# Estimating Reinforcements for a Concrete Hollow Block (CHB) Wall

There are many ways to estimate the quantity of reinforcements for a CHB Wall: by area method, by direct counting and by unit block. The easiest method and the one we will be discussing in this article is the area method.

#### HOW TO CALCULATE FOR QUANTITY OF STEEL BARS FOR A CHB WALL:

1. Determine the area of the wall:

2. Determine the area of your wall. The formula for a square wall is Length * Height.

Square Wall Area = Length * Height

Make sure to take into consideration the often overlooked information that will affect the area of your wall – for example, the depth of your beam or the underground foundation CHB.

3. Determine the specified vertical and horizontal reinforcement spacing:

4. You may get the specified spacings from the construction drawings or from your engineer. However, if you need an idea about the minimum and maximum spacings that can be used, you may refer to this table:

5. Get total required length of vertical and horizontal steel bars:

6. Based on the specified horizontal and vertical spacing, multiply your area with the corresponding values from the table to get the total required length of vertical and horizontal steel bars total required length of vertical and horizontal steel bars

Vertical Steel Bar Length = Wall Area * Vertical Spacing Multiplier Horizontal Steel Bar Length = Wall Area * Horizontal Spacing Multiplier

7. Get the total length of steel bars needed:

8. Add the vertical steel bar length and the horizontal steel bar length.

Total Steel Bar Length Needed = Vertical Steel Bar Length + Horizontal Steel Bar Length

9. Determine the quantity of steel bars needed to be ordered:

10. Determine the commercial length of the steel bar to be ordered and divide it with the total steel bar length to get the quantity of steel bars needed to be ordered.

Total of Steel Bars to be ordered = Total Steel Bar Length Needed / Steel Bar Commercial Length

#### SAMPLE PROBLEM

Compute for the quantity of 6 meter long steel bars needed for a wall that is 3 meters high and 5 meters with the following given specification:

Horizontal Spacing: Every 3 layers Vertical Spacing: 80cm O.C.

SOLUTION

1. Determine the area of the wall:

2. Square Wall Area = Length * Height
= 5m * 3m
= 15m2

3. Determine the specified vertical and horizontal reinforcement spacing:

4. Horizontal Spacing: Every 3 layers Vertical Spacing: 80cm O.C.

5. Get total required length of vertical and horizontal steel bars:

6. Vertical Steel Bar Length = Wall Area * Vertical Bar Spacing Multiplier
= 15m * 1.60m
= 24m2
Horizontal Steel Bar Length = Wall Area * Horizontal Spacing Multiplier
= 15m * 2.15m
= 32.25m2

7. Get the total length of steel bars needed:

8. Total Steel Bar Length Needed = Vertical Steel Bar Length + Horizontal Steel Bar Length
= 24m2 + 32.25m2
= 56.25m2

9. Determine the quantity of steel bars needed to be ordered:

10. Total of Steel Bars to be ordered = Total Steel Bar Length Needed / Steel Bar Commercial Length
= 56.252 / 6m
= 9.375 ~ 10 pcs. of 6 meter long steel bars