Exterior Painting Prep

Is exterior painting prep necessary? The decision to take on an exterior house painting project is usually made because the existing paint is looking weathered and worn. Conditions may vary from slight fading and loss of luster to severe peeling and paint failure.


One thing you can be sure of is that a fresh coat of paint is only as good as the surface to which it is applied. Proper painting prep is the key to a quality paint job. Good preparation will not only enhance the appearance of the paint work, but will also increase its durability. Make sure to prep it before you paint it.


Tools for Painting – Prep

Most of the paint prep tools are relatively inexpensive. Some items to add to your tool box include flexible putty knives, scrapers, 5 in 1 tool, caulk gun, palm sander, and orbital sander. The orbital sander and the palm sander are big time savers for sanding exterior siding.

Painting Supplies

Paint supplies for prep include items such as sandpaper, fillers, caulk, and primers. All of these products have unique characteristics and should be used for the proper applications

Paint Prep for Different Materials

The various building materials used to construct the exterior portions of homes have different properties from one another, which greatly affect the performance of paint coatings. A closer look at the unique characteristics of the most frequently used building materials is helpful in determining what painting prep steps will be necessary.

Wood
While all buildings materials are subject to some amount of expansion and contraction due to temperature fluctuations, wood is also greatly affected by moisture content. When moisture is allowed to penetrate into the pores of the wood it causes the substrate to swell up and become somewhat unstable. The consequences are often peeling and flaking of paint coatings. This is an all too common problem that may require extensive painting prep.

A solid effort should be put toward preventing moisture from entering into wood surfaces. Caulking joints that form between all the different architectural elements and filling holes are important steps toward waterproofing. Caulking and filling also improve the appearance of the painted surfaces.

Wood is also vulnerable to the effects of ultra violet rays from the sun. Inadequate protection of a wood surface can result in damage to the outward layers of wood fibers. The sunburned wood fibers need to be removed before a new coat of stain or paint can be applied. This is often the case with stain coatings on wood.

Stucco
Stucco is another material that generally needs some amount of exterior painting prep. Even though stucco is a much more stable material than wood, it does have its drawbacks. Cracking is one of its inherent characteristics. At one time or another just about every home with exterior stucco has had some number of cracks

Hairline cracks are small cracks usually formed during the curing process of new stucco. They can also occur from slight movement due to expansion and contraction. Larger stress cracks are usually caused by movement in the underlying foundation or other structural problems. Patching stucco cracks should be addressed before new coats of paint are applied.

Sun beaten weathered paint on stucco often breaks down and becomes chalky. This is easily remedied by washing thoroughly and applying a masonry conditioner/primer

Minerals such as lime and calcium can leach out from stucco and damage paint coatings. This happens when new stucco is not allowed to adequately cure before the paint coats are applied. If these mineral salts are visible on the surface of the stucco, a thorough washing and a proper primer coat can usually solve the problem.

Masonry (Brick and Block)
Mineral salts can leach from brick and block and damage paint coatings. A thorough washing and a proper primer coat is the solution.

Large cracks often form in masonry walls, especially in the corners. Caulking will keep moisture out and greatly improve appearance.

Cement Fiber Board
Several cement fiber board products are pre-finished and do not require painting. However many of these products are painted. Prolonged sun exposure can cause paint to break down and become chalky. Before applying caulk to joints check manufacturer’s specs.

Galvanized Metal
Gutters, downspouts, and roof metal are often made of galvanized metal. If galvanized metal was not etched and properly primed when it was originally painted, it may be subject to blistering and peeling. The sun can also take its toll on galvanized metal, especially with dark colors. Hot temperatures over a long period of time can cause flaking of the paint. Some painting prep is usually in order for this type of substrate.

Ferrous Metal
Iron railings, gates, windows, and other ferrous metal components are susceptible to rust forming at any area that is not adequately protected by paint coatings. Good painting prep consists of removing or converting the rust spots and properly priming these areas.

Final Thoughts

You can determine which facets of painting preparation are necessary for your project by doing a thorough visual inspection.

Houses built before the mid-1970s have a high probability of having been painted with lead based paints. Do a lead-test on your house. You can purchase a lead-test kit at paint stores. This test can detect the presence of lead in your existing coats of paint. Make sure to observe all applicable laws and regulations regarding lead based paints. For additional information, go to the EPA/lead paint.

Exterior painting often requires the use of ladders. Please take all the necessary safety precautions when undertaking an exterior house painting project because safety always comes first.

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