By: Mark J. Donovan
When building a
home or home addition, the question frequently comes up on whether concrete
blocks or poured concrete should be used in constructing the foundation walls.
Both have advantages and disadvantages.
Wall Foundation Advantages
blocks are sold as 16” x 8” x 8” in length, width and height, respectively.
Their true dimensions are 15 5/8th x 7 5/8th x 7 5/8th
in length, width and height, respectively.
|The slightly reduced actual measurements are to allow for
mortar to yield the 16” x 8” x 8” finished dimensions.
blocks contain hollow cells designed to support rebar / steel reinforcing rods,
as well as poured concrete/mortar, to maximize wall strength. Besides the
standard size concrete block there are a number of alternative sizes, shapes,
textures and color tones to choose from.
Concrete blocks for
building foundations are large compared to standard brick. As a result,
foundations built with concrete blocks can be constructed more rapidly than one
might initially think.
walls can be constructed by homeowners with some basic masonry knowledge and
back strength. The basic masonry knowledge can quickly and easily be obtained
via a number of resources. The back strength: that may take a little longer
pending your specific genes and age.
If the concrete
blocks are properly filled with concrete and rebar during the wall construction,
a very large thermal mass is created. This large thermal mass provides for an
excellent high thermal and acoustic insulation factor in the walls.
Wall Foundation Disadvantages
walls can look somewhat ugly if they are not parged or stuccoed on the outside
wall surface. Parging or Stuccoing the outside wall involves the process of
applying a thin layer of mortar to the outside concrete block wall to produce
one smooth flat finish surface. The mortar can be tinted to achieve different
earlier, standard concrete blocks are heavy. So if considering a Do-it-Yourself
foundation project, keep this in mind.
If concrete block
walls are not filled with concrete and rebar they can be weak and structurally
unsound. In addition, they will have a limited insulation factor.
Just as with poured
concrete walls, it is imperative that a concrete block wall be installed on a
proper concrete footing. In addition, a perimeter drain is critical when
building a foundation wall with concrete blocks. Due to the seams associated
with concrete block construction, foundation walls are more susceptible to water
Foundation Wall Advantages
walls can typically be constructed much more quickly than concrete block based
foundations, thus saving both time and money. The complete process of installing
concrete forms, pouring the concrete, and breaking the forms down can take as
little as 2 or 3 partial days of work.
foundations are usually 6-10 inches thick and joint-free, unlike concrete block
walls. Consequently they are considered to produce stronger and drier foundation
walls, critical for basement walls.
foundations provide for highly flexible floor plans. Jogs in the foundation
walls are easily constructed using pre-fabricated concrete forms.
Foundation Wall Disadvantages
walls usually can not be performed by a homeowner. Large pre-fabricated forms
are required to first be installed, sometimes requiring the use of small cranes
and unique fasteners.
whether you choose concrete block or poured concrete for building your
foundation walls, be sure to apply a waterproof sealer to the outside surface to
help prevent leakage. Also install rigid insulation on the outside of the walls
before backfilling to maximize the insulation factor of your concrete
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