An important first step although not a structural consideration.
Make sure you or your builder have all the necessary permits and the ok from
your local building authority to actually place a permanent structure in the location
you have in mind. Make sure you are within the given lot coverage percentage,
proper front-yard, side-yard and rear-yard allowances.
2. Build on good Solid Ground. A foundation is only as
good as the ground it's sitting on. Always excavate out any organic matter,
topsoil etc and get down to undisturbed soil. If your building site has any
depth of organic type black soil then it must be dug out down to a solid layer.
If you need to raise the elevation of your structure then you need to use good gravel
as fill and compact it in 1 foot lifts to ensure a solid base.
If you are building in an area where there is an expansive clay soil problem make sure you or your builder read any soil report before deciding on a foundation type. Colorado is the State with the biggest problem but other States do have unstabe clay soil problems also. A pier and beam foundation is the best in areas of expansive soil.
Footings should always be below the frostline in colder climates and above
the water table where possible otherwise an adequate mechanical drainage system
must be installed. If in doubt about whether your ground will support your building project,
have a soil test done and a review on what size of footing is required for the particular ground.
3. Always use an appropriate sized Footing. The type of soil base you have on your site will govern the size of footing you'll need to support the foundation walls. The softer the ground the wider the footing. In a case where you have bedrock and are using cast in place concrete you can pin the foundation walls right to the rock with 5/8" steel dowels.
Not all footings need to be of concrete. In the case of a pre-cast foundation, a layer
of compacted crushed rock is used. Again, your soil conditions will govern the width
and thickness of the base. A slab foundation must also have a footing poured right
in and be sitting on a solid base of compacted gravel. Pier foundations must be sized for
the firmness of the ground and the number of piers and their spacing depends on the load of