garage floors

To withstand the weight of cars and small trucks, a garage floor slab should be at least 4 inches thick. It should be strengthened with reinforcing wire mesh and be poured on top of at least 4 inches of solidly tamped gravel or sand.
A footing running around the perimeter of the slab adds extra support for the garage walls. It can be shallow if there is no significant frost danger in your area or if local building codes permit a "floating" slab--one that can rise or fall an inch or so with frost heave. Otherwise, the footing should extend below the frost line. Anchor bolts in the footing allow you to firmly attach the bottom plate of the wall framing. To handle condensation, blown-in rain or snow, and moisture from vehicles, the slab should slope toward the floor drain or garage door at a rate of 1/4 inch per foot.

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footings

Before building a masonry wall, you must pour a solid footing or the wall will crack. (The exception is a dry stone wall, which has no mortar joints.) How extensive the footing is depends on how much weight it will carry. For a low garden wall you need only a small pad. A tall masonry or concrete wall, however, requires a substantial footing that extends below the frost line.

To support posts for a deck, gazebo, or similar project, you need to set post footings below the frost line in areas with frost or your structure will move up and down with the changing seasons. Simply dig holes and pour in the concrete footings. Or, insert cylindrical concrete tube forms into the holes before pouring the concrete.

If you want to lay a patio of bricks, concrete pavers, or tiles that are 3/4 inch or more thick, the most common way is to set them in a bed of sand that rests on a stable surface. If your soil is stable, 2 to 4 inches of sand alone may be enough of a base. But to be sure that your patio does not develop waves and splits, excavate deeper and start with a bed of gravel. Either way, it is important to thoroughly tamp down both the soil and the substrate, using a vibrating tamper, which you can rent. Once the sand is level, install the finish material and fill in the joints between the bricks or pavers with fine sand (see Laying Brick Patios in Sand, Related Projects).

Other techniques can be used for patio construction. You can set tiles designed for outdoor use in mortar on a solid concrete base or set flagstone directly on firmly tamped soil (see Laying Flagstone Surfaces, Related Projects).

To hold back the weight of soil, a wall built below grade must be strong. But even the strongest wall cannot withstand the hydraulic pressure that builds up behind it when soil becomes saturated with rainwater. So, in addition to being built solidly, the wall must have a way for water to escape. Weep holes, small in diameter and spaced 4 to 10 feet apart, allow water to come through the wall. Or, in the case of a foundation wall, you can direct water to one or both sides of a wall. The most common way to do this is with perforated drainpipe set in a bed of gravel and sloped slightly.

A landscaping retaining wall commonly is battered, that is, sloped toward the soil it retains. This gives the wall strength. Structural walls cannot be battered, so build them strong, with plenty of reinforcement.