Laying Out the Job
You should sketch a scale drawing of your project including any existing structures and landscaping elements. You should also draw in your planned joints to prevent cracking. There are three types of joints you should know about:

Control joints are used to control cracking. This means sawing or tooling grooves to a depth of one-fourth the slab thickness (e.g., 1” deep for a 4” slab) at specified intervals. The intervals are determined by the type of project.
Isolation joints are used to separate existing dissimilar construction using ¼"—½" thick pre-formed joint material to the depth of the slab.
Construction joints are used where concrete work is interrupted or stopped. If you coat these joints with oil they can also work as control joints.

Layout – Walks
The width of the walk depends on whether it is a sidewalk, front walk, or service walk, and may be determined by individual preference, type of landscaping, expected traffic, building codes, or lending rules. The width of a walk has a subtle bearing on its utility as well as on the appearance of the yard, and thus deserves careful consideration. Walks are usually 4 in. thick, but should be thicker if trucks will frequently cross over them. Walks should be sloped ¼ in. to the foot for drainage.

The panels formed by control joints should be approximately square. Panels with length-to-width ratios exceeding 1½ to 1 are likely to crack. Isolation joints should be provided where the walk abuts the house, porch, driveway, steps, curbs, or other construction.

Layout – Driveways
Single-car driveways are usually 8 ft to 9 ft wide, double-car driveways about 15 ft to 18 ft wide. Drives should be wider at curves because the back wheels make a track with a smaller radius than do the front wheels. When the approach to a two-car garage is short, the entire drive is usually double width; long approaches can be single-car width and then widened near the garage to accommodate both stalls. Driveways should also be sloped ¼ in. per ft for drainage.

The thickness of a driveway for passenger cars should be 4 in. If heavier vehicles will come onto the drive regularly, a thickness of 5 in. is recommended. Transverse control joints should be spaced not more than 10 ft apart. A wide drive (12 ft or more) also requires a longitudinal control joint. Tie bars can be placed in the longitudinal joint to prevent the crack from opening wide. Suggested ties are No. 4 rebars, 36 in. long, spaced about 40 in. apart.

When a garage or carport is considerably above or below street level and is close to the street, the slope of the drive may be critical. Preferably grade should not be steeper than 14%. The grade should be changed with as gradual a curve as possible so that bumpers and undersides of cars will not scrape on the drive or sidewalk.

Additional paving for off-street parking, turnaround areas for safe head-on street entry, and perhaps paved areas for sports or games are worth considering during the planning stage.

Layout – Patios
The patio can be designed as a square, diamond, rectangle, circle, or just about any shape you would like. The outline can be adjusted to the shrubs, trees, or layout of the yard. A good rule for determining size is to make it larger than the largest room in the house. The concrete slab for a patio should be at least 4 in. thick, and control joints should be provided at maximum intervals of 10 ft each way.

Layout – Steps
Steps for houses are usually slightly wider than the walk leading to them. If you have more than five or six steps it is desirable to divide them with a landing; landings should be at least 3 ft long.

Common requirements for outdoor steps attached to a house are that the sum of the riser and tread dimensions should be 18½ in., the riser should not exceed 7½ in., and the tread should be at least 11 in. The nosing width is added to the tread width. Since people take longer strides away from the house, the rule for steps not attached to the house is that the sum of the tread plus twice the riser dimensions should be 26 in.; risers should not exceed 6 in., and treads should be at least 12 in. plus nosing.

If the steps are for terracing in the yard, no extra foundation support is required. However, if the steps connect with a supported porch or the landing is at the house door you will need to add concrete foundations to the frost line.

(Information provided by Portland Cement Association )


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