A Foundation Course to Work in the Construction Industry
Grow your awareness and understanding of what is involved in building things - houses, commercial and public buildings, garden features, fences, walls, bridges and more.
Note that each module in the Qualification - Certificate in Construction is a short course in its own right, and may be studied separately.
Learn How Critical a Good Foundation Must Be
All construction needs to be built on sound and appropriate foundations. If foundations collapse, everything else in a construction will collapse. Whatever you build, from roads, paving or garden walls to small sheds, homes and large commercial buildings; all must have appropriate foundations if they are to survive for any length of time.
Foundations must be strong enough to support the structure and prevent movement. Your choice of foundation and the dimensions will depend on what you are building. It will also depend on the soil with regards to swelling, freezing or shrinking of the subsoil. For example, clay soils may swell or shrink and settlement may occur over the long term due to compaction. Soft clays also lose their strength when disturbed. Clays which contain sulphates may also cause corrosion of foundations. Gravels and fine sandy soils may lose smaller particles which are washed out. Peaty soils are spongy and easily compressed so cannot take great loads. Chalky soils are very prone to frost heave, and areas of land fill should be avoided unless they are scrupulously compacted.
Some structures will not require a foundation e.g. a small Wendy house or cubby for children might just sit on a lawn, perhaps secured to a wall. In other cases, a suitable foundation might already exist e.g. the end of a concrete or bitumen driveway could be used to support a lean-to, small shed, or garage. You might be rebuilding a greenhouse on an existing slab foundation. If in doubt, have an engineer check the suitability of an existing foundation.
Some common types of foundations are as follows:
These are used for most houses and large buildings as well as a number of different types of small buildings. They are comprised of a continuous 'strip' of concrete beneath the load-bearing walls of the building. The minimum depth of strip foundations is 150mm for a wall up to 1m in height. Concrete is generally a mix of 1:3:6 (cement/sand/gravel).
Wide strip foundations may be needed where the soil is oft clay or peaty. In this case the foundation strips are made wider and are reinforced with iron bars.
These are strip foundations which are adapted for use on sloping sites. A continuous strip of concrete is laid but as the ground level increases the next strip is laid to strip on the first. The minimum depth beneath the step would be 2 x 150mm = 300mm. This saves on the amount of earth which needs to be excavated and removed when laying the foundations.
Raft Foundations (Slabs)
These are made from reinforced concrete slabs which cover the whole area of the building and which are thicker beneath the load bearing walls. If there is any movement of the foundation it moves as one and so will not cause structural damage to the building above.
Short Bored Pile Foundation
These are created by boring a hole (2.5 - 3.5m deep, 30-35 cm diameter) into the ground. This is done using an augur to drill beneath the corners and junctions, beneath the building. Light concrete reinforced beams are laid over the top.
Piled foundations are used beneath high rise buildings where the pile is taken down to a more solid lower stratum of the soil.
These are something like pile foundations. A wooden post is supported in a concrete foundation either above or below ground, but the concrete foundation is sunk into the ground. This type of foundation is ideal for beneath decks, use on uneven or unstable land, for fence posts, gate posts, and pergolas.
These are pre-fabricated concrete blocks which may be situated beneath the corners and load-bearing parts of a building something like pile foundations. They need to be sighted on top of rock or compressed hard-core or gravel. They are sometimes used where the ground is rocky beneath making digging difficult or the ground is sloping - in which case a longer post would be set into the block on the deeper side. Some of these blocks have slots formed into them to take floor joists.