Waterproofing before the screed device - materials and technologies. Waterproofing the floor on the ground - choosing the most effective way How to waterproof the floor before the screed

Any floor covering must be reliably protected from moisture. In cases where the floor is laid on the ground, this task is most relevant. Floors of this design are often built in warm regions. In places with dry soil, there are practically no problems with waterproofing. Otherwise, a base made up of several layers is required.

The device of a waterproofing layer is a radical way to deal with penetrating moisture

Consider the factors dictating the need for reliable waterproofing of the base floor on the ground:

From a water-saturated layer located at a certain depth, water rises through capillaries. Moreover, the denser the soil, the thinner the capillaries and the more active the capillary rise.

Interesting! Even if the soil consists of dense and oily clay, the water in it is able to rise above the water-saturated layer by about 12 m.

If there is a concrete floor in the way of rising water, then the floor made of concrete or wood will be saturated with vapors and drops of water. Salts dissolved in groundwater have a detrimental effect on these building materials.

Water penetrating into the pores of concrete structures freezes at sub-zero temperatures. At the same time, it expands by 9% and destroys the material. The cyclical freezing and thawing of water in the pores of concrete and wood causes their gradual complete destruction.

Rules for preparing a multilayer base

During the construction process, a multilayer “cushion” is created under the house. It prevents the possibility of holes and dips due to natural subsidence of the soil and provides the primary protection of the floor from moisture.

The rules of the “pie” device, the activities are listed in the “bottom-up” direction:

The first layer is dense soil. Work begins with markup. Using an optical or laser level, set the zero mark. Soil compaction is carried out using rammers.
Rubble-sand layer. For its device, crushed stone of a large fraction and not too fine sand are used. This backfill interrupts the capillary rise of the water and provides a foundation for subsequent work. It is recommended to fill the layers in turn in the following order: crushed stone - 300 mm, sand - 300 mm, crushed stone - 150 mm, sand - 150 mm. Pegs, which are installed in the corners of the perimeter, help control the height of the stacked layers. The horizontality of the backfill is adjusted using the building level.

If groundwater is located below 2 m, then it is allowed to replace crushed stone with expanded clay. Broken brick for these purposes is prohibited.

The technology for further work depends on the type of floor.

Ground waterproofing concrete floor

Stages of the device of a concrete floor on the ground:

Laying a hydro-vapor barrier. It is created using a polyethylene film laid on the top sand layer. Joints are insulated with tape. The film should not have any damage.
A rough cement-sand screed is laid on top of the film, the thickness of which is in the range of 50-70 mm.
A waterproofing layer is again mounted on the rough screed using gluing roll materials or a polymer-based membrane. The strips of one layer are rolled out in the same direction with an overlap glued with adhesive tape. There should be two layers in total. There should be no dressing between the layers. Waterproofing material must be brought to the walls by 150-200 mm. After the complete installation of the floor structure, the excess parts are cut off with a sharp knife.

The gaps at the exit points of the pipes are sealed with non-hardening sealants.

A heater is laid on top of the waterproofing. In this case, mineral wool, hydroextruded polystyrene foam or expanded clay are used.

One of the insulation options is hydroextruded polystyrene foam.

The device of a finishing cement-sand screed.

There is another way to construct a concrete floor on the ground:

In this technology, the top layer is crushed stone, which is poured with a cement-sand mortar.

The rough screed is smeared with bitumen and roll-up waterproofing is laid on it

Two layers of rolled waterproofing material are laid on top of it. When using roofing material, the joints are heated with a gas burner.
After the device of the heat-insulating layer, a finishing screed is performed.

Features of waterproofing a wooden floor on the ground

The height of the ventilated subfloor should be 150-200 mm

The wooden floor must be arranged in such a way that a warm ventilated subfloor remains between it and the base. If its height is less than 150 mm, ventilation worsens, if more, heat losses increase. The most effective option is to lay the log on brick nightstands.

Wooden floor installation scheme:

On the ground create a substrate. For loose soil, crushed stone impregnated with bitumen is used for this purpose. Crushed stone is poured with a layer of 50 mm and tightly compacted into the ground.
On the basis obtained, the locations of the brick supports are marked, they are poured with a cement-sand screed. After it dries, laying of bedside tables begins.

For laying supports under a wooden floor, you can not use artificial stone or sand-lime brick.

Brick bedside tables serve as a support for the log. Two layers of roofing material are laid between the brickwork and the tree.
The bars are usually placed across the room, and around the perimeter they are tied with crossbars.
The subfloor is wrapped with a hydro-vapor barrier membrane in such a way that equal spaces are formed between the lags, in which insulation is laid - rolled, polystyrene, expanded polystyrene, expanded clay. A waterproofing material is spread over the insulation.
The plank flooring is laid on the logs in such a way that the boards are as close as possible to each other.

Modern technological developments offer many ways to build a subfloor on the ground and carry out waterproofing measures. If you want to continue this topic - write to our website.

But it is not without a number of shortcomings. If you forget to make vents in the strip foundation (or incorrectly calculate their cross section), then over time this can lead to problems. Due to insufficient ventilation of the underground, wooden logs become covered with fungus, mold and rot. Excess moisture in the basement also leads to the destruction of the concrete floors of the floor of the first floor.

To avoid this, you can replace traditional vents with a closed ventilated underground. This is detailed in the article. “Do I need air in the basement” . But there is another option - to abandon the underground and build a floor on the ground on the basis of a strip foundation, as FORUMHOUSE experts advise.

Floors on the ground: what is itsuch

This design is a monolithic concrete base (screed). Here is the arrangement of the floor on the ground: the screed is poured inside the perimeter of the strip foundation onto well-packed soil, with which the sinuses of the foundation and the insulation layer are covered. Underfloor heating can be installed together with a concrete base. This design accumulates heat, so it is well suited as an element of an energy-efficient home.

The composition of the floor on the ground for a residential building.

There are the following options for floors on the ground:

On the prepared base (well-compacted soil), a floor slab is poured, rigidly connected to the strip foundation;
A floor slab is poured onto the prepared base, which is not connected to the strip foundation, the so-called "floating" screed.

Let's take a closer look at the pros and cons of these options.

Michael1974:

- If you fill in a “floating” screed, then the construction of the tape and the floor is “untied”. If shrinkage occurs, then the floor screed structure on the ground will “play” regardless of the foundation, cracks will not appear in the structure, because. no stress. This is a plus. But there is also a minus - the design "lives its own life", separate from all other structures.

Floor device on the ground.

With a rigid structure, the foundation / screed unit works as a single unit. The screed will not shrink, because lies on the foundation. But if the soil is not compacted well enough, after a while it may sink, and the screed will “hang” in the air. With a heavy load, if there are walls, partitions, supporting elements on the screed, this can lead to deformation of the base, cracks and loss of the bearing capacity of the entire floor structure on the ground.

How to make a floor on the ground

Both screed options have both pros and cons. The quality of the concrete floors on the bulk soil depends largely on the quality of the compaction of the bulk soil and on how correct the design will turn out.

Michael1974:

– When pouring a “floating” screed, the “foundation wall / screed” assembly must really be untied, otherwise the structure may be pinched in the tape frame. Those. the floor inside the tape frame must move relatively freely, otherwise the whole point of the floating screed is lost.

To do this, a damper is made of an elastic material between the screed and the foundation (wall), which restores its original shape after the load is removed - in this case it is appropriate to place an isolon 8-10 mm thick. This will allow the concrete screed to “float” freely and compensate for its thermal expansion.

A common mistake is to tie all nodes as tightly as possible. As a result, increased loads occur in the structures. In the case of a floating screed, the "floor" and "foundation" elements work independently of each other.

Ground floor: device.Basic principles

An important rule: a well-prepared base is the key to a long service life of the entire structure. The filling base (the best backfilling of the floor on the ground is sand) must be spilled with water and carefully compacted in layers of 10-15 cm.

Due to the backfilling of crushed stone, when the rammer passes through it, a local impact occurs, as a result, there is a deep additional compaction of the soil layers lying at the lower levels. It is worth building up attention on the correct method of tamping sand.

- In all the instructions for vibrating plates it is written that the plate rams sand to a depth of 20-30 cm, but how well this layer is compacted, I doubt that it is enough. Therefore, I believe that for reinsurance it is better to compact the sand in layers of about 10 cm. It looks like this:

We spread the sand in a layer of 10-15 cm;
We pass through the sand with a vibrating plate "dry";
Spill sand with water from a hose. It is necessary to do this not with a jet of water, so as not to break the layer, but through a spray nozzle;

It is necessary to spill water so that the sand is wet, but not oversaturated with moisture. If the amount of water is too large, then the sand base is practically not rammed.

We pass through the moistened sand with a vibrating plate 2 times with a change in the orientation of movement;
Spill the sand with water again;
We pass along the moistened sand with a vibrating plate 2-3 more times with a change in the direction of movement.

What kind of waterproofing to put on the floor on the ground

After thorough preparation of the base, we proceed to laying the hydro-vapor barrier, which will protect the floor structure from moisture. It is often asked whether it is necessary to make a footing before laying this layer. After all, welded or glued waterproofing, in order to avoid damage, must be placed on a flat, rigid base.

Floor on the ground - the most common solution in the construction of small country houses. Also, a similar method is in demand in the construction of outbuildings, the creation of cellars and in a number of other cases. The arrangement of the floor on the ground is considered a very laborious undertaking, however, the cost of the entire complex of works is low, which allows the technology to occupy a leading position in the work carried out independently. In order for everything to be done with high quality, and the house turned out to be comfortable for living, it is especially important to complete all the stages, taking into account their specifics. Floor waterproofing on the ground is just one of these.

As is clear from the very word "waterproofing", its task is to prevent the penetration of moisture into a certain space. As for the implementation of floors on the ground, then the need for high-quality insulation is obvious. Groundwater in the soil layers tends to permeate the subfloor materials by capillary action, thereby destroying them.

Harm from penetrating water manifests itself in two aspects:

Water vapor and liquid droplets gradually saturate the foundation materials of the house. The salts dissolved in water are corrosive and slowly destroy the structure of both wood and concrete, shortening the life of the floor in the house.
Climatic changes lead to the fact that water that has entered the pores of wood or concrete, freezing and melting, creates an increased porosity of materials. The result of the processes is the slow transformation of wood into dust, and concrete to gradual cracking.

Thus, the creation of a waterproofing layer allows you to protect the floor of the house from the negative influence of the aquatic environment.

Very often you can hear questions about whether it is possible to create a floor on the ground in any house. Practice shows that there are no restrictions in this matter. The soil can be completely dry or with close groundwater - it's not scary. Properly selected layers of the base, waterproofing and other coatings allow you to get a high-quality result in any case.

The floor on the ground is suitable for small country houses, utility rooms, verandas, basements

Mandatory stages of work and materials used

The floor on the ground is created on a layered base, the task of which is to prevent the appearance of holes and failures due to the natural subsidence of the earth. This structure is called a "pie". Its design directly depends on what kind of soil is under the house under construction.

Important ! It is worth noting that the floor on the ground and its waterproofing must be carried out only at the stage of building construction. Otherwise, it will not be possible to correctly perform all technological processes.

If we consider the location of all layers, regardless of the type of soil, the depth of groundwater and other factors, in the “bottom-up” direction, then the sequence will be as follows:

High density soil. There are no additional materials - the work is carried out with a natural earthen base, which must be strongly compacted. To carry out the work, special equipment is used, most often a level.
Bedding. There will be two layers, each about 10 cm. The materials will be crushed stone and sand. In this case, the crushed stone should be of a large fraction, any sand. Their main task is to prevent the capillary penetration of water into higher layers, as well as to create a leveling base for further work. You can replace crushed stone with expanded clay, but only on condition that groundwater is located no closer than two meters to the base. Both layers must be compacted as much as possible.

For information ! It is unacceptable to replace crushed stone with broken bricks or other similar material.

Ground floor pie

After all three layers (soil, crushed stone and sand) are sequentially laid and compacted, you can proceed to the next stages, the choice of which is determined by the ultimate goal of construction activities. It all depends on whether the floor will be wooden in the house or concrete. The waterproofing work also depends on this decision.

Wooden floor: structure and features of waterproofing

Laying a wooden floor is carried out in the following sequence:

The erection of support columns for laying the log.
Surface treatment of columns with coating waterproofing.
Roofing material laying as an additional barrier against water penetration.
Laying wooden logs.
Subfloor equipment. Two solutions are possible here: a plank floor or a floor made of sheets of moisture-resistant plywood.

At the stage of creating a subfloor, there comes a moment when it is necessary to solve the issue of waterproofing. There are two options.

The first technology for the formation of waterproofing is that moisture-resistant plywood is used for the subfloor, thick sheets of which are distinguished by high insulating parameters. To achieve the best result, it is worth laying plywood with any of the options for waterproofing film. It can be a rolled diffusion membrane or a polyethylene film (at least 200 microns). The laying features include the presence of a mandatory overlap of 15 cm, as well as the mandatory use of adhesive tape for gluing joints. After laying the waterproofing, a subfloor from the boards is mounted.

Wooden logs are covered with plastic wrap - this is how one of the waterproofing layers is formed

The second technology is that the laid subfloor is covered with polyethylene film, providing a margin of 20 cm for the vertical walls. After that, it is worth laying a layer of polyethylene foam, which is known as a reliable waterproofing material.

Important ! If you combine both technologies, the issue of floor waterproofing on the ground will be resolved. In addition, there will be a reserve of insulating properties in case of uncalculated water manifestations.

The structure of the concrete floor and the specifics of waterproofing

The concrete floor on the ground is also equipped on the basis of the three primary layers of the "pie", but requires a more thorough and serious approach. The specificity of the work lies in the fact that the soil has a mobile structure, and concrete is a solid monolithic material. The formation of layers, including waterproofing, must combine these two conflicting factors. The issue can be resolved in one of two ways.

The first option implies the following sequence of work on the formation of layers:

Fine gravel layer. Follows immediately behind the sand layer.
An analogue of a rough screed, that is, a thin cement-sand layer, poured as a mortar onto the laid gravel. Permissible height differences in the rough screed are no more than 3 mm for every two meters.
Two layers of roll waterproofing. In this technology, roofing material or roofing felt is recommended for use. The only restriction is that there should not be any sprinkles between the layers. Joint insulation is provided by a gas burner.
Thermal insulation layer.
Clean screed.

Standard concrete floor waterproofing

The second option for laying a concrete floor on the ground differs significantly in layers and materials:

Polyethylene film. Creates the first waterproofing barrier over the sand base layer. The required coating thickness is 200 microns. All joints must be sealed with adhesive tape or other impervious adhesive-based material.
Important ! The layer will not serve as insulation in the presence of even minimal damage. Therefore, a mandatory requirement for a polyethylene film is its integrity.
Rough screed, for which a standard version of a cement-sand mixture based on fine gravel and river sand was used. The layer thickness is limited to 50-70 mm.
Waterproofing layer of rolled material. You can use any option: a membrane or roofing material.
Insulation.
Clean screed.

If necessary, which is shown by calculations on the location of groundwater, additional waterproofing of the floor on the ground can also be carried out.

The polyethylene film will serve as an excellent waterproofing layer only if it does not have any kind of damage on it.

Additional floor insulation measures

The whole feature of the technology is that a layer of oily clay is added, and then the layered structure of the “pie” takes on the following form:

Soil that is compacted to maximum density;
A layer of oily clay - can be replaced with two layers of roofing material;
crushed stone;
Sand;
Impregnation of the last two layers with bitumen;
Rough screed with a thickness of 50-70 mm;
Waterproofing using roll materials;
Vapor barrier;
Clean screed.

The final stage - the device of the finishing screed

conclusions

It often seems that it is not difficult to reproduce the layered structure of the "pie". However, the floor on the ground includes not only waterproofing work. This also includes determining the height of the floor in relation to the doorway, and modifying the layers according to real conditions and soil characteristics. In addition, you need to understand exactly how it is worth positioning the floor on the ground relative to the strip foundation and take into account a lot of various little things.

High-quality floor waterproofing on the ground - a reliable barrier to water molecules

All this is easy when the approach to work is professional, that is, the floor is laid on the ground by people who have repeatedly performed such actions. When specialists work, the probability of errors tends to zero.

Smooth beautiful floors are an integral part of modern renovation. To do this, you first need to make a high-quality screed that ensures the smoothness of the coating and, as a preparatory stage, the waterproofing of the floor under it. Waterproofing works can protect buildings from the penetration of water and other liquids, which, over time, can destroy all previous efforts invested in repairs.

Why do waterproofing before floor screed

Many believe that repairs in living rooms without high humidity do not require additional floor work. But the first judgment may be wrong. Waterproofing works are needed absolutely everywhere, and there are several proofs of this:

Protection against external leaks. In a living space, the bathroom and kitchen are the areas most prone to flooding. At the same time, the global nature of the process will not affect the final result. And, provided that the apartment is located above the ground floor, even an overturned bucket of water can cause contention between neighbors. Another type of external leakage is a screed. More precisely, water, which is a significant component of the casting mixtures. And which can also seep to people living on the floor below.
Protection against internal leaks. The level of humidity in rooms located close to the ground will definitely be increased. Such buildings include private houses, basements, apartments on the ground floors and garages. Needless to say, concrete is a porous material that is easily saturated with water. And in order to prevent moisture from spreading over the floor and walls, leading to cooling and destruction of them, experts recommend doing double waterproofing - before and after the screed. This is especially true for the construction of private houses.
Improving the quality of the screed. In order for the concrete screed not to crack when setting quickly, it needs to dry very slowly. Experienced craftsmen even additionally moisten the coating by covering it with polyethylene. Thus, the drying time of the concrete screed is significantly extended. From a professional point of view, the waterproofing layer will contribute to this process in the best possible way.

Varieties of insulation

There are several types of materials for waterproofing under the floor screed in the apartment. Thanks to them, not only a protective layer is created from water, but also the floor in the room is qualitatively leveled for further repair actions with it.

Plaster. Such insulation consists of several layers with a total thickness of up to 2 mm and is used in two forms - cold or hot. It can be used well in brick and concrete buildings, but it is completely unsuitable for a wooden floor.
Painting. This coating is applied with a wide paint brush until a thickness of 2 mm is reached. Coating materials can be bituminous mastics, as well as polymer paints and varnishes. Paint insulation also comes in two types - hot and cold. The cold look is considered to be the most convenient due to the ease of application and high performance resulting from the use of an epoxy-rubber mixture. With the hot method, bitumen has to be melted, which is not always possible in a closed space.
Okleyechnaya. The essence of such insulation is to fix waterproof roll coatings on the floor, for example, roofing felt, isospan, technonicol, etc. Roll strips are laid in several layers with a slight overlap. To fasten them, they take mastic or a gas burner. The latter is used by specialists in the surfacing method. Such insulation is universal and can be used both in concrete houses and in wooden ones.
Impregnation. It consists of a porous material, which is pre-impregnated with moisture-resistant binder mixtures. These can be polymer varnishes, bituminous resins, as well as petrolatum. The use of such insulation is recommended by professionals for wooden houses. In this case, it is desirable to impregnate not only the floor, but also wooden poles with all available ceilings.
Cast. According to experienced builders, this method is considered the most durable and reliable. For a protective coating, a mixture of hot asphalt and bituminous mastic is used. It is poured in 2-3 layers to a thickness of 10-25 mm. Naturally, this greatly affects the cost of insulation and its weight. Therefore, in order to avoid unforeseen consequences, it is necessary to do all calculations with great care.
Zasypnaya. Here the name speaks for itself - this is insulation, which consists of bulk materials of increased moisture resistance. For reliability, bicarbonate powder and asphaltoizol must be covered with a thick layer - at least 50 cm, which, in comparison with other methods, is unrealistically much. However, such a thick pillow has an undeniable plus - good additional thermal insulation, which is most often used either in the basement or on the basement floor, where the cold is felt the most.
Mounted. The components of such insulation can be different - from profile tapes to plastic or metal plates. They are attached to the floor with special mounting ligaments.
Injection. This is one of the best modern and high-tech solutions that creates protection against water by filling all microcracks with a liquid material. Thanks to a special formula, the mixture penetrates the concrete and hardens in the form of crystalline formations. At the same time, the integrity of the structure is completely preserved and, moreover, withstands the penetration of moisture under pressure. Also, this insulation increases the resistance of the floor to aggressive chemicals.

Waterproofing materials

Floor waterproofing technologies in the apartment before the screed

Depending on the type of material, the technology of waterproofing works will be very different. The most common methods of such processes are presented below.

gravel and sand cushion

Preparatory stage. Before starting construction on the site, it is necessary to remove fertile soil with organic impurities and level the soil itself.
On the leveled soil, over the entire area of \u200b\u200bthe future floor, crushed stone should be poured, the size of the fraction of which should be no more than 50 mm. Next, the rubble must be tamped and leveled to avoid height differences. Depending on the location of groundwater, different layer heights are needed - from 0.2 m to 0.5 m.
The next layer will be coarse sand. It must be covered with a surface 0.1 - 0.4 m thick, and then well watered. After moistening the sand, it should be carefully compacted with a hand roller.
On top of the gravel-sand cushion, it is necessary to put strips of geotextile and glue them with a building hair dryer. This material is resistant to fungus, mould, rodents, rot and environmental chemicals without releasing toxic substances. It allows water and moisture to pass through perfectly, but prevents the layers from mixing, preventing larger particles such as sand, gravel, etc. from passing through. Geotextiles are needed as a shock absorber and protect the insulation from damage.
The next step is to lay the foam insulation, for example, foam or polystyrene.
After completing all the above works, it is possible to carry out waterproofing with roll materials or immediately proceed to the screed on an already prepared area.

Important! Styrofoam insulation cannot be used due to instability to mechanical damage.

Floor waterproofing with roll materials

There are two types of insulation in rolls - built-up, when special gas burners are used during installation for melting bitumen, and pasting, the roll of which is fixed on the base.

Roll insulation technology is as follows:

First, along the perimeter of the walls, it is necessary to lay a damper tape, which is a foamed polyethylene. It is needed in order to avoid cracks in the joints between the floor and the wall. This comes from the fact that temperature fluctuations affect the floor area - it can expand and narrow accordingly, leaving huge gaps after that. To attach the damper tape, you can use dowel-nails or glue.
The next step is to level the floor area. Sometimes there are potholes in the floor that need to be covered with sand or sealed with a cement-sand mortar.
Roll insulation is laid on the floor in strips with a slight overlap of at least 10 cm, and with “climbing” onto the walls - 15 cm. The roofing material must be glued to the floor with bituminous mastic, which is also glued with joints (overlap).
When using built-up materials, for example, glass isol, they are attached to the base of the floor with a construction gas burner. And the overlapped polymer films can be easily welded with a building hair dryer.
Waterproofing materials in a roll are laid unequally. Ruberoid needs at least a double layer, and for polymeric materials with deposited films, a single layer is enough. After performing waterproofing work, reinforcement and floor screed are carried out. And the final feature will be cutting off excess pieces of insulation flush with the floor.

Important! Primer (primer) treatment is needed only when using roofing material, and when using polymer waterproofing films, you can do without it.

Coating waterproofing

First, it is necessary to remove debris, various contaminants and dust from the concrete base. Particular attention should be paid to ensure that there are no sharp objects, cutting protrusions and chemical stains, for example, from oils, solvents and other active substances, which, when in contact with the waterproofing coating mixture, will destroy its properties.
For this waterproofing, it is best to use bitumen-rubber mastics with a cold application technique. First, you need to go over the entire surface with a primer (primer) suitable for the mastic used. Combinations of materials in the work of the same manufacturer will be ideal to guarantee the best result.
The primer must be applied with a paint brush in one layer, while carefully smearing all inconspicuous areas. Its action will reduce the amount of dust and improve the uniform adhesion of the mastic to the floor. Particular attention should be paid to the processing of places near the pipes and at the joints with the wall. Primer drying time usually ranges from 2 to 5 hours. However, in a cold room, other times are possible for complete drying.
Applying mastic requires certain rules. It should be applied in several layers only after the previous one has dried and each time changing the direction of the roller. Again, hard-to-reach places near the batteries are treated with a thin brush with special care.
Complete drying of the coating waterproofing usually takes about two days. After that, you can begin to perform the screed. When laying reinforcement, it is necessary to use plastic guides to avoid contact of metal structures with coating waterproofing - under load, they can damage it.

Important! For reliable waterproofing of the floor, you can use several methods at once.

Features of waterproofing under a warm floor

There are no special restrictions for waterproofing a warm floor. The material can be laid both on top of the cable and under it. This is due to the fact that manufacturers expect the cable to work in various conditions, incl. and to the aquatic environment. The only condition is the prohibition of the location of the cable in direct contact with the waterproofing. To distinguish between these layers, you need to use a metal mesh or a separating screed.

When under the tile, the insulation itself lies above the cable. Therefore, experienced specialists strongly recommend pouring a cement-sand screed over the cable.

With bituminous waterproofing, using burners, the exposed parts of the cable must be protected from flame and high temperature with special materials.