Concrete preparation for the foundation

A high-quality foundation guarantees the durability and strength of a residential building. Proper preparation of the foundation will ensure a long service life of the structure, eliminate the flow of cement during pouring. Works are carried out in accordance with regulatory documents, in strict sequence.

The need for underlayment

The area prepared for pouring cement mortar provides for a hardened and leveled base. The concrete layer is assigned the role of a barrier that can protect the underground monolith from shrinkage, seepage of materials into the ground. Footing, laid under any foundation, will contribute to:

• elimination of cement mixture leaks;
• rapid set of volume by the fundamental design, improvement of its operational performance;
• leveling the impact of moving soils by uniform dispersal of the mass over the area of ​​the product;
• weakening the influence of intumescent soils;
• creating conditions for the installation of a reinforcing frame.

Thanks to concrete preparation, evenness of the soil surface is achieved, conditions are created for comfortable and fast work.

Standards for organizing footing

The device for concrete preparation for the foundation is regulated by regulatory documents. Builders are guided by SNiP 52-01-2003, which indicates the type of base material - crushed stone, profiled membrane or lean concrete. The document also contains instructions for the calculation, manufacture and operation of cement paste bases. The content of the regulatory rules is reduced to several key provisions:

• the use of the composition of the M50 brand for the manufacture of lean concrete;
• construction of a sand and gravel cushion before pouring the mixture;
• arrangement of footing with a layer of 10 cm;
• exposure of the filled mass for 28 days;
• design and arrangement of the base, taking into account the type of soil, the nearest architectural objects, load, seismicity and environmental friendliness of materials;
• the use of reinforcement for the frame (hot-rolled with a diameter of 3-80 mm, hardened with a diameter of 6-40 mm, cold-formed with a diameter of 3-12 mm).

It is necessary to calculate the load of the structure if the soil gives compression in the cold season, the building will be placed on a slope or in a hilly area, and the base of the foundation is located on a surface with an unstable composition. In addition to the main collection of standards, SP 50-101-2004 and SP 52-101-2003 are used.

Digging a pit - preparatory activities

The main purpose of the work is to prepare the construction site for the future foundation. At this stage, the soil is processed so that it can withstand the construction and fit snugly against the sole of the structure. Tasks are carried out sequentially:

1. A pit is dug across the width of the building.
2. The bottom is cleared of debris, stones and the root system of plants.
3. The bottom surface is compacted by tamping.
4. Moisturizing or draining of soils is carried out according to the type of follow-up activities.

The pit must be equipped before the construction of the footing. In private housing construction, it is advisable to dig manually.
Depending on the load of the building, the mobility of the soil, there are two traditional methods - laying crushed stone and pouring concrete mixture. Modern manufacturers offer special membranes that are convenient for concrete preparation.

The use of crushed stone

Crushed stone preparation for the foundation will reduce the cost of construction activities and reduce cement consumption. Gravel and crushed stone are laid when it is planned to build a base from a monolithic slab or on pile grillages. When organizing a pillow, it is worth considering some nuances:

• The crushed stone layer is laid to a thickness of 10-20 cm.
• Loose medium fraction material is compacted and then filled with bitumen.
• The crushed stone type of structures is relevant in order to maximize the saturation and compaction of the earth.

Laying rubble will not provide the required rigidity for the substrate of a private house. In a similar way, a footing is prepared, intended for the foundation of utility buildings, technical structures.

Making a pillow out of lean concrete

Concrete preparation for the foundation is a reference type of work that creates the most durable product. In this case, the earth will not sag, and the building will be securely fixed. Before the start of events, cement dough is made.

What is lean concrete?

A mortar containing 6% B15 strength cement, gravel or crushed stone fillers is called lean concrete. The composition is kneaded from cement brand M100. Due to the minimum number of components, the mixture is quickly hydrated, produced and solidified. The recipe for lean concrete includes:

• use of 275 kg of cement, 590 kg of sand, 1377 kg of gravel and 165 liters of water per 1 m2 of mixture;
• backfilling in a concrete mixer with a volume of 200 l 44 kg of cement, 94 kg of sand, 220 kg of gravel and 26 l of water;
• consumption per bag of cement weighing 25 kg 54 kg of sand, 125 kg of gravel and 15 liters of water.

All components are carefully measured. If the developer has a concrete mixer, water is poured into it and cement is poured. Sand and gravel are introduced gradually, water is added to them in a small amount. Liquid plasticizers are also mixed with water and added at the end of kneading. The mixing time of the composition should not exceed 5 minutes.

Building a footing from lean concrete dough

Preparation for the base using lean concrete is performed according to the following algorithm:

1. Calculations of the bearing capacity of the building are carried out, taking into account the type of soil, GWL.
2. The marking of the territory is done and the formwork is mounted by 30 cm.
3. A solution is being prepared. The ingredients are selected based on the height of the pillow - 4-10 cm.
4. A pit is dug out and 10 cm is covered with rubble. The material must be compacted.
5. Under the upper edge of the formwork, concrete dough is poured from lean material.
6. The footing is reinforced with reinforcement with a cross section of at least 8 mm, compacted with a vibrating plate. The rods should protrude 20-30 cm.

When carrying out construction, keep in mind that you need to protrude 10-15 cm beyond the base - this increases the size of the preparation and strengthens the structure. The thickness of the concrete preparation will be determined by the characteristics of the soil, the load on the base and the area of ​​\u200b\u200bthe house. The parameter specified in SNiP is 4-10 cm.

Construction of profiled membranes

Profile membranes are polyethylene plates reinforced with stiffeners. In addition to preparing the foundation, the products are able to waterproof basements by holding the pressure of soil water on the walls. The footing device is carried out sequentially:

1. The surface of the pit is cleaned of debris.
2. Equip a pillow of crushed stone up to 13 mm in size, raising it by 10 cm. This neutralizes the capillary action of water.
3. The substrate is poured with concrete dough, which, after drying, is treated with a primer or primer.
4. Bituminous mastic is applied to the surface of the plate.
5. The profile membrane is rolled out, placing it down with protrusions. When laying the geotextile, the protrusions are brought out.
6. The membrane tapes are overlapped, and then each seam is glued with butyl rubber tape, which eliminates the overspending of the cement mixture.

At the last stage of laying the material, the joints are sealed with self-adhesive tape or liquid sealant.

Footing for various types of foundation

In private housing construction, monolithic and prefabricated strip bases are popular. Concrete preparation is a necessary condition for the construction of each of the foundations.

Footing for the base-tape

The work is carried out sequentially, adhering to the requirements of building codes:

1. They make markings for the tape monolith, level the soil.
2. Backfilling with crushed stone is carried out to a height of 10 cm, rammed. The laid material is poured with liquid bitumen.
3. Formwork is installed and reinforcement is carried out. A grid of rods with a diameter of 8 mm is placed according to the project.
4. The concrete mixture is poured along the height of the formwork and compacted with a vibrating plate.

After the composition has hardened, the formwork frame is dismantled and the side surfaces are waterproofed with mastic.

Preparation for prefabricated strip base

The pouring of the footing occurs intermittently, and special blocks are purchased for the manufacture of the foundation. The workflow can be done step by step:

1. Arrange a base of sand, spilling and ramming each layer. The layer of material is made no more than 10 cm.
2. Formwork is mounted on top of the sand embankment.
3. Concrete dough is poured according to the level of the sections.

The sand cushion is relevant only for outbuildings.
Concrete preparation of the construction site for the necessary foundation, carried out in accordance with regulatory documents, saves materials. At the same time, the quality of roughing and marking measures is preserved. Footing is not done when forming a self-leveling floor screed on a flat slab. In other cases, preparation is needed to increase the operational life of the building.