31/05/2022
10 Identified problem areas with waterproofing projects in the Cape
1 - Poor and inadequate design of the waterproofing specification.
2 - Inadequate details provided at the tender stage of a project.
3 - The short time frame in which developments are being constructed.
4 - The lack of general knowledge, education or care by all concerned with the waterproofing.
5 - A decline in the quality of workmanship and scarcity of qualified tradesmen with the right skills.
6 - The lack of preparation before installing waterproofing systems on surfaces
7 - The lack of any qualifications in the waterproofing industry.
8 - The duration of guarantees required on waterproofing systems.
9 - The initial cost of waterproofing. Often price takes preference.
10 - The lack of proper roof maintenance.
1 - Poor or inadequate design of the waterproofing.
The details of the waterproofing system are a very important consideration when waterproofing a building. Unfortunately, this aspect is so often ignored or overlooked. This can mean that waterproofing materials are expected to perform miracles! But, no materials will compensate for poor design or detailing.
Nonetheless, basic principles of good waterproofing practice must always apply.
A typical example of a different construction method used is that in the inland and generally “summer rainfall” regions, external structural brick walls are built solid, whereas, in the wetter coastal regions, external structural brick walls are built solid, whereas, in the wetter coastal regions and “winter rainfall” areas such as the Western Cape, the external walls are a double skin cavity construction, with a stepped damp-proof course (DPC). (Solid walls would have a horizontal DPC.)
More money and consideration are often given to expensive finishes on top of the waterproofing system, because waterproofing itself has no aesthetic value, or will not be seen. As one professional quantity surveyor (PQS) commented: - “Waterproofing doesn’t get tenants into buildings, aesthetics do”. However, if a building leaks it doesn’t keep tenants for very long either!
The total percentage cost of waterproofing on a contract is very small, normally around one to one and a half per cent of the contract sum; with waterproofing such an important element of the building, beware of false economies.
Plastic sheeting is sometimes the only specified vertical tanking material to combat moisture or even leakage in basements and lift pits etc. Proper thought must also be put into the interfaces of vertical and horizontal waterproofing and DPCs.
Simple items such as falls on a roof, balconies, or parking decks are often insufficient and, on many occasions, plants and equipment placed on roofs obstruct the free flow of water to the outlets.
Rainwater outlets are often merely small diameter PVC pipes built through walls or cast in the concrete, totally inadequate to drain the roof or balcony efficiently.
Frequently, too, there are no substantial differences in levels between the inside and outside on balconies, terraces, parking decks etc. Sometimes the concrete slab is cast at one level, especially when a precast slab system is used. This means that the finished floor level inside will be lower than that outside once the screed to falls, waterproofing system and trafficable finishes have been laid. This could mean disaster.
Another aspect, nearly always overlooked, is a properly bonded inter-face of the damp-proof course (DPC) with the waterproofing system; again drastic consequences can ensue for the building.
Above are but a few of the oversights occurring in waterproofing design. With the ever more complex design of building structures these days, the design and the choice and correct detailing of their waterproofing are vital and should never be left to chance!
2 - Inadequate details at the tender stage.
Too often tender documentation does not reflect the complete picture of the work required. This can be due to many reasons:-
• The Architects, due to time constraints, are often not in a position to produce complete drawings, specifications and details before the Bills of Quantities are compiled. There are areas where specific waterproofing details should be given to the quantity surveyor when he is compiling his Bill of Quantities for pricing.
• The Quantity Surveyors often rely on the ASAQS (Association of South African Quantity Surveyors) “Model Bills of Quantity” as a guideline for their measurement. The current “Standard System of Measuring Builders Work 6th Edition – Revised” does not include the “completeness” clauses. Therefore, the true extent and scope of work are not described requiring too much to be left to guesswork!
• Sometimes the Quantity Surveyors lack the understanding of the methods of application and material requirements of waterproofing systems in specific situations, where the work could be slower and extra materials are required. Therefore, “everything is deemed to be included” does not allow the contractor to price the works correctly – again, certain items are left to guesswork.
• The client’s brief to the Professional team (the Architect and Quantity Surveyor) can be too “basic” and impose financial constraints on the costs of the required development and reduce fees for the Architect, Quantity Surveyor and Engineer. This may result in insufficiently detailed drawings, leaving the responsibility on the waterproofing contractor after the main contractor has merely built to the few drawings provided.
Documents incomplete from the start can only lead to disputes between the Main Contractor, Architect and Quantity Surveyor, especially at the final account stage when extra costs have arisen.
More often than not, the waterproofing contractors will simply follow the Architects’ details, which as mentioned above could be too “sketchy”; or the main contractor’s instructions, even if incorrect, because when they point out errors or recommend a detail, they are not reimbursed for the more difficult types of work – so, therefore, why do it?
The Quantity Surveyors cannot continue to use the excuse that everything is “deemed to be included” or “as per the Manufacturers’ instructions” where difficult or labour-intensive work is required. The contractors must be given a fair description of the works required at the tender stage: it is then their decision as to how to price the items and not leave it to guesswork as to what exactly is required. The Bill of Quantities must describe the required work fully and fairly to enable equal and fair pricing to ensure the best possible end product.
3 - Fast track development with very short construction periods.
With the high cost of money, developers require to have buildings “open for business” as soon as possible to generate an income, or ready to sell and maximize the potential profit, before it is eroded by ongoing interest costs. Contract periods are thus continually being reduced, whatever the size of the project. However, with short contract periods, there is often not enough design time for the Architects to produce detailed working drawings. In turn, the Quantity Surveyor cannot produce a comprehensive and descriptive Bill of Quantities to enable the main Building Contractor to establish a fair and correct price for the job. This carries over to all the sub-trades, including the waterproofing contractor.
The professional teams are reluctant to say to the client that their contract period requirements are unreasonable and should be extended to enable them to hand over a high quality and problem-free building. Indeed, some developers merely hasten to erect buildings and sell on as “complete”, leaving any possible problems for the new owner – a culture of “take the profit and run”.
One of the trades most compromised by shorter construction periods is the waterproofer. With the time restraints, there is very little coordination between the waterproofing contractor and other trades, and so sometimes the waterproofing is laid out of sequence. In certain parts of the country, particularly the Western Cape, the waterproofing may have to be laid in the middle of the wet winter period due to the tight programmes and finishing dates.
4 - The lack of general knowledge, education or care by all concerned as regards the ex*****on of waterproofing.
There is often a general lack of knowledge or education as to the importance and principles of all aspects of waterproofing. Too often the waterproofing is treated with little respect by others trades and site personnel, with resultant damage to the waterproofing membranes. This during construction invariably goes unnoticed and where such a system has eventually covered the cost and inconvenience of repairs at a later stage will be high.
During construction, flat roof areas are often used as “platforms” on which to erect scaffolding, or as work areas and “dumping grounds” for materials or rubble. Even after the waterproofing has been completed to such flat areas, these same activities may still be carried out on top of it! If the Waterproofing Contractor is made aware of any damage at this stage, it is normally very easy to repair. However, it is also easy for damage to go undetected – until leaks occur much later when the main contractor has long gone from the site. Occasionally a clause in the Bill of Quantities will state that it is the sub-contractor’s responsibility to protect his works. Without cordoning off or covering the area waterproofed with a temporary screed or protection boarding, this is impossible to do.
Careful programming of all works is therefore very important to try and have as little work as possible carried out over completed waterproofed areas. Few bricklayers appear to know the importance of installing damp-proof courses (DPCs) correctly, whether in brick walls or around doors and windows.
Keeping the cavity clean as the brickwork is being built can be overlooked and not checked. Other trades cut away the DPC membrane, especially the electricians and plumbers to install the conduits or pipes and normally on the outer brick skin, without consideration of the consequences.
The consequences of incorrectly installed or damaged DPCs and dirty cavity walls can be disastrous, especially if there is an interface between waterproofing turn-ups and the DPCs.
The lack of understanding of and respect for the waterproofing is shown not only by the main building contractor but also by the various trades on the building site, e.g., the plumbers, electricians, irrigation contractors and tilers. Unfortunately, in some cases, suppliers/manufacturers of waterproofing materials themselves do not truly understand the application problems that can occur on-site, especially “terminating details”. A lack of knowledge and understanding of actual site applications of waterproofing systems by the material supplier can even lead to incorrect information being passed on to the architect, resulting in incorrect systems being specified. Some waterproofing contractors may not have enough properly trained staff and applying waterproofing materials can prove disastrous. There can also be different codes of practice and methods of laying the same or similar material when supplied from different manufacturers, so creating arguments on which way is “right” and hence confusing the industry.
5 - An alarming decline in the quality of workmanship, or the scarcity of qualified tradesmen with the required skills throughout the building industry as a whole.
Unfortunately, there has been a marked decline in the quality of workmanship and experience in the building industry in South Africa, which not only occurs with the tradesmen, but it goes right up through the ranks to top management and even the professional consultants. The quality of the end product as a result of poor workmanship is compounded by high-tech building designs and components and by shorter contract periods.
6 - The application of waterproofing systems on unprepared substrates.
Whether due to pressure from the main contractor, lack of knowledge by the waterproofing contractor, or poor detaining, waterproofing systems are occasionally laid or applied to rough, uneven, “flat” (level) surfaces.
Any membrane can easily be punctured by any sharp protrusions, any voids under the membrane act as conduits for water to travel anywhere, and water allowed to lie on the membrane will find any weakness, e.g., a loose lap or a small hole, etc.
All surfaces to be waterproofed must be dry (except with cementitious waterproofing systems, which require the surfaces to be dampened); be sound, smooth, and even with no undulations; be free of protrusions or sharp objects; be without any voids; be free of dust and fine particles; and have correct falls to suitable outlets.
7 - The lack of any formal qualifications in the waterproofing industry.
There are no formal education programs for the waterproofing industry. Some manufacturers have workshops for their representatives and applicators, and there is a basic competency-based training course for beginners, compiled many years ago by the Building Industries Federation of South Africa (BIFSA). The topic of waterproofing is normally only briefly touched on at Universities and Technikons in their various building degrees. Through CETA (Construction Education and Training Authority) a skills register and unit standards are being produced.
8 - The duration of guarantees required on waterproofing systems. No other trades are asked to offer such long guarantees.
Probably as a result of the foregoing seven considerations, the client often feels he can only be secure with a long guarantee for the waterproofing on his building, well exceeding the customary construction maintenance periods. Some manufacturers even use such guarantees as a marketing tool for their products. The industry norm is to offer guarantees for a period of ten years on the waterproofing system, often subject to a maintenance clause, e.g., a maintenance re-paint every three to five years. A manufacturer may offer an insurance-backed warranty/guarantee on the product.
Do not expect the waterproofing guarantee to be the client’s insurance policy”. Remember the guarantee only covers the material, should it be defective, and the workmanship, should it have been laid badly (The manufacturer offers the warranty on the materials and the contractor offers the workmanship guarantee on the application). There is not such a thing as an “Unconditional Guarantee”. Taken alone, guarantees should not be a deciding factor in the choice of a waterproofing system on a building. Any guarantee will equally place a responsibility on the client to properly maintain his building and not “abuse” the waterproofing provided.
9 - The initial cost of waterproofing – often price takes preference. Life expectancy and replacement costs are frequently overlooked.
With the cost of the waterproofing of a building being as little as 1% of the contract sum, a “belt and braces” approach to the waterproofing might only increase this element by a ½% to 1 1/2% of the contract sum. This is not a big difference in value in terms of the end cost.
Too often the trend today is to build as cheaply as possible and make the development appear viable with no proper consideration given to future maintenance expenses. Where the ‘cheapest’ prices for waterproofing are used, invariably “you get what you pay for”. The ‘cheapest’ is very seldom the best in waterproofing!
Some careful considerations when specifying a waterproofing system are”- Is it right for the intended situation? Where has it been used before in a similar situation? What is the material’s life expectancy? Is the manufacturer/supplier a proven reputable company? Is there experienced technical back-up both for the product and its application? Is the Waterproofing Contractor experienced and reputable having a good track record? Price should not alone be the deciding factor.
10 - The lack of proper roof maintenance.
No waterproofing material can last indefinitely, and without due care and maintenance, its life expectancy can be drastically reduced. The South African climate is very harsh with tremendous changes in temperature, sometimes fairly sudden; high quantities of sunlight and ultraviolet rays occur, as do strong winds and heavy rain or hailstorms. This requires regular attention to all exposed roof waterproofing systems, something unfortunately often overlooked by the building owner. This responsibility should lie not only with the building owner but also with the original Waterproofing Contractor, who committed to advising the building owner when his roof maintenance becomes due. Such regular maintenance extends the life of the system, whether under guarantee or not.
Although some manufacturers of polymer modified bituminous membranes state that it is not necessary to apply any protective coating to their membranes, the norm in South Africa is to initially apply at least one, if not two coats of bituminous aluminium paint. The location of the roof will depend on how often a maintenance re-paint is required, e.g., in an industrial area where there is a lot of pollution, it might be necessary to re-paint every one to two years: wherein in a rural area, every four to five years might suffice. The industry norm is every three years.
