How to Build a Flat Concrete Roof

Lead Image
What You'll Need
Steel joists
Reinforcing bars
W1.7 wire
Portland cement
Concrete slabs
Work helmets
Work boots

Building a flat concrete roof requires proper planning. Before you begin the job, you will need to get proper building specifications from a professional. In addition, this is not a job that can be completed alone, so you will need a few friends to help you. Although this is a moderately challenging job, with the right building specifications and materials, you can build your own flat concrete roof with these few steps.

Step 1 – Taking Safety Precautions

Understand the gravity of the project and take the necessary safety precautions. Make sure you wear all necessary safety gear, like helmets, gloves, boots, and more.

Step 2 – Deciding on the Size

One of the most crucial step in building a flat concrete roof is to figure out the size of the concrete block you will need. The blocks come in several sizes, but this guide will assume you are using a 16 3/4 inch wide concrete slab.

Step 3 – Placing the Steel Joists

The steel joists will provide a strong foundation for the flat concrete roofing. As the width of the concrete slab is 16 3/4 inches, place the steel joists at this distance.

The bottom of the joists should rest on either a beam or a wall. This will give it the support it requires.

Step 5 – Placing the Concrete Slabs

Next, place the concrete slab on its face. The open end should face sideways. The L-shaped steel joists create a flange for the concrete slab to sit on. Place all the slabs, one row after the other.

Step 6 – Working on the Grooves

If you examine the blocks, you will find grooves on them. The general measurement of the grooves are 1/2 by 3/4 inches. You will need to place the W1.7 wire into the grooves. Bend the wire at the end of the row of concrete slabs.

Step 7 – Inserting Reinforcing Bars

Insert full-length reinforcing bars to the unit. It’s best to use the number-five variety of reinforcing bars. The bars should be inserted through the space between the joist and the slab end.

Step 8 – Preparing the Grout

A grout will hold the flat concrete roof in place. For this step, you will have to make the grout mixture.

To make a grout, you will need sand and Portland cement. Take a bucket and mix 2 1/2 parts of the sand with 1 part of cement. Add some water to get a flowing consistency.

Step 10 – Pouring the Grout

Pour the grout into the space between the rows of concrete slabs, covering the joists completely.

Step 11 – Repeating the Process

After you pour the grout, the concrete will absorb it. Moisten the top of the concrete, and then follow it up by introducing more grout. Spread it with a squeegee. The grooves should be filled with the grout to ensure the wires are properly embedded.

Step 12 – Curing

The final step in building the roof is to allow the grout to work on the concrete slabs. Let it cure completely. If you want to waterproof your concrete roof, you may do so now.