Introduction

Foundations provide support for structures, transferring their load to layers of soil or rock that have sufficient bearing capacity and suitable settlement characteristics. Very broadly, foundations can be categorised as shallow foundations or deep foundations.

Shallow foundations are typically used where the loads imposed by a structure are low relative to the bearing capacity of the surface soils. Deep foundations are necessary where the bearing capacity of the surface soils is not adequate to support the loads imposed by a structure and so they need to be transferred to deeper layers with higher bearing capacity.

Strip foundationStrip foundations (or strip footings) are a type of shallow foundation that is used to provide a continuous, level (or sometimes stepped) strip of support to a linear structure such as a wall or closely-spaced rows of columns built centrally above them.

Strip foundations can be used for most subsoils, but are most suitable for soil which is of relatively good bearing capacity. They are particularly suited to light structural loadings such as those found in many low-to-medium rise domestic buildings – where mass concrete strip foundations can be used. In other situations, reinforced concrete may be required.

Advantages and disadvantages of strip footings

The simplicity of design, the possibility to build the foundation without expensive tools as well as its long-term operation. Comparatively low durability, high cost in the final stages of construction (you must perform additional manual work, such as filling soil between the strips and its levelling, building floor etc), inability to make the monolithic binding of the floor to the basement.

strap footing

A strap footing is a component of a building’s foundation. It is a type of combined footing, consisting of two or more column footings connected by a concrete beam. This type of beam is called a strap beam.

It is used to help distribute the weight of either heavily or eccentrically loaded column footings to adjacent footings.  A strap footing is often used in conjunction with columns that are located along with a building’s property or lot line. Typically, columns are centred on column footings, but in conditions where columns are located directly adjacent to the property line,

the column footings may be offset so that they do not encroach onto the adjacent property. This results in an eccentric load on a portion of the footing, causing it to tilt to one side. The strap beam restrains the tendency of the footing to overturn by connecting it to nearby footings.

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