Floor insulation in the washing room of a wooden bath. The floor in the washing room from the tiles in the bath

Nowadays, a modern Russian sauna or bathhouse can consist of many rooms: a steam room, a dressing room and a washing room. In some cases, cold water drops or a pool, including a shower room, may also be present. In the bath, a special place is occupied by the washing department. People here have a rest from steam procedures. A functional feature of such a room is the use of a large amount of water.

For this reason, the arrangement in this room should be done with attention and special care to all details. And below we will take a closer look at how the floor should be repaired in the washing room with our own hands, after looking at the photos and videos.

Washing room (sink, washing room) is one of the main rooms in a Russian sauna or bath. In it, visitors spend most of the time between races in the steam room. Water is constantly pouring in the room, which means that it is important to equip it to the highest standard.

Throughout the year, it is subjected to strong temperature fluctuations and aggressive moisture. Depending on the type of floor and the quality of its installation, the flushing room will be either uncomfortable and cold, or comfortable and warm.

Requirements for floors in the washing room of the bath:

  • safety;
  • heat resistance;
  • moisture resistance.
  • strength;
  • ventilation.

Of course, repairing the floor in the washroom is an important and serious process. But before you start it, you need to consider all types of floors that are suitable for a bath and choose the best option among their number. Usually, for a wooden building, the floor is made of clay, wood or concrete. Thanks to these options, the sauna gets special features.

Wood is an excellent material in terms of thermal insulation and comfort. Concrete flooring is distinguished by its durability and practicality. A clay floor is not a very high-quality and outdated option, but still it can be found in our time.

In accordance with the functional requirements for this type of premises, experts recommend installing a floor made of concrete or wood.

Do-it-yourself floor repair in a washing room: photos and features of their arrangement

  1. Wooden floors.

In order to equip the washing room with a high-quality floor that would remove excess moisture, it is better to use wooden structures. Wood is an environmentally friendly material with many advantages, the main ones being ease of maintenance and operation, as well as ease of installation.

When installing wooden floors, we recommend the use of wood, which is considered to be particularly resistant to various types of moisture. It should be said right away that for these purposes it is better to use coniferous trees - spruce, pine, larch.

Since wooden floors are a rather complex structure, their installation will require a significant amount of different building materials: sand, cement, waterproofing materials, wood in the form of boards and timber, thermal insulation, bitumen, various antiseptics, etc.

Technologically correctly made multi-layer floor covering will serve perfectly for many decades. If you correctly approach the choice of structures, you can easily build floors in the washroom. Of course, the easiest way in this room is to install wooden floors, which can be of two types: non-leaking and leaking.

Leaking floor in washroom

A leaky floor is a simple wood flooring structure. Outwardly, it looks like a wooden covering with small gaps between the boards, made at an angle so that the water easily and quickly leaves the washing compartment of the bath.

Such floors in the washroom are always laid on a rough base made of crushed stone, stone, expanded clay or other hard material. To prevent cracking and additional insulation of the concrete coating, bitumen is used, on top of which a ball of hydro- and thermal insulation is laid.

If the washroom has a large area, it is better to use a metal reinforcing mesh during concrete pouring to prevent cracking of the coating. When installing the floor, it is more practical to use cement grade 500 and coarse sand in a ratio of 3: 1. It will also not be superfluous to use a plasticizer, which depends on the thickness of the coating layer. They slow down or accelerate the process of drying and setting of the solution, which has a positive effect on the properties of the screed.

For greater convenience, you can also add a small amount of laundry soap or washing powder to the solution. So, you will give plasticity to the cement mortar, from which it will become even more pleasant and easier to work.

Often, when repairing the floor in the washroom with their own hands, the owners resort to making a removable wooden flooring. It significantly speeds up the installation process, as well as its drying and future repairs. Such removable structures allow you to easily and quickly carry out various repair and cleaning work in the sauna.

Non-leaking floor in washroom

This type of flooring is more complex. The floor does not differ in removable elements and represents an already folded, monolithic and multi-layered wooden structure. To achieve a high-quality result, we recommend paying special attention to the initial preparatory stage of work. First of all, it is necessary to prepare a hard rammed base.

An excellent option would be compacted soil or a mixture of sand or gravel. Then you need to take care of how to properly insulate the floor. In this room it will always be warm and cozy if you use rigid and high-quality insulation: foam concrete, expanded clay, high-density foam.

Logs are laid on the layer of thermal and waterproofing, on which a wooden crate is installed on top of another layer of thermal and waterproofing. It is worth paying attention to the fact that wooden logs should be laid strictly according to the level, without giving a slope. The slope itself is given to the floor by mounting the lathing bars, on which the top layer of the flooring is attached.

To prevent moisture from entering the wooden floor, you need to connect the top layer of boards into a tongue and groove. It is better to mount the boards with screws, as this will greatly facilitate dismantling and future repairs (if necessary).

  1. Concrete floor.

This coating is the most durable, reliable and moisture resistant. The outwardly unattractive gray color of the screed can be hidden under a rug, tile or the same wooden flooring. But among the many advantages, such floors have one significant drawback - they are cold and absorb a lot of moisture.

A distinctive feature of this design is the high complexity. The ramming layer of sand, gravel, brick or other sealant must be at least 15 cm. Then a layer of thermal and waterproofing is laid.

Next, a layer of sand is poured over the insulation, which acts as the basis for the first layer of the screed. Upon its completion (the screed is made at an angle), it is necessary to fill in a layer of dry solid insulation. A layer of cement screed is applied over it.

Strictly adhering to all the necessary technological requirements, you are guaranteed to achieve the result and get a high-quality floor installation in the washroom. Such a floor will not be cold, it will quickly heat up and keep heat well, as well as quickly remove water from the room without having an unpleasant musty smell.

To get the desired result, you need to make the right choice. Of course, it is faster and easier to build leaky floors in the washroom. Thus, the water flow will be carried out directly to the drainage system, located under the wooden logs. In such cases, the water will not have time to completely evaporate, and there will always be a musty, damp smell in the room.

Leak-proof concrete or wooden floors will last much longer and give the room more comfort. But keep in mind that the cost of their construction will be an order of magnitude higher.

In any case, a comfortable stay in it can be achieved only in combination with high-quality work done, relating not only to the floors themselves, but also to drainage systems.

  1. Heated floor in the washroom.

Despite the large layer of insulation, the concrete floor will never be pleasant to the touch. In the winter season, the cold concrete surface often annoys the owners of the sauna. In order to eliminate it, the "warm floor" system is used. Usually infrared, water or electric heating is placed directly under the finishing layer.

For a washing room, the arrangement of a system of warm water floors, which are heated by a heater for supplying water to the room, is perfect. Installation of a water floor is practically no different from laying an electric one. There is only one difference - the thickness, which is commensurate with the height of the pipes.

In recent years, solid flooring with a 3D image has been increasingly used, which is perfect for a washroom.

Much less common in concrete floors, as it involves the use of concrete slabs. This option in the construction of small buildings is not very popular.

Do-it-yourself floor repair in the washing room: protection from dampness and water

Bath - this is the zone for which dampness, steam and moisture are quite natural things. For this reason, waterproofing a room is very important and necessary. Heat-insulating materials are laid on a layer of waterproofing. In this case, they can last a longer period.

Moreover, special antiseptic treatment with various means of protection will be required. Otherwise, the floors will forever make friends with various fungal infections, especially if they are made of wood. Any partitions, underflooring, logs, boards must be treated with a high-quality moisture-repellent compound and an antiseptic, which you can easily buy at any hardware store. Ideally, the treatment procedure is carried out at least two to three times after a few hours.

If at the stage of construction and arrangement of the bath, the processing and laying of the waterproofing layer was not completed, you will have to resort to a number of actions that will prevent the deplorable damage caused by moisture and dampness.

  • All wooden floor components must be carefully dismantled and allowed to dry in the sun.

Mistakes when repairing the floor in the washroom with your own hands

Being engaged in arranging the floor in the washing department, one should not miss oversights or shortcomings. As a result, they will lead to alterations and the need for dismantling. If the advice is not followed, novice masters often make many mistakes, and here are the most common among them:

  • you can not save on insulating materials. It is highly not recommended to lay a very thin layer of thermal insulation or replace the vapor barrier membrane film with a simple polyethylene one;
  • do not forget about the important vapor barrier layer, which cannot be dispensed with;
  • flooring with smooth tiles is prohibited. This material, combined with high humidity, can cause falls;
  • the use of plastic components in the finishing and installation of the floors of the washing area is prohibited;
  • the lack of a ventilation system is a serious mistake that entails negative consequences for the room.

Be that as it may, everyone can make the above mistakes, especially in such a labor-intensive and complex process as repairing the floors of the washing area with their own hands. But, following our advice and recommendations, looking at the photos and videos of the repair, your floor will be strong, reliable, safe and durable.

The device of the floor in the bath in the washing room is carried out with sufficient attention, since it is constantly exposed to moisture, therefore, when arranging it, some technological features are taken into account that will contribute to unhindered water drainage, quick drying and resistance to temperature changes.

Failure to comply with the stipulated norms and rules will lead to deformation of the floor and its failure.

Wooden floor installation


The leaking floor is the easiest to install, but it is used only in the warm season.

A leaky floor has the simplest design feature. From the outside, it is a wooden flooring with gaps of a certain size between the boards.

Replacement of such flooring is possible at any time. Floors are removed to dry. The main disadvantage is that such floors are not insulated and are designed for use only in the warm season.


Leaking floor device

A pillow of sand and gravel mixture is used as a sexual base. Water spills directly onto the ground under the pouring floor. In this case, the surface is covered with a waterproofing material. Wash water is drained into a sewer pit.


The non-leaking floor has several layers

The arrangement of a non-leaking floor is of great difficulty, since by its design it does not have removable structures. The floor surface itself consists of a multilayer monolithic wooden structure.

A draft floor is installed between the lags, which should be protected from moisture with a waterproofing film or roofing felt. Between the lags, a heater made of mineral wool, polystyrene or polystyrene is installed and covered with another layer of waterproofing.

The finish is a grooved board. As a disadvantage, it can be noted: if you need to replace the floor, you will have to disassemble the entire wooden structure.

The choice of design features of the wooden floor for the washing room of the bath depends on the characteristics of the foundation and walls of the building.

Concrete floor installation


When arranging concrete floors, be sure to lay a layer of waterproofing

In the washing department of the bath, concrete floors are often used, as the most reliable, durable and moisture resistant. Depending on the design of the bath building, they can be equipped in three ways:

  • over a wooden floor;
  • concreting the surface of the earthen floor;
  • over the concrete floor.

To install a concrete floor on a wooden floor, it is covered with polyethylene with an overlap on the walls. In this case, it is desirable to use a solid waterproofing sheet. If several canvases are used, then adjacent pieces should overlap with each other, and the seams should be glued.

To prevent the film from breaking through, it is covered with a thin layer of fine sand, on top of which a reinforced mesh is placed on stands. When pouring a cement screed, its horizontalness can be checked by a long rule.

The easiest way and much more correct to eliminate the unevenness of the screed is with a self-leveling liquid, which will serve as an additional waterproofing layer.


Dense polyethylene is quite suitable for waterproofing

Before concreting the earth base, it is necessary to compact the soil and level it by adding a layer of sand 50 mm thick. It is imperative to lay the waterproofing film in order.

For it, you can use a dense black polyethylene film or bitumen-based material. If the washing room of the bath is small, it is better to use a special reinforcing fiber for reinforcement, over which a concrete screed is poured.

Provided that the screed will be made on the prepared concrete floor, it is desirable to lay expanded clay concrete on the waterproofing layer, which has not only sufficient strength, but also good thermal insulation properties.

The table shows the calculation of proportions for small volumes of concrete mix:

ConcreteCementSandrubbleWater
Concrete grade Consumption in kg per 1 cubic meter
M100230 850 1200 140
M200305 825 1170 140
M300425 735 1080 140
M400483 695 1080 140

When performing concrete work, the pouring of the solution begins from the far corner of the washing compartment. The concrete surface of the floor is laid out with ceramic tiles. When choosing it, preference should be given to anti-slip tiles.

Choice of floor tiles


Use anti-slip tiles

The floor in the bath, finished with ceramic tiles, is considered the second most popular after the wooden floor. The main advantage of the tile is its resistance to water and steam.

However, not every type of it can be used in a washroom. Since the bath can be used both permanently and with some temporary interruptions, the tiles must be durable, frost-resistant, moisture-proof and anti-slip.

Porcelain stoneware has such characteristics. Its advantages in use in such a room are undeniable, since in addition to the characteristics that were indicated earlier, it differs in imitation of marble coating and other natural finishing materials that are not available to everyone at a price category.

For clarity, the table shows data on the technical properties of the tile:


Keep in mind that the tile adhesive and grout must also meet the requirements for heat and water resistance.

The choice of tiles for finishing the floor in the washing department depends on the desires and capabilities of the owner of the bath.

Heated floor in washroom


On top of the water circuit it will be possible to lay tiles on the screed

For significant savings on heating the bath, it is recommended to install a floor heating system. For the washing compartment, you can use any of the known types of such heating: electric or water.

Any of these types is installed under the floor tiles. However, water heating will be the most effective, the water in the pipes of which will be heated due to the operation of the heating bath stove. At the same time, water will be heated both for heating and for washing needs.

As floor heating pipes, you can use both a metal-plastic pipe for hot water supply and polypropylene pipes with a diameter of 16-20 mm. According to their characteristics, the pipes must withstand a water pressure of 10 bar, as well as a carrier temperature of 95 degrees. One pipe circuit must not exceed 60 m in length, the water to which must be supplied from the boiler through a distribution manifold installed between the washing room and the rest room. How to equip a warm floor in the bath, see this video:

An important part of any Russian bath is the washing room. It is here that the hosts and their guests spend time relaxing after their next visit. And it is here that there is always a lot of water, which means that special requirements are placed on the elements of this room. This is especially true for gender. After all, it must ensure the drainage of water and at the same time withstand its harmful effects for a long time. In this article, we will talk about how to make the floors in the sink of the bath with your own hands.

Gender Requirements

In this part of the bath there are always special conditions. First, there is constantly high humidity. Secondly, there are sharp temperature drops. The user can enter and exit adjacent rooms, visit the steam room. At this time, cold or hot air enters the washing room.

All these factors can ruin even a solid floor in a short time. To prevent this from happening or happen as late as possible, the following characteristics should be taken into account during construction:

  • the floor covering and its components must dry quickly;
  • the floor should easily withstand temperature changes;
  • have the ability to pass air;
  • the underground space should be ventilated, but not create drafts.

The choice of material and floor design

Considering all these factors, you can proceed to the choice of the material used and the floor structure itself. There are three main options to consider in this regard:

  • Clay floor. This design was quite common until recently. Clay flooring is easy to install and cheap. But recently, due to its impracticality and unaesthetic quality, it is becoming a thing of the past.
  • The use of concrete. practical, long-lasting and also do not entail too much expense. But such a coating looks unattractive, besides it is cold.
  • Plank floor. It is this option that can be considered the most suitable for installation in a wooden bath. First, it is warm. Secondly, the tree looks beautiful, and it is easier to work with it.

Which option to choose will depend on you. Wood can cost more than concrete structures. And the latter are more labor-intensive during construction, and it can take a lot of time. The concrete screed gains full strength only after 4 weeks.

Concrete floor

Now let's talk about how to make a concrete floor in a washing bath. This method will require physical effort from you, but it is done quite simply and quickly. The workflow itself will look like this:

  • First of all, the soil under the soaked room is carefully compacted. Next, a layer of gravel, crushed stone or broken brick with a thickness of at least 15 m is poured. Then a layer of concrete is poured, which will serve as the basis for the finished floor. All these procedures are done if the subfloor was not made at the construction stage of the bath.
  • Next, the first layer of screed is laid. If the area of ​​\u200b\u200bthe room is small, then everything can be done at one time. If this cannot be done in one go, then the floor is divided into sections using wooden bars and filled with stripes. It should be borne in mind that the desired slope to the drain must be started at this stage.
  • The next layer should be insulation. This stage is very important, because concrete cools down a lot in winter, and it will be very unpleasant to walk on it. Expanded clay or other bulk material that is not afraid of moisture can be taken as an insulating pillow. If there is a need for laying communications for the removal of wastewater, then this is done at this stage.
  • After laying the insulating pillow, the entire surface is covered with a reinforcing mesh. After that, you can fill in the second screed, not forgetting the necessary slope.

Note! Since concrete, even with insulation, still remains cold, many bath owners are satisfied with and. In washing it is better to use water heating. Since it will be constantly humid here, it is undesirable to use electric heating elements.

Wooden floor

It is this type of flooring that today can most often be found in the bath and in the washing room. The wood has an attractive appearance, it is warm and smells when heated, which creates a pleasant atmosphere.

Before starting work, it is worth deciding on the type of floor. With your own hands, you can make two varieties of it:

  • flowing structure. Such a floor is laid from boards that do not fit snugly against each other. As a result, gaps are formed through which water flows into the underground space, and then is discharged into the sewer system.
  • Leak-proof construction. In this case, the boards are laid tightly, with an inclination towards the drain. Such .

Note! A non-leaking design is considered the best option. It does not create drafts, which means that the floors will be warm. For greater effect in the underground space, you can lay a heater, protected by a layer of waterproofing.

When building a non-leaking wooden floor, the following work must be done:

  • Logs are laid on the foundation or brick pillars, to which the subfloor is attached.
  • Then a layer of waterproofing, insulation is laid, and again a layer of waterproofing and vapor barrier.
  • Next, another layer of boards is attached. This creates the desired bias. It is better that the slope is from the center in two directions (especially if the washing is large). On top, you can lay a plastic film for better protection against moisture;
  • After that, you can lay the boards of the finishing floor, tightly fitting them to each other.

If there is no desire to build such a complex "pie", you can simplify the task and build a leaky floor. First of all, it is worth deciding where the water will flow. If the soil under the bath is sandy, then you can simply dig a hole and strengthen its walls. In the event that the soil on the site does not pass water well, it is necessary to build a water inlet to drain wastewater. You can make a concrete screed with a slope or place a metal pallet.

The process of building a leaky floor does not take much time and does not require you to have great building skills. First of all, as in the previous case, the lags are laid. Then boards are nailed to them. At the same time, a space of 6–8 mm is left between them so that water can freely and quickly penetrate into the underground space.

Note! In order for the tree to serve as long as possible, it must be pre-th.

It is worth remembering that the leaking floors are quite cold, because there is no insulation under them and the wind “walks” freely. To somehow reduce this effect, it is necessary to insulate the basement of the bath. Make sure that the wind does not get into the underground space.

Video

This video will answer questions about the floor in the bath:

The process of laying bath floors is quite an important and crucial moment.

Depending on the floor material, we can talk about the service life of the entire floor.

The floor can be:

  • concrete;
  • wooden;
  • clay;
  • just earthy (with good tamping).

Wooden floor

This floor is considered very economical, therefore it is the most popular. When wooden floors are mounted, the most important thing is the right one. If this is not done, then such floors rot and collapse, exuding an unpleasant odor.

Before you make the floor in the washing bath, a special impregnation is required, which processes all the boards lying on the floor. At the end of the procedure, the room must be thoroughly ventilated. At high humidity, the wood becomes soft and wears out quickly, so it is recommended to change such a coating after 5 years.

clay floor

Clay does not let water through, but it swells from it, and then, when it dries, it cracks. Water can accumulate in cracks. There will be an unpleasant musty smell in the bath. That is, this option is also not the best.

Concrete floor

The optimal solution for . In fact, its price is relatively low, and its service life is long. To make it easier to wash, floor tiles are laid on top.

Before you make the floor in the concrete washing bath, please note that it must be inclined towards the drain pit. Wooden grates are laid on top of the tiles so that the legs do not burn on the hot tiles and do not slip on it. At the end of the “bathing day”, the grates are removed to dry.

Baths are built on the foundation.

The drain is done like this:

  • a drain hole half a meter deep is dug in the soil;
  • the finished pit is covered with masses of gravel or sand.

To prevent runoff water from entering the bath room, a pit is built a few meters from the buildings themselves. The bath is connected to it by a branch.

Floor types

The floors in the sink of the bath are leaking and those that do not leak. In the first case, moisture freely passes through the cracks in the floor. In another embodiment, the floorboards are stacked so tightly together that water flows over the surface towards the drain.

Both types have both positive and negative sides. Leaking floors are good because the boards are simply laid on the logs, which means that they can always be dried and ventilated.

The downside is the labor-intensive maintenance of such facilities. The insulation between them is removed every time regular cleaning is carried out.

First option

Do-it-yourself flooring of leaking floors in the bath is carried out as follows:

  1. a dug hole, the depth of which is 50 cm, is poured with concrete;
  2. brick pillars (25x25 cm) are erected on top of the concrete layer, logs are laid on top;

  1. boards are laid on the logs, the thickness of which exceeds 2 cm. In this case, the boards are taken up to 15 cm wide, and the distance between the logs is 60 cm. In some cases, the boards are attached to the beams;

Advice!
The flooring is carried out in such a way that the patterns of growth rings of wood are located in opposite directions.
Due to this, the floor plane will become more even.

  1. the logs are hoisted 10 cm above the gravel / sand. The instruction categorically prohibits laying the boards tightly, otherwise the floors will swell. The boards are laid so that the convex side lies on top. To form small gaps between the boards, galvanized nails are driven in.

Second option

Unlike the leaky type, non-leaking structures are used continuously until the tree rots completely. After that, a complete replacement of the coating is carried out.

For the manufacture of such a floor, a grooved board is taken. The segments are laid in the direction of the drain (ladder). The slope is mounted in two or four slopes, the latter variety is used more often.

For a tight connection, the boards have a special tongue-and-groove profile. A standard screed with wedges is used. The general slope is directed to the drain hole to which the siphon is connected.

It happens that the system is supplemented with a special gutter through which water flows. The space under the non-leaking version is filled with insulation (ordinary foam), sometimes it is replaced with perlite or expanded clay. You can use any insulation, because the space below always remains dry.

Moisture, flowing to the drain, is in the sewer. The warm floor in the bath sink should be soundly insulated. Sheets of water-retaining material are wound onto the walls and pressed against the skirting boards, so moisture will flow down them into the drain. Expanded clay is considered the best insulation in this case.

Important!
Properly bedded does not let moisture out.
To prevent rotting of the subfloor and lag, the foundation is equipped with holes (vents), which are closed for the winter and remain open in the summer.

Floors in washrooms

The floors in the washing department of the bath are equipped before the wall decoration begins. To prevent falls in the bath (the consequence of which can be serious injuries), you need to mount it very carefully, and lay a ladder on top, which is made of wooden slats.

When funds are not enough, a set of rubber bath mats is used, they should be in harmony with the overall design. Sometimes it is acceptable to use carpets or special light mats. However, they need to be constantly monitored, taking them out each time after use to dry.

For the arrangement of a wooden floor, moisture-resistant rocks are needed that can easily cope with a significant load. In the presence of wooden floors, ventilation in the room is especially effective.

Conclusion

It is impossible to imagine a bath or sauna without a washing room. The floors in it are made with special care, here everything should be thought out to the smallest detail. If everything is done correctly and competently, the floors will serve faithfully for a long time. The video in this article will help you get more information on this subject.

The fact that the floor will be cold should have been foreseen at the stage of building a bath. Therefore, if you wanted to make a leaky floor, then it was necessary to insulate the foundation and underground space well. What can be done now?

If you do this right now, then the best, in my opinion, option is to make the floor non-leaking. To do this, you must first disassemble the floorboards. If the floor beams are made of wood, then fill the bars for the subfloor along the bottom of the beams. Then lay boards or subfloor boards on them to close the underground space. Lay mineral wool mats on the boards to the height of the beams. From above, cover everything with a film or a hydro-barrier in two layers. Then lay the floorboards of the finished floor tightly in the tongue to prevent water from flowing. Make a drain hole in the floor through which water will drain onto the concrete trough. And be sure to make the slope of the floor towards the drain hole.

A second option for a non-leaking floor is also possible: a warm water floor. The flowing floor must be covered with a solid board from above, it can even be unedged. Then lay a film or hydrobayer in two layers. On the boards make a concrete screed, in which to lay the pipes of the warm floor. Top the whole cake with porcelain stoneware. Underfloor heating is carried out from an existing stove or put another stove in the rest room. But even on a warm floor, it is still desirable to put wooden ladders on top, so that it is more pleasant to walk barefoot.

Available and the third version of insulation. Leave the floor leaking, but insulate the underground space. To do this, disassemble the floor, remove the concrete trough, deepen the ground inside the foundation by 30 - 40 cm. Make a sand cushion, shed it well, tamp it down. Then lay sheets of foam plastic with a thickness of at least 10 cm. Cover with two layers of film or a hydro-barrier on top. And pour a concrete screed on top, in which to make a recess to drain the water. Be sure to provide for the slope of the screed towards the drain. It is also desirable to insulate the walls of the foundation with polystyrene foam (or polystyrene foam), which must first be waterproofed.

Which option to choose is up to you.