Garage Foundation
Garage Monolithic Poured Foundation
The footer and slab is poured at the same time
Picture from the Residential Code of Ohio by the ICC (international Code Council)
Garage Slab with Thickened Perimeter
Slab with thickened perimeter can only be used for detached garages. It is considered a non-frost protected foundation due to not going below the frost line of at least 30 inches below grade. When done correctly, it is reinforced heavily with metal to handle the frost heaving between seasons. This allows the whole structure to move together without being compromised. This movement is why some people call it a “Floating Slab”. If attached to a frost-protected foundation, it has to be heated year-round with additional foundation insulation. Minimum excavation, concrete forming, and being poured monolithic makes this the most economical foundation. The restraints are excessive grade variances and pour drainage. A curb can be formed with this style to create a small retaining wall or to allow a unidirectional sloped slab.
Turned Down Slab is the same concept with all the same characteristics as the “Slab with Thicken Perimeter” except for that the footer portion goes down below the frost line making this a frost protected foundation. There is significantly more concrete due to the width of the required wall but it is poured monolithic and requires minimum backfill.
Garage Footer and Stem Wall
A Footer and Stem Wall foundation is most commonly used. A concrete pad is poured below the frost line and wider than the stem wall to spread out the load of the structure. Metal rebar is used to tie the stem wall to the footer. The wall can be poured concrete or CMU (Concrete Masonry Unit). The purpose of the wall is to protect the building materials that are more volatile to moisture by keeping them out of the dirt and transferring the load down to the footer. This is an ideal foundation and can be used to work in most all conditions with limited effect on the surrounding grade but is very laborious with multiple steps.
Picture from the Residential Code of Ohio by the ICC (international Code Council)
Picture from the Cincinnati Building Department
Post-Frame Pier
Pier foundation is most commonly used for post frame construction and decks. It consists of cylindrical columns varying in diameter depending on carrying load and soil conditions that go below the frost line. The piers are strategically placed to carry all the load of the structure. In post frame construction the interior concrete slab most commonly floats independent from the structure. This type of foundation is also very economical but is limited with excessive grade variances.