Design and construction technology of a strip foundation with a basement

The design and construction of the strip foundation with a basement is one of the most important phases in building a house from the ground up. Because of its strength and the additional living or storage space it offers beneath the house, this type of foundation is very popular. You can make sure your home is built on a solid foundation by being aware of the fundamentals of strip foundation construction.

As the name implies, a strip foundation entails laying continuous concrete strips beneath a building’s load-bearing walls. This technique works particularly well for supporting large, weighty structures. As an extension of this foundation, the basement adds stability to the house while also providing additional space.

Planning and design are the first steps in the construction process, and they take into consideration the local building codes, the type of soil, and the building load. After that, trenches are excavated to the necessary depth and width. The strength of the concrete is then increased by adding reinforcement in the form of steel bars.

Precision and attention to detail are crucial because poorly built foundations can cause major structural problems later on. For the foundation of your house to be secure and long-lasting, every step—from the first excavation to the last concrete curing—must be meticulously carried out.

In what cases can it be arranged?

The kind of soil on the property and the depth of the groundwater must be considered when selecting a foundation for a home.

Because the strip foundation will be buried deeply—considering the basement—it is buried in stable, dense soil.

This base shouldn’t be used for:

• peat bogs,
• sandy loam,
• marshy soils,
• sand.

Clay and loam soils are suitable. Gritty, clastic, and boulder-pebble soil types are also appropriate, but excavation will be difficult and costly given the depth of the pit for a cottage with a basement.

For residential construction, a strip foundation with a basement is a wise and long-lasting option that provides substantial structural support and useful additional living space. This article examines the fundamental design ideas and methods for constructing a strip foundation with a basement, including soil testing, preliminary planning, excavation, reinforcement, and waterproofing. Homeowners and builders can guarantee a sturdy and long-lasting foundation that satisfies their needs and raises the property’s overall value by being aware of every stage.

Recommended depth

The distance between the base of the foundation and the soil’s surface is referred to as its depth. Depending on the subsequent elements:

• depth of soil freezing (data is taken from publicly available information for a specific region);
• type of soil;
• groundwater level – the foundation sole should not be below this mark.

The height of the basement ceiling, which must be at least 2 meters, is also considered because the building will have one. A suitable foundation depth is typically regarded as 2.5–2.7 m, with the foundation sole lowered by 10–20 cm below the soil freezing level.

If the water level is higher than this, a forced or gravity drainage system is used to artificially lower it.

The soil surrounding the foundation and the foundation itself are insulated if the freezing depth is high; this lowers the depth and lowers costs. Insulation is provided by foam plastic or other materials that are resistant to moisture, rot, and low temperatures.

Do it under the entire area of the house or under part of it?

Either the entire base or just a portion of it may be used as the basement. In the first instance, auxiliary space is designated:

• billiard room,
• sauna,
• workshops,
• boiler room and so on.

In the second, it serves as a pantry and cellar.

Of course, only the portion of the foundation that is occupied by the basement gets buried. The remaining portion of the foundation can only be buried up to the suggested depth (10–20 cm below the freezing point of the soil).

Stages of arranging the foundation

Determine the base’s depth and thickness before beginning any work.

The basement walls are thicker to stop the tape from moving horizontally. The base base’s width increases as a result of the structure’s increased overall weight.

Building monolithic is advised over block tape because it can support loads better and is more resilient to frost heaving.

Prior to beginning work:

• purchase the necessary materials,
• order special equipment,
• determine the work schedule.

Calculation of sole area and wall thickness

The area of the sole affects how evenly the weight is distributed throughout the house. Additionally, the foundation’s base carries out the following tasks:

• prevents local soil heaving;
• strengthens weak soil layer;
• increases the uniformity of the arrangement of the structure along the plane of the site.

Using the reference book’s formulas and data, the area of the sole and the wall thickness are determined. The following table shows the average values for a building with walls up to 3 meters long and a basement depth of 2.5 meters:

Wall material	Sole width, mm	Basement wall thickness, mm
Rubble stone	900	600
Rubble concrete	600	400
Brick	770	380
Concrete monolith	400	200
Concrete block	500	250

Using an online calculator and publicly available reference data, you can carry out independent calculations.

Excavation

Future foundation markings are done at the start of work. Ordinary pegs with a rope stretched over them are used for these purposes. A pit is excavated manually or with the aid of machinery in compliance with this marking. The pit’s walls and bottom need to be level and stable.

Water drainage and drainage

The second phase of the project is this. Three different kinds of groundwater are removed from the structure:

• groundwater, which rises during the rainy season or snowmelt;
• capillary – rises from aquifers;
• surface water – formed in the sinuses of the backfill, communication trenches after floods, heavy rains, etc.

A drainage system, which consists of a perforated pipe placed in a technological trench between the foundation and earthen walls, diverts groundwater. A layer of crushed stone encircles the pipe, and geotextile is layered outside. Water is redirected into a lowland, ditch, or reservoir close by. There is a pipe 30 centimeters below the foundation.

Storm drains are used to remove water after precipitation. A layer of crushed stone, geotextile, and sand is created at the bottom of the pit to remove capillary water; the layer is approximately 30 cm thick overall.

Bookmark LF

They start by creating a pit and taking care of the drainage before starting to lay the foundation. The following are the stages:

1. Bottom waterproofing – roofing felt. The strips are laid with an overlap of 15 cm, the edges of the strips should extend onto the walls of the pit by approximately 50 cm. The roofing material is covered with bitumen mastic on top.
2. Making formwork – from boards about 2.5 cm thick (removable) or from polystyrene foam boards (fixed). Expanded polystyrene is also insulation for the foundation.
3. Installation of reinforcement – these are metal rods with a diameter of 12-16 mm, which are installed at a distance of 3 cm from the foundation walls. The step between the rods is no more than 40 cm. Horizontal reinforcement is carried out with wire or reinforcement, every 30-40 cm. The corners of the structure are reinforced with metal elements, U-shaped or L-shaped. Reinforcement rods are connected by simple knitting. In the corners of the structure, the reinforcement is bent.
4. Pouring concrete to a height of 30 cm. Use grades of concrete not lower than M200; it is recommended to fill it simultaneously.
5. Complete pouring of the foundation.
6. Hardening of concrete.
7. Dismantling removable formwork.

Waterproofing

Using penetrating compounds, roll materials, or bitumen mastic, external foundation walls are vertically waterproofed.

Applying materials in multiple layers for coating and penetrating. Two layers of rolled materials are placed, overlapping, and all joints must be glued.

Mastic is used to insulate the base’s horizontal surface before roofing material is applied. Mastic is the top layer. Formwork that can be removed is used to perform waterproofing.

Insulation

This is an essential item for building an energy-efficient home or in areas where soil freezes deeply or where groundwater levels are high.

Insulation is applied to the base:

• foam plastic slabs,
• expanded polystyrene,
• thermal panels,
• sprayed polyurethane foam or special mixtures with polystyrene foam/vermiculite.

As long as the foundation was filled with detachable formwork, thermal insulation is required. No extra insulation is needed when permanent foam formwork is installed.

Ventilation

A room like that unquestionably needs ventilation in order to get rid of moisture and soil radon, which regular ventilation is unable to do.

Natural and forced ventilation are the two varieties. Exhaust ducts of the first kind are situated 15-20 cm above the floor, beneath the ceiling. This is basic ventilation that works well in the summer but is insufficient in the winter.

As a result, installing a forced or combined system is advised. It works well for large spaces because fans provide air movement, so ventilation efficiency is not affected by the season.

Common Mistakes

The following are the most frequent errors made when building a strip foundation:

1. Saving on materials. The use of low-grade concrete, poor-quality waterproofing, crushed stone, sand reduces the cost of construction, but significantly reduces the reliability of the foundation.
2. Using blocks instead of a monolith. The blocks are great for shallow foundations or for a home without a basement. But with a basement, the soil pressure on the foundation walls increases, which leads to a shift in the blocks.
3. Incorrect foundation calculations.
4. Connecting reinforcement by welding, if it is not intended for this purpose, or in violation of technology.
5. Insufficient coverage of the reinforcement with concrete – the layer of mortar should cover the rods by 5 cm, no less.
6. Pouring concrete without using formwork.

The suggestions are straightforward: stay away from technological errors, don’t skimp on supplies and tools, and give foundation calculations enough thought.

Aspect	Description
Foundation Design	Plan the dimensions and depth of the strip foundation according to the building"s load and soil type.
Excavation	Dig trenches to the required depth and width, ensuring a level base for the foundation.
Formwork	Install formwork to shape the concrete and hold it in place during pouring.
Reinforcement	Place steel bars or mesh inside the trenches to reinforce the concrete and enhance its strength.
Concrete Pouring	Pour concrete into the formwork, ensuring even distribution and proper compaction to avoid air pockets.
Curing	Allow the concrete to cure properly by keeping it moist and protected for several days to achieve optimal strength.
Waterproofing	Apply waterproofing materials to the foundation walls to prevent moisture infiltration into the basement.
Backfilling	Fill the excavated areas around the foundation with soil, compacting it in layers to provide stability.
Basement Construction	Build the basement walls and floor, integrating them with the strip foundation for structural integrity.

Every step of the planning and building process for a strip foundation with a basement requires meticulous attention to detail. This kind of foundation is a strong and dependable option that gives extra room for living quarters or storage while offering superior support for a variety of constructions. Its ability to combine durability and functionality makes it a popular option among many homeowners and builders.

It is essential to use high-quality materials and adhere to the suggested guidelines in order to get the best results. A foundation’s overall stability and longevity are largely dependent on the completion of crucial tasks such as precise excavation, precise placement of reinforcement, and thorough concrete pouring. Every stage, from preliminary design to completion of construction, is essential to building a sturdy and reliable structure.

The property gains a substantial amount of value when the strip foundation design includes a basement. By adding additional rooms that can be used for different purposes, it makes the most of the available space. A well-built basement increases the building’s usefulness and adaptability, whether it is utilized as a workshop, living space, or storage.

In the end, putting time and money into creating a strip foundation with a basement that is designed and built correctly guarantees a solid foundation for your building. It is an investment well worth making because it adds extra space, durability, and value to the property. You can build a foundation that endures over time by following best practices and keeping quality in mind at every stage.

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