One of the most important steps in any construction project is building a solid foundation. One of the most common kinds is the strip foundation, which needs a base that is ready to go in order to guarantee stability and durability. The cushion layer, which helps distribute the load evenly and prevents foundation settlement, is an essential part of this base.
Although building a cushion beneath a strip foundation may appear difficult, it is a task that is manageable with the correct equipment and some basic knowledge. Using clear instructions and helpful advice, we will walk you through the process of creating a dependable cushion layer in this post.
For a solid and long-lasting foundation, every step—from choosing the appropriate materials to correctly compacting the cushion—is crucial. Our step-by-step instructions will assist you in creating a strong base for your strip foundation, regardless of your level of experience with construction or do-it-yourself projects.
| Step | Description |
| 1 | Mark the foundation perimeter |
| 2 | Excavate the trench to the required depth |
| 3 | Compact the soil at the bottom of the trench |
| 4 | Add a layer of sand and level it |
| 5 | Compact the sand layer |
| 6 | Place a layer of crushed stone on top |
| 7 | Level and compact the crushed stone |
| 8 | Install formwork for the foundation |
- Purpose of a cushion under the foundation
- Basic parameters of the strip foundation
- Device and materials
- Device
- Height, thickness and waterproofing
- Video on the topic
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Purpose of a cushion under the foundation
A layer of sand or gravel known as the foundation cushion, or backfill, balances the load that the building places on the ground.
Gravel-sand backfill’s purposes
- levels the surface;
- promotes uniform distribution of the load created by the reinforced concrete foundation;
- prevents moisture penetration into the concrete base, swelling of the soil.
Sand is poured into a trench or pit after waterproofing is applied to the bottom if the building is located in an area where groundwater is near the earth’s surface. This will keep the cushion from silting.
Basic parameters of the strip foundation
Along the perimeter of each of the building’s walls, the strip foundation is installed to the depth of soil development. Furthermore, its breadth must equal the thickness of the load-bearing walls. However, this is frequently insufficient to give the foundation’s overall area the required load-bearing capacity.
It is possible to make the base as wide as it is tall, but doing so would require additional concrete use, which would not be profitable.
As a result, the foundation strip becomes trapezoidal as the depth increases in the foundation’s area.
A 45º angle is used for concrete foundation side walls and a 30º angle for brick foundations.
A design like this keeps the side faces from chipping, stretching, or extending in the event of frost-heaving soils.
With its excellent load-bearing capabilities, a reinforced concrete base shaped like a trapezoid helps you save a lot of money on cement mortar.
A critical first step in guaranteeing the longevity and stability of any building is to create a cushion beneath a strip foundation. You can learn more about your construction project and save money by doing it yourself. You will be guided through all of the necessary supplies and procedures in this guide, from choosing the appropriate gravel and sand to correctly compacting the layers. You will be able to build a sturdy and dependable foundation cushion that will sustain your building for many years to come with easy-to-follow instructions and helpful advice.
Device and materials
Materials for construction that can be arranged to form a foundation pad:
- clean coarse-grained sand without clay components;
- sand mixed with crushed stone;
- pebbles;
- concrete, reinforced concrete.
A cushion of sand and gravel is placed for the structure’s foundation on weak soils.
Percentage of the backfill components
- coarse sand – 6 parts;
- crushed stone – 4 parts.
Lightweight single-story private homes can be built on a concrete strip foundation since these cushions don’t need to be further moistened with ramming.
Compared to sand cushions, backfills made of crushed stone (gravel) and sand cause less subsidence. Compaction must be done layer by layer when building large country homes out of heavy block materials.
Device
Before beginning the backfill, a ditch must be dug. It is filled with sand in layers no thicker than 0.2 m, each of which is rammed in place independently.
The material should be compacted evenly by using a roller. A piece of log with handles incorporated is frequently used as a tamping tool in residential construction.
Before compaction, water is poured into each layer of backfill when working on solid soils. This makes it possible to complete the process more quickly.
Sand that has already been moistened and whose clay components have been previously washed out is poured into the ditch if installation work is being done on weak soil.
Height, thickness and waterproofing
Depending on the features of the land plot, backfill for a monolithic concrete strip can reach a height of 0.6 m, or up to 0.8 m in the case of soils that experience significant winter heaving. The cushion can span up to 3 meters in width, but on each side it should be 0.1-0.15 meters wider than the foundation base.
There are benefits to this option:
- on a concreted surface, it is easier to perform reinforcement in the cold season and install the formwork structure;
- Such a plane allows you to reinforce a concrete structure with increased stiffness indicators.
After establishing the future building’s perimeter, snacking beneath the concrete base is carried out. Next, a cheap brand of cement is used for the preparation of the concrete.
Regardless of the background option selected, the final foundation design’s dimensions must match the design specifications in the horizontal plane. The dimensions of the pillow and the reinforced concrete base itself are immediately considered when the ditch is being dug.
Applying concrete preparation reduces the layer’s thickness by half. Concrete is poured at a depth of 3-5 cm if a backfill of sand and gravel is completed at a depth of 5-7 cm. However, it is important to realize that the concrete base will be better shielded from the processing step the thicker the pillow is.
The structure needs to be shielded from groundwater’s harmful effects even though sand bedding or concrete preparation is done beneath the reinforced concrete strip.
In order to accomplish this, roller materials are used to create a waterproofing layer at the ditch’s bottom. To keep moisture from penetrating the concrete, waterproofing is also applied to the completed foundation’s surface.
It’s simple but important to make a cushion under a strip foundation on your own. It guarantees the stability of your foundation, averting structural issues down the road. You can avoid future expensive repairs by taking the time to properly prepare and lay the cushion.
You can handle this portion of the building process with confidence if you follow the steps that have been outlined. Every step is important, from choosing the appropriate materials to making sure the compaction is correct. Patience and attention to detail will result in a strong, long-lasting foundation for your project.
Recall that the durability of your strip foundation is directly impacted by the quality of your cushion. Long-term benefits include peace of mind and a solid foundation for anything you choose to build, so it will be worthwhile to put in the extra work now. Have fun constructing!
