Table of Contents
After the project is approved, the space for construction is chosen and all necessary approvals are carried out, it is possible to start earthwork operations on the site, namely – to arrangement of the base. This stage of construction is, perhaps, the most important. The wellbeing of construction and further operation of ready object depends on correctness of calculations and production of the base. Unfortunately, omissions at construction of the base are fraught with serious effects, and correction of the base attracts with itself considerable rise in price and increase in terms of construction.
Choice of the base
Deciding on the choice of the base, first of all, it is necessary to conduct engineering-geological researches on site of expected construction. For this purpose it is possible to address to the nearest design organization and to study the technical documentation which is available for them on soil in your area. If that documentation does not appear in this organization, will prompt to you where it is possible to find it. The choice of the base is influenced by the following objective factors:
- type of soil and its state;
- soil frost depth;
- availability of ground waters;
- constructive component of constructed facility;
- design load of the building;
- the planned use of the basement.
The base depth, depending on type of soil is accepted following:
- on unleveled soil (rocky and detrital; sandy, except fine-grained and dusty) – not less than 500 mm are not dependent on soil frost depth;
- on conditionally unleveled (dusty and fine-grained sands; all types clay strong consistence; macrofragmental with dusty and clay filling):
1) with frost depth up to 1 meter – not less than 500 mm;
2) with frost depth up to 1.5 meters – not less than 750 mm;
3) with frost depth from 1.5 to 2.5 meters – not less than 1000 mm.
- on heaving soil (clay, loamy, sandy loams) – on soil frost depth.
If the base lies at the level, soil frost depths are higher, it is necessary to make drainage system from it. This action will allow to protect the base from excessive remoistening, so, will prolong long duration of its operation.
What type of the base is suitable for owner-occupied dwelling or bath
In modern construction there are many kinds of the bases, for owner-occupied dwelling or other small construction choose tape or column type of the base.
The column type is chosen with small weight of constructed facility. This method of construction consists in production of brick base columns or stone the sizes of 51 x 51 cm and their installation in the holes which are in advance prepared in soil. Establish columns in all corners of constructed facility, on joints of external and internal walls and in places of the raised loading. Intermediate columns establish with step to 2 meters. Life cycle of such bases can make from 30 to 50 years. And strong are considered as the most long-lasting tape concrete and rubble on cement slurry, the term of their operation is 150 years.
Device of continuous footing
Production of continuous footing demands preliminary production of timbering. Just as correctly made base is the key to long accident-free operation of the house, correctly executed timbering is basis for laying of the strong base.
The timbering is carried out according to requirements Construction Norms and Regulations 3.03.01-87 where all moments of its production are lit. It is possible to make fixed or removable timbering. Most often apply removable since it is the most favorable financially. When performing shuttering works it is necessary to stop on three highlights:
- preparation of the place of assembly;
- material selection;
The place of assembly of timbering is the trench laid on the necessary depth accepted depending on type of soil and depth of their freezing. Prior to works it is necessary to remove trees and bushes from the construction site, to root out roots. Further it is necessary to make trench marking, tags which establish in all corners of future base for this purpose will be necessary. With big length of walls it is necessary to make also intermediate tags. They are made of two pegs and one cross-piece from thin bars about 4 cm wide. The design represents itself letter P fastened from parts about 30 cm long. The tag is forced down 4 nails so that the design was strong, below pegs have to be sharpened.
Before making tags, it is necessary to plan trench. For this purpose define axis of future design, from axis the first corner where the tag is driven in is planned and from it external circuits of trench and the subsequent corners are built. Further between tags it will be necessary to pull twine and, being guided by the flat line, to dig trench. Making marking, it is necessary to carry out strictly right angles, several times to check all distances, including diagonals.
For digging of trench it is possible to employ the excavator, but, most often, trenches under the base dig manually. It is connected with the fact that it is not always possible to adjust the excavator to the place of works, the mechanized digging not seldom leads to the collapse of walls, it is manually easier to achieve smooth and strong edges.
Width of the base has to correspond to thickness of walls of the built building + 10 cm (5 cm outside of walls and 5 cm from within the building for the overlapping device). Proceeding from these reasons, dig trench of the necessary width. Begin to dig from the lowest point of relief. Dredging is followed by big accumulation of the earth near the construction site. This question needs to be thought over in advance, soil can be loaded in carts and at once to take out out of borders of the construction site.
Selection of material for wood form has to be caused by the fact that future design has to be strong since it should sustain the big weight and pressure upon walls. In timbering there should not be slots through which solution can flow. By means of timbering the form of future base therefore it is necessary to build equal rugged construction is put. Wooden boards 25 mm thick can be material for production of timbering, it is not obligatory to use new material, it is possible to take the croaker, it is necessary only that boards were rather equal. It is recommended to fasten boards with bars 40 x 40 mm or 40 x 50 mm. Best of all for fastening to use self-tapping screws, further the design will be easier to be dismantled. Also strong wire, perhaps is required, props will be required if relief not equal, them it is possible to make of the boards cut at an angle to timbering surface also.
Mounting of timbering is made after the preparation of the basis assuming trench bottom charge crushed stone or sand layer in 15 cm and moistening with the subsequent ramming. Also the concrete tie is applied, it reduces losses of solution at its filling.
Bars on all height of timbering with calculation are driven in into corners of future design that they will remain out of her internal cavity. To these bars future design will also fasten. With big length of walls about two parties of timbering are recommended to drive in additional stakes with step about 80 cm, it is possible to apply also pulling together pins, but this method leads to suitability loss further of the used boards. In design struts are established. Not seldom use wooden collars which support design from two outer sides.
For production of boards, it is necessary to lay boards on plain surface and to bring down among themselves, it is desirable not to allow gaps between them. Preliminary alignment of edges of boards by means of plane will be not superfluous. The made boards from boards keep within on two parties of trench, fasten among themselves. Where it is necessary, it is necessary to prop up them additional corner posts. The timbering has to tower over trench on height not less than on 30 cm.
If the reinforced base is planned, then armature has to be mounted also at initial stage. For this purpose, reinforcing rods connect by strong wire, the design with cross cells 30 x 30 as a result has to turn out. Mesh reinforcement should not adjoin to soil and walls of timbering, it should be stacked on bricks or stones 5 – 7 centimeters high. It is also possible to make the supporting extensions of wire which to pass through boards and to strengthen on outer sides of timbering. On top armature fastens (is suspended) to perpendicularly to the laid boards.
Establishing timbering into place, it is necessary to watch the planes and corners, the planes have to be strictly vertical, corners 900. On inside face of shuttering design it is recommended to fix construction oilcloth or polyethylene film. It is possible to make it by means of the construction stapler, this action to provide plain smooth surface of the base.
Filling of concrete mix is made layer-by-layer, at the same time each layer 20 cm thick is recommended to be carried out at the same time on all design. Along with filling it is necessary to make mix ramming by special adaptation, distilling excess air which lays down on the surface of liquid mix light foam from cavity. It is also possible to tap timbering walls that solution kept within it more densely. The quantity of the filled-in layers depends on base height. Having executed the last layer and having stamped it, the surface is leveled trowel or other tool, it is necessary to pierce the last layer that there was excess air in several places. It is desirable to execute filling in one day, in 3 hours the surface of the grabbing base needs to be strewed well with sawdust, to cover with burlap or tarpaulin, it will prevent influence of external factors and will provide uniform drying. The base in 3 – 3.5 weeks will ripen, upon termination of this term timbering it will be possible to sort and start wall construction.
Calculation of quantity of concrete mix for filling of the base is made taking into account that the trench in 1 m of depth and 0.5 width demands 0.5 cubic meters of mix on 1 running meter. For production of the strong base use M400 brand cement; sand with fraction 1.2 – 3.5 mm; crushed stone, gravel, haydite, elimination or brick scrap; water. The recommended ratio of ingredients: 10 kg of cement + 30 kg of sand + 50 kg of crushed stone (gravel, haydite or brick scrap) + 5 liters of water. Solution needs to be filled in at once after its preparation.
The mixer since manually it is inexpedient to make mixing is necessary for mixing of solution. Not to pay idle time of the rented mechanism, it is necessary to prepare the place of its installation in advance, to clear access road and to organize continuous water inflow and dry mix.
It is the most reasonable to fill in the base in the fall, but at temperature not less than + 50. It is desirable that and for the next 3 weeks air temperature was plus. In general it can be filled in at all seasons of the year, but it will be necessary to provide additional heating in the winter, and there is risk of too fast drying in the summer. Filling at winter will allow the base to be stood, and it will be possible to continue construction of the facility in the spring.