Table of Contents
The plate base, perhaps, is least widespread in domestic private construction. The reason in high materials consumption: the consumption of concrete and reinforcement steel many times is more, than at construction of tape or column designs. Respectively, construction of the plate basis runs very into money.
However, such type of the base has obvious advantages over other designs. It allows to build buildings of any type, including heavy, multi-storey, on the most problem soil. If thickness of weakly bearing soil (peaty, oozy, fine sands, etc.) is so big that there is no opportunity “to punch” their piles to the basis with sufficient bearing capacity, plate design in general the only opportunity to build the house.
The plate base called still by floating represents the reinforced reinforced concrete slab serving as support for all parts of the building. Depth of underlay of plate does not play any role: for the building with basement storey it can be located lower than the level of freezing, for the house without cellar — to be located on earth surface. The plate represents integral, very rigid and rugged construction, in the minimum degree subject to external influences. Sags (including uneven) soil, force of frosty rebound to plate are not terrible. It can sink or move a little, but the design of plate allows to redistribute influences of third-party forces. Load-carrying structures of the building will not experience excessively high strain, deformations are excluded.
The plate minimum depends on condition of soil upon which is based. It moves independently, “floats” on earth surface. This property allows the base to transfer without effects even quite strong earthquakes. For this reason the floating base is applied everywhere in Japan. Unlike Russia, on the plate bases build considerable part of owner-occupied dwellings and in Western Europe. At least, in the countries with rather cold winters and not always strong soil. These are the British Isles, Scandinavia, Germany, Holland and Belgium, the Northern regions of France. And, it is difficult to suspect supereconomical Germans and their neighbors of wastefulness. And not always weakly bearing soil is the reason for the choice of plate design. For example, the Swedes and Norwegians living on the strongest rocky soil prefer to be under construction on plates. Basic reasons to that two. The first — reliability and durability of such base. The stone house in invariable look will stay centuries, he can be transferred to great-great-grandsons. The frame house when decays or will bother, it will be possible to sort and bring together another on the plate base, is more modern. Besides, the house on the floating base in the civilized real estate market will be more expensive and will buy it more willingly. The second reason — the high speed of construction of the plate base. The European construction companies build plate from the first peg before the full end of monolithic works of day for three.
Monolithic or assembly?
In domestic textbooks for builders, except monolithic, it is possible to meet the recommendations about design and construction of the national teams and assembly monolithic constructions of the plate bases. In the aspiration ordered by party and the government to industrialize and typify everything that is only possible, our engineers created also such, strange from the point of view of the western developers, design. Strangely enough, similar decisions can be met and today, though infrequently. We recommend not to consider even similar option whatever adherents of the Soviet study of the strength of materials spoke. Without going into details, say, that use of prefabricated elements considerably worsens strength characteristics of plate, and the promised economy is insignificant or in general is absent.
Continuous or lattice?
Real way it is considerable to cut consumption of concrete and steel — to build plate not continuous, but lattice. If simply to make in plate of “hole”. It is undesirable that their area exceeded 50% of the general. If more — it is necessary to strengthen reinforcing, economy on materials is small. But trellised plates put not so often into practice as it would be possible to expect. Rational Europeans do not use such decision in private construction at all. Three Basic reasons. The first: considerably the timbering becomes complicated, labor costs grow, construction terms increase. The second: it is more difficult to warm and waterproof framed structure, in it it is worse to carry out communications. The third: emptiness of grid all the same should be filled up with sand and crushed stone, to stamp, build concrete tie. If to weigh all these factors, economy on grid in comparison with continuous plate is not so obvious.
Independent construction of the plate base
Let’s note that it is real to build the plate base independently, “the hands”. The technology is quite simple. However, it is “simple” — does not mean that it is possible to neglect something. It is impossible “to bungle” at the plate device. As, however, and on other construction finishing work.
The first stage make marking and if necessary alignment of site. In the presence of fertile layer it is better to remove and store it in shoulder: vegetable soil is expensive now, and it is better to level it after the end of construction. If the building does not have the cellar, the plate can be built directly on soil of any type, having filled on it not less than 15 cm of sand-gravel mix. Under the heavy stone house it is necessary to pour at least 10 cm of large (size of 4-6 cm) crushed stone. If it is necessary to raise floor height of the first floor, thickness of adding is increased, and on base layers it is possible to use loams, construction waste. The made ground should be leveled and to stamp carefully. Rent of tamper with the gasoline engine for one-two days will manage cheap.
What the plate design depends on
Depending on relative positioning of different layers: the bearing plate, preparation, warmings and waterproofings, structure of the floating base can differ. Thickness and type of reinforcing of plate are determined by the nature of soil and mass of the built building.
Considering base heat insulation question, we have to consider the subsequent warming of floors. The bearing plate + floor design can be heat-insulated. Or only floor, base slab is not warmed. In the first case heater is located below, under plate. Over the bearing plate that floor was not cold (it especially relevant for more and more popular heat-insulated floors) the heater layer also keeps within. Thus, in design of plate and floor we receive two layers of warming. Other option is simpler: the plate is cast without warming, and the heat insulation is carried out in the course of construction of the house only under floor design. The first option is more effective (but also it is expensive) in terms of durability of design and heatsaving.
Apply to warming of plate and floor rigid hydrophobic (not absorbing moisture) thermal insulation materials. Foamglass has the best characteristics. It costs much and it is applied seldom. Polyfoams (polystyrene foam) are more often used. Extruded is stronger, but is time in two and a half more expensive than normal. In most cases it is enough to use normal polyfoam of the maximum density (the brand of PSB 50).
You should not save on thickness of heater. What has better warmed plate or floor, that less they will be exposed to the destroying influences of negative temperatures and subjects costs of heating will be lower. In northern Germany, with its quite temperate Baltic climate, today plate of the base warm expanded polystyrene 40 cm thick + additional warming of floor of 10 cm. Under our conditions it is simple to apply heater less than 10 cm thick there is no sense. Better — it is more.
The base also should be heat-insulated in addition sideways, down. It is better to apply extruded polystyrene foam, it is more resistant to frosts and mechanical influences. It is desirable to warm also soil around plate. For this purpose isolate horizontally from below blind area on meter – one and a half from the building, getting vertical plate is a little lower. Thus, under the heated building positive temperature all the year round remains.
As a rule, warming under plate is carried out not by continuous. The thermal insulation material is not brought to outside edge of plate on 25-40 cm. Similar gaps do also under internal load bearing walls of the house. After filling concrete part of plate has the form of the inverted trough.
As well as it is possible to warm, waterproof plate (from below) and floor, or only floor. In the first case we receive two layers, from below and from above structures of the base, in the second one — from above. Two-layer isolation is more preferable. It is necessary to isolate from moisture also vertical, side face of plate.
Material for isolation can be chosen any: bituminous mastic, rolled materials or cement mixes. The best result will be yielded by use of the built-up bituminous and polymeric rolled materials.
To plate construction it is necessary to carry out the main communications to its designs. In the presence of the project it is possible to mount the sewer and bringing water pipes. It is necessary to lay electric cable in protective cover or if there is no such opportunity, to lay hollow pipe with the minimum radiuses of turns. Useful will be to bring through plate out of the house (better from the place where electropanel board is planned) on the street several pipes. You never know what can be necessary: phone, on-door speakerphone, lighting of the site, automatic equipment of gate and so on.
Preparation and timbering
In many textbooks and grants it is recommended: before starting plate construction, on soil to execute the leveling concrete tie about 4-5 cm thick. Of course, superfluous it will not be. The tie will facilitate the subsequent works, on it it is convenient to go, spread heater and to build up waterproofing. However for normal low owner-occupied dwelling of special need for tie is not present. The European construction companies always do adding by crushed stone, pay much attention to soil consolidation, but very seldom do additional tie for construction of low-rise buildings.
Timbering for the plate base if it is not lattice, it is simple to make: total length are small. Many foreign companies in general do without timbering. On perimeter of plate install the L-shaped reinforced blocks limiting monolithic construction in the plan and for height. Under our conditions it is possible to replace partly them with road borders, having mounted on solution or in concrete layer bevel inside. It is better not to use prefabricated elements to the stone house, and to fill in completely monolithic plate.
If the lower preparation is carried out, apply waterproofing course on it. Isolation is done and directly on crushed stone, the passage by its melted bitumen, having rolled and having stuck together among themselves roofing material rolls. However, probability is high that during further works rolled material will tear.
In case the plate is filled in directly on the condensed soil, on crushed stone or sand display normal dense polyethylene film. It will inevitably tear in many places and cannot serve as waterproofing. Its only function — when filling plate to minimize “suction” in soil of water and cement milk from concrete.
On rather dry soil foreign builders often do not do the base waterproofing course at all. Directly stack heater on carefully condensed crushed stone, as a rule, expanded polystyrene. It does not pass moisture and substantially performs waterproofing functions. The rolled waterproofing is stacked only on sites where heater is absent (on perimeter and under load bearing walls).
Height of plate depends on specific sizes of loadings, but for houses height to two floors averages 25 cm. Thus, the total height of timbering is equal to height of the main part of plate + edge height if it is (as a rule, it is height of base layer of heater).
Assembly of framework
The framework for the plate base shall be two-level. Armature of both levels has to be located in 3-5 cm from the edge of concrete. To provide distance low, it is more convenient to use plastic or metal distantsiator. Grid cell — square with the parties from 20 to 40 cm. Construction armature of AIII of variable section is used (with notch). Metal rods connect among themselves by lashing wire, welding weakens the majority of steel grades. As the main elements bearing loading use armature with a diameter of 12-18 mm, for the responsible heavy building it is worth ordering calculation or to pick up the standard project with similar characteristics of the house and soil. Vertical armature is established in each cross line of grids. Load of it is small, it is enough to use 8 mm.
Concrete work needs to be performed at one time. Mix it is necessary to deliver continuous automixers, only in this case it is possible to be sure of quality. Concrete by class not below B12.5 is used (there corresponds M150). Useful will be to add the plasticizer to mix. It is possible to make it at the concrete plant at mix preparation, or on site, having poured in solution in ready-mix truck capacity. For the machine it is necessary to prepare possibility of entrance and unloading of concrete directly in timbering in advance. The quality of consolidation of mix and observance of horizontal level when leveling is of great importance. It is necessary to stock up with tools in advance: to take for day in rolling vibrorail, to have with itself enough long rules, levels, shovels and buckets. Unlike the previous types of works, concreting needs to be done quickly, to put off part of job it will not be got. Depending on amounts of works it is necessary to bring together crew. At least, one experienced specialist capable to handle vibrorail and having skills of similar works has to be its part. To help it, the sufficient number of helpers – “teapots” has to bring mix.
It is possible to fill in the small plate base under the shed at the dacha also most, preparing mix in the small country concrete mixer. But, we will repeat, step-by-step performance of monolithic works cannot provide due quality and the bases of responsible buildings need to be concreted at one time, with respect for all features of technology.
When to put walls?
On the ready base it will be possible to put walls not at once. After the end of monolithic works concrete has to gain 70% of durability. At appropriate leaving it will occur in three weeks. Concrete has to be constantly wet. But not to be exposed to direct impact of rain the first ten days. Right after concrete laying the plate should be covered with polyethylene film. And to water surface from watering can at the first signs of drying. Non-compliance with this condition leads not only to slow “maturing” of concrete, but also to decrease in its quality. Three weeks before achievement of necessary durability — term for temperature in 20ºС. The weather, the longer this time is colder or is hotter. At 5ºС it will almost double. At negative temperatures concrete can not grab at all. Therefore you should not postpone construction of the base for late fall, it is better to wait for spring.