South African property owners are learning some hard lessons about failed retaining walls.
They discovered that although their walls are insured with the rest of their fixed properties, when they fail, as some of them inevitably do, their claims for the repair work are often not met.
There are several legitimate reasons why insurance companies don’t simply pay up when presented with claims – inadequate wall designs, poor workmanship and defective materials being some of the contributing factors. However, by far the most common escape clause relates to the fact that 95% of the walls which fail weren’t designed by structural engineers.
For insurance claims to have any chance of success property owners must be able to submit approved structural engineering designs on walls higher than 1.5 m. This is one of the basic conditions stipulated in a typical home or property owner’s insurance policy.
President of the Concrete Manufacturers Association (CMA), and vice president of its Concrete Retaining Block Division, Silvio Ferraris, says the abnormally high rainfall pattern of late has seen a rise in retaining wall failures. aMost of the failures have occurred on walls built either with stone or brick walls, whereas the incidence on concrete retaining block and in·situ concrete walls has been relatively low.
“Many of the walls which have failed recently were built 30 to 60 years ago and most of the failures are caused by a rise in the underground water pressure. However, no matter how old the walls, provided property owners can produce a set of engineering drawings, their claims will usually be regarded in a positive light. That said, there are many instances in which the structural drawings have either disappeared during change of ownership, or simply did not exist in the first place.
Insurance policies cover subsidence and landsJip but exclude damage caused byexcavations and defective workmanship. Other typical exclusions include normal settlement, shrinkage, expansion or inadequate compaction. However, defective workmanship and inadequate compaction are very difficult to prove especially if the project was supervised by an engineer and more especially if photographs were taken during construction as supporting evidence.
People buying a house on steeply sloping ground should establish whether the retaining wall(s) on the property was designed by a structural engineer and should ask for the certification to prove it. If no documentation can be produced the new owner should either factor this in to the purchase price or get the existing owner to have the wall properly assessed by a structural engineer. This can involve considerable expense as the engineer may well recommend some improvements such as proper drainage. Of course it goes without saying that anyone wanting a new retaining wall built higher than 1.5 m must get a structural engineer involved, not only in the design of the wall but also to ensure that the contractor follows the design to the letter. Once the wall is built a copy of the drawing and design certificate should be lodged with the local council, and the original should be kept by the owner as record,” maintains Ferraris.