Before starting your project, it is important to properly plan & prepare. Here are some tips to help you get ready for your project:
For common household projects – driveways, walkways and patios – 4 inches thick should do the trick. You may require a thicker pour should the area see large amounts of traffic.
In the general Portland area we recommend using a ¾ minus crushed gravel compacted base.
Industry standard calls for a slope of ¼ inch per foot away from structures. Some projects may be able to use ⅛ inch slope.
While taking care to only dig as deep as necessary (keeping an eye out for power lines), ensure you remove tree roots, leaves, wood and any other organic matter in the desired area.
To ensure your slab does not settle or vary in thickness, make sure to compact the soil/gravel base in the desired area.
Take care to stake your forms securely to the ground, while paying close attention to the slope (for proper drainage). 2x4s are perfectly adequate for use as forms, though make sure you have the desired thickness (usually 4″) available at the edges.
Install premolded joint material anywhere concrete will meet existing slabs, steps or buildings. The joint must reach the bottom of the slab and ensures the new slab will be separated from existing structures.
Concrete Exposed to freezing and thawing temperatures should have a compressive strength of 3500 psi and have at least 5% entrained air (+/- 1.5%).
For our environment we recommend a slump of 4 inches (+/- 1″). Note: a slump greater than 4″ may prolong the time you have to wait before finishing, particularly in cool weather. It will also increase the tendency for shrinkage cracking.
In addition to air entraining admixtures, chemical additives may be used to accelerate or retard setting, reduce water or plasticize the concrete.
Now that you have your planning down, we suggest you review our Concrete Calculator below to determine your exact needs