Among the
main advantages of screw pile foundations is their ease of repair. If errors
were made during installation, loose piles can be repaired or replaced. Screw
piles are also suitable for restoring old strip foundations.
When Foundation Repair is Needed
The most
telltale sign that a foundation needs repair is when the building begins to
wobble. There are also visual signs: cracks, deformation, visible subsidence in
corners or part of a wall.
These
problems are especially common with strip foundations. Causes include seasonal
soil heaving, proximity to groundwater, temperature fluctuations, and errors in
calculations or execution.
Strip
foundation repair involves several stages:
•
Installing piles along the walls of the house (for private homes, along long
walls). Particular attention is paid to areas under load-bearing walls;
• Trimming
piles horizontally and installing strapping;
• Lifting
the house with jacks and dismantling the old foundation—partially or
completely;
•
Installing a channel support frame under the house. Installing the frame on the
pile collar;
• Lowering
the house onto the support frame;
• Decorative
pile capping (reinforcement) at the customer's request.
Theoretically,
it is possible to perform partial repairs by screwing in piles only in areas
where the damage to the old foundation is most significant. However, partial
repairs will, firstly, lead to uneven load distribution and, secondly, will
only correct the situation before further damage to the old masonry occurs.
Therefore, it is recommended to replace the foundation completely. Partial
repairs are only effective as a temporary solution.
Pile Replacement: When and How
A pile
foundation is strong and durable when installed correctly. If errors are made
during installation, the risk of pile loosening increases.
Reasons why
piles may loosen:
•
Insufficient screwing depth. The length of screw piles is calculated to reach
dense soil layers. Only this approach guarantees stability. Furthermore, during
the screwing process, the screw pile compacts the soil, ensuring reliable
anchorage even in loose soils.
• High
undercut without tie-in. The tie-in provides rigidity to the structure and
prevents pile displacement relative to one another. When piles are low above
ground, stability is ensured by the fixed underground section. However, with a
high above-ground section and no tie-in (or its insufficient rigidity), the
pile loses stability.
• No pile
caps. The caps are metal plates welded to the top of the pile and bear the
brunt of the load. Installing the caps ensures even weight distribution,
increases structural rigidity, and prevents distortion. Skimping on caps
reduces the service life of the foundation and inevitably leads to rapid
repairs. Any design errors can reduce the structural strength of a structure,
including incorrect selection of pile type and strength, inadequate
anti-corrosion treatment, or improper installation on a slope.
If the
foundation is improperly designed, its load-bearing capacity is inadequate to
support the weight of the structure, and the design is unsuitable for the soil
type on the site, a complete replacement of the structure is required. Partial
replacement is performed if individual piles fail due to other causes, such as
damage during other work.
Pile
replacement is carried out in the same manner as repairing other types of
foundations:
• Lifting
the building with jacks;
• Removing
the faulty pile;
• Screwing
in a new pile.
To
strengthen the pile foundation, the following work is performed:
•
Installing pile caps at at least three points;
• Strapping
the foundation around the perimeter;
• Strapping
is performed with a channel or angle.
There are
several ways to secure the angle:
• In a
single row - horizontally or diagonally;
• Crosswise
— used when piles are above ground heights greater than 70 cm and when
elevation changes occur.
The design
and installation of any foundation require precise calculations. The structure
will be strong and durable only if all types of loads are taken into account:
the weight of the building, soil type, wind, and precipitation. Trust the
professionals with this work, and you won't need to repair your screw pile
foundation.
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