Interior Paint Prep

Paint prep is the cornerstone for every quality paint job because a fresh coat of paint is only as good as the surface to which it is applied. Whether you are about to paint interior woodwork, drywall, plaster, masonry, metal or anything else, some amount of preparation for painting is probably needed.


The primary objective of painting preparation is to make ready existing painted surfaces in order to improve adhesion for new paint coats. Another major objective of painting prep is to improve the appearance of a painted surface by eliminating irregularities and imperfections.


Tools for Painting – Prep

Most of the paint prep tools are relatively inexpensive, but the cost can quickly add up. Tools for painting prep include the following:

Some essential items you should consider adding to your tool box include a couple flexible putty knives, 5 in 1 tool, and caulk gun. These tools will satisfy the most basic filling and scraping requirements.

The orbital sander and the palm sander are somewhat expensive items, often costing more than sixty dollars each. Either one of these electric sanders is a great tool to own if you are starting a painting project that requires extensive sanding or if you are planning to have numerous painting projects in the future. For limited prep, sanding sponges and sandpaper sheets are probably sufficient.

Painting Prep Supplies

Paint supplies for prep include items such as cleaning products, fillers, painters caulk, sandpaper, and primers. All of these products have unique characteristics and should be used for the proper applications. For example, you would not use hard wood filler on drywall.

Painting Prep Applications

cleaning interior surfaces
prepping walls and ceilings
sanding walls and ceilings
etching with liquid sandpaper
how to repair drywall - large holes, cracks, and broken corners
how to sand wood
how to caulk woodwork
how to use wood filler
prepping interior masonry surfaces – brick and concrete walls and fireplaces
prepping interior metal surfaces – windows, brackets, and miscellaneous items

Paint Prep – Adhesion

The first part of interior paint prep is to improve adhesion for a new finish. There are a few steps to consider

Previously painted surfaces should be cleaned before sanding and painting. Contaminants, such as mildew, grease, grime, wax, smoke, and soot can act as a barrier, preventing a new coat of paint from adhering to the existing paint. Mildew can also cause a new coat of paint to deteriorate over time. Kitchens, bathrooms, and areas adjacent to chimneys include surfaces that usually require special attention during the prep stage.

Sanding improves adhesion by breaking down existing painted finishes and making them more porous. This is especially important when painting over smooth, hard, and glossy surfaces

Liquid etching products for previously painted surfaces are generally referred to as de-glossers or liquid sandpaper. These products are a liquid substitute for sandpaper in so far as they break down a hard enamel finish, making it more porous. VOC content may limit availability of this type of product in some areas.

It is often advantageous to paint a primer coat before applying finish coats of paint. Because many different paints are not compatible with one another, a primer coat serves as a barrier coat helping to guarantee adhesion. One good example is to prime existing oil base paint before applying a new coat of water base paint.

Paint Prep – Appearance

Another important objective of interior paint prep is to improve the overall appearance of the surface to be painted. There are a few steps involved.

Some amount of filling, patching, and caulking is usually needed. The normal wear and tear that occurs from living in a house takes its toll on interior walls, ceilings, and woodwork. Walls often have many small holes from picture hangers and thumb tacks, as well as gouges from moving furniture. Moldings, such as door casings and baseboards, tend to take a beating from vacuum cleaners and furniture moving. Older moldings sometimes require extensive filling.

Years of paint build up can result in uneven paint. Sanding helps smooth out heavy brush marks and eliminate unsightly blemishes, such as paint runs. Sanding also removes any excess spackling paste or fillers left behind.

Spot priming stains such as those caused by water and ink will prevent bleeding through a new coat of paint. Spot priming over sanded fill spots will also prevent telegraphing through a new coat of paint. It is a good idea to apply a complete coat of primer when the existing paint requires excessive painting prep.

Interior Painting Tips for Paint Prep

  • Lightweight spackle is non-shrink filler that performs well for small holes in drywall.
  • Polyester wood filler is catalyzed filler that performs well for repairing woodwork.
  • Spot primer in an aerosol can is an easy way to prime over stains and fill spots before painting.
  • Sandpapers are graded according to coarseness. It is important to select the correct sandpaper for your painting application.

Final Thoughts

It is important to do at least a minimal amount of prep to assure that the new coats of paint properly adhere to the existing paint. Cosmetic prep such as filling imperfections in older wood trim can become very time consuming. Most painters do not put forward the effort to restore woodwork to its original appearance. If you have the time or you enjoy painting, it is a worthwhile endeavor.

Paint Prep involves sanding old paint coatings. Be sure to use a quality particle respirator to protect your lungs from the hazards of paint dust. Houses built before the mid 1970s have a high probability of having been painted with lead based paints. Make sure to observe all applicable laws and regulations regarding lead based paints.


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Professional Painting, Inc. is a full service painting company serving the San Francisco Bay Area since 1988.