Strip Foundation
The strip footing is the most common foundation for masonry structures, and is wider than the masonry above it.
It is typically made of concrete or floating concrete, poured between the foundation trench walls.
If the soil is not of sufficient strength, formwork is required for its construction.
If structural reinforcement is required, scaled reinforcement is also placed in the concrete.
The implementation process is as follows:
- The site clearing involves the removal of plants and the top layer of soil, humus.
- The batter boards are installed, fixing all the corner points and the boundary lines, which can be marked out on the surface of the soil, for example with lime powder.
- The next step is to dig the foundation trenches, either by machine or by hand, taking care to ensure that the levels are at the correct height.
- Formwork - only if necessary. In this case the foundation trench should be made wide enough to accommodate the formwork.
- Steel fixing - only for reinforced concrete foundations. A blinding layer is prepared for the steel fixing.
- During concreting, penetrations must be positioned in advance, and the upper plane of the foundation body must be marked on the earth bank or formwork.
Concreting takes place using a rotating drum mixer or by pouring ready-mixed concrete, in layers of approximately 25 centimetres.
The layers must be compacted with a rod vibrator.
During solidification, the concrete must be watered to avoid rapid loss of moisture, which could lead to the concrete overheating.
- Removal of formwork
- Backfilling in layers of 15 cm and compaction around the foundation.
The foundations of the partition walls are made in the same way as the main walls, but with a smaller cross-section.
The cross-section can be further reduced by using reinforced beams.
For light loads, it may be sufficient to reinforce the substrate with reinforcing steel.
In the case of sloping terrain and the use of different foundation levels, the strip foundation must be stepped.
The maximum level difference (step height) is 50 cm, and the maximum angle of inclination for the stepping is 30 degrees.
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Spread Footings, Strap and Grid Foundation
Spread Footings
Supporting columns or pillars are typically made of monolithic reinforced concrete, but the spread footing can also be a prefabricated reinforced concrete structure, a so-called sloped foundation.
The construction of monolithic reinforced concrete is the same as for steel footings, except that the footings are island-like and not continuous.
When they are constructed, the longitudinal formwork of the pillar typically continues into the base body, creating a captive connection.
Waterproofing can be accomplished by waterproofing the pillar, by metal sheeting under the pillar, or by insulating around the entire spread foundation.
For precast spread foundations, the typical solution is to first construct the concrete block foundations and then raise the pocket foundations on top of these.
The placement requires first making 8 to 10 cm of precast concrete on top of the block and then placing the cup base in the bedding mortar laid on its surface.
The pillar is then lifted into the chalice and secured first with wedges and finally with concrete.
Waterproofing can be achieved with a waterproofing pillar.
Strap and Grid Foundations
This may be necessary if the load is too heavy, resulting in point bases that are too large or too close together.
It may also be necessary where there is a risk of subsidence or slipping.
The construction is the same as for a strip foundation.
Mat Foundation
A mat foundation is particularly needed in poorly bearing soils, but most of all in high groundwater.
The mat foundation resists the water pressure by its weight and its uniform design, which provides protection against flotation.
Construction of the mat foundation:
- After site clearing and setting out, drainage follows.
- After the excavation work min. 10 cm thick insulation protector concrete substrate is made, on which there is the ground waterproofing.
The substrate is wider than the mat in all directions and is provided with a perimeter beam to receive the insulation retaining wall, which can be built, for example, from small bricks.
- 5 cm of precast concrete is laid, if necessary formwork and ironwork follows.
- Then the concreting is completed, preferably in one session.
- After the insulation retaining wall has been built, the ground waterproofing is completed around the entire mat foundation.
- Finally, the earth is backfilled.
