Table of Contents
In construction it is important to consider others experience of achievements and mistakes. To study on the mistakes happens expensively and offensively: the witness to that the cracks in houses warped porch and gate, the inclined fences. And it only at best. Happens, huge malls “develop” as houses of cards. The lion share of all construction accidents happens because of incorrectly calculated or poor built bases. Of course, we are not going to tell how to build the airport. However, the principles of construction of the bases for lonely column of fence, rural toilet, wooden log hut and aquapark are uniform. Only scales and constructive decisions differ. And estimate, of course.
Let’s try to understand how to build for giving or country house the reliable base, having efficiently and thriftily invested the honestly earned kopek. To make it, we have to understand what happens to our house underground. Let’s begin from scratch theories, from soil:
What it is necessary to know about soil and climate?
Southern Europe, North Africa, the Middle East strike us with abundance of stone monuments of ancient architecture. Ancestors of the northern people of Europe, including ours, did not leave in inheritance to us, the descendants, similar constructions. However, druids of Britain have constructed quite big cromlech — Stonehenge. However and for many centuries rather has warped it, unlike temples of Ancient Egypt.
The architecture of ancient Slavs, Celts and Germans was wooden not only because of lack of stone, abundance of wood and technology backwardness. Matter still in climate and structure of soils of those places where our ancestors lived.
Builders of the Jerusalem temple not especially bothered with the base. In the hot stony area it is possible to begin laying directly from the earth. It is very convenient to be under construction was to Entre Rios, Ancient Greece, Rome and Egypt. Under legs, generally stone or good sand, +20 ºC — cold weather.
The moisture which is in the soil freezes in the winter, ice crystals extend. Soil increases in volume, begins “to swell out” it. On the building constructions which are in frost depth zone, heaving soil makes extremely strong impacts. The strong base will resist, and weak will squeeze out up, will warp, there will be cracks. High heaving clays, smaller have loams, low sands.
One more trouble — quite often found high level of underground water (LUW). It is difficult to build, lay communications. If UGV is higher than frost depth, winter water saturation and soil pressure also increases. And to build the cellar and underground constructions (for example, septic tank), irrationally and very expensively.
Before beginning construction, it is necessary to learn what composition of the ground on the site. If there is no opportunity to use the drilling rig, it is possible to make holes in corners of future house by means of normal garden drill. Sand — was lucky, loam — so-so, clay — it is necessary to pay special attention to base durability. Peat, quicksand, high water — prepare for additional expenses.
The tower well-known for the inclination in Pisa costs crookedly just because medieval builders have neglected pilot survey of soil, have not considered their different bearing capacity and level of underground water. The tower tends on the South where the rigid sand base is replaced by less dense and saturated moisture clay with layers of marsh silt.
Structures of the bases
The choice of design depends on type of soil and foundation load. That is from building weight: stone houses — heavy; wooden, frame, the VULTURE panel and similar it — lungs.
The continuous buried footing
Continuous concrete or reinforced concrete foundation. Is suitable for sands and clays, it is not suitable for peat bogs and quicksands. Has high bearing capacity, maintains heavy houses. Ideally continuous footing has to be buried lower than frost depth of soil. In this case forces of frosty rebound will not be able to push out it upward. Width of tape depends on loading, but there have to be not less than 2/3 width of wall of the house and not already 20 cm. It is irrational to build too wide base for the one-two-storeyed house. Under walls from foam mortar or ceramsite blocks 40 cm thick there will quite be enough film of 30 cm support for soil is carried out through concrete pad. It has to be wider than tape on 15-20 cm from each party and have height about 20 cm.
At big burying and high socle it is logical to arrange the cellar under the house, the base will serve as walls. In this case it is necessary to consider soil pressure outside in the cellar, the base needs to be proarmirovat. You should not construct sites of walls between load bearing walls more than 4.5 meters long. If more — it is necessary to strengthen reinforcing.
Continuous footing can be built assembly or monolithic. To the national teams — from FBS blocks. Block to build quickly and conveniently. But it is expensive: finished products are more expensive than concrete mix, there is crane much, mounting is rather difficult. The monolith on costs of materials will cost cheaper, however to expose timbering is rather labor-consuming, besides it is necessary to make independently or to take boards in rolling. Under identical conditions it is more correct to prefer monolith nevertheless: at appropriate execution it stronger and more exactly. Besides, at construction of the cellar seams between blocks — the potential place of leakage, and well condensed mass concrete is deprived of this shortcoming. One more option — butobetonny tape. It needs to be done wider, not less than 40 cm and the full thickness of the house wall leaning on it from above.
Whether to reinforce the buried continuous footing? Not necessarily. And here walls of the cellar it is necessary. FBS can be reinforce, having laid construction armature with a diameter of 10-12 mm in seams of each number of blocks.
Continuous shallow-depth footing
It is possible to save, having built shallow-depth continuous footing. Height in the earth is accepted approximately in 0.4-0.5 from the normalized freezing, also do basic pillow. If soil strong and unleveled (coarse sand), trench is dug out on the planned tape depth. At heaving soil trench tear off a little lower than frost depth, and fill up its lower part with unleveled sand-gravel mix and layer of crushed stone. The charge is well spilled water and carefully rammed. The shallow-depth tape is reinforced surely regardless of type and the weight of the building.
Pile and column bases
These two types of the bases are very similar: both there and here the support is the share of separate points, but not of continuous tape. Rather easy wooden and frame houses can be put directly on columns and piles, the design of walls does not demand the device of solid base. The step of support can be big — 1.5-3 meters, and even it is more. Intervals between columns can be sewn up with flat asbestos cement sheets and to warm. For the heavy house with stone walls it is necessary to build grillage — the continuous steel concrete tape leaning on columns and located above ground level.
Piles and columns can bear loading not only from the house. They are used at construction of support of porches, terraces, fences.
In what differences between piles and columns.
The pile base is applied at weak soil. The pile “punctures” top weakly bearing layer and rests against strong underlying. If thickness of weak soil is too big, it is irrational to arrange piles or in general it is impossible. Three technologies of the device of piles are most widespread. Drive steel concrete and drilling demand use of special equipment (boring machines), will run into money and to perform these works independently it will not turn out. If stones do not get, two persons with the feasible help of the third can twist metal screw pile in soil as screw, manually. On pipe end there is nozzle drill, and on height openings for the fact that to insert short scrow-bars levers for twisting are drilled. The grillage on metal piles can be built from channel steel.
The pile bases are very reliable and allow to build not only on problem soil, but also on very steep slopes: piles will not allow construction “to move down” from the hill down.
In a similar way Venice is constructed. At first hammered piles from the mountain larch brought from the Alps into soil. Then constructed oak flooring. And already on it constructed the top, stone level of the base and filled the basis of floors.
The column base is constructed on soil with normal bearing capacity. The most rational and economical option for easy frame, panel and wooden houses. Columns concrete (it is obligatory to reinforce), depth of underlay can be lower than height of freezing or above, as in shallow-depth tape. Heaving soil is replaced with carefully stamped sand and binding gravel all the way down by freezings. The form of columns does not matter. If to dig out wide hole manually, it is more convenient to concrete in rectangular timbering. The good result is yielded by hand drill TISE. As well as for continuous footing, the column has to lean on pillow which area bearing is one soil more, than column section.
The pile and column bases are very economic on material consumption.
Extremely reliable design. Is suitable for any types of soil, but it is especially effective for weak soil and seismodangerous areas. Under all area of the building continuous is carried out, the trellised monolithic reinforced concrete slab about 25-30 cm high with double frequent reinforcement is more rare. The plate distributes load from the building of all area of the basis, compensates movements of soil, including seasonal. If there are any shifts and sags, the plate is displaced entirely, deformation in the building does not arise. The plate base gives the chance to build heavy buildings even on problem collapsible soil on which application of pile design is inapplicable because of impossibility to reach more rigid base. All the plate is good, however the consumption of metal and concrete is big that does it very expensive.
Pile and plate designs can be applied also in the presence of the cellar. In this case over piles not the grillage is carried out, and the wall is put up.
Let’s generalize told above. For descriptive reasons we will present recommendations about the choice of the base in tabular style. Designations, as in the traffic light: green — the rational choice, yellow — admissible, red — unacceptable.
Let’s try to define approximately price ratios between different structures of the bases. Let’s consider only the cost of materials (concrete, metal, sand, gravel) and special equipment (the crane 2 changes, transport). We do not consider excavation equipment. We are under construction not in solitude, concrete we carry the mixer ready-mix truck on distance of 40 km, the prices of materials averages, the central region. Concrete mix of class B15 (brand 200), filler gravel. Armature with a diameter of 12 mm is applicable. We do not consider the timbering price too, it is possible to take it in rolling or to make most if it is possible for reasonable money to buy tree. Works can be performed the hands, to employ assistants or crew, here as you will agree. Let’s assume that we build the house of cellular blocks, walls 40 cm thick, without cellar. Respectively, base width — 30 cm. We will raise socle by 40 cm above ground level, the site equal. For the column base step of columns — 1.25 meters. Grillage — 30х30 cm. We do not consider pile design because of need to use special equipment or impossibility to provide support of the necessary area. The house size in the plan — 9х12 meters, length of the bases is 50 running meters, the area is 108 sq.m. There is one central load bearing wall. We will carry out calculations for frost depth of 1.3 meters. The buried base or columns we lower by 10 cm below, their height with socle — 1.9 m shallow-depth — 50% of freezing, total 115 cm. Under all designs we will make concrete pad of 15 cm and adding of layer of crushed stone of 20 cm, under shallow-depth additional sandy adding on frost depth. We enter data in the table.
Now easy house: felling, frame or panel. The same dimensions, width of the base are 25 cm. We do not consider the buried design, its application is irrational. The pile option — metal piles with a diameter of 13.3 cm, depth is 2.5 meters. Step of piles or columns — 2 meters. We do not consider grillage, structurally it is not necessary. Columns of small burying. Plate 20 cm high.
As we see, for stone houses the shallow-depth bases, for lungs — column are most economic. If to get not ready concrete mix, and to buy the concrete mixer and to prepare solution on building site, it is possible to reduce still expenses on materials on third or even more. Let’s repeat that we only considered costs of materials.
Of course, final digits depend on set of factors: nature of soil, relief of the site, availability of materials and equipment, haul distances, regional prices.