FLAT ROOF WATERPROOFING
In South Africa there is enormous variance in climatic conditions - from desert conditions to a Mediterranean climate. Temperatures can range from below zero to the mid-thirties. Whilst this, in itself, is not unusual, what does make it a factor in structural waterproofing is the fact that these variations occur all in the space of 24 hours. Rain, driven by gale force winds, hits some of the coastal regions and other regions go from drought conditions to floods. All these dramatic climatic conditions affect our building in one way or another and accordingly climate must be taken in consideration when designing structures. When drawing up specifications for flat roof merely to state Waterproofing strictly to manufacturer's specification can be dangerous philosophy to follow, as it will not always provide the required job. Poor specifying details are one of the major failures of waterproofing, and hence leak. Also, locating all the plant equipment on flat roofs must be planned carefully to prevent any problems with the flow of water and easy access to the waterproofing.
There are many waterproofing materials on the market, most of them good, but every material has its performance limitations. Unique emphasis is often placed on a material's guarantee, merely a warranty on their materials, ie. that it will be free of defects for a specified period. They certainly do not guarantee that their materials will work, regardless of the circumstances.
It also appears to be easy to operate today as a waterproofing contractor. There are many companies from which to choose, with more and more springing up all the time. Clearly the reason for this is that it is not a capital-intensive industry. These days, with the varied selection of available materials, however, coupled to the complexity of modern building design, many buildings are in fact neither straightforward nor simple to waterproof. A depth of experience and knowledge of the trade is essential to provide a waterproof building.
Designers, it seems, are constantly trying to create the most complicated structures, in order to test the ingenuity of engineers and the abilities of contractors to execute design work. It seems also as though designers expect the material to perform miracles in extreme situations. Not to mention, of course, the ludicrous time scales the clients set, time scales that barely allow the concrete to cure… and all for a suicidal price as well!
No wonder some buildings leak.
The design of the waterproofing to flat roofs is the first important stage, which takes place on the drawing board. It is not just a question of plotting dotted lines on a drawing: careful consideration and thought needs to go into the detailing but also the construction sequence. Can the principle be put to practice? It is always advisable to ask the advice of experienced waterproofing contractors who not only have the practical knowledge of fixing waterproofing systems but who also can demonstrate a long successful track record. Once the detailing is correct a suitable waterproofing system can be selected. The same details are relevant to all waterproofing systems, but specific requirements may call for certain specific systems ie. gussets at internal and external angles, or fillets formed in the material. An important factor which should be pointed out at this stage is that, in designing a watertight roof, the DPCs in walls, relevant to the roof, must be considered at all times. The waterproofing details must be correct, after which the right materials for the situation can be selected. Then the first stage to produce a leak-free building has been achieved. Correct detailing is possibly far more important than material selection, as there are a number of materials that will perform in the same situation.
Many of the waterproofing material manufacturers and suppliers offer warranties on their material and possibly sells their systems on guarantee. The old saying that ' A guarantee is not worth the paper it is written on" must seriously be taken into account when deciding on a waterproofing system. A history of the material should be obtained in the credentials of the manufacture checked.
Of course, the same also applies to the waterproofing contractor. In selecting the waterproofing contractor care should be taken to ensure that the company has the expertise and knowledge, the financial ability and the qualified manpower to carry out the work and to produce a first class job. Ideally, the company should be a member of the Waterproofing Federation of Southern Africa. It is important that the professional team, the building contractor, waterproofing material manufacturer/supplier and the waterproofing contractor work together as a team, and not against each other.
Supervision of all aspects of the work and frequent checks on site to ensure that the detailing is being done without any compromises is vital; especially in the case of major projects where many trades are involved. The main contractor and especially the other trades (such as plumbers, electricians, bricklayers and tiler), must all be made aware of the importance and principles of waterproofing. It is not always easy and on occasions impossible, to repair the waterproofing after it has been damaged.
In conclusion, the success of a "leak-free" roof lies in the initial design, selection of the correct material for the job and careful, uncompromised application by a reputable and experienced waterproofing contractor. There are no "wonder" materials. Prices and guarantees should not necessarily be the only, or main criteria applied when selecting and specifying waterproofing - and neither should it determine the choice of the waterproofing contractor.