# How to Estimate Painting for Walls, Roofs, and Wood Surfaces

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Ray is a licensed engineer in the Philippines. He loves to write about mathematics and civil engineering.

## Introduction About Paint Estimations

Before coating your walls, ceiling, doors, and windows, it is critical to identify the appropriate volume of gallons to apply first. Paint estimation is quite easy. Calculations here for estimating a paint are easy to follow and understand. You have to consider the type of paint to use and the typical coverage area per gallon. There are also other values obtained aside from topcoat and primer coat. Tutorials about getting the amount of neutralizer, quick-drying enamel, and paint thinner are also available here. There are three problems provided to help you understand how to estimate painting works.

## Problem 1: Painting for Concrete Firewalls

A concrete firewall of a residential building measures 20.00 meters long and 9.00 meters high. Solve for the number of gallons required using neutralizer, Acrylic Concrete Sealer Primer, and Acrylic Latex Paint if the concrete firewall is:

a. Wooden Finished (Coarse to Rough Surface)

b. Paper Finished (Fine to Coarse Surface)

c. Smooth to Fine Surface Finish

Note: Acrylic Latex Paint is for interior and exterior masonry surfaces. Acrylic Latex Paint's drying time is 30 minutes. Perform recoating after 6 hours.

Table 1: Simplified Estimate for Three Categories of Surface Texture

Surface TextureSquare meters (Coverage Area)

Coarse to rough surface

30

Fine to coarse surface

35

Smooth to Fine surface

40

### A. Solving for the Coarse to Rough Surface

1. Solve for the whole area of the concrete firewall.

Area = 9.00 m. x 20.00 m.

Area = 180.00 m2

2. Use 30.00 square meter coverage area of neutralizer for a course to rough surfaces. Divide the total area by the coverage area per gallon of neutralizer.

180.00 m2 / 30.00 m2 = 6.00 gallons

3. Solve for the number of quarts of neutralizer. Neutralizers are necessary since it improves paint adhesion. Neutralizers are mixed with water to function well. Say, you will use 2.5 gallons of water. One quart of neutralizer mixed with 2.5 gallons of water. Divide the number of gallons by the gallons of water to use.

6.00 gallons / 2.50 gallons of water = 2.40 quarts of neutralizer

4. Solve for the Acrylic Concrete Sealer as the primer. According to Table 1, 30.00 square meters is the coverage area for a course to rough surfaces. Divide the total area by the coverage area.

180.00 m2 / 30.00 m2 = 6.00 gallons of Acrylic Concrete Sealer Primer

5. Solve for the Acrylic Latex Paint as the final coating. According to Table 1, 30.00 square meters is the coverage area for a course to rough surfaces. Divide the total area by the coverage area.

Scroll to Continue

180.00 m2 / 30.00 m2 = 6.00 gallons of Acrylic Latex Paint

Summary of Quantities

2.40 quarts of neutralizer mixed with 2.50 gallons of water

6.00 gallons of Acrylic Concrete Sealer Primer

6.00 gallons of Acrylic Latex Paint

### B. Solving for the Fine to Coarse Surface

1. Solve for the whole area of the concrete firewall.

Area = 9.00 m. x 20.00 m.

Area = 180.00 m2

2. Use 35.00 square meter coverage area of neutralizer for a fine to coarse surfaces. Divide the total area by the coverage area per gallon of neutralizer.

180.00 m2 / 35.00 m2 = 5.20 gallons

3. Solve for the number of quarts of neutralizer. Neutralizers are necessary since it improves paint adhesion. Neutralizers are mixed with water to function well. Say, you will use 2.5 gallons of water. One quart of neutralizer mixed with 2.5 gallons of water. Divide the number of gallons by the gallons of water to use.

5.20 gallons / 2.50 gallons of water = 2.10 quarts of neutralizer

4. Solve for the Acrylic Concrete Sealer as the primer. According to Table 1, 35.00 square meters is the coverage area for a fine to coarse surfaces. Divide the total area by the coverage area.

180.00 m2 / 35.00 m2 = 5.20 gallons of Acrylic Concrete Sealer Primer

5. Solve for the Acrylic Latex Paint as the final coating. According to Table 1, 30.00 square meters is the coverage area for a fine to coarse surfaces. Divide the total area by the coverage area.

180.00 m2 / 35.00 m2 = 5.20 gallons of Acrylic Latex Paint

Summary of Quantities

2.10 quarts of neutralizer mixed with 2.50 gallons of water

5.20 gallons of Acrylic Concrete Sealer Primer

5.20 gallons of Acrylic Latex Paint

### C. Solving for the Smooth to Fine Surface

1. Solve for the whole area of the concrete firewall.

Area = 9.00 m. x 20.00 m.

Area = 180.00 m2

2. Use 40.00 square meter coverage area of neutralizer for smooth to delicate surfaces. Divide the total area by the coverage area per gallon of neutralizer.

180.00 m2 / 40.00 m2 = 4.50 gallons

3. Solve for the number of quarts of neutralizer. Neutralizers are essential since it enhances paint adhesion. Neutralizers are mixed with water to function well. Say, you will use 2.5 gallons of water. One quart of neutralizer mixed with 2.5 gallons of water. Divide the number of gallons by the gallons of water to use.

4.50 gallons / 2.50 gallons of water = 1.80 quarts of neutralizer

4. Solve for the Acrylic Concrete Sealer as the primer. According to Table 1, 40.00 square meters is the coverage area for a smooth to light surfaces. Divide the total area by the coverage area.

180.00 m2 / 40.00 m2 = 4.50 gallons of Acrylic Concrete Sealer Primer

5. Solve for the Acrylic Latex Paint as the final coating. According to Table 1, 40.00 square meters is the coverage area for a smooth to light surfaces. Divide the total area by the coverage area.

180.00 m2 / 40.00 m2 = 4.50 gallons of Acrylic Latex Paint

### Summary of Quantities

1.80 quarts of neutralizer mixed with 2.50 gallons of water

4.50 gallons of Acrylic Concrete Sealer Primer

4.50 gallons of Acrylic Latex Paint

## Problem 2: Painting for Roof and Plywood Ceiling

A residential house with general dimensions of 5.00 meters wide and 8.00 meters long requires painting of the roof and plywood ceiling. Below are the specifications for the paint:

Acrylic Roof Shield Paint: 2 coatings

Quick Drying Enamel for Ceiling: 2 layers

Prepare an estimate for the following painting materials:

a. Acrylic Roof Shield Paint

b. Wood Primer for Ceiling

c. Quick Drying Enamel for Ceiling

d. Paint Thinner

Table 2: Simplified Estimate for Coverage Area of Roof Paint

Square Meter (Coverage Area)

Acrylic Roof Shield Paint

40 - 50

Portland Cement Paint

30 - 40

Davies Roof Paint

30 - 40

Table 3: Simplified Estimate for Coverage Area of Wood Primer

Square Meters (Coverage Area)

Interior Primer and Sealer

25 - 30

Exterior Wood Primer

30 - 40

Table 4: Simplified Estimate for Coverage Area of Quick Drying Enamel

Square Meters (Coverage Area)

Quick Drying Enamel

30 - 40

Interior Semi-Gloss Enamel

25 - 30

Flat Wall Enamel

40 - 50

### A. Solving for Roof Paint

1. Solve the total inclined area of the roof. The sloping roof length is 6.00 meters.

Area = (6.00 m. + 6.00 m.) x 40.00 m.

Area = 480.00 m2

2. According to Table 2 above, 40.00 to 50.00 square meters is the coverage area for Acrylic Roof Shield Paint. In this case, use 45.00 square meters coverage area.

480.00 m2 / 45.00 m2 = 10.70 gallons = 11.00 gallons

3. The plans specify to use two coatings for Roof Shield Paint. Multiply by 2.00 the obtained from step 2.

11.00 gallons x 2 coatings = 22.00 gallons

4. In this case, there is no required paint thinner.

Thus, use 22.00 gallons of Acrylic Roof Shield Paint.

### B. Solving for Wood Primer for the Ceiling

1. Solve for the total area of the plywood ceiling including the eaves of the roof.

Area = 9.00 m. x 40.00 m.

Area = 360.00 m2

2. According to Table 3 above, the coverage area per gallon of wood primer is 30.00 to 40.00 square meters. Use 35.00 square meters for wood primer.

360.00 m2 / 35.00 m2 = 10.30 gallons of wood primer

Thus, use 10.30 gallons of wood primer for the ceiling.

### C. Solving for Quick Drying Paint for the Ceiling

1. Solve for the total area of the plywood ceiling including the eaves of the roof.

Area = 9.00 m. x 40.00 m.

Area = 360.00 m2

2.. According to Table 4 above, the coverage area per gallon of quick-drying enamel is 30.00 to 40.00 square meters. Use 35.00 square meters for wood primer.

360.00 m2 / 35.00 m2 = 10.30 gallons of quick-drying enamel

Thus, use 10.30 gallons of quick-drying enamel for the ceiling.

### D. Solving for Paint Thinner for the Ceiling

1. Add the number of gallons obtained for wood primer and quick-drying enamel.

Total = 10.30 gallons + 10.30 gallons

Total = 20.60 gallons

2. Multiply the total number of gallons at an average 1/2 liter per gallon of paint.

20.60 gallons x 0.50 = 10.30 liters or 3 gallons of paint thinner

Thus, use 3.00 gallons of paint thinner for the ceiling.

### Summary of Quantities

22.00 gallons of Acrylic Roof Shield Paint

10.30 gallons of Wood Primer for the Ceiling

10.30 gallons of Quick Drying Enamel for the Ceiling

3.00 gallons of Paint Thinner for Ceiling

## Problem 3: Painting for Masonry and Wood Surfaces

Determine the amount of primer coat and topcoat required given the following specifications.

Area of masonry surfaces: 800.00 square meters

Primer coat: 1 coating with 35.00 m2 coverage area per gallon

Topcoat: 1 layer with 40.00 m2 coverage area per gallon

Area of wood surfaces: 950.00 square meters

Primer coat: 1 coating with 30.00 m2 coverage area per gallon

Topcoat: 1 layer with 35.00 m2 coverage area per gallon

### A. The Solution for Paints Required for Masonry Surfaces

1. Given the area of the surface, solve for the number of gallons of the primer coat.

800.00 m2 / 35.00 m2 = 22.90 gallons of primer coat

2. Given the area of the surface, solve for the number of gallons of the topcoat.

800.00 m2 / 40.00 m2 = 20 gallons of topcoat

Thus, use 23 gallons of the primer coat and 20 gallons of topcoat for the masonry surface.

### B. The Solution for Paints Required for Wood Surfaces

1. Given the area of the surface, solve for the number of gallons of the primer coat.

950.00 m2 / 30.00 m2 = 32 gallons of primer coat

2. Given the area of the surface, solve for the number of gallons of the topcoat.

950.00 m2 / 35.00 m2 = 28 gallons of topcoat

Thus, use 32 gallons of the primer coat and 28 gallons of topcoat for the wood surface.

## Other Costs Estimations

Ray (author) from Philippines on July 14, 2018:

You are very welcome, Ma'am Peggy Woods. It is frustrating when the gallons of paint you prepared is inadequate. These mathematical calculations will be very helpful once you re-paint your house or any surface. Thanks for stopping by. Have a great day!

Peggy Woods from Houston, Texas on July 14, 2018:

I used to be very good at estimating the amount of paint needed to paint interior rooms of our home since I have done much of that through the years. When we lived in Wisconsin my husband and I painted the exterior of our home several times. We learned the hard way that the cheapest paint is not always the best. Once would probably have been enough given the time we spent there had we paid for more expensive paint the first time. Thanks for your calculations of how much paint is needed to complete a job. This should be very helpful to many people taking on such a project.

Ray (author) from Philippines on June 26, 2018:

Hi, FlourishAnyway. It is hard to estimate the gallons of paint to use without mathematical calculations. Hope they could use this guide next time they decided to paint any area of their house. It is very easy to understand. Thank you!

FlourishAnyway from USA on June 26, 2018:

A friend of mine painted their dining room bright red. They got to the very last (large) wall and ran out of paint. Ouch. They could have used something like this.

Ray (author) from Philippines on June 22, 2018:

I hope he uses this guide in the future. Thanks, peachy!

peachy from Home Sweet Home on June 16, 2018:

I must hand over this hub to my hubby, he paints the wall.