There are different types of foundations on which houses and other buildings are built, all of them are the basis of strength and reliability; it depends on them how warm the room will be and how long the structure will last. The most popular and requiring minimal costs is a strip foundation. But it can sag. In order to avoid this and prolong durability, it is necessary to properly perform reinforcement, for which you need to correctly tie the reinforcement. For each type of foundation there is its own type of knitting. Let's consider how to make reinforcement and how to do it correctly for a strip foundation, as the most popular and frequently used.
To knit reinforcement cages for strip foundations, you will need wire 0.8-1 mm in diameter.
The beginning of the correct reinforcement of the strip foundation
In a strip foundation, the main tensile load falls on the reinforcement, and the concrete itself bears the compressive load. Therefore, it needs to be reinforced correctly, namely, to reinforce the upper and lower parts, but the middle part does not bear any load, so there is no point in reinforcing it. For the durability of the foundation, you need high-quality reinforcement, and for this you need to choose the right reinforcement.
When purchasing fittings, you need to pay attention to the markings on them.
Thus, indicator C indicates that this reinforcement is suitable for welding and it would be correct to use it for these purposes, and indicator K indicates that it is resistant to corrosion cracking. Tip: Please note that if the rebar is not marked, it is not suitable for use in foundations. It is wrong to save when purchasing, since a low-quality product will lead to cracks in the foundation of the building, which will subsequently spread to the walls.
In order to knit reinforcement, you will need:
- fittings;
- annealed knitting wire 0.8 - 1 mm in diameter;
- special hook for knitting (you can use pliers).
It will be very difficult for one person who has no experience in tying to do the reinforcement on their own. It is better to find an assistant in advance, or better yet two, who can help you knit correctly, since installing the reinforcement in the designed position will require three people.
In order to reinforce a monolithic strip foundation, you need to prepare boxes from reinforcement that will have a square cross-section with a side length of 350-400 mm. But their length, if, of course, dimensions allow, should be 3 meters. It is better to knit them in advance, and for this you need to calculate how many boxes will be needed.
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Step-by-step instructions for wire reinforcement
When reinforcement is being made, instead of wire, you can use special plastic clamps, but you should pay attention to the fact that their use is only advisable if, while pouring concrete, no one will walk or stand on the reinforcing frame. In all other respects, no one was dissatisfied with their astringent properties.
Sequencing:
- Cut a piece of wire whose length will be 30 cm.
- Fold the cut wire in half (in half).
- The wire should be in your left hand, and your right hand should have a crochet hook.
- We bring the wire under the reinforcement, under the joints of the rods.
- The crochet hook must be inserted into the wire loop.
- We completely bend the wire around the reinforcement and place its free end on the hook.
- Turn the hook clockwise to wrap the ends of the wire together. Tip: do not overdo it with twisting, as there is a risk of breaking the wire. Practice has proven that three turns of the hook are sufficient to securely fasten the reinforcement.
- Remove the hook from the loop. The connection is completed.
This process describes only one connection, and since for
Sooner or later, many country property owners decide to increase their living space by adding an extension to their house. In order for the connection of the main house with the extension to occur without problems, it is important to achieve a reliable and durable connection of the foundations. As practice shows, there are two main ways to attach the foundation of an extension to the existing foundation of a house:
- rigid connection using reinforcement;
- expansion joint.
Each of the options for connecting the main foundation to the base of the extension has its own characteristics and nuances that should be considered more thoroughly.
Most often, a rigid connection between the foundation of the main building and the extension is used on soils that are not subject to heaving. Most often, this method is used in the process of low-rise construction in situations where the extension is functionally connected to an existing building and is located with it under a single roof.
To make a base for an extension, a special hole is drilled in it to a depth of about 35 cm. Its diameter should be equal to the diameter of the reinforcement that will be used for driving. If the construction of an extension is carried out according to a scheme that assumes the estimated length of the reinforcement is greater than the width of the foundation, holes in the base of an existing house are drilled only part of the width. The reinforcement is installed using the anchor principle.
If the contour is planned to be closed, the holes should be made at two levels and in a checkerboard pattern. As for the reinforcement, it must have an anchor wedge at one end and a welded washer at the other.
A rigid connection is also used in situations where the house has a recessed strip base, and the construction of the extension is planned from monolithic reinforced concrete.
A foundation with a rigid base can be available in two versions:
- tape-tape;
- slab-slab.
When installing such a foundation, the following list of works is expected to be performed:
- dig a trench, the depth of which corresponds to the existing foundation of the main building;
- fill the bottom of the trench with sand (create a sand cushion) and compact it;
- drill holes in the base;
- drive reinforcing bars with a longitudinal slot into pre-prepared holes;
- insert a wedging liner (for example, made of wood) into the reinforcement slot;
- drive the reinforcement into the holes in the corners of the base;
- form the frame using the remaining extract from the reinforcement that has already been driven in (for this purpose, parts with a length of 300 to 400 mm are specially left;
- after making the frame, fill the base tape with concrete;
- wait for the concrete to dry completely.
In order to attach a foundation to a house, you will need a whole list of equipment. First of all, we are talking about the following tools: a shovel, a building level, reinforcing bars, sand, wood inserts, a mixture of concrete and boards for making formwork.
Foundation with expansion joint
An extension to a house with a foundation with an expansion joint is most often used in industrial and multi-story construction. That is, where the soils under the structure can differ significantly in their deformation properties. For example, quite often an extension of another number of storeys is connected to an existing house of one storey by laying a foundation with an expansion joint.
In any case, an expansion joint must be provided at the construction design stage.
At its core, any expansion joint, through which a foundation for another building is connected to a house, is insulation in the gap between the basement floors and the walls. Often, ordinary tow is used as this insulation. The place where the connection to the house is made is fenced off with a special decorative overlay, which is attached to the house wall.
When building a house on heaving soil, experts recommend making the floor level of the extension lower than the floor level of the main structure. The magnitude of the difference must correspond to the expected deformation.
To attach a foundation to an existing house using an expansion joint, the following significant points should be taken into account:
- Leave a small gap between the main house and the foundation of the extension (no more than 5 cm). In order to comply with this requirement, before starting to lay the foundation, you should attach boards pre-treated with waterproofing material to the foundation of the house. In the future, it is they who will perform the function of an expansion joint assigned to them.
- In single-story construction, the thickness of the expansion joint can be no more than 2 cm.
- If desired, the expansion joint can be filled with any heat-insulating material. Most often, penoplex and polystyrene foam are used for this purpose. From the outside, everything is covered with a decorative overlay.
If the main purpose of an extension to an existing house is to form a separate zone, and not to expand an existing premises, a rigid connection of two foundations between one house and another should not be done in any case, since the consequences may be the most undesirable. In this situation, it is much more advisable to use an expansion joint.
If we are talking about a small extension, it can be built on a shallow strip foundation or a foundation on stilts.
Choosing the type of foundation for an extension
Experienced specialists strongly recommend that for the construction of an extension, use the same type of foundation that was used for the construction of the main building. This is due to the fact that different foundations react differently to contact with the soil and also react differently to shrinkage of the building.
Accordingly, if the main house is built on a strip foundation, and the extension is built on columnar piles, sooner or later the auxiliary structure will collapse. Thus, you should not skimp on things like connecting foundations under any circumstances.
If you plan to connect the building to the house, you can use different foundations. Most often we are talking about the following options:
Strip foundation
For those who decide to use a strip foundation for the extension, the following list of work will be required:
- make markings in parallel with the tracing at the site of construction of the base structure (this will require wooden pegs and an ordinary rope);
- dig a trench along the marking;
- secure the fittings;
- prepare a trench;
- fill in a sand cushion (approximately 100-120 mm) and carefully compact the bottom of the trench;
- lay a waterproofing film;
- install reinforcement structure;
- Fill the trench with a solution of cement and gravel.
The pouring of a strip foundation should be approached as responsibly as possible. It is better to do the work in several passes. One third of the trench is poured as the first layer, and after drying - one second. The technology, in principle, allows the use of foam blocks, but not in all cases.
After the cement-gravel layer has completely dried, the formwork is built. The formwork is filled to the brim with concrete. After laying, the concrete is pierced simultaneously in several places. This prevents the formation of air bubbles. After the concrete has completely dried, the formwork is removed.
And finally, just before the walls are erected, the almost complete structure is covered with a layer of waterproofing material. Most often, roofing felt, tar, liquid rubber or bitumen mastic are used for this purpose.
Columnar foundation
If your plans include building a house that is small in size and light in weight, the use of a columnar foundation is quite acceptable. It is usually made of either concrete or brick. For a medium-sized building, 6 support pillars are most often sufficient.
To install such a base you will need:
- dig a hole (depth below the soil freezing level);
- pour a sand cushion on the bottom;
- install metal (or fiberglass) fittings;
- treat the reinforcement with moisture-proofing material (for metal reinforcing bars);
- install formwork;
- fill the base with concrete.
Construction can begin immediately after the concrete has hardened. If there is a need to increase the height of the pillars, you can lay a brick on top of the concrete.
Foundation on screw piles
A foundation on screw piles is the simplest and most cost-effective type of foundation. Please understand that it is only designed for structures that are not too heavy, as it cannot support much weight. But if you are going to add a wooden veranda to your house, this option is quite suitable.
This type of foundation in most cases does not require the participation of specialists. Even a person who has no experience in construction is quite capable of screwing in screw piles with his own hands. It is probably for this reason that many people choose a foundation on screw piles.
If the foundation on stilts is installed correctly, it can last for a long period of time.
But no matter what foundation needs to be installed, on screw piles, columnar or some other, the most important thing is that all work is carried out in accordance with the technology. Therefore, if you do not have enough construction experience, it would be most advisable to entrust the pouring of the foundation to experienced and qualified specialists.
Increasing the usable space in a private property by adding new premises that stand on their own foundation begins with solving the problem of how to connect the foundation to the house so as not to damage both structures. The construction of additional structures usually begins after several seasonal cycles, during which financial resources have been accumulated, a desire has appeared for a new round of site development, and the standing buildings have begun to shrink normally in the ground. Building codes provide the answer to how to connect two foundations to each other, taking into account mutual influence.
Connection requirements
It is necessary to determine how to connect the new foundation of the extension with a residential building at the design stage, taking into account already existing factors. These include the following incoming conditions:
- type and design indicators of the foundation of the existing building;
- characteristics of underlying soils;
- time elapsed since the previous construction (the main shrinkage occurs in 1 - 2 years);
- commensurability of the weight load of 2 structures that need to be combined.
Full requirements for the calculation are contained in the set of rules SP 50-101-2004, which was developed in development of the regulatory rules contained in SNiP 2.02.01-83*, SNiP 3.02.01-87.
In any case, the help of experienced professionals is not superfluous, since mistakes can be costly later.
The result of linking the base and attached building structures with different values of foundation shrinkage is shown in this video
The construction of a new building begins depending on the season. In the spring, it is not recommended to start laying next to existing foundations, since at this time of year the soils are in the most loose and water-logged state. The settlement value of a new extension on heaving soil may be much greater than the calculated value in the project and may be uneven around the perimeter. At the same time, there is a risk of movement of the undermined old support due to the high groundwater level in combination with possible precipitation (rain or snow).
Before starting work, it is necessary to take into account that any new foundation (MZLF, piles, pillars, slab) will certainly settle, even if it is made identical to the existing support.
Shrinkage
In construction, there are established settlement standards for various structures, the foundations of which are designed and manufactured in accordance with current state standards.
You can find out the standard and make a forecast for the design of your individual home using data from the reference tables:
When comparing the calculated indicators, a new support unit is attached to the foundation of the old building at a given depth, taking into account its own settlement after a certain time.
The upper marks of monolithic strip foundations of combined buildings are made according to calculation, and not according to level, as in this photo.
It is the possibility of displacement relative to each other that determines what kind of connection between two foundations can be made. The following types of connections are used:
- Rigid bond (concrete with reinforcement).
- Separate installation (installation of an expansion joint taking into account the mutual influence of the supports).
The possibility of a rigid connection into a single structure is significantly influenced by the geological factors of the site - in case of mobile or heterogeneous soils, for buildings with a large support area, it is necessary to make intermittent foundations (sometimes with different widths of the tape).
Starting the independent construction of a new extension module to a residential building is permissible if the following requirements are met: issue permits for the installation of a new structure, maintain distances no closer than the minimum permissible to nearby buildings and communications, ensure independent settlement of all structures in relation to each other.
Combining foundations
It is best to attach a new room to the existing foundation of the house using a rigid coupling. In this case (if all conditions are correctly taken into account), it is possible to connect the above-ground surfaces into a single whole without the expectation that gaps and distortions will appear between the elements and the floor level. But such a design solution is limited to sites with non-heaving soils that have high load-bearing characteristics.
In practice, this method is used for low-rise buildings, provided that the extension being built is functionally connected by one roof to the building that is already in use.
Another condition for unification is the same type of foundation. If the strip base of a residential building turns out to be insufficiently wide, then it needs to be strengthened.
Such work includes connecting the reinforcement of an old support with a new frame or laying connecting anchors by drilling, followed by filling the belt with branded concrete. The reinforcement belt prepared for applying the solution is shown in this photo.
The connection of buildings consisting of several floors is carried out according to a more complex scheme, which involves the construction of covering walls with dividing seams on each side, as shown in the drawing.
The rigid type of connection is chosen for cases when the problem of how to connect an old established foundation with a new building is considered, for buried strip foundations. The extension is also designed with a monolithic reinforced concrete structure.
Strip foundations
For a permanent building attached to a house, with a commensurate weight of the building materials used, a stable support of a large area and load-bearing capacity is necessary. This request corresponds in most cases to a strip foundation.
- Expose the entire depth of the existing tape. You need to dig a trench in parts (1.5 m - 2 m), not along the entire length at the same time, since the exposed part loses lateral support, which can lead to its deformation. An old building can be further strengthened with inclined supports.
- Drill holes along the side of the connection corresponding to the size of the reinforcement Ø. In the middle of the tape, holes are drilled in a checkerboard pattern with a depth of about 0.75 of the width of the foundation itself, in the corners - 0.5 m. Reinforcement is driven into the middle holes, in which longitudinal slots are made with an inserted wedging liner for strong fastening in the hole. Reinforcement Ø 14 mm, having a periodic profile, is driven into the corner holes. The output of rods must be at least 0.3 - 0.4 m.
- The frame of the new foundation is knitted and welded to the released reinforcement.
- Fill with concrete mortar.
If there is access to the subfloor for work, the holes for pin-type tension elements can be made through, with the rods secured by flat plates.
Rigid connections of tapes in the form of an open contour (U-shaped) are made in the same way, but the reinforcement is placed in rows with smaller spacing. If the connection side is long in the open strip, you can make several additional support points different from the monolith, as can be seen in the photo.
If there is a need to change the depth of support on the soil of the foundation being added, it is filled with ledges, the height of which varies in steps of no more than 0.5 m. The first ledge is located at a distance of about 1 m from the old foundation. The connection is made with a reinforced concrete strip of the same thickness as the existing foundation of the house.
Each option for rigid connection of foundations has its own characteristics for specific cases, which it is advisable to entrust to professionals to consider and calculate.
Plates
It is possible to ensure the rigidity of the connection between the slab foundations of the house and the extension provided that they are sufficiently thick, about 0.4 m, and also if the old slab protrudes beyond the boundaries of the supporting walls of the building. Such protrusions are usually left during the construction of aerated concrete cottages. The outlet dimensions must be at least 0.3 m. This will make it possible to clean the reinforcing mesh of the slab and make a welded connection to the frame of the new extension.
The connection of monolithic bases is carried out according to the following scheme:
The slab of the old house, which has already settled, in this case not only becomes one with the new fill, but also receives additional reinforcement in the vertical connection of cement mortars due to 0.2 m - 0.3 m of fill underneath it.
Separate supports
If there is a large discrepancy in the weight of the old and new structures, the degree of shrinkage of these structures will differ significantly in magnitude. In such cases, it is not recommended to make a rigid connection for the foundations - it is necessary to choose separate construction of the supporting elements. It is possible to attach other types of foundation to the existing foundation and to do this use the principle of connection through an expansion joint.
The weight of the ceilings and walls of the extension should be distributed over its own support area, without creating tearing forces for the main foundation of the building.
Depending on the operating conditions, the expansion joint can be:
- sedimentary;
- temperature;
- seismic.
The sedimentary option (in the absence of other significant influences) has a width of 1 - 2 cm. According to the conditions of the mutual influence of the supports, attachment to the load-bearing wall of an old house can be carried out with a deformation gap reaching 0.2 - 0.4 m, filled with elastic, moisture-proof material.
Frame wooden extensions are successfully operated on a pile foundation with a metal grillage, as in this photo.
Light verandas or summer kitchens can be built on screw piles, even if there are already several nearby buildings around. This is especially convenient if the site is located on a slope, slope or with uneven occurrence of hard supporting rocks.
At the design stage, the external design of expansion joints that visually separate the facade is envisaged in an open or hidden form, for example, hiding the gap with a subvertical drainpipe. On the façade side, they are usually covered with strips of a special flashing and sealed with low-strength decorative material, which will not prevent the outer walls of buildings from moving relative to each other with possible uneven settlement. Under the roof deck, gaps are bridged using a compensation device.
An extension to a house, installed on separate supports, is a much less labor-intensive process than installing a rigid link, requires significantly less time and financial costs, and can also be done with your own hands without ordering special equipment
A far-sighted solution is to provide for the possibility of an extension at the design stage of the main building of a private house. This will greatly simplify subsequent work and will contain ready-made design solutions, planned uniform settlement over the entire area of the foundation and will ensure the reliability of the foundation.
Strip foundations are the most popular in private construction. It is ideal for the construction of small houses, garages, bathhouses and other outbuildings. All construction work can be done with your own hands, and the relatively low consumption of materials and the minimum amount of excavation work can reduce the price and production time. Of course, for everything to go as expected, you need to know how to properly reinforce the foundation.
Before telling you how to properly reinforce a strip foundation, it’s worth saying a few words about the choice of reinforcement.
- If you need to reinforce the foundation for a one-story or two-story house, as well as lighter buildings, you should take reinforcement with a diameter of 10-24 millimeters. Thicker material will cost too much and its high strength will not be used. Less thick reinforcement may not withstand the load.
- It is advisable to use special corrugated fittings. It provides a better connection to concrete, guaranteeing its high strength and reliability. The smooth analogue costs a little less, but is not suitable for use due to low adhesion. The only exception is cross connections. The load on them is significantly less.
- If the soil is homogeneous over the entire area of the foundation, then you can use material with a cross-section of 10-14 millimeters. With heterogeneous soil, the load on the base increases, so it is advisable to invest in rods with a diameter of 16-24 millimeters.
Of course, buying thick corrugated fittings is quite expensive. But if you decide to reinforce the strip foundation with your own hands, then the amount of work is not too large. So, you will have to overpay a maximum of a few hundred rubles - this is fully compensated by the high durability and reliability of the finished structure.
When independently calculating and selecting reinforcement for the reinforcement frame of a strip foundation, there is a high probability of error. In the future, it may cause the destruction of the house, so the best solution would be to order a foundation reinforcement project from a designer, and carry out the binding of the frame yourself according to the drawing.
How much reinforcement is needed?
Before you go to the store to buy material, you need to find out how much it will be needed to reinforce the strip foundation. To do this, you should think in advance which reinforcement scheme for a strip foundation will be the best choice and carry out calculations for a specific object.
An example of frame reinforcement for a foundation
When building small houses, garages and bathhouses, the following frame configuration is usually used:
- 2 belts: upper and lower;
- each belt consists of 3-4 reinforcement rods;
- the optimal distance between the rods is 10 centimeters. Please note that the distance from the reinforcement to the edges of the future foundation should be at least 5 centimeters;
- The connection of the belts is carried out using clamps or pieces of reinforcement at a pitch of 5-30 centimeters, depending on the area of reinforcement.
This scheme is optimal. Now, knowing the dimensions of the future building, it is not at all difficult to carry out the appropriate calculations.
Let's say you want to build a spacious frame or wooden cottage with an area of 150 square meters with external walls with a perimeter of 50 meters. Let's carry out calculations based on this. When reinforcing the strip foundation, we use SNiP and the characteristics described above.
We have two belts with three rods in each. Total - 6 multiplied by 50 = 300 meters of main reinforcement. We take into account the number of jumpers, which are laid in increments of 30 centimeters. To do this, divide 50 meters by 0.3. We get 167 pieces. The transverse jumpers in this base will have a length of 30 centimeters, and the vertical ones - 60 centimeters. For vertical jumpers you will need 167x0.6x2=200.4 meters. On horizontal ones - 167x0.3x2=100.2 meters. In total, 300 meters of thick corrugated reinforcement and 300.6 meters of thinner, smooth reinforcement will be required. Having received these numbers, you can safely go to the store for material - a strip foundation without reinforcement will not last long. Some experts recommend taking reinforcement with a margin of 10-15%. After all, a certain amount of material will be needed to strengthen the corner parts of the strip foundation and will be used for joining.
How to knit the frame?
The rules for reinforcing strip foundations force one to abandon the use of welding in favor of knitting, since when welding is used, in the places of welded joints, metal rods lose strength up to 2-2.5 times. In addition, this is where corrosion most often appears, which can damage the reinforcement within a few years, significantly reducing the reliability and durability of the foundation. Only connection by knitting is permissible. This is a rather complex stage, which will take a lot of time for an inexperienced user. However, a lot here depends on what tool you use.
Reliable knot for tying reinforcement with wire
The classic tool for tying reinforcement in strip foundations is a special crochet hook. Using it, experienced craftsmen can produce up to 12-15 knots per minute (of course, if the knitting wire is prepared and cut in advance). The main advantage of this option is its affordability - a hook can be bought in many stores for a hundred rubles or even cheaper. The downside is that the speed of working with it is not great even for experts. Please note that you will have to make many hundreds of ties even if you have to reinforce small foundations.
Wire and hook for knitting the frame
If you want to finish the job quickly, you can use a special knitting gun. Working with it, even an inexperienced user can easily produce 25-30 knots per minute. That is, productivity will increase at least 2 times. Alas, the cost of such equipment is not low - from 50 thousand and above. In addition, to work with it you need a special wire - a regular one may not be suitable. This further increases the cost. But if you have the opportunity to rent a knitting gun for a few hours or a day, feel free to agree to such an offer, just don’t forget to find out the maximum diameter of the reinforcement that it can tie. Working with high-quality tools, you will spend a maximum of a day assembling the frame - correct reinforcement of the strip foundation becomes much easier and faster. When working manually, this process can take a week or more.
How to make a frame correctly?
Before proceeding with the reinforcement of the strip foundation, drawings of suitable frames should be studied. After all, the strength of the frame determines whether the foundation will serve for many decades or will become covered with cracks in the first spring due to seasonal fluctuations in soil level.
In order not to make mistakes during manufacturing, you need to remember a few rules:
- The overlap (the distance from the place of knitting to the edge of the rod) should be at least 5 centimeters.
- At corner joints, perpendicularly running rods must be connected to each other - in no case should you use two separate blocks that are not connected to each other. The ideal solution would be corners made from bent reinforcement - this type of foundation reinforcement scheme is the most reliable. But for this you need to have special equipment; if the reinforcement has a diameter of 14 millimeters or more, smaller diameters can be bent at home.
- Connections using wire must be tight - if you use a crochet hook, then tighten the wire until it stops so that there is no free space between the clamp and the main reinforcement. Also check with your hand; if the clamp moves when touched, you should make an additional tie with wire.
- The overlap during reinforcement should be equal to 40-50 diameters of the reinforcement. There must be a separation between adjacent connecting rods and the top and bottom layers, according to the design.
- The reinforcing frame must stand level in the formwork. It is also necessary to take care of a protective layer of concrete for the reinforcement, done according to the requirements of the drawing. It should be remembered that the minimum protective layer is equal to the diameter of the reinforcement.
Bending of all elements for foundation reinforcement is performed cold. Do not heat the reinforcement under any circumstances, as this will lead to a loss of its strength.
As you can see, the rules are as simple as possible. But some inexperienced builders are unaware or forget about their existence. This leads to the fact that the reinforcement technology of the strip foundation is disrupted and its service life is significantly reduced.
Excavation and preparatory work
One of the advantages of a strip foundation is the relatively small amount of excavation work. A couple of people, working every day with short breaks, can easily dig a pit of a suitable size on normal soil. When the foundation pit is ready, you can begin to arrange it.
The first step is making the foundation cushion. Thanks to it, the negative impact of groundwater on the foundation is reduced, and the load from the foundation itself and the entire building is distributed as evenly as possible over the ground. Here you can use different materials. Most often sand or crushed stone is used. They do their job well - the main thing is that the thickness of the pillow is at least 15-20 centimeters.
But some experts recommend a concrete pad. Yes, it costs the most. Expensive cement and the need to reinforce the cushion greatly increase the cost and time of construction. But as a result, you get the most reliable foundation for the foundation, guaranteeing that it will last for many years. Therefore, we can say with confidence that this money will not be thrown away.
An example of a reinforced strip foundation
If work is carried out on weak, heaving soil, or if you plan to build a heavy brick house, but the use of a monolithic foundation is undesirable for some reason, then you can use a strip foundation with a sole. The widening (glass) can significantly reduce the load on the ground. Of course, do not forget about the reinforcement of the foundation shell - on heaving soils it will regularly withstand significant tensile and bending loads. It is very important to provide it with sufficient strength.
When using a foundation with a sole, the volume of excavation work increases. In addition, you will have to spend additional money on reinforcing the base of the strip foundation - if it fails, this will lead to the rapid destruction of the entire structure.
Formwork is installed on top of the finished cushion. When choosing the width, keep in mind that the finished foundation should be 10-15 centimeters thicker than the external load-bearing walls.
The next step is to install waterproofing. Some builders use roofing felt, but this is a rather expensive material. And the heavy weight makes the installation process difficult. Therefore, it is quite possible to use construction polyethylene. Yes, it is less durable. But it is only needed for a few days - so that the cement laitance does not go into the sand. Therefore, cheap and lightweight polyethylene is quite suitable. It is laid on top of the formwork. At the joints, make a larger overlap - at least 10-15 centimeters - and glue with wide tape.
This concludes the preparatory work. Now we’ll tell you about pouring and reinforcing the foundation with your own hands.
We install the frame, pour concrete
It is best to assemble a frame from reinforcement directly in a prepared pit - this allows the elements to be most firmly fixed. But if we are talking about reinforcing a buried strip foundation or if the pit is too narrow for work to be carried out directly in it, then you can assemble the frame from the outside above the trench, and then carefully lower it into place. Problems usually do not arise here and step-by-step instructions are not needed.
The last and one of the most critical stages is pouring the foundation.
Pouring a strip foundation with a concrete pump
It is advisable to use concrete grade M200 or higher for this. It has high strength to withstand significant loads, and also has sufficient frost resistance.
It should be said right away that the work will require a large amount of material. Carry out all the necessary calculations in advance - you need to pour concrete in one go, avoiding delamination and other separations. Otherwise, the strength of the foundation will significantly decrease, and this will affect the safety of the house. For the same reason, it is advisable to rent a concrete mixer. Today many companies offer such a service. In addition, renting cheap models is relatively inexpensive - less than a thousand rubles per day. If you work intensively during this time, it is quite possible to cope with the work. In addition, the presence of a concrete mixer allows you to increase productivity - you just need to throw in sand, cement and pour in water, soon getting a finished product that just needs to be poured onto the frame installed in the formwork. Working with shovels, such productivity cannot be achieved.
After pouring concrete, you must wait 28 days. During this time, the concrete will gain sufficient strength and it will be possible to begin building a house, garage or bathhouse.
We recommend watching a video where an experienced civil engineer will talk about the important nuances of foundation reinforcement. What should you pay attention to when performing work first, so that the foundation of the house is reliable.
Now you know how to reinforce a strip foundation with your own hands. To do this, it is not at all necessary to have highly specialized skills or buy expensive equipment. It is enough to know, at least in theory, how to reinforce a foundation. Experience will come with the process, and all tools can be replaced with cheap analogues or rented, saving money and time.
The most popular foundation in private buildings is strip foundation. Most often this is a concrete strip on which the walls of the house rest.
Concrete can withstand large static loads (because it can withstand enormous compressive forces), but is vulnerable to dynamic loads.
Under tensile stress, which often occurs during movement and frost heaving of the soil, the tape may crack.
To prevent this from happening, it is reinforced with a metal rod. How to properly reinforce a strip foundation with your own hands?
Which reinforcement is best for a strip foundation?
Reinforcement of a strip foundation can be done with steel or composite materials, i.e. metal or fiberglass rods. They are sold in coils from 50 to 100 meters, sometimes in the form of cut metal from 6 to 12 meters.
The advantages of fiberglass reinforcement for foundations are corrosion resistance, chemical inertness, non-magneticity, lack of electrical conductivity and static electricity. This material is used, for example, when constructing foundations for technical structures, for which the absence of radio interference is important.
It is rarely used in private buildings: due to poor bending stretch, it does not perform its main function very effectively.
Features and diameter of reinforcement for strip foundations:
- for verticals and crossbars, a smooth or corrugated rod about a centimeter thick is used;
- for the longitudinal part of the frame, which takes on the main loads, choose corrugated material up to two centimeters (for a private house this is enough);
- for knitting use steel wire or clamps;
- sometimes welding is used to connect the rods. Metal marked “C” is suitable for it.
For foundation reinforcement it is not allowed to use:
- profile corners;
- metal pipes;
- chain-link mesh, incl. with a large cell;
- iron cables;
- plastic bottles, etc.
How to calculate reinforcement for a strip foundation
For shallow foundations (no deeper than 90 centimeters), the frame is made of two longitudinal rows, two rods per row. For buried ones (below the freezing of the soil, i.e. deeper than one and a half meters), longitudinal rods are placed at three to four levels.
Distances:
- between verticals the step is from 40 to 80 cm;
- between horizontal lines – from 30 to 60.
note
01/52/2003 SNiP specifies the minimum amount of metal: 0.1% of the foundation cross-section. For example, if the height of the tape is 1.2 meters and the width is 0.4, then the total cross-section of the reinforcement is from 480 square millimeters.
The minimum diameter of the rods depends on the reinforcement conditions:
- longitudinal rod for a side up to 3 meters long - 1 centimeter;
- more than three – 1.2;
- crossbars with a frame height of up to 80 cm - 0.6 cm;
- more than 80 – 0.8 cm.
For clarity, we give an example of calculation.
Initial data:
- Construction: 5 by 5 meters;
- Tape height: 0.6 meters (a two-level frame will be required);
- Width: 0.3 m;
- Step between verticals: 0.5m.
Quantity of reinforcement for strip foundation: (to the obtained figures you need to add a margin of about 10%):
- Length of longitudinal rods: 20 meters multiplied by 4 = 80 meters;
- Vertical pins, with a five-centimeter indentation from the surface: 1.4 meters multiplied by the number of intersections (51) equals 71.4 meters;
- Cross members: 40*0.3*2 = 24 meters;
- At the intersection you need 30 centimeters of wire for knitting, four joints per section. With a reserve - about 70 meters.
Strip foundation reinforcement scheme
The procedure for reinforcement is as follows:
2. Fill the concrete base with a layer of 5 centimeters to protect the metal from corrosion. Instead of a sole, you can use a more economical option: place stones or broken bricks under the vertical rods. But this is a long and energy-intensive method.
4. Place the calculated number of transverse rods on the concrete in increments of 0.8 cm.
5. Lay two rows of longitudinal rods along the walls of the ditch. Link intersections. Fragments of horizontal lines are overlapped together. The overlap length is 50 rod diameters minimum.
6. Install vertical rods at the joints. They are placed perpendicular to the laid lower level; there should be no deviations from the vertical. Bind.
7. Attach the upper tier of crossbars to the verticals. The overlap of the ends of the frame should be at least 20 centimeters.
8. Lay the upper longitudinal rods and fasten them to the rest of the structure with clamps or wire.
9. Fix the frame relative to the formwork. There should be at least five centimeters between the metal and the boards. The same minimum distance is left between the rods and the upper border of the concrete.
To protect both the frame itself and the concrete from the development of corrosion, the reinforcing bars should be cleaned of rust and dirt before installation.
To work, you will need a tool: clamps, special hooks for tying wire, cloth or metal scissors.
A homemade hook can be made from a piece of reinforcement: sand the end of the rod 6 or 8 millimeters, bend it and put a wooden or plastic tube on the opposite end. The handle should be located at an obtuse angle to the working part of the hook. It is fixed on both sides with thrust washers, and the washers are secured by welding.
Actions when linking:
- Place a wire bent in half under the desired joint of the rods.
- Hook the fold loop.
- In two or three turns, tie a loop to the other (double) end of the wire.
A problematic point during installation is corner reinforcement. Concentrated tension is formed in the corners; these are the most loaded points. To compensate for the load, L-shaped or U-shaped reinforcements with clamps are used. L-shaped ones are used for obtuse angles.
A) using an overlap and a paw, B) using an L-shaped clamp. 1. horizontal reinforcement, 2. overlap, 3. tab, 4. vertical reinforcement, 5. transverse reinforcement, 6. additional transverse reinforcement, 7. L-shaped clamp, d - reinforcement rod diameter
Clamps of the required size and cross-section are installed instead of ordinary vertical rods. In corner connections there should be twice as many clamps as in linear sections.