced by the light & noise eminating from the functions they have during weekend that goes late into the night/ next morning.Their stromwater is draining into my backyard.The building remains incomplete from 2004. After lodging numerous complaints for years with the Municipality, the municipality had issued a letter of non-compliance and summons twice, and no further action was taken by the municipality.

    Now the municipality has notified me that according to the National building regulation I am oblidged to give the Trust permission to construct a storm water drain over my property to be deposited into the bottom stream at their cost which the municipality will oversee.

    Do i have a right to have them remove the boundary walls with widows and deny them use of my property to construct a storm water drain?

    • Anoop, I would refuse them access and notify the municipality that you are doing so because of the fact that they have ignored the municipality’s non-compliance notifications. Further, I would demand that the municipality take urgent steps to have the illegal building demolished. At the moment it seems that you have the upper hand in terms of the stormwater drain… Probably the people at the municipality who are making these recent demands are not aware of the previous actions. Go into their offices with all the details and any proof you have, and demand to talk to a senior person. From your email address, I’m wondering where you work 🙂

  10. Subject:
    Storm water management

    Good Day. I would like to see the wording of the law that states that a neighbour whose property is lower than yours are not allowed to prohibit the natural flow of storm water. Also is there a cost sharing
    implication if a drainage system must be put in place to manage the water between to neighbouring properties?

    • Alleen, Part R of SANS 10400 covers stormwater disposal. I don’t have a copy of that available to me right now, so can’t give you the wording, but you can buy a copy from the SABS online store, or have a look at it at one of their libraries. However the legislation states that the owner of any site “shall provide suitable means for the control and disposal of accumulated stormwater which may run off from any earthworks, building or paving.” If necessary, the local authority may (according to the Act) insist on a “rational design prepared by an approved competent person” e.g. an engineer. They may also insist on plans for this. Part R – which is the “deemed to satisfy” part of the regs – gives guidance on how stormwater should be disposed – e.g. gullies, drains, downpipes and gutters etc
      So you will see that the owner of a property is obliged to take care of his/her own drainage of stormwater – and this does NOT mean that you must expect your neighbour to take the flow of water onto their property (unless there is a registered servitude for this purpose). There is no law that states neighbours must share costs of anything.

  11. Subject:
    Pipes underground

    Recently I installed a Jojo Tank and pump to increase water pressure. The installer ran the water pipes just about 15 – 20 cm below the garden lawn. What is the regulation regarding the depth water pipes and underground electricity pipes/conduits? Kindly direct me to relevant literature. Thanks and regards. Ahmed

    • Ahmed, the regulations regarding electricity are not contained in the NBR. Plus both plumbing and electrics need to be undertaken by qualified professionals who are registered with the local authority. So I suggest that you contact a registered electrician and a registered plumber for advice. Alternatively you can contact IOPSA for plumbing issues, and ECASA for electrical issues. They should be able to point you in the right direction. Sorry I can’t be more helpful.

  12. My neigbor drains his pool every month all the water into my yard, not just backwash, I am talking about draining his pool, he floods my braai area and my grass is completely muddy from this. He is very difficult to talk to, what can I do .

    • Juanita, People are not allowed to simply drain their swimming pools onto other people’s properties. It isn’t a building regulation issue, though drainage is. It needs to be drained into a drain or directly into the road. If he is difficult to talk to – write a letter that states he has no right to do this and that you are going to hold him liable for damage if he does it again – and public nuisance since he regularly renders your garden unusable. If he doesn’t stop then you may need to pay a lawyer to write a letter for you. Nobody needs a neighbour like that!

  13. Good day,

    About a year ago my house was build with proper stormwater drainage pipes in the boundary walls. My neighbour started building about 4 months later when I started. Since I am at work during the day, I have not really noticed any problems with draining of excess water, until recently. What I noticed was that the paving of my neighbours house blocked one of the stormwater drainage pipes with about 10% of the pipe open for draining. This unfortunately results in a very slow draining on my side to such an extend that the water level builds up higher than the pipe. Speaking under correction, blocking of stormwater draining pipes is not allowed and these pipes should be kept open at all times? How do I proceed with this issue and is this semi-blocking legal?

    Thank you.

  14. I stay in Port Elizabeth <
    I am staying in the same house for 12 years, its a panhandle property and my storm water have been draining into my one neighbour property.
    A year ago new owner build on and we have discussed the "drain hole", as he want to put a floor down. I have agreed to put a pipe down at my cost so to control the water and the floor can go on top.
    Two weeks ago I spotted the hole was completely closed of with concrete , spoke to another neighbour and she had the same issue.
    If it rain now my house will be flooded, what to do??

    • Hi Kobus, Here is an extract from the Jhb bye-laws:
      “Where, in the opinion of the Council, it is impracticable for stormwater to be drained from higher lying erven direct to a road, the owner of the lower lying erf shall be obliged to accept and/or permit the passage over the erf of such stormwater: Provided that the owners of any higher lying erven, the stormwater from which is discharged over any lower lying erf, shall be liable to pay a proportionate share of the cost of any pipe line or drain which the owner of such lower lying erf may find necessary to lay or construct for the purpose of conducting the water so discharged over the erf”
      All the municipalities will follow the same bye-laws, so PE wil be the same. You can call the local building inspector and report your neighbour for violating the law.

  15. Hi Penny, I am in a complex and adjacent stand is being developed. It has a close to 60% coverage ratio and I guess about 40% of the remaining land will be paved. The developer has informed me that approx 2/3 of storm-water will be directed to the road via gutters etc. The stand slopes back from the road and, for last 1/3, the developer plans to channel any overflow into adjacent stands including mine. Mine may be marginally lower (a couple of cms) at the boundary, but that is the low point of my stand so storm water could pool up to an estimated 15 cm. I have asked the developer to use french drains etc to improve the stand’s water carrying capacity but have not met any enthusiasm.
    Our suburbs by-laws do indicate that a lower lying stand should take overflow with the higher stand contributing to the cost of any extra drainage requirements on the lower stand.
    Does ‘lower’ mean lower at the boundary or lower on average than the other stand’s boundary?
    Does of the owner, have a unilateral right to make a drainage hole in my wall?
    How far does the owner have an obligation to mitigate storm water run off via, e.g. french drains?
    Is there any guidance on what ‘contribute’ means?
    Lastly, what are my obligations?
    I’d appreciate your suggestions and guidance. Thanks v much for your help

    • Peter, I would think that “lower” means lower anywhere or overall. i.e. Parts could be even lower than on the boundary – or higher on the other side.
      Nobody has the right to make a drainage hole in your wall without your permission.
      But you probably need a lawyer to do a proper interpretation of the bylaws. You might also call the SA Institute of Plumbing (you’ll find regional contact numbers on their website) and ask to speak to one of their committee members who can advise you. In addition to plumbing and drainage issues detailed in SANS 10400 (the National Building Regulations) there are a number of other Standards that deal with drainage.

      • Peter, IOPSA’s technical advisor, Martin Coetzee (who works for Cobra Watertech) is incredibly knowledgable. Why not give him a call? Or ask Iopsa to pass on your message and get him to call you. Good luck

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