Groundwork and Foundations
All buildings should have adequate foundations, normally concrete, and will vary depending on each circumstance
Foundations
The foundations transmit the load of a building safely to the ground. Therefore, all oak buildings should have adequate foundations, normally concrete, and will vary depending on each circumstance. There are different types of foundations so choosing the correct one is vital and it means taking into consideration:
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Load size or size of the building
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Ground conditions and type of soil, presence of trees
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Presence of water including drains and sewers
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Space and accessibility, adjacent buildings
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Sensitivity to noise and vibration
Visit the UK Government Planning Portal website as it and provides good guidance for all building projects ranging from planning permission to foundations and building regulations.
There are two reasons why the type of soil that the foundations will rest on are important: firstly, it should be able to bear the weight of the foundation and secondly, is the way it reacts to moisture or dry temperatures. Generally foundations fall into two categories, shallow-fill or deep-fill.
Shallow-fill Foundations
These are used where loads imposed by a structure are low in comparison to the bearing capacity of the surface soils. The most common types of shallow foundations include pad, strip (or footings), or raft.
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Pad
Pad foundations are generally square, round or rectangular holes that are filled with concrete, where a staddle stone is positioned on top and used to support a single post or column. The staddle stones are made locally and can be flared or straight.
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Strip or Footings
Strip or footings foundations provide a continuous strip of support for a wall or closely spaced columns built above them. Strip foundations are used where the soil has good bearing capacity and is suitable for light structural loads such as domestic buildings. The width of the foundation depends on how wide the wall above is. The depth of a traditional footing to be filled with concrete, will depend on the load bearing ability of the soil and it should be agreed with the structural engineer and building control officer (who is responsible for passing the building regulations).
Raft
Where ground conditions are poor such as soft or loose soils where settlement is likely, or where it is impractical to make strip or pad foundation, then raft foundations are recommended as they are slabs that cover a wide area often the whole of the building's footprint. A structural engineer should design this type of foundation as it is specific to your site.
Base
There is usually a layer of compacted hardcore followed by a layer of sand blinding, then a 1200 gauge waterproof membrane covered by steel mesh and a layer of reinforced concrete. All our buildings sit on at least three courses of brickwork above floor level and the independent posts are pinned to staddle stones.
Deep Foundations
Deep Foundations are used where the bearing capacity of the soil is unable to support the load, therefore it is necessary to go to deeper layers with higher bearing capacity. For example, the presence of clay that has a high moisture content can lead to expansion and contraction. This affects ground movement and requires the foundations to be much deeper especially if the area has trees nearby. Depths of more than 2.5m can be impractical and costly when filled with concrete, therefore, piling methods are often used whereby long slender columns typically made from steel or reinforced concrete, although occasionally timber are used.