New Concrete Foundations

Any structure, whether a house, a garage, or workshop, is only as secure as the foundation on which it rests! Typically, foundations will be of either a shallow or deep design.

A shallow design foundation will be set about three feet into the soil. A spread footing design is typical, with concrete pads extending below the frost line, and transfers load from the walls to the earth. Another type of shallow foundation used is the slab-on-grade design, which transfers load to the earth through a slab of concrete. Slabs also allow for the use of radiant heating.

A deep design foundation is generally more complex and will be used in cases when soil conditions are poor (such as a hillside for example) or the structure must be raised to prevent flooding if the structure is being built in a flood zone.

A deep foundation transfers load from the structure through a weak top soil layer down into a stronger layer. Several variations for deep foundation designs can be used and naming conventions tend to vary, but include caissons, piers, piles, drilled shafts, and earth-stabilized columns.

Footings should be approximately two feet in width, with an extra two feet on both sides so that you have plenty of work space, which means your trenches will have a total width of six feet.

Setting Footings, Installing Drainage and Waterproofing

Drainage pipes and radiant heat tubes should be placed and attached to the wire mesh before pouring your concrete slab. The slab should be pitched from the back towards the front of your garage for proper drainage.
There are some features to your garage or workshop you will not be able to add after your foundation is complete, so decide up front during the planning phase which features like a drain or radiant heating you will include in the foundation.

Slab Advantages

Some claim that termite issues may be less of a concern with this type of foundation, because of a lack of wood supports and empty spaces leading from the ground to the house itself. Keep in mind, though, that if you have wood siding extending to the slab, those critters would have easy access to your new home.
In warmer climates, temperature extremes are rare, so there may be no need for heating ductwork underneath the flooring. Ground freezing in these locations would be unlikely, thus hopefully, minimizing the chances of the slab cracking.