Foundation - First Task
The location of the foundation is determined by the site survey or plot plan. The plot plan will show all property line setbacks,
dimensions, easements, and any other normally determined by flood plane restrictions or city and county codes. The surveyor can
provide a marker or benchmark that serves restrictions that might be required. Another important item required for the foundation is
the elevation of the foundation. The elevation is normally determined by flood plane restrictions or city and county codes. The
surveyor can provide a marker or benchmark that serves as a reference to establish the finish floor elevation (FFE). In order to be able
to start the foundation, the building pad needs to be complete. If fill dirt is required, it needs to be compacted and rough graded to the
correct elevation Once the pad is complete and the corners established, batter boards can be put up. The batter boards and string lines
will allow you to get a true picture of the footprint Once the pad is complete and the of the house and finish floor elevation. After the
string lines are checked for correct dimensions and corners established, batter boards can be put up. The batter boards and string lines
will allow you to get a true picture of the footprint of the house and finish floor elevation. After the string lines are checked for correct
dimensions and being square, you will be ready to start putting up forms and digging footings. The foundation forms can be wood as
in most residential construction or metal as in commercial construction. Once the forms are set, they need to be braced off in order to
prevent the concrete from pushing the forms out. After the foundation forms are set and braced, the underground plumbing can be
installed. The plumber can use the form boards to lay out the position of the plumbing walls and pull string lines. With the plumbing wall
lines in place, the plumber can dig the plumbing ditches and be sure that the plumbing is installed correctly. After the plumbing is
installed, the ditches should be left uncovered until inspected by county or city inspectors. Sanitary lines are checked for slope and for
leaks. Sanitary lines should have at least a 1/4 inch slope per foot. The sewer lines are checked for leaks by using a ten foot stack test.
The stack test is accomplished by extending the main vent stack, usually a 3 inch PVC vent up ten feet. The whole house sewer system
is then filled with water up to the top of the ten foot vent stack. All the underground plumbing connections are then checked for leaks.
Concrete is one of the main building products used in the construction of a house. Depending on where the concrete is used in the
construction process, it can become a very critical factor in the overall structural strength of the house. Just because the concrete comes
premixed in the concrete truck does not mean that the concrete is always good.
In normal residential concrete, the first conversations might be with the concrete company's outside sales person. The size of the
foundation and how much concrete will be required are usually the first questions to be answered. The quantity of concrete is
expressed in "yards". One cubic yard of concrete is equal to twenty seven cubic feet of concrete. An example would be if there was a
hole three feet wide, three feet long, and three feet deep it would require one yard of concrete to fill the hole. Another value that is used
when pouring sidewalks and driveways is that a yard of concrete will cover eighty one square feet of area (driveway or sidewalk) when
the concrete is four inches thick.
The next issue discussed might be the strength of the concrete. Years ago, the only strength concrete used in house foundations was
2000 psi (pounds per square inch) concrete. It's not unusual today to see builders pouring 3000 psi and 4000 psi concrete, depending on
the size and complexity of the project. Some of the larger homes are designed by an architect and might require a structural engineer.
The structural engineer might require mix designs from the concrete company for his approval.
The sales person might ask next what kind of "slump" is required. This is sometimes where the concrete subcontractor and the builder
might try to reach a compromise. The lower the slump the greater the strength but the harder the concrete is to work. The higher the
slump the lesser strength but the easier the concrete is to work. When a structural engineer is involved, he might specify that the
concrete is to be 3000 psi with a three to five inch slump. If this is specified, it is very important to stay within these limits do not allow
anyone to add water to the mix on site without permission from the individual doing the testing. If the concrete is being pumped, there
are additives that can be added to the mix in order to allow a higher slump but not jeopardize the strength of the concrete. These
additives can also be used in dry and windy climates to allow a wetter mix and hopefully prevent surface cracking due to the fast
dehydration of the concrete. If the concrete is tested, the slump might be checked every fifty yards and the cylinders might be taken at
the same interval. Concrete cylinders are taken and tested to verify the compressive strength of the cured concrete. The cylinders are
compressed and broke at specified intervals. A cylinder broke after 28 days should break at the designed strength or greater.
Also, usually the temperature of the concrete will be checked at this time. The temperature of the concrete might become more of a
factor in the summer rather than the winter. A rule of thumb might be that if the concrete temperature is above 95 degrees it is not
acceptable to pour in the foundation or footings. Sometimes a good starting point to monitor the temperature of the concrete in a truck
is to check the ticket and see when the truck was loaded at the plant. In warmer climates, the longer the concrete is in the truck the
hotter the mix. In cooler climates the temperature might not be out of range but the time in the truck might become a factor. Usually a
rule of thumb might be that, if it has been forty five minutes to an hour since the truck was loaded, the load may have started setting up
and might not be acceptable to use.
As you can see there are a few more things to consider in foundation concrete other than just pouring the concrete out of the truck. As
in most any other construction process, a little pre-planning and basic knowledge might prevent a major mistake that could cost a lost of
time and money.
As stated previously, the foundation is one of the most important phases in the construction of a house. This phase will
require you to be familiar with reading plans, dimensions, and formulas to determine quantities of required materials. Some
of the more common quantities will be expressed as length, width, depth, linear feet, board feet, square feet, cubic feet and
cubic yards. All the materials in the foundation will be ordered and bought with one of these descriptions. In order for you to
be able to estimate and order materials correctly, there are certain formulas that can help you calculate the correct quantities
The following formulas are ones that will be necessary in order to calculate and order the required material for your
Linear Feet is probably the simplest quantity to calculate. Lumber yards sometimes sell lumber by the linear foot which
makes it easy to calculate the cost per piece.
Linear feet = number of items X the item length
220- 2 x 4's lumber X 16 feet in length = 3520 linear feet
Lumber is one of the main items that might be bought by the linear foot for a foundation. If you dig footings, labor might be
charged by the linear foot.
Board Feet will add two other dimensions to calculating the cost of materials. Lumber suppliers sometimes sell their lumber
per thousand board feet. A board foot is one linear foot of lumber - one foot wide - one inch thick. A 1x12 piece of pine which
is 12 feet long will equal 12 board/feet. In the same way a 2x6 piece of pine 12 feet long will equal 12 board/feet.
Board feet = Linear feet X ((thickness inches X width inches) / 12 inches)
(3520 linear feet of 2x4) X ((2-inches X 4 inches) / 12 inches) = 2347 Board Feet
Lumber may be sold by the board foot form the building supply. The board foot price will be expressed so much per
thousand board feet. Example: 2 x 6’s might be sold as 565.00 per M (Thousand board feet). This will equal .565 cents per
Square Feet is a simple process of multiplying the length X the width. You will need to know how many square feet there is
in the foundation in order to estimate how much vapor barrier to buy and to determine how much the termite pre-treat will
Square Feet = Length X Width
Cubic Feet adds one other dimension to square feet. This dimension is depth. Items that require you to know the amounts
of cubic feet are fill dirt and concrete. Concrete and fill dirt are both sold by the cubic yard. There is 27 cubic feet in a cubic
yard of fill dirt and concrete.
Cubic Feet = Length X Width X depth
Cubic Yard is used to determine how yards of concrete or fill dirt might be needed for the job. There is 27 cubic feet in a
cubic yard of fill dirt and concrete.
Cubic Yard = Total Cubic Feet / 27 cubic feet
Category Construction Glossary