Types of Masonry Foundations, Their Construction and Uses
When it comes to constructing a building, the foundation plays a vital role in providing stability and support. Masonry foundations, constructed using concrete block or brick masonry units, are a popular choice due to their cost-effectiveness and durability.
In this article, we will explore different types of masonry foundations, their construction methods, and their various uses in building construction.
1. Masonry Strip Foundation:
The strip masonry foundation is commonly used directly below bearing walls. It is suitable for areas with good quality soil. The foundation is wider at the bottom and gradually narrows towards the top, ensuring the uniform distribution of the load and preventing cracks or damage at the edges of the wall. In clay or silt soil, it is crucial to bed the masonry units in mortar and fill all joints with mortar to prevent groundwater from softening the clay material. If the soil’s bearing capacity is poor, adding a concrete layer beneath the strip footing is recommended. The dimensions of the strip footing depend on soil conditions, applied loads, and the construction method of the structure it supports.
2. Masonry Spread (Isolated) Footing:
Masonry spread footing is commonly used in residential buildings with basements. The bottom of the isolated footing is wider than the load-bearing masonry wall above it. This wider portion helps distribute the load over a larger area, improving overall stability. Similar to strip footing, a concrete layer with a recommended thickness of 100 mm to 225 mm can be added under the isolated footing if the soil strength is not satisfactory. The design and layout of the masonry isolated footing are primarily governed by the imposed loads.
3. Stepped Masonry Footing:
Stepped masonry footing is a variation of strip footing specifically designed to prevent sliding on sloped grounds. The introduction of vertical steps provides horizontal bearing for the foundation, overcoming the action of horizontal vectors and ensuring satisfactory stability. Careful construction is essential, particularly for stone masonry, to achieve a strong bond at the steps. It is recommended to create long sections for the stepped foundation whenever possible.
4. Inverted Arch Masonry Foundation:
Although not commonly used today, the inverted arch masonry foundation consists of an inverted arch constructed from brick or stone masonry, upon which masonry walls or piers are placed. This type of foundation was suitable for soft soil conditions and was commonly employed in the construction of multistory buildings. However, the use of reinforced concrete has largely replaced this type of footing due to the challenges associated with constructing a strong inverted arch. Skilled and experienced masons were required to achieve the necessary strength for this type of foundation.
Masonry foundations offer a reliable and durable solution for building construction. The choice of foundation type depends on factors such as soil conditions, building loads, and construction methods. Whether it’s the simplicity of strip foundations, the load distribution of spread footings, the stability of stepped footings, or the historical significance of inverted arch foundations, each type has its unique applications.
Understanding the characteristics and construction techniques of these masonry foundations is essential for architects, engineers, and builders to ensure the long-term stability and safety of structures.