How to Determine Bricks, Cement, Sand and Water Needed to Build a Wall

1. Introduction

2. Step 1: Calculate the Number of Bricks Needed

3. Step 2: Determine the Volume of Mortar Needed

4. Step 3: Calculate the Dry Volume for Mixing Mortar

5. Step 4: Calculate the Volume of Cement Needed

6. Step 5: Calculate the Volume of Sand Needed

7. Step 6: Work Out How Much Water You’ll Need

8. Summary of Materials for the Wall

Core concept or idea

In this post, you are going to learn how to calculate the quantity of materials for building masonry walls.

The major materials required to build a wall are bricks, cement, sand and water.

Considering a wall of 12m long and 3m high built with bricks,

How to calculate exactly the quantity of each:

1. Calculate the Number of Bricks Needed

You need to calculate the number of bricks by using the formula: bricks = Volume of the wall ÷ Volume of one brick with mortar

Let's consider a standard stretcher bond brick wall that is 12 metres long and 3 metres high. If the bricks are 230 mm (length), 160 mm (width), and 70 mm (height)

Volume of the wall = L X W X H

Volume of the wall = 12m X 0.23m X 3m

Volume of the wall = 8.28 cubic metres

The volume of the wall comes out to 8.28 cubic metres.

When calculating the volume of one brick, we also have to include the mortar thickness, which we'll assume is 15 mm.

For one brick, the volume with mortar is 0.003332 cubic metres, while the volume without mortar is 0.002576 cubic metres. Using this method, you'll need 2,485 bricks to build a wall that is 12 m long and 3 m high.

Step 2: Determine the Volume of Mortar Needed

Now, you need to figure out how much mortar is required.

The formula is: Volume of mortar needed = Volume of brick (with mortar) - Volume of brick (without mortar)

For each brick, this difference is 0.000756 cubic metres.

Since you need 2,485 bricks, the total volume of mortar required is 1.87866 cubic metres. If you're buying pre-mixed mortar, this is the figure you'll use.

If you're mixing it yourself, move on to the next step.

Step 3: Calculate the Dry Volume for Mixing Mortar When you're mixing mortar yourself, you buy cement, sand, and water separately.

So instead of using the wet volume, you’ll need to convert it into dry volume.

Dry volume of mortar = wet volume × 1.33 (this accounts for drying shrinkage)

Dry volume of mortar = 1.87866 × 1.33 For this project, you'll need 2.4986178 cubic metres of dry mix.

Step 4: Calculate the Volume of Cement Needed

Now that we have the dry volume of mortar, we can break it down into the separate materials.

First, let’s figure out how much cement you need.

We’re assuming a mortar mix ratio of 1:4, meaning one part cement to four parts sand.

So, the total ratio is 5. Volume of cement = dry volume × (1 ÷ 5) Volume of cement = 2.4986178/5

In this case, the total volume of cement required is 0.49972356 cubic metres.

Now, you don’t purchase cement in terms of volume but weight.

To calculate weight, we multiply by the density of cement, which is 1,440 kg per cubic metre.

Total weight of cement = 1,440 x 0.49972356 = 719.6019264 kg

That gives us a weight of 719.6019264 kg of cement.

Since one bag of cement typically weighs 50 kg, 719.6019264 kg/14.392038528 = 15, you'll need 15 bags of cement for this wall.

Step 5: Calculate the Volume of Sand Needed

For the sand, we’ll use a similar process as with the cement, but remember we’re using 4 parts of sand in our 1:4 ratio mixture.

Volume of sand = dry volume × (4 ÷ 5)

Volume of sand = 2.5 cubic metres

After the calculation, you’ll need approximately 2 cubic metres of sand.

Again, let’s convert this into weight.

Sand has a density of about 1,600 kg per cubic metre. 2.5 x 1,600 = 4,000 kg So, the weight of sand you’ll need is around 4,000 kg.

Step 6: Work Out How Much Water You’ll Need

The final material is water.

The general rule is to use 20% of the weight of the dry materials (cement and sand combined).

Weight of cement + weight of sand = 720 kg + 4,000 kg 20% of this total weight (4720) = 944 litres

Summary of Materials for a 12m x 3m Wall To put it all together, here’s a quick summary of what you’ll need: Bricks: 2,485 bricks Cement: 15 bags Sand: 2.5 cubic metres Water: 944 litres