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Exterior Project - Clapboard (Wood) Surface Preparation Steps

We have learned there is a significant difference between painting and contractors regarding the amount or degree of surface preparation done to exterior wood surfaces. It is our goal to help educate you to what we believe is the "correct", or at the very least, a thorough preparation process for your exterior home surface.

We live in the Northeast and are exposed to temperatures that can have a 100-degree range; from 10-degree winter temperatures to high 90's with high humidity in the summer months. Surface preparation is the most critical step in the paint performance and longevity. (This also relates to manufacturer product warranties.) Therefore, it is important to understand what a thorough "prep" process is.

Thorough work requires additional labor time which equals money. As you gather exterior estimates, there are several questions that we encourage you to ask each contractor you are obtaining a bid from.

Questions To Ask

  1. What type of scraper blade will be used?
  2. After scraping will you do any sanding? (Hand or power sand?)
  3. Do you use latex-based or oil-based primer?
  4. Do you spot prime exposed wood or apply a full coat of primer?

After we protect all vegetation and surrounding grounds, let us share with you the steps we take to prep wood surfaces:

  • Scrape wood siding to remove loose & peeling paint; our primary and preferred scraping tool is a carbide blade. This durable blade can remove more challenging and stubborn paints. We complement this with a sharp (5-in-1) putty-like blade to assist with removal. If only one were to be used, the carbide blade is a must. Unfortunately, this is not customary amongst painters.
  • After scraping, we utilize a power sander with coarse sandpaper to smooth and feather down rough edges and surfaces. This feathering will inhibit the future lifting of the paint and will increase the life of the paint job.
  • After surfaces have been cleaned, it is time to apply primer. As noted above in questions 3 and 4, the two relevant questions about primer include, "What kind of primer are you using? How much priming should be done?" You will receive different answers depending on which contractor is asked. The two types of primer in question are either water-based (latex) or oil-based (oil). We suggest talking to a manufacturer product expert to verify this information, but in our opinion, an oil-based primer is far superior to a latex primer. Oil primer will penetrate exposed wood, will create a harder surface after drying, and will do a superior job preventing old paint from lifting in the future. Latex primers sit on top of the exposed wood and are a "thin" coating, just by the very nature of having water as its base. We do not recommend latex primers on exterior surfaces in the Northeast. Unfortunately, a large percentage of painters only use water-based primers.
    • Note: To be clear, we are talking about primers, not top coat finish paints. The high-quality latex (water-based) paint, such as Sherwin Williams or Benjamin Moore is exactly what you want for the finish coats.
  • In terms of primer application, this is where we differ from most painting contractors. We will apply one full coat of oil primer to every square inch of clapboard siding and wood trim, even if the surface doesn’t appear to need the primer. Why? Because often there are many fine paint cracks on the surface that a scraper blade won’t affect. However, if not oil primed, it is often these vulnerable areas where the peeling and lifting will most likely occur over the next few years. For the incremental amount of labor time required, a full coat of oil primer will pay dividends for the longevity of your paint project.

Regarding finish work, we always apply two topcoats of latex paint. Not all contractors do this. That’s one final critical question to ask your other contractors.

Now you have a better understanding of what is involved with an exterior estimate and will be able to more accurately compare apples to apples when it comes to different bids.