Plastering Calculation: How To Calculate Materials Required For Plastering

In this post, You’re going to learn:

• An easy process of plastering calculation

• Calculating the quantity of mortar required for plastering

• Calculating required cement quantity

• Calculating sand volume

And,

• Getting to know the required water to prepare mortar

After showing the process, I’ll disclose a quick way to calculate the quantity of cement and sand for plastering.

So, let’s get into learning the process without further ado…

How To Calculate Plasterwork?

Either it’s a wall or ceiling, plastering calculation is really easy.

You just need to get the area of the wall or ceiling and deduct the opening (if any).

Let’s see an example with the following wall.

Suppose, you need to measure the plaster quantity for the inside face of this wall.

For that:

First, Calculate The Area Of The Wall.

The formula is,

= Length × Height

= 12’-4” × 10’-0”

= 123.33 square feet.

Next, Calculate The Area Of The Opening.

The formula is,

= Length of the opening × Height of the opening

= 3’-4” × 7’-0”

= 23.33 square feet.

Finally, Get The Quantity Of plasterwork.

And, the formula is,

= Area of the wall — Area of the opening

= 123.33 — 23.33

= 100 square feet.

This is the required plaster quantity for our desired wall surface.

To know the quantity of required cement and sand for this plastering, you first need to…

Calculate The Volume Of Mortar

To do that:

First, Decide The Thickness Of The Plaster

The general rule of plaster thickness is,

• The inner face of walls = ½”

• The outer face of walls = ¾”

• RCC surface = ½”

[NOTE: Most of the time, the thickness of plaster varies on a surface.]

But, for the sake of our calculation, let’s take it ½”.

Now, Calculate The Volume Of Mortar

And, the formula is,

= Area of the plaster × Thickness of plaster

= 100 × ½” [½” = 0.04 feet]

= 4 cubic feet.

This is the exact quantity of mortar for our desired plasterwork.

With that, let’s…

Calculate The Required Bags Of Cement…

… needed for our plastering.

For that:

First, Calculate The Dry Volume Of Mortar.

The required mortar volume for our plasterwork is 4 cubic feet (We calculated this above).

But that is the wet volume of mortar.

We need to calculate the dry volume of that to get the cement quantity.

And, the dry volume is,

= 4 × 1.33

= 5.32 cubic feet.

Read More: Dry Volume Of Cement Mortar: Everything You Need To Know

Next, Calculate The Volume Of Cement In The Mortar

The formula is,

= (Dry volume of mortar ÷ Sum of ratio) × Cement ratio

= (5.32 ÷ 5) × 1

= 1.06 cubic feet.

[NOTE: The common cement-sand ratio for plastering mortar is 1:4 or 1:6. I used 1:4 cement-sand ratio for the sake of our calculation]

Now, Convert Cement Volume Into Bags.

The formula is,

= Volume of the required cement ÷ Volume of one bag cement.

= 1.06 ÷ 1.25 (One bag cement is equal to 1.25 cubic feet)

= 0.85 bag.

With this, you can now easily…

Calculate The Required Sand Quantity For The Plastering…

…Applying the formula below:

The sand quantity is,

= Required bags of cement × Volume of one bag cement × sand ratio

= 0.85 × 1.25 × 4

= 4.25 cubic feet.

You can also use this alternate formula:

= (Dry volume of mortar ÷ Sum of ratio) × Sand ratio

= (5.32 ÷ 5) × 4

= 4.25 cubic feet.

The result will be the same!

Bonus: How To Calculate The Required Water For Mortar

Water isn’t actually material for plastering.

But we sometimes need to calculate this.

For that:

First, Convert The Required Bags Of Cement Into Kilograms.

And, the formula of calculating the weight of cement is,

= Required bags of cement × Weight of one bag cement

= 0.85 × 50 [Weight of one bag cement is 50 kilo]

= 42.50 kilograms

Now, Calculate The Required Water Quantity

And, the formula is,

Weight of water = Water-cement ratio × Weight of cement

= 0.50 × 42.50 [Let’s say, we will use a 0.50 water-cement ratio for our plastering mortar.]

= 21.25 kilograms or litres.

This is the required volume of water for our plastering mortar.

Summary:

The required materials for 100 square feet of plastering,

• Cement = 0.85 bags.

• Sand = 4.25 cubic feet.

Adding 10% wastage:

• Cement = 0.94 bags. Say, 1 bag.

• Sand = 4.67 cubic feet. Say, 5 cubic feet.

A Quick Way To Calculate Cement And Sand For Plastering

From the above calculation:

For 100 square feet plastering –

• Cement = 1 bag.

• Sand = 5 cubic feet.

So,

For one square feet plastering:

• Cement = 0.01 bag.

• Sand = 0.05 cubic feet.

Now, you can calculate materials for any quantity of plastering.

Let’s say you want to know the required materials for 1000 square feet of ½ inch thick plaster.

For that:

• Cement = 0.01 × 1000 = 10 bags

• Sand = 0.05 × 1000 = 50 cubic feet.

Conclusion:

Calculating the required materials for plastering is easy. You just need to know the exact area of plasterwork, the thickness of the plaster, and the cement-sand ratio for the mortar.

With these three things, you can calculate the required cement and sand for plastering.

And the best way to quickly calculate materials for any masonry work is to make a chart for the required materials for one unit of the masonry work and keep that in handy. So that you can easily use the chart whenever you need that.

In my case, I use a pdf version of the chart and keep that on my mobile device.

You can Download The Chart from my Free Resource Library here (Freebie#1).