A concrete slab is more than just cold stone lying outside your back door. It can serve as a
walkway or carport, and concrete has served as a low maintenance base for many a porch or
patio. Here's how to make your own.
Materials
string
stakes
hammer
string level
level
2x4 lumber
nails
shovel
rake
ready-mixed concrete
wire cutters
steel wire mesh
safety gloves
safety goggles
- Determine the slope of the grade from front to back by measuring up from the ground to a fixed point, like the edge of a porch or other structure you're building next to, or a level string line between two stakes.
- Determine the slope of the grade from side to side. One way to do this is to lay a 2x4 on the ground with a level on it. Raise the lower side until it is level.
- Measure up 3-1/2" from the ground, put a nail at the mark, and run a string line to the opposite end. Use a line level on the string so the placement of the side form would be level.
- Dig out the dirt from the marked area deep enough to result in a level edge for the slab.
- Place a 2x4 in the trench, make sure it is level, and nail it to the post using two-headed nails. The nails will make it easier to remove the forms later. Be sure to wear safety glasses while hammering.
- Use the side 2x4 as a starting point to attach the back form. Use a level to create a slope for water run-off.
- Attach the third and fourth pieces of the form to the front.
- Dig out the dirt level to the bottom of the form. You want to make sure you have the proper depth all around the form for the slab.
- Next, backfill behind the form for added support. Wet concrete is very heavy and could cause the form to bow out. Fill in the low spots inside the form and rake all the debris out using a bow rake and a shovel.
- Roll out the wire mesh, wearing gloves to protect your hands.
- Measure the length of the pad and cut two pieces of the steel wire mesh to length with a helper holding on to one end of the mesh roll. Measure and cut the pieces so that when in place, they edges will be 3 inches away from the form. Use bolt cutters to cut the mesh, and place it inside the form. To eliminate the mesh curl, flip the mesh sheet over, opposite the way it was rolled up.
- Overlap each mesh sheet and join them by twisting the cut ends together. Space bricks out evenly under the mesh throughout the form. Be sure the edges of the mesh are at least 3 inches away from the form.
- To determine the number of cubic yards of concrete you need, measure and multiply the width, length and depth of the excavated area inside the form, and then divide that number by 27. Add an additional 15 percent for normal waste, the variation of the slab thickness and the slight spreading of the forms. With this information, the ready-mix company is able to determine just how much concrete the truck would deliver to your site.
If you'll be working the concrete into the form yourself, locate the cement truck chute to the farthest point of the pad. The driver will control the rate of flow as you work the concrete into the forms, overfilling the forms slightly. Wetting the tools before using them will make for an easier clean up. Using a bow rake, spread the concrete out to fill the corners and eliminate any holes or voids.
Work quickly and push the concrete into gaps, tapping the forms to help settle the concrete. Tamp the concrete to remove the air pockets to strengthen the mix and keep it workable.
Reposition the chute as the form fills. Make sure to move the chute in a sweeping motion to prevent the concrete from piling high in one spot.
When the concrete is dry...
Remove the nails from the forms and pull them away from the slab.
Clean around the perimeter, removing any debris, and then backfill around the slab to bring the dirt even with the top edge of the slab.
Note: If your concrete slab is serving as a carport, protect the front edge and make a ramp for it using wash out (an aggregate that is left over when concrete is made). Shovel the wash out from the truck to the edge of the slab and taper it away from the slab. When packed, it makes a good solid entrance for the carport.
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