# Estimating Concrete Hollow Block (CHB) Quantity

Concrete Hollow Blocks are used for a variety of purposes and are classified as load-bearing and non-load bearing blocks. Local hardware stores usually have a variety of 3 commercially-available CHBs – 4”, 6”, 8”.

#### HOW TO ESTIMATE THE QUANTITY OF CHB FOR YOUR CONCRETE WALL:

The easiest way to estimate CHB quantity is by the Area Method. A piece of standard concrete hollow block (CHB) has a surface area of 0.08 m2. In accordance to this, a one square meter area will require 12.5 pcs of CHB.

1m2 / 0.08m2 = 12.5 pcs of CHB
1. Determine your initial wall area:

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 door and window areas:

4. Determine if there are any openings in your wall – e.g. windows or doors. If there are, get the total area of the openings.

5. Get your total wall area:

6. Subtract your total openings with the initial area of your wall.

Total Wall Area = Initial Wall Area – Total Wall Opening Area
7. Multiply your total wall area by 12.5, the number of pieces needed for a 1m2 wall:

8. No. of CHB = Total Wall Area * 12.5

#### SAMPLE PROBLEM 1

Compute for the quantity of 4” concrete hollow blocks (CHB) needed for a wall that is 3 meters high and 2 meters long.

SOLUTION

1. Determine your initial wall area:

2. Square Wall Area = Length * Height
= 2m * 3m
= 6m2

3. Determine door and window areas:

4. There are no specified doors or windows.

5. Get your total wall area:

6. Total Wall Area = Initial Wall Area – Total Wall Opening Area
= 6m2 – 0m2
= 6m2

7. Multiply your total wall area by 12.5, the number of pieces needed for a 1m2 wall:

8. No. of CHB = 6m2 * 12.5
= 75 pcs. of CHB

#### SAMPLE PROBLEM 2

Compute for the quantity of 8” concrete hollow blocks (CHB) needed for a wall that is 3 meters high and 5 meters long with a door that is 2.1 meter high and 0.6 meter wide and a window that is 0.6 meter wide and 1 meter high.

SOLUTION

1. Determine your initial wall area:

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

3. Determine door and window areas:

4. Door Area = 2.1m * 0.6m
= 1.26m2

Window Area = 1m * 0.6m
= 0.6m2

Total Opening Area = 1.26m2 + 0.6m2
= 1.86m2

5. Get your total wall area:

6. Total Wall Area = Initial Wall Area – Total Wall Opening Area
= 15m2 – 1.86m2
= 13.14m2

7. Multiply your total wall area by 12.5, the number of pieces needed for a 1m2 wall:

8. No. of CHB = 13.14m2 * 12.5
= 164.25 pcs of CHB
~ 165 pcs. of CHB

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