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How to properly install house waterproofing?

by | Oct 4, 2022 | Building process, Insulation, Pre-build preparations | 0 comments

Proper waterproofing of the house implies the application of adequate technical solutions for this purpose on all structural parts of the house that are or may be exposed to water and moisture.

One of the main technical requirements when designing a house is protection from external influences. To ensure this, it is necessary, among other things, to provide proper drainage and waterproofing of the house. We especially emphasize the importance of this process in the design phase, because subsequent execution is, most often, complicated and expensive.

What is house waterproofing?

This is a system of membranes in all places that are sensitive to the penetration of water from the atmosphere, directly (rain, snow, ice…) or indirectly (from the ground, from moisture…), as well as from the moisture in the house itself, to protect the structural elements of the house, to increase sustainability, to improve appearance and, most importantly, to ensure a healthy living space. Structural elements that must be waterproofed are: foundation, basement, walls, windows and doors, roof, bathroom, terraces and balconies, swimming pool… Each of these elements requires an individual approach.

Which waterproofing techniques are in use today?

There are many options, and the choice depends on the price, efficiency and most importantly, whether you install it yourself or you are taking subcontractors:

  • coating
  • plastering
  • polymerization
  • injection
  • penetration
  • rolling

More details about these techniques are on this link.

Which materials are used for waterproofing?

type of material
coatings, spreads and pastes
stripes or ribbons
they are dried or polymerized on site, and reinforcement is installed in places of cracks in the substrate and corners to strengthen the waterproofing | good for detail processing
Sensitive to extreme temperatures and weeds | the latest polybitumens generally overcome these problems
they are dried or polymerized on site, and reinforcement is installed in places of cracks in the substrate and corners to strengthen the waterproofing | good for detail processing
System resistant to all types of precipitation and UV radiation, acid rain and bird droppings, which withstands large temperature oscillations extremely well

Materials are divided according to the chemical composition and physical form in which they are delivered. As a general rule, coatings are easier for amateurs to use, and stripes are quick to apply for professionals. Bitumen-based materials are usually cheaper, but synthetic materials are more efficient and environment friendlier.

type of material coatings, spreads and pastes stripes or ribbons
bitumen they are dried or polymerized on site, and reinforcement is installed in places of cracks in the substrate and corners to strengthen the waterproofing | good for detail processing Sensitive to extreme temperatures and weeds | the latest polybitumens generally overcome these problems
synthetic System resistant to all types of precipitation and UV radiation, acid rain and bird droppings, which withstands large temperature oscillations extremely well

How do you waterproof a foundation?

First of all, fully reliable information is needed on the type of water load to which the building is exposed. The water load depending on 4 factors:

  • Geographic location;
  • Topography;
  • Soil/ Water table conditions;
  • Depth of foundations.


How do you waterproof a foundation

All parts of the building that are in contact with land and water must be protected. In particular, this includes the foundation slab, walls, floors, foundation and planned terrain elevation as well as structural details such as penetration and movement joints. In rare cases, for example, due to moisture in the walls or water splashes inside the basement, the boundary surface of the wall / foundation must first be waterproofed to prevent moisture penetration from the back, before applying bituminous products.The coating should cover about 50 cm above the planned ground level and about 30 cm below. After that, the finishing of the foundation can be mortar or brick.

What are the types of water loads on foundation?

There are two types of water loads on foundation:


Soil moisture is water bound in the capillary system of the soil; it can grow by capillary action even against the force of gravity. Soil moisture is always present as a minimum water load. Another type of water load that can be compared to soil moisture is non-accumulated leachate that occurs due to atmospheric precipitation.

This type of load can realistically be expected only if both the construction site and the backfill material consist of highly permeable soil types, for example sand or gravel. If the land is not sufficiently permeable, it must be equipped with an adequate drainage system that has sufficient drainage capacity to avoid water accumulation.


This type of load occurs when the outer walls of the basement or foundation slabs at the foundation below ground level are in low-permeability soil without drainage. In addition, the type of land and the topography of the location must be such as to predict only the accumulated water.

The long-term reference water level must be below the lower edge of the basement foundation. Note: In accordance with the standard, it is necessary to dig a trench that completely surrounds the building to ensure complete waterproofing of the building surface on all sides that are in direct contact with the ground.

How do you waterproof walls, doors and windows?

The concept is simple. Every component of the drainage plane from the footings to the roof must be applied “shingle fashion” to direct water down and out. There are a lot of materials for this purpose on offer and you just need to find the most economical one and precisely follow the manufacturer’s installation instructions.

When under full assault by wind and rain, the drainage plane should protect the sides of the building as effectively as the roof protects it from the top. In order to achieve this, walls should be treated similarly to the roofs. In addition to window and door openings, a house typically has 20 or more mechanical penetrations on the outside walls. They all need to be properly sealed:

  • Electrical and gas service entrances.
  • Heating and gas fireplace air intakes and exhausts.
  • Air conditioning lines.
  • Outdoor water faucets.
  • Light boxes.
  • Outdoor outlets.
  • Phone and cable service entrances.
  • Ventilation system intake and exhaust hoods.


How do you waterproof a basement?

Basement walls can be insulated from either the outside or inside. You
should carefully compare the advantages and disadvantages of each method
and choose the one most suitable to your situation.

Insulating outside

This method involves attaching a layer of insulation to the outside of the
basement wall. Flashing is installed to prevent water from running down
behind the insulation. Insulation exposed above grade level is covered to
provide a finished appearance and to guard against damage.


  • Previous interior work (shelves, plumbing lines, finished rooms etc.) isn’t disturbed;
  • If the basement is damp or leaky, the walls can be waterproofed and drain tiles installed or repaired at the same time as the insulation is installed;
  • Since the basement walls are on the warm side of the insulation in winter, stresses on the wall from freeze-thaw cycles are reduced;
  • The possibility of foundation damage is minimized because frost is less likely to penetrate under the footings and the soil can’t freeze directly to the basement wall;
  • No loss of interior living space.


  • Extensive excavation work is required;
  • Existing landscaping is disturbed;
  • Only practical during the warmer months;
  • Existing driveways, sidewalks, porches, lot lines, etc. may make it difficult or impossible to excavate;
  • Expensive to achieve high insulation values;
  • May detract from the appearance of some homes.

Insulating inside

This method typically involves installing a wood frame wall inside the
basement walls. Insulation is added to the frame wall and then covered by a
continuous air-vapour barrier.


  • Cost is relatively low, especially if you are finishing your basement anyway;
  • Can be done any time of the year and in any weather;
  • Existing landscaping doesn’t have to be disturbed;
  • Can economically accommodate high insulation levels.


  • Interior finishing may already be completed;
  • Obstacles such as electrical panels, wiring, plumbing, stairs, etc. can make it difficult to insulate;
  • Should not be used in a basement with a severe moisture problem;
  • Increased potential for foundation movement if the basement is shallow or built on frost-sensitive soil;
  • Hard to seal the air-vapour barrier in the floor joist header area;
  • Interior living space is diminished.


How do you waterproof a bathroom?

Bathroom waterproofing is one of the most important items when renovating or building a new bathroom. There are several types of waterproofing, and most often they are based on polymer cement intended for bathrooms, which can be one-component (mixed with water) or two-component (two substances are mixed without the use of water).

There are also polyurethane (PU) and epoxy ready-made waterproofing, which are used less often because these insulations require exceptional dryness of the screed and walls by about 2% – as for parquet.

How do you waterproof a bathroom

The base for waterproofing should be flat and clean. If there are larger dents or cracks in the floor or wall, they must be repaired with tapes that are also used for corners. Thoroughly clean or vacuum the substrate.

Before applying the waterproofing, it is recommended to apply the substrate with a stabilizing roller with which the waterproofing is easier to apply. First, waterproofing is applied to the walls and then to the floor.

The height of the waterproofing in the shower cabins is mostly done up to a height of 2 meters. In the rest of the bathroom, outside the shower, a height of 15 cm is sufficient.

How do you waterproof a flat roof, balcony or terrace?

Waterproofing of flat roofs without falls, terraces and balconies should not only be waterproof, elastic, resistant to weathering and long-lasting, but it is also necessary to have excellent resistance to standing water.

Of all the structural parts of the house that you need to waterproof, the least compromise should be made on these parts.

The damage that can occur due to leaks tenfold any possible savings!


How do you waterproof a bathroom

Over 80% of the damage to flat roofs was caused by poor design and execution of works, according to some research in the EU. That is why it is necessary to properly design and report all the layers of a flat roof. Waterproofing is one of those layers, for which it is very quickly shown whether it is well done or for some reason there was damage.

When we talk about roof waterproofing, we mean “flat” roofs with a base whose slope does not exceed 2.5% or 3% for passable roofs, or up to 7% for impassable roofs. In any case, the slope must not be less than 0.5% in order to ensure fast drainage of atmospheric water from the roof surface, which protects the waterproofing layer.

Passable roofs serve as terraces, squares, spaces for traffic or parking, as green areas, etc. They end with heavy protections made of hard material that protect the lower elements and layers of the roof covering from damage, and their slopes range from 2 to 3%.

Impassable roofs are not intended for longer retention of people, for traffic or landscaping. They are used during installation and maintenance of technical installations. They are usually covered with protection from a layer of gravel, and their slope is up to 7%.

Another important difference that occurs with flat roofs is whether they are ventilated or unventilated.

In unventilated, so-called ”warm” roofs, all layers are on the supporting roof plate and there are no air layers between which more efficient ventilation of the roof could be performed. They are used mainly in residential and public buildings.

Ventilated roofs are made for unfavorable external and internal climatic conditions.

No matter what type of flat roof (terrace or balcony) is on your property, the waterproofing is made of the materials we listed in the table at the beginning of the text. Apart from the fact that it is not advisable to save money on waterproofing flat roofs (terrace or balcony), there is another important difference, when it comes to waterproofing these elements compared to the others. It is necessary to regularly maintain and control the waterproofing!

Damage to flat roofs is not uncommon – natural disasters, poor design and construction, roof loads, wrong choice of waterproofing and poorly executed layers of flat roofs (including waterproofing), for example. Damage caused by natural disasters is unpredictable, but there are also those that can be predicted and avoided in time. Therefore, it is necessary to regularly maintain a flat roof, which includes inspections, controls and repairs, as well as timely repair of damage after it occurs. The roof should be inspected at least three times a year to check for any changes.

Whether the flat roof is passable or not, it must be kept clean. Care must be taken to prevent the appearance of vegetation and the drains and gutters must be regularly cleaned of leaves and other waste, so that they do not become clogged. A flat roof should be used for the purpose for which it is intended and designed, to avoid mechanical and other damage. In the case of impassable roofs, movement is only permitted for maintenance purposes.

When clearing snow, care should be taken to remove snow from fences from passable roofs with heavy protection, because when melting, water can pass over the insulated hollows into the lower layers of the roofs. In the case of impassable roofs, the snow should be cleaned with wooden shovels, taking care not to mechanically damage the waterproofing.

Do I need to waterproof a sloped roof?

Yes, sometimes!

Most of the roofs are sloping, and tiles, tegola, sheet metal, etc. are mainly used as the roof covering. This type of roof covering protects the roof from water and atmospheric influences by good drainage, but it cannot do that completely and that is why it is sometimes necessary to do quality waterproofing.

The key question is when?

First, whenever the attic space is used for living space and second, when the slope of the roof plane is less than required for effective sealing for a particular roof covering, and this is most often 22 degrees for roof tiles.

Waterproofing of the roof plane is done with foils. As an indicator of their quality and characteristics, we have several parameters, noted by manufacturers, that describe them:

  • weight per m2;
  • SD value – indicator of vapor permeability of the foil;
  • WDD value – an indicator of the amount of water vapor that the foil passes within 24 hours;
  • static watertightness shows how impermeable the foil actually is. It is expressed as the water level in mm and represents the static pressure that the foil can withstand without the appearance of 3 water drops on its underside.
  • longitudinal and transverse strength, ie durability of the foil to impacts;
  • UV stability – the time after which damage to the foil occurs due to direct exposure to UV radiation;
  • fire resistance, applicable in the temperature range from -40 to +85 C°.

In practice, the most important is the compressive strength of the roofing foil in the longitudinal and transverse directions and SD value. Today, the highest quality roofing foils achieve a strength value of 500N / 5cm, while those with a strength of 250N / 5cm are considered good and high-quality foils. The SD value represents the resistance to water vapor diffusion. It is expressed in meters of the thickness of the air layer that provides the same resistance as the foil for which the parameter applies.

According to the SD value of the foil, we distinguish:

  • Vapor-permeable foils for which the Sd value is less than 0.5 m. These foils are vapor permeable, allow the passage of water vapor from the insulation and are used in the construction of roof structures that have a single ventilation layer.
  • Active steam dams are foils with an SD value of 2-5m. These are vapor barriers that prevent the penetration of water vapor from inside the building into the thermal insulation.
  • Steam dams are vapor-tight foils with an Sd value above 20 m. These foils are used in traditional roof constructions with two ventilating layers (above and below the roof foil). In this case, water vapor is not drained from the insulation through the roofing foil, but into the lower ventilating layer located under the roofing foil or board formwork. 


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