Table of Contents
Continuous footing — the universal design suitable for construction of buildings of any types on soil with normal bearing capacity. Not always the device of continuous footing is justified economically, but for stone houses it is one of the best options. Let’s consider how to construct continuous footing for owner-occupied dwelling the hands.
Burying of the base
Two schemes of burying of continuous footings are applied: lower than depth of the maximum winter freezing of soil and small burying.
- The base which basis of tape is placed below frost depth accepted for this area is not treated to the pushing-out action of frozen soil and, respectively, is not subject to vertical deformations. Can be assembly (put from concrete blocks), concrete. In most cases does not need reinforcing though superfluous it will not be. The more frost depth, the is the full-buried base more expensive. For the Moscow region, taking into account half-meter socle, height will be two meters.
- Will cost much cheaper shallow-depth continuous footing. Such decision will be suitable for construction of owner-occupied residential building even on heaving soil. In this case it is necessary to dig out trench 20 cm deeper than frost depth and to replace clayey ground with not heaving: coarse sand, sand-gravel mix, crushed stone. Adding needs to be stamped carefully. It is better to do it layer-by-layer, spilling water. The tape of the base is buried at 40-60 cm. Application of packaged units is possible, but it is hardly rational because of small height. Butobeton it is possible to use for easy houses, but from above it is necessary to build the reinforced monolithic belt not less than 20 cm high. For the stone building it is better to build monolithic reinforced concrete continuous footing.
Marking and trench
Special attention should be paid to correctness of marking. All outside and internal corners designate by pegs which from the beginning of works should be removed. At distance 0.5-1.5 meters from peg outside of perimeter of the house take out railing: in opposite corners of each line establish approximately at height of the planned top of the base of board, located parallel to tape. On boards do pro-saws and pull cord so that it accurately was located over marking pegs on upper mark of the base. Thus, we receive outside contour of future concrete structure. It is possible to note cord and internal contour. For the period of earthwork operations the cord should be removed, before installation of timbering to pull again. Will help to make the correct marking two simple methods. Precisely to expose right angle, it is enough to mark triangle with ratio of the parties 3:4:5, the last digit — hypotenuse. To check marking, it is possible, having measured diagonals of rectangular segments: if they are equal, work is performed correctly.
The trench is dug manually or by means of the small-size excavator equipment. In the showered soil it is necessary to increase its width, will strengthen slopes. Dimensions should be chosen taking into account convenience of further works: installations of timbering, waterproofing and warming.
If we build on soil with normal bearing capacity the easy frame or wooden building, it is optional to do pillow. For stone construction it should be built. Surely the basis for concrete blocks will be required. The pillow — concrete or steel concrete tape about 60% high of width of the base and is wider than it twice. Its function — to redistribute load of the big area of soil in order to avoid its sag. Besides, on pillow it is possible to lay horizontal waterproofing course. It is desirable to execute adding from layer of crushed stone ten centimeters thick. Reinforcing will increase pillow durability.
Mounting of combined continuous footing
Instead of monolithic pillow it is possible to use ready basic elements — FL blocks. However, they are expensive and in private construction are applied seldom. Length of concrete blocks of FBS is 240; 120 and 60 cm. Height — 60 cm. Width — 30, 40 and 50 cm. Blok has to be not already ¾ overlying wall. To use big, than it is required, width, it is inexpedient. Construction of combined continuous footing — business difficult and, without having skills of work with the lifting equipment, it is hardly worth undertaking independently it. Rent of the crane costs much and it is necessary to do work quickly. That process was not dragged out, assembly of the base several people have to conduct, at least, three. One has to mix and give solution for mounting of blocks, another to work with slings, the third to govern blocks. Durability of the combined base can be increased, having laid in the course of assembly in horizontal seams two reinforcing rods with a diameter of 8 mm. The blank intervals should not be put brick as quite often do. It will be correct to expose timbering and to fill in emptiness with concrete. After installation of all blocks into place it is necessary to fuller carefully all seams both outside, and from within. The quality and bearing capacity of the combined base will be much higher if be near over upper blocks to arrange the reinforced steel concrete belt 20-25 cm high.
Installation of timbering for monolithic works
For a start we will note that continuous footing cannot be filled in directly in earth trench as quite often practices. The surface of the base has to be whenever possible smooth and it should not extend up that has not squeezed out design by forces of frosty rebound. Therefore it is necessary to establish timbering. It is possible to use any: factory or to bring down boards from boards in the place. The main thing that the timbering has been rigidly fixed and it was not deformed during filling. It is desirable that the surface of boards was equal, especially outside, it will be simpler to do waterproofing, warming and finishing. Boards can be enveloped roofing material or tolyyu. Except stakes, emphasis and wedges, the pieces of plastic pipes on base width placed inside timberings will help to hold form. It is possible to place couplers which will accurately record boards in pipe and will not allow them to part. The timbering for butobeton and mass concrete is arranged according to one scheme.
Apply construction corrugated AIII armature to reinforcing of the bases. It is enough to use diameters of 10 or 12 mm. It is necessary to build metal framework, its segments can be collected above, then to lower in timbering and to connect with each other. Framework section — rectangle, in it has to be not less than four parallel rods going along tape. Step of horizontal elements on height — 40-60 cm therefore the framework for tape 120 cm high will consist of 6-8 rods. Cross communications from short pieces of armature it is enough to arrange through 40 cm. It is better to connect corners not end-to-end, and by means of-shaped elements. It is more convenient not to weld elements of prefabricated reinforcement cage, and to connect by lashing wire. Besides, welding worsens durability of many grades of steel. The size of framework has to consider that from edge of armature to border of concrete (timbering) the distance of 3-5 cm has to be sustained. Let’s pay attention that the bottom flange of armature should not lie on soil. To observe the put distance, under framework it is possible to enclose plastic, steel distantsiator or stones of the corresponding size. In the same way reinforce also steel concrete belts over combined tape.
Fast (and qualitative) way to fill in monolithic construction — to make it by means of autoready-mix truck. Though each cubic meter of ready concrete brought by ready-mix truck is more expensive, than delivery by the dump truck approximately for 600 rubles, the difference in the price pays off due to high quality and high plasticity of mix. The construction site needs to be prepared in advance that the machine could unload concrete closer to places of filling. It is necessary to understand that concrete laying — work physically heavy and to complete the work for change (and differently it is impossible), it is necessary to have crew of strong men.
Other option — long, labor-consuming, but less costly on materials — independent preparation of concrete and filling on site. Separate components: cement, sand, crushed stone or gravel will always cheaper cost factory mix. But for this purpose it is necessary to have, at least, a lot of free time, the concrete mixer, connection of electricity and source of water. And some shed.
To achieve the put quality of laying of mix, concrete in timbering should be rammed carefully. If filling is made in one-two changes, simply and cheap will be to take in rolling the submersible vibrator for concrete mix, the result will be excellent. If there is no such opportunity, it is necessary to do it manually by means of wooden bar.
Waterproofing, warming, finishing
Whether it is necessary to waterproof the base? There is no definite answer to this question. On the one hand, the concrete structure which is not affected by moisture will serve longer. With another, the frost resistance of concrete is much higher, than at any of wall materials. The base made of the condensed quality concrete will serve hundreds of years and, most likely, longer than other parts of the building. Therefore, in terms of durability, need of waterproofing of continuous footing — matter of taste. In terms of the subsequent finishing and warming, it is better to execute isolation.
The first stage of waterproofing — horizontal. It has to be located on basic pillow on all perimeter of the base. Apply coating structure on basic pillow or roll on it rolled material (surely with release on the parties not less than 10 cm). The second — vertical isolation, it is necessary to execute it as outside of the house, and from within. Let’s highlight that the waterproofing needs to be arranged on all surface of the base, both horizontal, and vertical, accurately to carry out joints. If in it there are “tears”, moisture will inevitably find the way and all efforts will be, at least, ineffective.
Isolation from bituminous and polymeric materials is popular: coating or backing rolled. Coating manages cheap, it is simple to do it, but it is easily damaged. Backing it is more reliable, is more long-lasting, demands availability of special blowpipes and certain skill. The lack of bituminous structures is that mineral structures (glues, plasters) have no adhesion to them at all. On bitumen will stick to nothing. For the subsequent finishing on the base covered with bituminous and polymeric materials it is necessary to fix the metal gauze and to plaster quite thick layer of sand-cement mix. Heater it is necessary to fix practically only on dowel. Glue can apply on the surface of the base, but hardly it will provide adhesion at least for 10% of declared the producer.
The polymeric and cement waterproofing allows to avoid many problems with finishing inherent in bituminous structures. It costs not much, it is reliable, very strong, long-lasting, is not afraid of the sun and frost. The technology simple — structure is applied with spatula or brush. It is one of those works which sin not to execute the hands. And, it is possible to apply structure and on wet concrete that considerably expands possibility of its application: it is not necessary to wait until material dries out, it is possible to work in inclement weather. Directly it is possible to apply plasters on polymer cement structures, to carry out facing works. Heater reliably fastens at the same time on dowels with big hat and glue.
Whether it is necessary to warm continuous footing? It is desirable. First, to these we reduce heaving influences of frozen soil. Secondly, we reduce costs on heating of the house. Thirdly, we increase, it is though a little, life cycle of concrete structures. Warming in complex with full waterproofing allows to achieve the best results. It is necessary to warm not only socle over ground level, but also underground part. It is only possible to apply not hydrophobic (not absorbing moisture) heaters: extruded or normal cheap polystyrene foam; strong and durable, but expensive foamglass. Heater needs to be protected: to paste polymer – cement glue inexpensive plastic grid. After that at once to apply decorative plaster. Or to revet heater with thin tile from easy porous ceramics or the facilitated cement and sand mix. Under heavy stone, concrete or keramo granite facing it is necessary to make stronger bearing plaster layer on the metal gauze.