How to Form and Pour a Concrete Patio

  • Building a concrete patio is not a real major project for a homeowner. With little help on pour day to move and finish the concrete, you can depending upon the size of the patio, form, and prep a patio one weekend and pour and finish it the next. If you can reach the patio with the ready-mix concrete truck the work is much easier but if you have to wheelbarrow the concrete, you need to look real hard at what is involved. We will use a ten-foot by twenty-foot patio as our example.


    That size patio four inches thick would use 2.45 cubic yards of concrete. (10 x 20 x.33 /27=2.45) You would order three yards of concrete. A real good idea is to pre-make some stepping stones forms and use whatever concrete is left over from your patio pour. Once your new patio area is cleared of any rocks, brush or other debris you must remove any topsoil or sod that remains behind. Topsoil is very unstable when wet and can cause the ground to shift and thereby crack the patio. If you are filling in an area and want to pour right away it is strongly suggested you fill in the low areas with pure gravel. Gravel does not compact like earth and will not sink when wet. If you do not plan to pour the patio until a few months pass, you can use earth as a backfill. Mother nature will help compact the earth with rain.


    If you can use a mechanical vibratory tamper, so much the better. In any case, the ground beneath the patio has to be rock solid. If the patio has square edges you can form the patio with two-by-four lumber. Since the edge face of the patio will not show, the condition of the two by fours only need to be straight to provide a nice straight edge of the concrete.


    Knots or other blemishes do not matter. Frame the patio edge and anchor the two by fours using wood stakes driven flush with the top of your form if possible. This will make screeding (leveling) of the concrete and edge finishing that much easier. If you desire a curved edge to your patio, cut some 1/4 inch plywood strips for forms as they are easily bendable.A ten-foot by twenty-foot patio can easily be poured and finished by two people. Tools you will need are, a straight edge twelve feet long, hand trowels or magnesium floats, an edging finisher tool, a center line finisher tool, and a light wide broom for finishing. Assume that you can access the patio with the concrete truck, starting at one end the driver will drop the concrete right across the formwork as you use your straight edge and trowels to push the concrete into its rough shape. A good driver can see how fast you are working and speed up or slow down the concrete placement.


    He can also place the concrete at an almost perfect four inches thick or nearly so. This saves lots of back-breaking labor pulling and shoveling the concrete into place. Once the concrete is in place some edge work can be done right away to smooth any areas that did not come out properly using the screed board. The concrete will have to sit for a short time depending on the weather and outside air temperature to get what's called an initial "set".


    You must keep a careful eye as if the concrete is set up too much it will become unworkable for finishing. As soon as a finger leaves a dent in the surface when lightly touched, use the edger tool and place a nice smooth rounded edge on the exterior of the patio. Using the center line tool creates a double edge crease, place a dividing line in the center of the twenty-foot dimension, making two ten by ten foot squares. This is done to control any cracks that may develop later.


    Using your hand trowels, gently smooth any ridges left by the edger tools. There is a magical moment when you must start using the broom to apply a broom finish. Too wet and the broom will sink, too dry and the broom will not leave brush marks. Just keep checking and you will know when to start. DO NOT leave the concrete to go eat or whatever. It is often a grave mistake that may ruin the entire job. Some words of caution. If you are pouring on a hot summer day in the sun, the concrete will dry very quickly. Make sure you have enough help to handle the concrete. Lastly, if you cannot access the patio area with the ready-mix truck use this info to help figure how many extra people you will need.


    A yard of concrete is approximately 6-7 masons wheelbarrows. Not the homeowner's little plastic barrows, but the steel deep wheel barrows used on construction sites. They will be very heavy. Uphill they are even heavier. Three yards means there will be eighteen to twenty-one trips made back and forth. You will be placing the concrete as it comes to you so you need plenty of extra hands. Tools all have to be washed after using them as well as anything that the concrete was splashed on during the work. Concrete has lime in it which will etch glass, anodized finishes, cloth, vinyl siding, and so on.


    Remove it as quickly as possible. Lastly, wear protective goggles and long-sleeved shirts if your skin is sensitive. If you wish to apply a concrete stain for color, keep foot traffic off the patio to keep it clean and apply stain at the manufactures recommended time.

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