Proper waterproofing of buildings: Common errors and the most effective solutions

Water can do a lot of damage to various types of buildings: it may cause an infestation of mould, bad smell or destructive cracks, as well as damaging the finish. However, all these challenges can be resolved through waterproofing. Waterproofing protects buildings against water damage and helps you avoid time-consuming, labour-intensive and costly repairs in the future. Our Product Manager Robertas Matusevičius explains the importance of quality waterproofing and the stages of this process, also listing the main errors and the solutions for rapid, reliable and effective results.

Serious challenges to be expected down the line

Waterproofing buildings, in essence, is preventing later challenges that can be caused by water damage. Therefore, waterproofing must be done properly, conscientiously and at the right time. Otherwise, water may cause irreversible damage to the building. Fixing this damage, R. Matusevičius points out, will be both complicated and costly.

“In areas where water seeps through or moisture accumulates, one should always expect to see certain damage such as mould, bad smell or damage to the finish. Add to this the effect of cold and we end up with cracks that are destructive to the building. Therefore, proper waterproofing is crucial when building a house, as failing to do so will result in defects that will not only present a financial challenge, but also require a lot of time and effort. Suppose water seeps through the basement wall. You would then need to dig out around the outside of the wall and mess up the tidy surroundings. Or if water starts accumulating on, say, a flat roof, it will be very difficult to locate the exact spot of leakage, as roof insulation will have become saturated with moisture. Now, drying that is a tough challenge indeed,” says R. Matusevičius.

Resolving issues like that is a difficult task. However, according to Matusevičius, proper waterproofing prevents these problems from occurring in the first place.

Five-step process

When asked how to ensure proper waterproofing, R. Matusevičius explains that there are multiple ways of doing so. However, with respect to liquid bituminous coating in particular, the process is divided into 5 steps.

“First, you need to prepare the surface. The base surface needs to be dry or lightly damp. You should then clean the surface to make sure it is free of dust or mechanical particles. If it is noticeably uneven or there are cracks, these should be taken care of, too. The second step is priming. For this, you will need a primer that permeates the surface and binds it, ensuring better adhesion and durability of the waterproofing coating. Next, you apply the filler. If there are any small imperfections or cracks, these should be taken care of. Corners, vents and joints must be coated with a bituminous filler, which is viscous and highly elastic. In these areas, the use of a filler reduces the likelihood of cracks appearing as the building moves over time,” says Matusevičius.

The fourth step, according to him, is applying a waterproofing mastic. Usually, two, three or four layers of this coating are applied on the base surface. We recommend applying every new layer crosswise to the earlier one, and if one is working with a flat roof, a polyester fleece should be embedded in the first layer.

“A polyester fleece is used as reinforcement, much like a reinforcement mesh for concrete. I would then recommend applying mineral dry shake hardener on the last layer of the waterproofing coating, which will increase its UV resistance and improve the durability of the roof. Once these steps are completed, you proceed to the last one, which is thermal insulation. For example, if you need to thermally insulate a basement wall after waterproofing, you will need to use PS and XPS insulation boards. These are fixed to the wall using a bituminous glue-mastic. Finally, once the wall is thermally insulated, you apply a special membrane and cover it with soil,” says R. Matusevičius.

Mistakes to avoid

One should not only follow these steps to ensure proper waterproofing, but also take care to avoid the most common mistakes, the expert says. Asked what those mistakes are, R. Matusevičius points out that, first and foremost, people tend to forget to clean the base surface, which then compromises adhesion.

“Another common mistake when waterproofing is the failure to take care of all kinds of cracks and to use a primer. Many are unaware that it should be used, and others try to save money. To give you a parallel: people sometimes fail to use a primer before painting walls, which causes the paint to peel off some three years later. The same goes for waterproofing,” he says.

When waterproofing the foundation walls, one should carefully assess how many layers of the coating are needed, Matusevičius emphasizes. Two layers provide light protection. They protect against moisture and temporary soil saturation when soil permeability is high. The thickness of this waterproofing coating is between 1 and 1.5mm.

“Medium waterproofing, on the other hand, consists of 3 layers. This is the preferred option when soil permeability is not very good, which leads to the accumulation of rainwater in the soil for an extended period of time. Its thickness is between 2 and 3mm. Finally, heavy, 4-layer waterproofing is used when soil permeability is poor, with constant accumulation of rainwater and pore water pressure. The thickness of this waterproofing coating is between 4 and 6mm. There is also another common mistake. Thermal insulation boards should never be attached to the foundation using mushroom-head fasteners. If you drill a hole in the wall to insert a mushroom-head fastener, you compromise the waterproofing coating. When applying a seamless waterproofing coating on the roof, it is important to embed a polyester fleece in it,” says R. Matusevičius.

Offering an innovative solution

We are launching a new waterproofing system in Lithuania’s market, which ensures rapid, high-quality and eco-friendly waterproofing.

This our innovative Fome Flex product line, which lets you complete the work in as quickly as one day. These are water-based emulsion products, which means that they dry quickly, odourless and can be used both indoors and outdoors. The innovative bituminous waterproofing system consists of four products, R. Matusevičius explains.

FOME FLEX Rapid Hydro Defence Primer bituminous primer. It effectively permeates the base surface, binding the dust and other impurities that remain after cleaning. The primer is less viscous than a mastic, which ensures better surface penetration. If a mastic is applied without a primer, its adhesion will always be compromised, and the mastic may even detach from the surface over time. This will likely lead to the accumulation of moisture and cold, which will cause further damage to the waterproofing coating.

FOME FLEX Rapid Hydro Defence Filler bituminous filler. This filler is purposely made to be viscous and highly elastic, which allows it to fill any gaps and even out the imperfections. Using the mastic alone will not be enough to seal any cracks that are wider than 1 or 2mm. The mastic will never be able to completely fill such gaps. This may lead to the accumulation of moisture and cold, which would in turn cause damage to the waterproofing coating. The filler is also essential for sealing various corners and joints (such as chimneys or vents on the roof). In these spots, the likelihood of cracks appearing as the building moves over time is greater. A thicker layer of the filler acts as a buffer here, preventing the cracks in the waterproofing coating.

FOME FLEX Rapid Hydro Defence Mastic bituminous mastic. This is the product that creates the waterproofing coating itself. It is neither too liquid (the primer itself does not provide sufficient protection), nor too viscous (while the filler can, in theory, be used for waterproofing, doing so would slow down the work and increase the costs). The mastic can be applied to large surfaces in a very short time, dries quickly and ensures reliable waterproofing.

FOME FLEX Hydro Defence Glue-Mastic bituminous glue-mastic. In Lithuania, the foundations are usually waterproofed using bituminous-based mastics. Then, PS and XPS thermal insulation boards are often fixed to the wall using polyurethane foam adhesives; however, not every adhesive of this kind ensures good adhesion with the waterproofing layer. This is why the safest option for thermal insulation of the foundations is the bituminous glue-mastic. This product ensures excellent adhesion with both the waterproofing layer and the PS and XPS thermal insulation boards.

“All of these products are safe for the environment, solvent-free, non-flammable and odourless. They can be applied on damp surfaces. These products are also very simple to use: compared with thinner-based solutions, the Fome Flex products are much more liquid, which makes them much easier to apply and distribute evenly. One may use putty knifes, rollers, brushes or air compressors to accomplish this. Also, when all work is done, there is no need to clean the tools with a solvent. If the substance has not yet hardened, you can simply wash it off with water and a sponge; if it has hardened, you can scrape it off with a putty knife. It is important to bear in mind that these products provide a 1.5 to 2.5 greater output by weight and offer UV protection, yet their greatest advantage is the speed of work. The Fome Flex range allows you to complete the waterproofing process – that is, apply the primer, the filler and 2 to 3 layers of the waterproofing coating – within a single day or 6 to 10 hours,” explains R. Matusevičius.