How to make a concrete floor on the ground in a country house?

When arranging a concrete floor in a private house, the option of laying them on the ground with simultaneous insulation is most often chosen. This method makes it possible to obtain a durable monolithic screed, suitable for laying any floor covering, at medium investment and labor costs, and to prevent heat loss through the bottom of the building. All stages of work can be done with your own hands, the mandatory requirements of the technology include the correct alternation and sufficient thickness of the layers of the cake.

The design is a multi-layer cake, laid on dry and stable soil layers, taking into account a pre-measured level. The mandatory conditions for its construction include GWL below 4.5-5 m, the presence of an established foundation and constant heating. The standard scheme includes the following layers (from bottom to top):

1. Compacted soil, by analogy with a monolithic slab, accepting the main weight loads.

2. At least 10 cm of sand, which reduces the forces of frost heaving of the soil and performs drainage functions.

3. From 10 cm or more of compacted crushed stone and / or expanded clay, distributing weight loads and preventing subsidence and displacement of the remaining layers of the floor.

4. Flooring of waterproofing materials, combining two functions of protection: from capillary moisture and water loss when pouring the solution. In this case, it is the roll varieties that are laid with a mandatory overlap of 10 cm and above that have the optimal characteristics.

5. Draft base, which performs separating, bearing and protective functions.

6. An insulating layer of expanded polystyrene or stone wool.

7. Another waterproofing that protects from getting wet and extends the life of the cake.

8. Reinforced screed with a thickness of at least 5 cm, which performs the main load-bearing functions and serves as the basis for the installation of floor building materials.

The above scheme is the only possible one; pouring a concrete base over the beams is extremely difficult due to its massiveness. The resulting screed can withstand significant loads, including its own weight, the weight of furniture and ceilings, and is suitable for installation of any type of flooring: from self-leveling mixtures to light linoleum. You will find more information about pouring concrete floors.

What to consider during the preparation stage?

The main requirement is the presence of a stable bearing layer; when building on sites with an unsuitable type, the expediency of sampling the soil and replacing it is considered. In other cases, the emphasis is on compaction and alignment. Work begins with markings - a zero level is marked around the entire perimeter of the premises of a private house and a cord is pulled, after which the soil is removed to the desired depth (if necessary, on the contrary, it is poured). Chernozem or soils with a high organic content are recommended to be selected until stable layers are reached, loams and sandy loams are simply leveled. It is difficult to perform high-quality ramming without the right tool yourself, at this stage it is advisable to use a vibrating plate, in its absence, a log with a nailed handle is used.

Sand and gravel are poured in layers (from 10 cm each), ensuring the maximum possible shrinkage. On heaving and frozen soils, the thickness of the first layer is increased to 20 cm, under normal conditions 10-15 cm is enough. Sand is poured with water and compacted every 10 cm, its quality and grain size do not play a special role, but small and dusty varieties are not recommended.

The next layer is filled with dense crushed stone or gravel from a coarse fraction (20-40 mm, from 1000 kg / m 3). Dolomite rocks are not suitable for it because of the low grade strength. By analogy with the sandy layer, this layer is carefully rammed (but without watering). In order to increase the waterproofing properties, it can be impregnated with liquid bitumen, heat-insulating - covered with expanded clay.

The preparation stage is completed by rough concreting - a thin layer of lean mortar with a strength grade within M100. There is no need for its careful smoothing, but air distillation is mandatory. The thickness of the layer in this case depends on the parameters of the soil and the expected loads and varies from 3 to 10 cm; when building on stable and dry soils, it can be replaced by pouring cement laitance over crushed stone; at the risk of frost heaving and significant weight of structures, the feasibility of reinforcing with metal is considered .

The nuances of thermal insulation and reinforcement

Given the high thermal conductivity of concrete surfaces, the presence of an insulating layer between them and the ground is mandatory. Moisture-resistant varieties have suitable characteristics: foamed crumb or foam plastic slabs, stone wool impregnated with hydrophobized compounds, expanded clay or perlite granules. The thickness is determined by the heat engineering calculation, in the middle zone of the Russian Federation, the recommended minimum is 50 mm of extruded polystyrene foam, in the northern latitudes - at least 100. Insulation is placed above the flooring made of polyethylene film or roofing felt, with protection on the sides from moisture. The second waterproofing layer is made of similar materials, with a 15-20 cm upward bend and fixation. The stage is completed by placing a damper tape or strips of polystyrene foam around the perimeter of the room and around the supporting columns, if any.

Reinforcing products are placed on top of plastic supports at a distance of 3-5 cm from the upper layer of waterproofing. A metal wire mesh with a cross section of about 3 mm and a mesh spacing of 5×5 has suitable characteristics. It is important to leave the plastic film or membrane intact; wetting of the insulation during the process is unacceptable. Simultaneously with the reinforcement, the installation of beacons is carried out: taking into account the future level and the recommended minimum screed thickness of 5 cm, on mortar or with welding to a fixed element.

As beacons, a T-shaped plaster or ordinary galvanized profile or even rods are used, the placement step depends on the length of the rule (10-15 cm less) and the experience of the installers.

Instructions for concreting

The most important stage is started after setting the composition under the leveling elements. Taking into account the high expected loads, a strength grade of at least M200 is needed, which does not form cracks after solidification. The recommended ratio of binder and filler is 1:3 (PC M400 or M500 and sand) or 1:2:4 (PC, sand, fine crushed stone, respectively), in case of doubt as components or the possibility of observing exact proportions, it is better to use ready-made dry mixes, in particular - sand concrete.

An important requirement is a monolithic screed, with a large amount of work it is extremely difficult to prepare and level the required amount on your own, the forces of at least two people are involved. In any case, the mixture is stirred mechanically (using a concrete mixer or mixer), and not with your own hands. Filling is carried out from a far corner, with simultaneous alignment and compaction of the resulting area. The process is completed by removing the beacons and carefully filling the gaps, then the surface is covered with a film and gains strength within 28 days with constant wetting in the first week.

Ideally, the thickness of each layer justifies the calculation; when choosing a heater, it is mandatory. The use of expanded clay when laying floors requires caution: at the risk of underflooding or constant dampness, it is prone to moisture accumulation and increases the strength of frost heaving. The only problem-free insulation is polystyrene: taking into account the pouring of concrete from all sides, its poor combustibility does not matter, with a minimum thickness of the layer, it effectively retains heat. In case of doubt in the GWL, a drainage system is placed around a private house.

Possible errors and violations of technology include:

• Lack of compensatory materials around the perimeter of the room. Ignoring the laying of the damper tape leads to cracking of the screed during the thermal expansion of concrete.
• Filling at a groundwater level of less than 2 m on the surface, it will not be possible to provide reliable waterproofing in this case, dampness will penetrate inside a private house. The ideal occurrence is 4.5-5 m and below.
• The laying under the leveling beacons of materials subject to decay, this leads to subsidence of concrete floors during operation.
• The laying of an insulating layer below the zero mark in the absence of a heat-insulated base, such an error is fraught with the formation of a freezing zone.