As any general contractor knows, a concrete basement floor must be level, and it must be poured in sections to prevent cracking. If you are building a new house and plan to pour your first basement, you will need a good set of instructions such as those below.
Step 1 - Place Plumbing Stubs
Before pouring concrete, lay plumbing stubs that can be used in the future for sewer drainage. Be sure to cover their openings to keep debris out of them.
Step 2 - Cover Your Dirt Floor with Sand
Cover your dirt floor with 3-inches or more of sand. It is the best insurance you can use to give your concrete floor a base that is compact and less likely to crack.
Step 3 - Install Rebar
Reinforce your concrete by placing rebar and rebar chairs. Space the bars at least two feet apart. Place chairs beneath them where the bars intersect. Doing so will place your rebar in the center of the pour where it will give you the greatest reinforcement.
Step 4 - Mark Your Proposed Floor Surface
For greater assurance that your basement floors will be level, place a mark on the wall that indicates where the poured top surface should be after you have poured the floors. There are two ways to accurately determine these level marks. The first way is to measure down from the top to a point 3.5-inches above your compacted sand. That is where you mark should make your mark on the wall. The second and most accurate way is to use a laser level.
Step 5 - Install a Screed Guide
To give yourself an accurate and level guide to use when you screed your freshly poured concrete, make a screed guide. Use a piece of 2x4-inch lumber, about the same width as the wall where you'll be pouring your concrete.
To mark where the top edge of this guide should be, place a mark 5.5-inches above the floor surface mark you made earlier. Use concrete nails to fasten this board to the wall with its top edge at the mark you just made.
Step 6 - Make a Screed
Make your screed from a 2x6-inch board that is 12-inches longer than the width of your poured floor. Attach the screed vibrator to the middle of the screed you've just made, then run its cord to the open side of your pour.
Step 7 - Make a Screed Cleat
Make a 2-foot cleat from a 1x2-inch board. Fasten it to the screed top, leaving an overhang of 2-inches. You'll use this cleat to level the concrete.
Step 8 - Set Up a Second Screed Support
Create a second support for your screed at the far side of the screed, the top of which will be the same level as your poured floor surface. When finished, you are now ready to pour your concrete.