How to Calculate Needed Paint and Prepare the Wall?

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We have prepared a step by step guide to help you calculate the amount of paint needed for your project.

How to calculate the amount of needed paint?

Step 1: define surfaces to paint

Define which surfaces you plan to paint. Do you want to just paint the walls or also the ceiling?

Step 2: measure height and width

With a measuring tape measure the width and the height of each wall. To calculate the area of each wall, multiply the width by the height for each surface. If there are many doors and windows, subtract the area they occupy.

If there are not that many doors or windows, don’t worry about it. For the ceiling, do the same area calculation by multiplying its length by its width. For example, if a wall is 3.50m wide and 2.50m high (ceiling height), it has an area of ​​8.75 m².

Step 3: how many coats

Add all the areas that you have calculated and divide this new total square meter measurement by the number of coats you will need. For example, if the sum of the wall areas gave 40 m², then, divided by two coats gives 20 m².

A general recommendation is to consider, at least, two coats. Think that the higher the quality of the paint you will use, the fewer coats you will need. Cheaper paint does not always mean savings.

Step 4: what type of paint

Calculating the needed amount of paint is then just dividing the total from Step 3 by the number of m² / liter the paint yields. Each paint can should have this information in the description on the can. And you can also check it on the manufacturer’s site. Or you can also use an estimate, usually, each liter of standard paint is enough to paint around 5 m².

There are Economic, Standard, and Premium inks, they have differences in their yields, price, and quality. This is a subject for another post (to be linked shortly).

Step 5: final calculations

Now that you know how much you will need for your project, you can easily tell if you need 3.5 liters or 18 liters, for example. The yield information, as we talked about, comes on each package. To get a rough idea, a gallon of 3.6 liters can paint around 18 m².

Considering two coats, this then gives 9 m² of surface that you will be able to paint with one 3.6-liter gallon. One 18-liter gallon will paint around 90 m². If you are going to do two coats, this comes to 45 m² of the final painted surface.

Did you find the walkthrough difficult? There are virtual paint calculators that can help. Just search the Internet for “virtual paint calculator”.

And don’t forget to prepare the wall well before painting. Let’s be renovative!

Read also: How to paint a perfect wall? – in this article. And, How not to paint? – in this article.

How to prepare a wall for painting?

Preparing the wall surface well for the painting is fundamental for you to have the best final result and prevent problems afterward.

Begin by observing how the wall currently is. See if the surface is dirty, if it has molds, if there is paint peeling, or if it has cracks or holes.

Initial preparation of the surface

Even if the wall looks great (no dirt, no stains, no cracks, no holes, no peeling paint), there is still a basic way to prepare to paint the wall. Wash and dry the surface and then sand the wall (sanding paper # 36). Remove the dust with a broom and a damp cloth.

Your painter should also wash, dry and sand the wall too, before painting. This is a basic preparation and needs to be done. Otherwise, the paint may peel afterward.

If the wall has stains or grease, it should be washed with mild soap and water.

If the wall is moldy, wash it with bleach and leave it on for one hour before rinsing. Wait for the wall to dry before applying paint.

If you have paint peeling from the wall, whether it is the paint itself, or wallpaper, this wall should be well sanded or even scraped with a spatula if the surface is too uneven.

Using spackling paste

Only after the initial preparation is done, it is the right time to begin to use spackling to correct wall irregularities and to cover small holes (like the nail holes, for example). Use PVA spackling paste for indoor environments and acrylic spackling paste for outdoor or wet areas (bathroom, kitchen, laundry).

If the imperfections are too deep, apply filling grout to start with. Allow the repaired part of the wall to dry before using the spackling paste. And if the holes are really large, the affected part of the wall should be first repaired prior to applying any paint, grout or spackling paste.

The spackling should be allowed to dry and then wall preparation needs to be done. And only after that, you can start your painting job. This preparation will assure that the newly painted wall makes you happy for a long time.

Preparing a new wall

If the wall has just been constructed, the surface needs to dry for around 28 days prior to any painting preparation. It is recommended to use a sealant on the wall prior to applying the plaster mass. This serves to fill very porous surfaces because it penetrates and expands leaving the surface more uniform. Such a surface is able to better receive paint and gives a better yield to it.

Using plaster mass

You can also use a repairing background (plaster mass) before applying new painting. It fixes the imperfections and improves the adhesion of the new paint.

Preparing a brick wall

If you plan to paint a brick wall, for the bricks to remain visible, obviously you will not be able to apply either plaster or mass. Still, a brick wall should be waterproofed. After this is done, you can paint it.

Problems on the wall? Paint does not help.

If there are cracks, mold or leakage on the wall, do not paint. Fix the problems first. Painting alone does not solve these problems. It will make them worse, as you will have to redo the work, once these problems start to re-appear after the painting is done.

Painting does not solve cracks or leakage

If the intention is to paint to resolve crack, leakage or leakage stains, it is time to change your mind before you will have wasted your time. Spend time to repair these wall problems first.

Painting these problems over will not solve them. It will mask these problems for some time. Then they will start to re-appear. In the meantime, you may get a false idea that everything worked out well. Your improvisation was worth it and you had this great idea in disguise.

Let’s take a look at what must be done before painting:

Repairing wall cracks

If the wall has cracks, there could be different types. In case these cracks are inclined (diagonal), this may indicate problems in the building structure, which may be showing further problems in the foundation. Call a qualified engineer or civil service in your city to help you evaluate the problem and then make a conclusion of what needs to be done.

If the cracks are narrow and vertical or horizontal, see if these cracks become wider or not with time. Such cracks may have appeared when different materials get in contact within the wall. This could be concrete of beams and pillars, ceramic or cement blocks, wood, etc. If those cracks are rather simple and not large, a painter will fill them with plaster mass and then paint them over.

Repairing leakage or leaked spots

If the wall has leaks and infiltrations, call the plumber for repair them first. Only after this work is done, a painter will be able to take action. It will be necessary to:

  • first, locate where there is water in the wall,
  • then, open to find the source of this leakage,
  • after that, see if it did not compromise the wall structure, and
  • finally, fix the problem before closing the wall.

What spackling to use?

The irregularities and small holes in the wall should be filled with spackling mass before applying paint.

  • Use PVA is for indoor surfaces only.
  • Use acrylic mass is for outdoor or wet areas (bathroom, kitchen, laundry).
  • If the imperfections are too deep, apply filling grout first and wait for it to dry before using the plaster mass to preparer the wall.

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