Frequently asked questions

Waterproofing is divided into two main categories – rolled and plaster. Rolled waterproofing materials are divided into bituminous and synthetic membranes.

Bituminous materials are of several types:

• Depending on the base
  • Glass veil
  • Fiberglass
  • Polyester
• Depending on the plasticizer
  • АРР – atactic polypropylene
  • SBS – styrene-butadiene-styrene
• Depending on the top surface
  • With quartz sand
  • With mineral shale
  • With polyethylene foil

Synthetic membranes are of several types:

• PVC – polyvinyl chloride
• FPO – flexible polyolefin
• TPO – thermoplastic olefin
• HDPЕ – high-density polyethylene
• LDPE – low-density polyethylene

Plaster waterproofing is divided into three groups – polyurethane, bitumen and cement-based.

The right choice of the waterproofing material and laying technology is mainly dependent on the project specifics.

Foundations

When working with foundations, the most suitable is the bitumen waterproofing, which is applied in two layers – both under the foundation and on the basement walls. The most widely used is the SBS bitumen waterproofing. The waterproofing of the basement walls is protected with XPS thermal insulation and a drainage membrane. Sometimes synthetic materials are used in practice, most commonly those being the PVC membranes without UV protection. They are used much more seldom than the bitumen ones, as the likelihood of injury is significantly larger and they therefore need additional protection. Of great importance in the implementation of the overall underground levels waterproofing system is the correct choice of material for the processing the working joints between the foundation and the basement walls and for the processing between the individual casting stages of the basement walls.

Another method for underground levels waterproofing is the use of plastered waterproofing – both cement and bitumen based. They are relatively less commonly used and less reliable. Their main disadvantages are related to the cracks that appear in the building’s subsidence over time and with more difficult processing of the working and expansion joints.

In general, the global experience has demonstrated that the most reliable and accordingly most widespread is the waterproofing made with rolled bituminous membrane.

When stopping leaks in the underground levels of buildings, after the backfill has already been completed, the most widely used are injection resins and crystallizing cement-based plastered waterproofing.

Terraces

At terraces waterproofing, the most widely used are bitumen membranes, particularly for areas over 20 m². Cement-based plastered waterproofing materials are also used, but they are recommended for small terraces of up to 20 m².

Of great importance for the quality performance of the waterproofing works on terraces is the protection of the waterproofing membrane with additional cement screed or concrete.

Synthetic membranes find a more limited application in outdoor terraces waterproofing.

With terraces waterproofing, it is highly recommended to perform a water test before applying the protective screed and the finishing coating.

Roofs

The quality waterproofing system installation in roofs construction depends largely on the structural and architectural features of the building. For example, buildings with metal construction and flat roofs are most often made with layered installation of vapour barrier, thermal insulation of stone wool and waterproofing of TPO or PVC membrane. The most widely used system is a TPO or PVC membrane with mechanical fastening. Relatively less often the so-called ballast systems are used, in which the membrane is protected from UV rays and wind impact by applying a layer of river gravel.

In buildings with reinforced concrete load-bearing structure, two-layer bitumen systems are most often used. In them, thermal insulation (most often XPS) is applied over the reinforced concrete slab, followed by cement screed or concrete for slopes, and finally two layers of bitumen roll waterproofing are laid. In such buildings, synthetic membranes are also used, especially for roofs with large areas and a relatively small number of details. Plastered waterproofing based on bitumen and polyurethane is used relatively rarely.

Tunnels

In tunnels waterproofing, almost only PVC membranes are used. The protection of the membrane from mechanical damage is most often carried out by applying geotextile in two layers – respectively on the side of the primary and on the side of the secondary lining.

An important role for the waterproofing system overall reliability is played by the installation of PVC WaterStop tapes, which allow leaks localization only in a certain area in case of possible waterproofing compromising. This localization allows precise leaks removal by resins injection in an extremely short time.

Bridges

Bridges waterproofing is always made of single-layer rolled bitumen waterproofing with very high strength and temperature indicators. The most important factor for the correct implementation of the waterproofing is the humidity of the base. If the normative requirements for low humidity of the base are not observed, during the hot asphalt laying vapours are formed, which peel off the waterproofing from the base and form air balloons. After the waterproofing application, tests are always performed to prove the good adhesion of the waterproofing to the base.

Landfills and tailings ponds

Landfills and tailings ponds waterproofing is used in order to prevent the soil from the infiltration of harmful substances. In this area, only HDPE membranes are used in combination with bentonite waterproofing and drainage geo-composites.

Tanks

Waterproofing systems in tanks can be built using all types of membranes – synthetic, bituminous and plastered. The most common practice is the application of synthetic membranes.

There are two types of tanks requiring the construction of waterproofing systems – for drinking purposes and for fire purposes. Each type has its own specific requirements and norms regarding the materials utilized and the technology used.

Drinking-water tanks must be implemented with synthetic materials, specially designed for this type of objects. The implementation of waterproofing systems in tanks for firefighting purposes does not require the use of strictly defined materials and this type of tanks are waterproofed with synthetic, bituminous or plastered membranes.

Waterproofing systems can be built successfully in all seasons, in compliance with a basic rule – the choice of material to comply with weather conditions! The requirements to the base on which the waterproofing will be laid are of paramount importance for the quality performance of the system. These requirements are mostly connected with the humidity of the base and the ambient temperature.

At bitumen waterproofing systems laying during the cold months, as a rule, SBS bitumen membranes are used, which have better flexibility indicators at low temperatures. In the warmer months, APP membranes are mostly used, which have better heat resistance. However, modern manufacturers use plasticizers and additives which make both APP and SBS membranes suitable for use in all seasons.

Synthetic membranes are used at all ambient temperatures and have no requirements for the humidity of the base due to the fact that they are mechanically fixed.

As a rule, waterproofing is not laid in rainy weather.

Difficulties in choosing a contractor for waterproofing works stem mainly from the extremely large number of companies offering this specific service and the lack of clear parameters to guide customers on the level of professionalism, competence and experience. The companies performing waterproofing works are not subject to certification and for this reason the contracting authorities can make only a subjective assessment, which is based exclusively on implicit characteristics.

The most frequently encountered problems with contractor companies stem from their poor knowledge of waterproofing materials and the respective properties thereof. In most cases companies do not select the right materials tailored to the specifics of the project and weather conditions during application.

A significant problem is the low competence and poor qualification of the executive staff. Lacking enough experience and low-skilled, workers often compromise the waterproofing system even if the highest-class materials have been selected. Extremely often, mistakes are made in the processing of details, in the preparation of the base and in the waterproofing laying itself. In many cases, the materials burn out or do not stick well enough, which is a prerequisite for very serious problems in the future.

One of the most serious problems is the incorrectness of many companies carrying out waterproofing work. In recent years, the corrupt practice has spread to replace the materials predefined under the contract with cheap and poor-quality membranes, to default on significant implementation deadlines and to claim additional payment beyond the financial conditions agreed. The companies often require full-amount advance payment, then terminate any communication with the clients and never start work on the project.

Another widespread problem in practice is the non-compliance with the commitments under the assumed warranty conditions. Accordingly, in case of poor performance of waterproofing works and the consequent occurrence of leaks, the contractor does not take any responsibility to eliminate the problem.

SAT Engineering advises all contractors to do a serious preliminary study of the industry before choosing a company to assign the waterproofing work to. One should never look for the cheapest offer or the shortest lead time. Our advice is to choose a large company with solid professional experience, good reputation, large enough engineering and executive staff in place and a rich portfolio of successfully implemented projects.

One of the most common problems are the leaks and flooding of basements, garages and other underground levels of buildings. The main method of basement leaks stopping is the injection of resins of various types. The choice of the most suitable resin for injection depends largely on the type of joint – expansion or operational – to be injected. The repair of sections with destroyed concrete using various cement-based materials is also used.

Recently, the use of the so-called acrylic curtains forming a waterproofing film on the water pressure side becomes popular.

The quality execution of the waterproofing system on a green roof largely depends on the correct choice of the membrane. Bitumen waterproofing with a special chemical composition preventing the effects of the vegetation roots are mostly used. The layers performing the system’s drainage functions are also crucial, as their optimal choice depends mainly on the type of vegetation and the soil layer thickness.

In the case of intensive roofs, medium and large-size plant species with deep root systems are planted. This requires the use of drainage composites with much higher robustness. The vegetation on extensive roofs is mostly grassy with a weak root system. Accordingly, the choice of drainage composites in this case is less important.

The most common problems during the warranty period arise due to the poor choice of the optimal type of waterproofing.

When laid at high temperatures, some of the SBS-modified bitumen waterproofings yield large linear extensions during the winter months and lead to compromises in the welding areas and the details. Some types of synthetic membranes do not have good UV protection and therefore age and crack before and after the warranty period. The wrong choice of the drainage system is also an important prerequisite for problems during the warranty period. The poor quality of roof drains and barbican often crack due to the weather impact or do not make a good solder with the waterproofing material. This leads to leaks.

At building foundations insulation, the correct interaction among the individual participants in the construction process is extremely important. Quality protection of the insulation from mechanical injuries at reinforcing and formwork activities, as well as the implementation of backfilling is extremely important to preserve the waterproofing system integrity.

At outdoor terraces waterproofing, problems often occur in the connection areas between the waterproofing and the millwork.