Jun 022014
 

The Implications of Building Retaining Walls

Retaining Walls

A retaining wall constructed from specially designed, interlocking blocks

Part K of SANS 10400, Walls in the National Building Regulations (NBR) covers the structural strength and stability of all walls, including those that form part of a house or other building, and both garden and boundary walls.

They also deal with retaining walls which, by definition are intended to “resist the lateral displacement of materials”. If the wall is not designed the right way, it simply won’t resist the pressure of soil or other materials pushing against it, and it might collapse injuring or even killing people. It is for this reason that it is essential for all retaining walls to be designed by a competent person, preferably an engineer, and for plans to be drawn up and submitted to the relevant local authority for approval before building begins.

Over the years we’ve had numerous queries from visitors to this site regarding retaining walls, many homeowners wanting to know whether plans are required. The only walls you may be build without plans are those that are considered, by the National Building Regulations to be minor building work. Specifically, Part A of SANS 10400, General Principles and Requirements says “any free-standing wall constructed of masonry, concrete, steel, aluminium or timber or any wire fence where such wall or fence does not exceed 1,8 m in height at any point above ground level and does not retain soil,” is regarded as minor building work. Even though plans are not required for minor building work, it is essential that minor building work complies with the NBR, and you should notify the local authority of your intention to build the wall.

All retaining walls require plans that are approved, and they must be designed by a competent person or build it in accordance with the SABS “deemed to satisfy” rules that are laid out in Part K 4.2.4 Free-standing boundary, garden and retaining walls.

retaining walls

How to build retaining walls using bricks

Freestanding retaining walls must be designed and built so that:

  1. the height of any fill retained by the wall does not exceed the values given in he table below, provided, however, that where x (see figure above) exceeds 0,3 m, the height retained shall be reduced by the difference between x and 0,3 m
  2. piers, where required in terms of the table below, project on the opposite side of the wall to the fill that is being retained
  3. control joints are located at intervals that do not exceed 10 m
  4. no surcharge of fill is placed within a distance equal to the height of the amount of fill being retained, and
  5. subsoil drainage is provided behind the wall by weepholes formed by building into the waIl, and 50 mm diameter plastic pipes, with the non-exposed end covered with geofabric, at a height that does not exceed 300 mm above the lower ground level, and at centres that do not exceed 1,5 m.
retaining walls

Table: Retaining Walls

Note that the specifications for garden walls that do not retain earth are different.

“The term ‘minor building work’ was intended to cover certain building work which, because of either its nature or magnitude (or both), was such that it would not be necessary to submit full plans or, in certain cases, where no plans or any other documents would be required.” South African National Building Regulations

What Happens When Retaining Walls are not Built in Accordance With the Building Regulations

retaining walls

A young boy stands next to the collapsed retaining wall that injured six of his friends – Photograph Sbonelo Ngcobo (Independent Newspapers)

Incorrectly built retaining walls can be downright dangerous. Just a couple of months ago an adult and six children were injured when a retaining walls collapsed on them in Quarry Heights, Durban. At the time, the children and several adults were helping Busisiwe Shabane backfill a retaining wall with sand and rubble to create an area that was level with her house. Two of the children were trapped under the wall.

According to Shanbane’s husband, Caphius, they were trying to strengthen the wall which appeared to be about to collapse. He said they were afraid that if the wall collapsed, the house would then collapse. He said they had used tyres, but these had been dislodged by heavy rain. They had also built two retaining walls using hollow cement blocks. When these began to crack and show signs of falling, they broke one down and rebuilt it.

The wall was apparently six blocks high, which would have made the wall about 1,2 m high. Clearly it was not built according to the NBR, and there were certainly no approved plans. Thankfully no-one was killed, but two weeks ago 18 people died and three were injured when a retaining wall collapsed on a shack in China’s Shandong Province. This collapse was also caused by heavy rain.

Properly Built Retaining Walls

Although to the layperson low retaining walls might appear to be simple structures, the risks of badly built walls are acknowledged by engineers. When an engineer designs a retaining wall he or she will evaluate the soil and any rocks that are behind or below where the wall is to be built. They will also determine the best material for backfilling the wall and design drainage so that rain does not cause collapse.

 

 

  55 Responses to “Retaining Walls”

Comments (55)
  1. Good evening,

    We are beneficiaries of a RDP house for 3 months now. 6 metres from our backdoor stands a house erected on a almost 3 metres high sandhill which retains a lot of water and which deals heavily from the soil especially after rainy days. The soil also break away from the house on the hill when it rains. Anytime we dig a whole to erect a pole for wire fencing we bare dig half a metre and the hole fills up with water in no time. After much effort and quarrel with the municipality and the construction company someone finally decided that this is indeed a very dangerous situation in need of a retaining wall which should have been erected in the first place before either house were build. Let me just mention that according to both plans received from the land surveyors and the municipal building offices 5 of the 6metres between these two houses belongs to us. The same construction company that built the houses got the job to build the wall. The decided to erect the wall only at me and my neighbors houses (adjoined) because the hills (soil) are at its highest there, the highest point being behind my house. They are taking all kinds of shortcuts to not have to spend much money. They decided to dig the foundation for the wall 200m and then another 300m but the deeper they dug the more water seeped from the soil so the order was given to dig another 300m deeper but the water got even more they then decided to fill it up again to only 300m as the depth the dug was filled to the brim with seepage water and buying that much concrete would be too expensive. The wouldn’t hire a jetvac truck or something similar to drain the water and instead ordered workers to use cut 2litre coke bottles and buckets to drain the water at which they failed badly. Everything was done in water from the steel rods to the concrete to the 1st 2rows of bricks (190(size) cement blocks). From the start we asked whether pipes (sigpype) would be put in place to assist with draining water from the soil they refused. The wall is now 6blocks high about 3metres then takes a step down to 5 and then down to 4blocks. It’s a single layered wall with a few iron rods and building wire here and there and the soil is still higher than the wall which both my neighbor and I complained about as the wall needs to be lifted at least 2more rows.they started filling up behind the wall almost to its height with more soil as they didn’t want to buy concrete. They planted poles (olie pale) behind the wall and is planning to erect a wire fence in the soil. This is what they are doing after they originally promised a double re-inforced concrete wall which would be able to hold the earth and stop the house from collapsing and falling 3metres and landing on top of our house. Furthermore there excavations took 2 or more metres of our 5metre backyard as whatever land is behind the fenced wall would automatically belong to the house behind the fence which I wouldn’t mind if it was given to me at the front where fence was order to be pushed back 4metres from the street as the sidewalk is apparently to small at 2.7metres which applies only to my neighbor and me one other person the rest of the street gets to fence their yards at 1.5metres from the street. Can someone please advise on whether this is lawful because we really feel like we are being robbed and bullied. We also feel like we are losing land from our plot that was approved for us and subsidized to us by the state as payment for their negligence. I have photos and videos of house that could fall and of different stages of the construction of the wall and the seepage water. They did put pieces af pipe in the wall which by now is blocked by the soil fill but they didn’t put any pipes to lead the water to a drainage system or the street if water does ever come through those little pieces of pipe it wil lie dormant cause puddles everywhere including the backdoor. That water smells bad as it is said to come from the graveyard which is on higher ground about 20 or 30metres away. Please please advise as we do not understand how such things can be approved and get the go ahead. Today some or other municipal lady told us we should count ourselves lucky we are getting a wall for free like they are doing us a favor and not like they are doing disaster management after the fact as the wall should have built before our house was or better yet they shouldn’t have build a house in such a dangerous place.

    • If you are saying that the wall has been built so your neighbour gets extra land you have a case against the council. You should also report the construction company or whoever is doing the building – I’m just sure who to. This article might be of some help. It gives a number for the legal aid board. They might be able to help.

  2. What are the regulations governing the height of a retaining wall and when were they implemented?

    • SANS 10400-A mentions retaining walls in the context of minor building work (which is the only building work that does NOT require plans): “any free-standing wall constructed of masonry, concrete, steel, aluminium or timber or any wire fence where such wall or fence does not exceed 1,8 m in height at any point above ground level and does not retain soil. This clearly indicates that any wall that retains soil is NOT regarded as minor building work and therefore requires plans. However the Council does have the authority to waive the need for plans.
      SANS 10400-K (2011), Walls has comprehensive guidelines for retaining walls that vary according to height.

  3. Good day:-) Hoping someone can offer some assistance to my dilemma… recently in Durban we had very heavy rains and my studio, which is in an office park, flooded. The water seeped through my back wall and upon inspection I actually realised that the property directly behind our building, had a very high remaining wall which is actually right up against my back wall of my studio. Is this legal? His wall is a retaining wall holding the soil of his yard on that side and which places my studio at below his actual ground level! I am very concerned about safety and what would happen if his wal had to give way under the pressure of tons of soil, worsened by days of heavy rain. What building laws, if any, could explain how this type of building could have been done?

    • All retaining walls must have approved plans – so contact the local authority and ask them to investigate as a matter of urgency.

  4. Hi my neighbour excavated her land, now that the heavy rains came the bank collasped,they was no wall erected,Can you tell please tell me whom is responsible for this/.
    I have lost a metre of land which the sand/bank caved in,can i go into her property and start erecting a wall,or must she erect a wall frm her side,and i can do my side ,,,

    • The best would be to come to a plan that is mutually acceptable. But in the event of a dispute, I would hold her responsible.

  5. I have an existing terraforce retaining wall approximately 1m high. I am wanting to extend the wall by a further 600m in high (3 additional blocks) in order to level out my yard. Would I require plans?

    • I suggest you contact Terraforce. Their engineers will know exactly what you can and can’t do. However, ALL retaining walls required plans.

  6. Hallo,
    There is a retaining wall that has been constructed on our common property. On the one side is the garden which is fill and the wall is about 6 meters high and a sheer drop.
    Is there a legal requirement to have a ballistrate? I would imagine this could be dangerous without some protection.
    If legally this is a requirement, could you please reference this requirement.
    Many Thanks,
    Bev

    • Balustrades are not required for walls of any sort. However it seems obvious that this is a public safety issue. There may be some sort of legal requirement but not in the NBR.

  7. “Are there good, less cost effective…” Should read “Are there good, MORE cost effective”

  8. I need some advice my father died and he had drawn up a plan for boundary walls but he died before he could have build it,i have red that approved plans is valid for 12 month is it possible that i could get the plans re-approved because i’m his son and his estate is still not finalized and i need to build the wall because the neighbors taking the current sink plates that’s forming the barrier between us to sell for there own benefit ,or can i just built the wall according to the plans that was approved.

  9. Hi

    Does retaining walls require ballastrudes and if so in which instances?

    Regards

    • Retaining walls would not normally require a balustrade unless the wall retains earth below an area that will be used perhaps as a patio or similar.

  10. It has been a year now and I have received ni reply! This matter is VERY URGENT! Please respond

    • What matter Cherylene? Please be advised that we reply as quickly as we can to queries – however this is a free service and we aren’t able to respond to the many thousands of questions we get. We are doing the best we can.

  11. I happened to come across your website and we are in URGENT need of help as the City of Tshwane say they cannot help and dont want to get involved. We are against a mountain and our neighbor at the back decided he wanted to form a plateau and dug out tons of ground. He then packed loffelstein blocks right against our boundary wall which has caused our wall to crack and started leaning over into our property. It has damages our pool as well as our entertainment area. His engineer passed away and the new guy suggested move the wall back. He started off with 3 meters, but ended at 2.1 meters away from our wall and he only has ground filling and stone in between the blocks. He has pushed ground right against our boundary wall with no drainage. We had an engineer out who will now charge us R14 000 to right a full report, money we do t have. We are told this is now a Civil case for which we dont have the money. Our house is in the market, but the bank refuses to give us a bank valuation until the wall has been rebuilt. Our neighbour was going to rebuild it, but refuses to as he says he has reduces the preassure to our wall. We have tried everyrhing and no one can tell us who we can turn to for help. I have hundreds of photos of how i wall looked before rhe loffelstein wall and he results now. We are from Magalieskruin in Pretoria – who can help us. This is really an uegent matter as our wall can fall over at any time. Regards Chery

    • Frankly the City of Tshwane should not have allowed this. They have the authority to insist that the wall is demolished and as far as I can see, they are the ones who must take action. Apart from anything else retaining walls of this calibre must have approved plans – which it sounds as if they might have had if there was an engineer involved. The question is, if there are approved plans, has the structure been built in accordance with them? You could try approaching a local newspaper and asking them to write an article with pictures. Unfortunately this type of scenario is very common and usually the only way to solve the problem is to take legal action… Which I can see is a huge Catch 22. Maybe you could get an attorney to write a letter to the City demanding they take action. That wouldn’t cost a lot, and might just force them to do something. If you did this and had the newspaper add this info into an article, it might work. At the end of the day, if the wall does collapse, your neighbour and the City will be liable – I have no doubt about that.

  12. Hi

    I’ve recently bought a plot on an estate. At the back of the land there is a slope to the adjourning plot. I’m looking at clearing part of the slope to create additional building space. I’ll need to put up a retaining wall; my question on this is whether the cost of this should be shared with the neighbour as it is holding up his plot. Surely he cannot have built with the notion that the land below will always have the slope as is.

    Regards

    • Hi Jitesh, boundary walls and retaining wall construction is covered in the Regulations not who pays for them. The costs etc. should always be negotiated between the neighbouring parties before building and this should be put in writing and signed by both parties.

  13. Hi, I own a panhandle property on an estate. Along the side of my panhandle driveway the neighbour has built less than a metre from the boundary line. The land sloped up the panhandle, this owner filled sand along that boundary to create a platform in order to build soo close to the boundary line, as he has a small plot and I suppose wanted to make use of all land that he could. I queried this with the estate and was told they gave him permission to do this. However my big issue is that he filled sand on that boundary to build his house and retained it with sand bags and created a bank. When it rains those sand bags have collapsed into my property in the past, and each time he puts the sand bags back. He now says that it is my responsibility to retain the bank he created as I am the “lower neighbour” which doesn’t make any sense. My understanding is that if you cut, then you retain. If you fill, then you retain. Please can you advise what the actual regulations are regarding this. He created this bank with the permission of the estate and now they have put my property at risk and put me in a position where I should pay for a bank he created.
    This guy is a developer and trying to steam roll over me. Please can you advise the rule regarding building lines and the responsibility of retaining.

  14. Hi, I live in Fourways Jhb. The behind me was bought by a complex developer and I am having a number of problems with them. Firstly, the boundary wall between us – they have twice started raising the wall, without my permission. In fact the 2nd time was after I expressly told them that it is illegal to do so. The wall is will be over 2.5m on my side as they are higher than I am. And it is a retaining wall. They are trying to co-erce me into agreeing to the raising of the well. The project manager is arriving at my house after hours and ringing my intercom & phoning me, also msgng me over weekends! They have told me that they do not need approved building plans, that they can raise the wall and just get the work appproved afterwards if they want! Furthermore, they have said that the wall needs no work done to it, beyond just adding bricks on top. However, I believe that given that the wall a) will be over 2.5m on my side and b) retaining wall it will need to be rebuilt from the foundation up, with support pliers? Secondly, in addition, in Dec, they did groundworks too close to my house – they broke the join in my side wall and the wall has split and is falling over. The said they will “get around to fixing it”! I really need your help. Can someone pls advise me on what my rights are, what actually needs to be done, what I need to ensure is put in writing by them and agreed on etc? Your help is very much appreciated!!

    • What they are trying to do is indeed illegal. ALL retaining walls require plans (however low they are) and permission, and there are very strict requirements laid out in Part K: Walls of SANS 10400.
      Put your complaints in writing to the planning department of your local authority. Phone, email … and demand the council stops them. You are well within your rights. They are also liable for damages – there is no question about this. And tell the project manager if he doesn’t stop harassing you you will lay a criminal charge of harassment against him.

  15. good day,
    to whom it may concern;

    I was told that when constructing a wall using interlink blocks does not require a plan;
    further more my wall was damaged by a municipality dam that burst about 12 to 15 years ago,
    I tried in vain for municipality to re-erect a wall,
    because we bought the property a long time ago, nobody checked if the previous owner had done things correctly, thus the wall that was there didn’t have any plans, now that it has become a major problem because we live bellow road level, I had to act & erect a wall using interlink blocks
    Please advise!

    • Hi Rakesh, This sounds like you are talking about a retaining wall. All retaining walls that are above 1 (one) meter high will need to have plans submitted and approved. Depending on the slope and cutback and the amount of soil the wall retains you might well need an engineers report to accompany the plans. Drainage is also a critical factor and the engineer will have to design the wall accordingly. Whoever told you that no plans are required is possibly not aware of the laws, you can check with your local council planning department to confirm this.

      • I stay in a complex in Roodepoort. Its a sectional Title. Me and my neighbor have walls that are 1.5m high. We would like to extend it to 1.8m for some privacy. We both agreed to it, but the current wall is a single layer wall with good foundation pillars (2 brick layer). Can we extend to 1.8m with a single layer or must we get plans and do a double brick layer wall

        • Kenneth, a 1,8 m high wall is considered minor building work so you don’t need plans. You should be able to add to the existing brickwork. You will though need to notify the council of what you are doing; they may have additional requirements.

 Leave a Reply

(required)

(required but will remain confidential and not be published)

   
© 2012-2017 SANS 10400 • © Notice Sitemap • Contact Us • Terms & Conditions Suffusion theme by Sayontan Sinha