Building a concrete slab patio on your own
A well designed patio is an attractive addition to the front or back yard of your home. By using your imagination in combination with various slab sizes, you can come up with a unique design that will personally fit any home. The end result will be an enjoyable patio for barbeque, gardening, or simply relaxing outdoors.
How it works:
Concrete slab paving works because friction of tightly packed sand in the joints locks all the slabs together. In addition, the outside border material holds slabs together for the designed shape of the patio.
First measure the area you intend to pave. Measure width and length to get the total square footage. This will give you the necessary information in determining the total amount of materials needed for the job. Remember to add 5% for breakage and cutting. Drawing the particular shape, size, and design of your patio on paper first, will give you a constant reference while constructing. Then mark off the area of ground to be replaced by the patio and drive stakes in each corner to show the patio outline.
Preparing the base:
Using a flat shovel, cut evenly to remove soil from the area to be replaced by the patio. Remember to remove roots, rocks, and any obstructing materials from the working area.
The thickness of your base depends upon the soil; lowlying, wet soils need a thicker base than well drained soil. Place stakes every 4 to 6 feet and at corners. These stakes should be 4 to 6 inches outside the planned edge of the slabs.
Line the stakes up for proper sloping so draining water will flow away from the house/building. Depth of the excavation should be consistent with the designed slope. It is best for the slope grade to be at least 1/4″ per foot drop, but try not to exceed 1/2″ per foot drop.
Using a string line on top of the stakes will show the correct level of slope and will assist in the filling of base material. Better drainage will occur if patio is slightly above ground level. A 5 to 6″ base thickness is recommended for proper installation. This thickness will allow for settling. Depending on soil condition, you might have a 3″ layer of gravel followed by a 3″ layer of sand on top.
Make sure the sub-base is compacted before laying materials. In some cases, straight concrete sand can be used for the base.
Concrete sand should be the material used in patio installation. Ideally the sand should have some moisture content, but it is not critical. What is important is that the sand is consistently of the same moisture content throughout the work. It is always a good practice to cover your sand supply to ensure consistent moisture throughout.
This is always necessary. It can be either concrete garden edging, wood, metals, existing walls, or any other material which will not only confine the slabs, but also the sand they are laid on. By using a string line you can accurately follow the border lines while securing down the edge restraints.
Screeding the area:
Prior to laying the slabs, you must first smooth off the sand surface in which slabs will be laid. Using a wooden 2×4, 6 to 8 ft. in length, screed the top surface of sand. Use a side to side motion while pulling the sand forward on the surface to be worked on. Do not walk on screeded surface.
Laying concrete slabs:
Before starting, place materials and equipment to be used in an area that will not obstruct your pathway to the freshly laid slabs. Start by laying slabs from a permanent edge such as a house, driveway, or even a secured border restraint. As you are laying the slabs, work from right to left, then left to right and so on, one row of slabs at a time.
Should you find the patio slabs not aligning, stop and find the problem. By running a string line every 4 feet in front of the laid edge you can check alignment. If there are some slabs lagging behind, go back about 3 rows, and using a small pry bar, wedge between the slabs and pry forward until they are in line. After laying ech slab, place a piece of wood on the slab and successively tap the wood with a hammer or mallet in the same direction until slab positions in the sand.
Cutting concrete slabs:
It may become necessary to cut slabs into various sizes due to posts, trees, or existing structures which can cause different desired radii. This is easily dony by first marking line of the cut to be made on both faces and sides of the slab, using pencil or chalk. Now lay the slab on a mound of sand so that it is fully supported under the center, and using a hammer and masons chisel, mark a groove along the line on both sides, Use 2 or 3 moderately sharp blows from the hammer at each chisel position.
Now, deepen the groove by repeating the operation. Then turn the slab face down on the sand, and tap firmly along the cut line with the hammer. Two or three blows should be sufficient to split the slab cleanly under the cut line. If not, repeat the grooving operation. This process can also be done by using a mason saw with a masonry blade or diamond blade. After achieving desired slab shape, place slab into position and tamp to secure.
Shovel sand into piles at evenly spaced locations on top of patio slabs. Using a broom, sweep sand into the grooves or joints between the slabs until cracks are filled. Using the same tamping process as before, alternate filling sand with the tamping process. After all joints have been filled and each slab has been tamped securely, excessive sand may now be swept off the patio.
Remember that sand may settle and wash off from the first couple of rains, so have extra sand available for refilling. Alternately, you can use a joint sand stabilizer to lock the sand together on a permanent basis.