Combining the advantages of concrete and rubble stone, a rubble concrete strip foundation provides a sturdy foundation for buildings on a range of soil types. This kind of foundation uses concrete and crushed stone or gravel (the rubble), which is layered carefully to disperse the weight of the building uniformly across the ground. Certain guidelines are followed during construction to guarantee stability and longevity.
The flexibility of a rubble concrete strip foundation to accommodate different soil types and uneven terrain is one of its main benefits. This type of foundation reduces the chance of settling and structural damage over time by utilizing concrete, which offers strength and stability, and rubble stone, which serves as a natural drainage layer. It works especially well in places with expansive soils or high groundwater levels.
There are things to keep in mind, though, just like with any construction method. Careful planning and execution are necessary for a rubble concrete strip foundation in order to avoid problems like differential settlement. It is essential to properly mix and pour the concrete as well as compact the debris. In addition, compared to more straightforward options, the cost of labor and materials for this kind of foundation may be higher.
To guarantee the efficacy of a rubble concrete strip foundation, a number of guidelines must be adhered to during construction. First, the foundation trench needs to be dug out to the necessary depth and width, taking into consideration the building’s dimensions and the soil’s ability to support weight. The trench is then filled with a layer of compacted stone rubble, and if needed, reinforcing steel bars, or rebar, are added.
After that, the concrete is poured to completely fill the trench, covering the rebar and debris. The strength and durability requirements of the particular building project should be carefully considered, and the quality of the concrete mix should be carefully inspected. For long-term stability and to avoid cracking, concrete must be properly cured.
- What is it, its features
- Advantages and disadvantages
- In what cases do they use?
- Design and characteristics of the base
- Construction stages
- What materials and tools are needed?
- Calculation of parameters
- Proportions of components for masonry
- Construction site preparation
- Installation of formwork, pouring concrete
- Waterproofing, thermal insulation
- Video on the topic of the article
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What is it, its features
A reinforced concrete foundation and a rubble concrete foundation are similar in terms of geometry and construction principles. Formwork and a trench solution are still required.
However, since stone is added straight to concrete, it serves all of the purposes of reinforcement, so none is needed. The mixture is then poured into the formwork after that.
After that, the same tasks as building a reinforced concrete base are completed: removing formwork, waterproofing if needed, installing thermal insulation, and building a basement.
Advantages and disadvantages
The following benefits of the stone in the mortar are enjoyed by the foundation:
- High strength – with correct calculations, the foundation can withstand the weight of a two-story brick house.
- Easy to buy all building materials.
- Installation does not require special skills, you can do it yourself.
- Cost savings due to the absence of fittings.
- Environmental friendliness.
- Resistance to moisture – rubble has low hygroscopicity.
- Low temperature resistance.
- The base does not require additional finishing; due to the rubble, it has an attractive appearance.
- Suitable for all types of soils (although there are certain conditions for design).
But it’s not perfect. Thus, it is preferable to use a bottle-concrete base for one-story attic homes rather than a heavy mansion. When building a two-story cottage, it is preferable to use light materials such as frame and aerated concrete for the second floor.
The requirement for base thermal insulation and waterproofing is the second, somewhat negative aspect. The drawback is relative because, even in the middle lane, current foundation requirements require isolation in all circumstances.
In what cases do they use?
For country homes, one-story cottages, and cottages with an attic made of slightly heavier materials, a base of stone and concrete is constructed. A foundation like this is appropriate for garden structures (greenhouses, sheds, arbors). You must consider the kind of soil when calculating the foundation.
The only installation on non-heaving soils is a coarse sand cushion that is the same width as the tape. A broader cushion with another layer of compacted soil underneath is required on heaving soils. Furthermore, the tape’s shape should taper upward, creating a blind area on the ground’s surface.
Design and characteristics of the base
The properties of the solution determine all of the base’s characteristics, so the composition of the solution is carefully considered.
A minimum strength grade of 200 cement is utilized. Additionally, medium-grained sand is required, and it is combined with cement in the standard ratio of one part sand to three parts cement. Additionally, five parts crushed stone.
Use fraction 20–30 rubble stone for filling. A straightforward formula is used to determine the precise dimensions of the stone: one third of the foundation strip’s width equals the size of the rubble. Roughly half of the mass of concrete is composed of rubble.
There should be no cracks in the stone. Strength testing is required; if the stone still holds together after being pounded with a hammer, it is suitable for use.
The stone is cleaned with water before being poured into concrete because contaminated rubble will not adhere as well to the mixture.
Construction stages
Making a list of supplies and equipment and computing design parameters is the first step in any construction project.
What materials and tools are needed?
To construct, you will require:
- cement;
- sand;
- crushed stone;
- rubble stone;
- sand for foundation cushion;
- boards for formwork;
- fasteners for removable formwork;
- waterproofing materials (mastic, roofing felt);
- thermal insulation boards;
- tools for excavation work (shovels, wheelbarrows);
- materials for marking (pegs, twine);
- pipes for drainage (if necessary);
- concrete mixer;
- level;
- tools for clearing the area and preparing the site (if necessary).
One option is to purchase pre-made rubble concrete mixture in place of the first three points. Although it will save labor, this might end up costing more than preparing the mixture yourself.
Thermal insulation is the second point. If you use permanent formwork instead of removable formwork, it won’t be necessary. The same holds true for fasteners and boards. Brick or stone masonry in a single row can also be used as permanent formwork for a concrete rubble base.
Calculation of parameters
You must know the future house’s weight, payload, and snow load in order to determine the foundation’s depth, height, and width.
The mass of all building materials, including fasteners, finishing, wind protection, and so forth, is added up to determine the first indicator. For this reason, you should begin your computations from the house rather than the foundation.
It is preferable to use an online calculator for these purposes, such as Stroy-Calc. Generally, a house’s useful load is equivalent to 180 times its area. In addition, the average payload is 180 (kg/m2). The corresponding map of the regions contains information about the snow load.
Utilizing SNiP 2.02.01-83 formulas and tables, find the foundation’s area. The depth of the foundation should be 10–20 cm below the level of soil freezing in your area. To determine this, you must first determine this. For the most part, rubble concrete foundations are subject to the same regulations and standards as reinforced concrete ones.
The amount of concrete for the base is simpler to determine—you just enter the tape parameters into the same Stroy-Calc and get the answer—but only for a standard solution. Additionally, half of the necessary solution is made up of rubble stone. As a result, they perform computations and divide the outcome by two. The quantity of mortar and the quantity of rubble stone make up one part each.
Proportions of components for masonry
As previously stated, rubble concrete mortar consists of a combination of regular masonry mortar and rubble. Thus, it is pertinent to use the standard ratios of sand, cement, and crushed stone, which are 1:3:5. Half of the volume is made up of stone.
Construction site preparation
It consists of:
- Clearing the site. This includes removing garbage, uprooting trees, bushes, grass, demolishing old buildings, etc.
- Geological survey (probing) – to determine the type of soil, groundwater level.
- Marking the foundation area. This is carried out on the basis of an accurate drawing and calculated tape parameters. Wooden pegs are usually used for marking, on which a string is pulled.
- Excavation work – digging a trench for the tape. The depth of the trench should be 10-15 cm more – this is necessary for the sand cushion. The width of the trench should be sufficient for arranging the sole of the foundation, the foundation itself, including hydro- and thermal insulation, plus backfill.
Installation of formwork, pouring concrete
Inch boards are utilized in the formwork construction process. Wooden boards are used if it is assumed that the base is high.
Following the fabrication of the frame components, a sand or sand-crushed stone cushion is formed and then the pit’s bottom is compacted. Overlapping roofing felt sheets are placed on the cushion, with a tiny overlap on the trench walls.
Concrete pouring is done in multiple steps:
- Pour a 15-centimeter layer of ordinary mortar, without stone. This is necessary so that the rubble is not pressed into the cushion in the future.
- Install the formwork.
- Pour a 25 cm layer of rubble concrete mixture, immerse rubble stones in it, with a step of 5 cm – the solution should cover them halfway.
- The next layer of concrete – it should completely cover the first row of stone and leave space to cover the next row, also halfway.
- The operation is carried out until the required height of the foundation is reached.
- The top layer is clean concrete, which completely covers the rubble.
Concrete cannot be allowed to dry out while the job is being done; instead, its surface needs to be moistened or covered with a waterproofing gasket.
Waterproofing, thermal insulation
The formwork is removed once the concrete has dried completely, and the tape’s surface is treated with waterproofing mastic, coating, or spray type. By shielding the base from the effects of subsurface and melted water, this processing prolongs the base’s lifespan.
Applying thermal insulation is advised once the waterproofing has dried. To increase the foundation’s lifespan, this is required. Furthermore, the "warm" foundation lets you save money on home heating. Use stoves made of polystyrene for insulation.
Video on the topic of the article
The narrative of the video centers on a bottle-concrete foundation:
Constructing a rubble concrete strip foundation has a number of clear benefits. First off, the excellent drainage provided by the use of rubble stone keeps water from pooling around the foundation. Over time, this aids in preserving the building’s structural integrity. Second, the addition of concrete strengthens and stabilizes the foundation, ensuring that the structure can support the weight of the building with effectiveness. Because of this combination, rubble concrete strip foundations are especially well-suited for locations with high groundwater levels and a variety of soil types.
The affordability of this kind of foundation is another advantage. Construction costs can be kept to a minimum when using locally accessible materials like concrete and rubble stone instead of other foundation types. Because of its affordability, it is a recommended option in many construction projects, particularly those with tight budgets.
When building a rubble concrete strip foundation, there are things to keep in mind despite its benefits. In order to guarantee the durability of the foundation, the site must be properly prepared. This entails complete excavation to the necessary width and depth, then soil compaction to produce a stable base. To avoid settling and guarantee consistent support for the building, the rubble and concrete layers must be placed and compacted carefully.
In order to improve the concrete’s tensile strength and prevent cracking, care must also be taken in the design and positioning of the reinforcement. Enough drainage space must be made available around the perimeter of the foundation in order to reduce the possibility of water-related damage and extend the life of the structure.
For an article on "Advantages and disadvantages, rules for the construction of a rubble concrete strip foundation" on the site "All about construction and repair," we"ll focus on explaining the key points clearly. We"ll discuss how rubble concrete strip foundations combine the strength of concrete with the cost-effectiveness of rubble, making them suitable for various soil types and building loads. We"ll cover their benefits like good load distribution and adaptability to uneven ground, along with potential drawbacks such as labor intensity and potential settling issues if not constructed properly. The article will also outline essential rules for building these foundations, emphasizing proper preparation, material ratios, and construction techniques to ensure durability and stability over time.