Pile foundations are one of the most cost-effective, versatile, and reliable methods for constructing foundations for private country houses. However, for certain reasons, screw piles under a frame house or log structure can settle (either a few or a large number of them). In this article, we'll explore in detail how to align steel supports horizontally, why they become uneven, whether this undesirable phenomenon can be prevented, and what measures should be taken to prevent it.
Possible Causes
The main reasons why piles sink into the ground in the
spring are:
•
Installation
procedures were not followed. The main violation is that the support was
not screwed to the design depth due to an obstruction (rock, rootstock), which
later shifted due to water damage. As a result, the pile sinks deeper. Another
possible cause is poor installation—it became difficult to screw in, so the
workers left it as is. According to the procedure, the blade should sink into
the supporting layer.
•
Poor quality metal posts. If a pile sinks, it
may indicate damage to the blade during installation. The blade bends due to
poor quality steel or even falls off due to poor welding. As a result, the
bearing surface of the structure on the ground decreases, causing the shaft to
sink below the design mark when loaded.
•
Exceeding the design loads. When heavier (than
planned) materials are used during renovations or expansions (attic, second floor),
the pile foundation invariably settles under the increased weight. The problem
can occur in different areas of the foundation, depending on the bearing
capacity of the soil.
How to fix it?
If foundation subsidence has appeared in one or more areas,
you can do the following:
•
Leveling
a few centimeters is easily accomplished by placing metal plates or wooden
beams (boards) of the appropriate thickness. If using metal, place a
layer of waterproofing material (such as roofing felt) between it and the wooden
parts of the structure.
•
Leveling,
if significant subsidence is observed and the underlayment is ineffective, can
be accomplished by the following procedure. The structure is raised with
jacks, a section of the floor is removed in the desired area, the posts are
tightened to the required depth using a reducer, and extensions are welded on.
•
Raising
the house with a foundation replacement is the most radical and expensive
method. It is used if the screw piles extend into the ground across the
entire foundation area and there is no other way to repair it. Powerful jacks
are placed under the house, and it is lifted and placed on temporary supports.
New posts are screwed in next to the old posts, carefully following the correct
procedure, taking into account the frost depth and the location of the solid
layers. After leveling the tops, the shafts are filled with cement-sand mortar,
a channel frame is installed, I-beams are installed under the structure, welded
in place, and the house is lowered onto the repaired foundation.
•
Raising
and shifting the house by tightening the piles. If subsidence is
observed on one side (for example, the first three rows), then the supports are
tightened on the opposite side and the house is raised with jacks. Then, the
joists are inserted and supported on the tightened posts. After this, round
pipes are placed on the joists under the foundation, rotated, and the structure
is shifted to free the front three rows. The settled supports are tightened
with extensions until the soil level is firm, leveled, and capped. Finally, the
structure is moved back using the method described above.
Correcting errors is much more difficult than anticipating
them. Therefore, if you lack specialized knowledge and lack confidence in your
abilities, it is better to entrust the design and, if possible, all
installation work to professionals.
Expert
Recommendations
To prevent pile foundation subsidence, it's worth
considering the advice of experienced installers and engineers even during the
design stage:
•
Conduct
a comprehensive geological survey before designing (you can do this yourself,
but it's more reliable to hire someone else). Know the precise depth of
the solid layers, the frost line, and the location of the groundwater. All this
information will help you choose the correct length for the steel supports so
they are installed precisely according to the required specifications—below the
freezing point of the soil and into the solid layer.
•
Use metal bracing. At a minimum, angle iron,
which is the cheapest and most readily available rolled metal. A metal grillage
made from a channel creates a more rigid and durable connection than a wooden
one, and is less susceptible to deformation due to ground movement.
•
To
ensure high-quality installation, use only experienced installers. Professional
builders perform all operations in compliance with technical requirements,
eliminating any errors.
•
Periodically
inspect the foundation and identify any slight deformations, cracks, or areas
of soil subsidence. While such changes are minimal, they can be easily
corrected, but if the problem worsens, it will lead to the destruction of the
pile structure and even the building itself.
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