The issue of environmental friendliness is one of the most pressing concerns for future property owners when choosing a building material. In this regard, all experts agree: there is nothing better than wood. For a building to be reliable and durable, it requires the same foundation. In our article, we'll discuss the types of timber building materials, which timber house foundation to choose, and the specific features of each option.
Types of Timber House
Foundations
Like houses made of brick, aerated concrete, SIP panels, or
precast concrete, timber buildings require a strong and durable foundation.
When choosing the most appropriate solution, consider several factors:
• Building dimensions. The area is the most significant
factor, but the number of floors also plays a role. The area of a one-story
and a two-story house may be the same, but the latter will exert twice the
pressure per unit area of soil.
• Weight of building materials. Not only the weight of the
timber is taken into account, but also the weight of the floors, rafters, roof,
etc.
• Soil characteristics on the site. Before design begins, a
geological survey of the site must be conducted to determine the soil type and
structure, frost depth, and groundwater level.
Useful (furniture, occupant weight, utilities) and
additional (wind, snow) loads are included separately. After calculating the
sum of all possible loads, the building's pressure per unit area of soil is
calculated and compared with reference data for the soil type determined by
geologists. However, the building's area does not always correspond to the size
of the foundation (except for a slab), meaning the pressure on the soil may be
greater when choosing a strip foundation or piles. Let's consider the pros and
cons of each possible option.
Monolithic Slab
This is a reinforced concrete slab that is laid on a
prepared surface and follows the contours of the building. The advantages of
this technology are:
•
Versatility
– it can be built on any type of soil, including marshy (after drainage), peat,
heaving, and unstable soil.
•
Strength
and reliability – it is an ideal option for buildings made of heavy materials
(brick, reinforced concrete panels).
•
Durability
– if the technical requirements are met, it can last up to 100 years or more.
The main disadvantage preventing the widespread use of such
structures is their cost. The heavier the house, the thicker the slab must be,
which increases the cost of construction materials. There are restrictions
regarding the terrain – the site must be level; on a slope, the foundation may
slip. Drainage is essential, and only professionals can perform the
installation correctly – to achieve a monolithic foundation, the pouring must
be done in one go (requiring a crew and a mixer). A large amount of excavation
work is required, which almost always requires specialized equipment. This
option is typically chosen when other geological conditions are unsuitable or
when a foundation is required for a very heavy house.
Strip Foundation
A reinforced concrete strip foundation is constructed along
the building's perimeter and under load-bearing walls. This solution is more
cost-effective, but also has its own nuances. Depending on the foundation
depth, it can be deep, shallow, or non-deep. Advantages:
•
High load-bearing capacity. With proper design
and reinforcement, this is a reliable foundation not only for frame and wood
houses, but also for brick houses.
•
Comparatively low costs. The amount of materials
required to construct a shallow foundation for a log house is several times
less than the cost of constructing a slab.
•
Suitable
for areas with high groundwater levels. Drainage will be required, but
with proper waterproofing, the strip foundation will not be damaged by high
humidity.
•
Long service life. Strict adherence to the
installation technology ensures a service life of up to 150 years.
•
Possibility
of adding a basement. By creating a recessed structure, the space under
the floor is transformed into a spacious basement.
The most common choice is the shallow option. Although it's
relatively inexpensive, it has its drawbacks: it's not suitable for waterlogged
soil or swampy areas. While it's possible to build such a structure yourself,
the labor-intensive excavation work, formwork, and reinforcement required for
one person is high—at a minimum, assistants are needed. Nevertheless, until
recently, this method was the most popular in the private sector and was used
to build summer houses, outbuildings, and bathhouses.
Pile foundation
This type of foundation consists of supports driven into the
ground to a solid layer below the freezing point and connected by a grillage
(wood, metal, or reinforced concrete) for stability. Depending on the installation method and
material, there are several types of such foundations.
DRIVED
These are reinforced concrete square columns with a pointed
bottom. They can be combined with a foundation slab or strip. These supports
can withstand heavy loads, are resistant to temperature fluctuations, and last
up to 100 years. Construction can resume immediately after installation. The
use of specialized equipment is required, hence the high cost of installation.
SCREW
These are metal pipes with a pointed bottom end and a wide
blade welded to it, which helps anchor them in the ground. This technology has
many advantages: ease of installation (can be done by hand), construction in
any season, high installation speed, a long service life (for factory-made
ones, 100 years or more), and readiness for further construction. Furthermore,
the site can have any type of soil (swamp, loam, clayey sand) and terrain
(slopes, elevation changes). For a small outbuilding or summer cottage built
from timber, the supports can be screwed in by hand within a day. In some
cases, additional support is provided using channels, angles, or profile pipes.
Installation and material costs are significantly lower than for reinforced
concrete foundations. The only drawback is the inability to install on rocky
areas.
BORED
These supports are created directly on-site: a reinforcing
cage is placed in drilled holes and filled with concrete. The technology is
simple and can be easily installed by yourself. The posts are ready in 4 weeks.
If manufactured correctly, they can withstand significant loads.
The disadvantages are quite significant: if the soil is
heaving, a footing must be constructed underneath for each support; at depths
greater than 2 meters, specialized equipment will be required to drill the
holes, and installation is labor-intensive.
Pillar Foundation
For this type of foundation, columns are constructed from
blocks or bricks; monolithic reinforced concrete piers with bases can also be
used. The depth depends on soil conditions, but is usually below the frost
line. These piers are spaced 2-3 meters apart around the perimeter and under
load-bearing walls. The tops are leveled horizontally, waterproofing is
installed, and construction continues. Installation is simple and quick, but
there are many drawbacks.
These structures cannot be used on heaving soils. Installing
the grillage is very difficult, as is insulation, and building a basement is
impossible. Pillar foundations are used for small, lightweight structures such
as sheds, verandas, bathhouses, and garden sheds.
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