Pouring a Concrete Slab:
Build a Form and Pour Cement for a Patio, Shed, Driveway, or Carport Foundation
© 2008 by Kelly Smith all rights reserved
This is the first in a DIY concrete series. It explains slab layout, digging the footing, building a
concrete form,
pouring concrete, and screeding the slab.
The first thing the homeowner should consider when building a patio, carport, outside storage shed, or
a
freestanding patio cover is the concrete slab. Pouring a concrete slab need not be difficult with the
right planning. Since this is a DIY project, the concrete slab cost is reasonable.
If the slab is to be a foundation for framing a house, it must be smooth and level.
This article in the DIY concrete slab series provides instructions for pouring a concrete slab.
The second will explain troweling and
finishing the concrete slab.
The third explains the different formulations of
premixed concrete.
Consider Electric and Plumbing Utilities
If there is any plumbing involved with the slab, consider it in the concrete slab design. The same goes
for any electrical conduit supplied to the slab.
Failure to prepare for these concerns means the concrete slab will need to be trenched and patched,
a tedious process not to be reckoned with!
Tools and Material Listg
These are the tools and materials you will need for this project:
- Hammer
Wooden stakes
- Mason's string
- 1” X 4” lumber for the concrete form
- 2” X 4” stud or aluminum screed
- Shovel
- Steel Wire Mesh for smaller projects, rebar for larger projects
- Side cutting pliers (Klein side cutting pliers
are the best)
- Tie wire
- Building code recommended vapor barrier material (if required in your area, always check first)
- 4' Level or laser level
Lay Out the Slab's Location
The initial thing is concrete slab design, the location and its size. Drive stakes at the corners and
connect the stakes with string. This is the the slab's boundary, the batter boards. Ensure that it's
square with the
3-4-5 method of squaring.
Make any adjustments needed.
Prepare the Form's Location
Dig up the grass inside the area defined by the string line. Level the dirt. Trench the footing around
the perimeter. It should be a shovel width wide and six inches in depth. The purpose of the slab's footing
is to lend strength and stability to the slab.
Some locales require that a vapor barrier be placed under on the dirt prior to pouring the slab.
Inquire with the regional building code to determine whether this needs to be done.
Steel mesh is now laid in the footing (rebar for larger projects; consult the local building code).
Wire it together with the pliers at the intersections using tie wire. Using the mesh is analogous to
using rebar in road construction. It strengthens the footing where the pressure is greatest.
Building the Concrete Form
The concrete slab needs a form to keep the concrete in place during the drying and finishing process.
The 1” X 4” boards form the form's sides. The string line ensures the form is square.
Nail the form together for stability purposes. Drive the stakes in every sixteen inches outside the
form and contacting the 1” X 4” boards. This contains the pressure of the wet concrete and keeps the sides
of the slab straight and true.
It's important to keep the slab level in all directions. Adjust the sides of the form to get
this right. Nail the stakes to the sides of the form securely.
Pouring the Concrete into the Form
Home improvement outlets and tool rental facilities rent out portable cement mixers. This is the way
to go for any patio or small shed project.
Once you get to something the size of a carport slab, it’s time to think about calling in a concrete
mixer truck.
Position the cement mixer's chute to pour the
concrete into one end of the form. Begin the pouring and use the shovel to push the concrete and work it
into all areas.
Screeding the Concrete Form
After filling the form, level it with the edge of the 2” X 4” or the aluminum screed tool.
Push and pull it in a sawing motion
across the form's top starting at one end and working down to the other end. This process is called the
”screed”.
The next article in the do it yourself concrete slab series explains
finishing the slab. It
revisits the screed and goes on to explain the darby, edging and grooving, and floating and troweling
the concrete slab.
After finishing the slab, stay off of it for a couple of days with anything heavy, and at least
five days for a driveway.
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