How to build a columnar foundation from 20-20-40 blocks with your own hands?

One useful method of laying the foundation for a strong structure is to build a columnar foundation out of 20-20-40 blocks. This kind of foundation is well-liked for its affordability and robustness, which makes it an excellent option for do-it-yourselfers. If you’re prepared to tackle this project, you’ll discover that you can create a strong and dependable foundation with a little forethought and a few standard tools.

We’ll take you step-by-step through the entire process in this guide, from assembling the supplies to setting the blocks. Everything you require to make sure your foundation is solid and stable will be covered. The foundation for a successful project is laid by knowing how to lay these blocks correctly, whether you’re building a new house or an addition.

You can tackle the task with confidence if you adhere to these simple instructions. Together, we will explore the fundamentals of building a columnar foundation, which will ensure that your project begins successfully.

Step	Description
Planning	Decide on the foundation"s location and layout. Mark the area where you"ll build the foundation.
Excavation	Dig holes for the columns. The depth and width should match the size of the blocks.
Prepare the Base	Level the bottom of the holes and add a layer of gravel for drainage.
Lay the First Layer	Place the first row of blocks in the holes. Use a level to ensure they are straight and even.
Build Up	Continue adding rows of blocks, staggering the joints for stability. Use mortar between the blocks for a strong bond.
Reinforcement	For added strength, insert rebar vertically in the blocks before the mortar sets.
Finish	Once the blocks are in place and the mortar has dried, fill in the surrounding soil and compact it.

What is it, photo

The most common FBS block size used to construct a columnar foundation for a house (shed, terrace, or veranda) on your own property is 20x20x40, as they:

• durable – withstand loads of 150 kg per square centimeter;
• frost-resistant – tolerate 15 or more freezing cycles;
• the approximate weight of one block is 32 kg, therefore no special equipment is required during construction.

Prior to beginning foundation construction, it is important to ascertain the type of soil present at the construction site, its freezing point, the groundwater table, and the existence of "water lenses" that shouldn’t be there. Groundwater should not come into contact with the base of the pillars any closer than 50 cm.

The depth at which the support must be buried beneath the structure depends on the freezing point. The freezing depth in the Russian Federation’s central zone is one meter at most, though there might be variations. The foundation’s lowest point needs to be below the soil’s freezing point.

You want to choose bricks that are made on brick presses because they are stronger because they are cast. A wooden grillage is used when building a shallow block columnar foundation.

A distinct foundation is constructed for extensions (terrace, veranda), which is subsequently not joined to the main structure by a grillage. This is carried out as a result of the different and lower load on the support of such structures. The furnace’s pillars are positioned apart from the main foundation structure.

Advantages and disadvantages

20x20x40 block columnar support is perfect for constructing a wooden house or frame out of logs or beams because:

• building materials (blocks) are inexpensive;
• work on laying the foundation does not require significant labor costs, therefore there is no need to attract outside labor;
• the size of all blocks is the same (GOST 13579-78);
• ease of assembly; if a mistake is made somewhere, the foundation can be disassembled and put back together.

Blocks’ primary drawback is that they can absorb up to 15% of the moisture in the soil, which can seriously damage the foundation. It is possible to overcome this drawback by using waterproofing.

Technology Basics

Any structure’s dependability and durability are largely dependent on its correct design. In order to compute a columnar foundation accurately, you must consider:

1. Small area of ​​support on the ground (when compared with a strip or slab foundation). Tying the pillars together with a grillage will help reduce the problem to a minimum.
2. Soil freezing depth. The best option is that the supports are buried below the freezing level, thanks to which the effect of extrusion forces is reduced. Backfilling the depressions with sand will help eliminate pull-out forces. It would be useful to install a drainage system around the perimeter of the building.
3. In general, a columnar support has worse characteristics than a monolithic foundation.

How to do the calculations correctly?

In order to calculate a columnar support from 20x20x40 blocks, you must determine the number and size of necessary columns. These parameters are contingent upon the anticipated future load on the foundation.

Factors influencing load determination:

• weight of the structure together with furniture, equipment and people;
• weather conditions (wind, amount of precipitation).

The columns need to be positioned appropriately on the website once the number has been determined. It is important to remember that:

• the columns must be located in the corners of the building;
• in places where the walls adjoin each other;
• if the walls are long, then the columns are placed a maximum of two meters from each other along the entire perimeter of each wall (if a monolithic grillage is planned, then the distance between the columns can be 3 m).

A hanging grillage is made for a shallow and above-ground columnar foundation, requiring a lot of reinforcement and the setting up of formwork.

The following data is taken into consideration when calculating the weight of the future building:

If the roof slope angle is more than sixty degrees, there is no snow load.

The approximate weight of the foundation is included in the computation of the house’s weight. We compute its approximate volume and multiply the result by 2500, which is the kg/m3 specific gravity of reinforced concrete.

The formula S = 1.3 × P/Ro is used to determine the total area of the pillar bases.

• P – mass of the house with foundation, kg;
• Ro—resistance (bearing capacity) of the soil, kg/cm2;
• 1.3 – a special coefficient showing the safety margin of the building.

The following table yields the Rо value:

Required materials and tools

The following instruments were used to build the foundation:

• roulette;
• level (laser or hydro-level);
• rubber hammer;
• wheelbarrow (manual);
• shovels – bayonet and shovel;
• construction mixer;
• rammer.

Using 20-20-40 blocks to build a columnar foundation is a doable and useful do-it-yourself project. You can build a solid and dependable foundation for your structure by carefully arranging the layout, making sure the blocks are aligned and leveled, and using mortar to hold them in place. This method not only saves costs but also provides you with practical experience in basic construction methods.

Step-by-step instructions for building a foundation

Detailed instructions for creating a columnar foundation on your own:

1. Choosing a site for construction.
2. Site preparation (destruction of bushes and trees along with roots, mowing grass, leveling the soil).
3. Marking the future location of the pillars with pegs and rope. The structure will be strong if the pillars are 1.5 m apart from each other. Pegs are placed outside the border of the future pillar (so as not to move them during laying the foundation) along the lines of the walls of the building.

Waterproofing must be done in one of the following ways:

1. Along the entire perimeter of the pillar, under its sole.
2. Drainage installation around the perimeter of the future structure, below the level of the sole.
3. Installation of a storm drain built into the blind area.

If communications (pipes) are required, they must be laid before the foundation can be installed.

Installation technology

An approximate list of steps to follow for foundation work:

1. After preparation and marking, you will need to make holes up to 40 cm deep for a shallow foundation. Pit holes for deep foundations should be 1.5-2 meters deep, since the most common level of ground freezing is 1 m. Using blocks to build such a foundation is not entirely rational, since it is necessary to dig very deep holes, which is labor-intensive.
2. The area of ​​the pit should be slightly larger than the cross-sectional size of the post (usually the pit is square with a side of 40 cm).
3. A drainage system is installed around the foundation.
4. All post holes must be the same depth. The check is done with a level.
5. A pillow under the pillars is made from a mixture of sand and gravel or sand alone.
6. The pillow is compacted using a log tamper. You can compact the sand cushion by pouring a lot of water into the hole.
7. The bottom layer of two blocks is placed on a cushion of sand and gravel or on a special leveling layer of a special masonry mortar consisting of cement and sand (1 part of M400-500 cement is taken for 3 parts of sand and water is added so that the consistency of the mortar is plastic and thick).
8. The thickness of the mortar layer between the blocks is approximately 1 cm.
9. A sand-cement mortar is applied to a row of blocks, and the next row of blocks is laid on top of it, perpendicular to the bottom row.
10. The top mark of all foundation pillars must be the same. Sometimes it is necessary to level with a layer of sand-cement mortar or even using solid red brick.
11. For fastening and wooden strapping, you can insert an anchor bolt into the seam between the blocks of the top row.

The top row needs to be waterproofed by applying bitumen mastic and roofing felt as the last step.

Waterproofing

Waterproofing the pillars is essential to preventing freezing and moisture intrusion that could destroy the foundation. There are multiple methods for waterproofing the foundation, which stops water from penetrating:

1. Coating. Molten bitumen must be brushed onto the blocks. Epoxy, bitumen, and polymer mastics are used for coating.
2. Polyurethane spraying. The most expensive method of waterproofing is a plastic, liquid mass that is sprayed onto the pillars.
3. Plastering. The most time-consuming of all methods. Special plaster mixtures containing plasticizing additives are used as a waterproofing layer.
4. Pasting. A film with glass insulation and membranes is overlapped on the polymer glue. Before and after pasting, coating with mastic (bitumen, polymer, epoxy) is carried out. When applying multi-layer pasting, a mesh is placed between the layers, used for plastering. Pasting must begin from the bottom, with a horizontal overlap of at least 30 cm, and a vertical overlap of 10 cm. Layers when pasting can only be positioned vertically.

With the exception of sand soil, the foundation pillars are set on a unique cushion. Pillow-making stages:

1. The bottom of the pit, covered with geotextile, is covered with sand in a layer 20 cm thick. The sand is compacted.
2. Crushed stone is poured onto the sand in a layer of approximately 20 cm.

The best option is a pillow composed entirely of gravel if the site’s groundwater table is near the surface.

Sole

Installing foundation pillars on a base—a compact, enlarged area of reinforced concrete—will ensure a more secure installation. A frame consisting of reinforcement is first constructed using a specific formwork, and then the frame is covered in concrete.

Guidelines for building the sole:

• the size of the sole should be 2 times larger than the cross-section of the pillar;
• waterproofing made of reinforced concrete is required;
• the laid footing will prevent the sharp edges of the crushed stone from damaging the waterproofing and serves as a layer that levels the surface of the cushion.

The footing is a 5-7 cm thick screed made of mortar mixed with sand and cement. Drainage outlets are created in the crushed stone if needed.

Pillars

The foundation is constructed after the base for the pillars is established. Reinforcement is used to connect the post and sole; multiple rods are released from the sole.

Sand-cement mortar is used to join the blocks together. Every masonry row is checked both horizontally and vertically and bandaged.

To aid in creating a qualitative connection between the grillage and the foundation pillars, reinforcement embedding blocks will be installed in the upper rows of the masonry. On the final row of masonry blocks, the side edges of the column are waterproofed by wrapping the waterproofing around the surface and securing it with bitumen mastic in two to three layers.

Grillage

Several varieties of grillage exist:

• monolithic – poured along the heads of pillars;
• prefabricated – mechanically attached to the foundation pillars.

There must be a space between the grillage and the ground to keep it from touching the ground. This space can be created in two ways:

1. A layer of foam plastic is placed under the base of the grillage.
2. A seven-centimeter layer of sand is poured onto the bottom of the formwork, which is removed after dismantling.

The negative impact of soil freezing on the foundation is lessened because of the space between the soil and the grillage.

How to buy: price and tips for choosing

FBS 20x20x40 for a columnar foundation comes with the following parts in the price:

• price of raw materials;
• cost of production work;
• transportation costs.

The price per piece of blocks ranges from 35 to 75 rubles. There are several reasons for the price difference:

• weak competition – a small number of productions leads to higher prices;
• quality and type of material – hollow expanded clay concrete blocks will be cheaper than solid ones;
• resellers on the market – it is cheaper to purchase building materials from the manufacturer;
• order volume – wholesalers often get discounts.

While selecting and making a purchase, it is important to consider the following factors:

1. Compliance of block sizes and weights. If the weight is below the specified value, and the dimensions are normal, this may indicate the presence of empty areas in the blocks or poor-quality compaction of the material. These shortcomings have a bad effect on the strength of the FBS, so they should not be used for the foundation of the structure.
2. Matching shape and size. Often there are batches made in different shapes and differing in size by up to 0.5 cm. You can check them with a template in the form of a plywood frame with a calibrated hole.
3. Compliance with GOST. There should be no cracks or deformations on the FBS blocks.
4. Compliance of building materials with requirements current regulatory documents. It will be confirmed by the presence of certificates and quality passports.

Possible errors during construction and ways to correct them

The most common errors made when building a do-it-yourself columnar foundation out of blocks are as follows:

1. Pillars without soles will quickly sag. Most often, a foundation is built without a sole, as this allows you to save on building materials and make the construction process less labor-intensive.
2. A columnar foundation cannot be placed in subsidence soil, since even a well-made sole for each column will not save such a building from subsidence (immersion into the soil) in the future.
3. You cannot build a columnar foundation in clay soil. In winter, the pillars will be pushed out (rise and go in different directions) from such soil, even if they are built below the freezing point and have a sole.
4. Incorrect calculation of the load on the foundation from the load-bearing structures of the structure leads to the appearance of a lateral component that pulls the pillar to the side.

Placing the building on jacks and raising the pillars to the necessary height will level out a sagging foundation.

Columnar base appropriate for a two-story frame building or a wooden home constructed of logs or beams. One story cellular concrete home (the weight of the building material should not exceed 1000 kg/m3) can be constructed on such a support. It is imperative that every pillar in the future building carries an equal amount of weight.

This page contains a wealth of significant and practical knowledge regarding columnar foundations.

Video on the topic of the article

Block-based columnar foundation that can be assembled by hand, with video instructions:

A useful do-it-yourself project that can support the weight of your building and strengthen your structure is building a columnar foundation out of 20-20-40 blocks. These steps will help you build a strong foundation that will increase the construction’s stability and longevity.

Make sure your site is level and ready to go before anything else. For a foundation to be successful, precise measurements and meticulous alignment are essential. The foundation’s overall strength and longevity will be impacted by how carefully you place each block, so take your time.

Your columnar foundation will be balanced between strength and handling ease if you use 20-20-40 blocks. To get the best results, use high-quality mortar and let it cure completely. Ensuring that the process remains on course can be achieved through frequent checks.

Building a columnar foundation can be a gratifying project if you are patient and pay attention to detail. You will not only build a solid foundation for your future construction endeavors, but you will also obtain invaluable practical experience.

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