paint brush on wood

Paint Adhesion-Why Is My Topcoat Coming Off?

Poor paint adhesion is an insidious problem. In some cases, the paint will bubble right away, but often the issue doesn’t become evident until some time has passed. The contractor might finish the job, assuming everything is fine, only to get a call six months later from the homeowner complaining about bubbling, cracking paint and a ruined finish.

In order to avoid this scenario, it’s important to be aware of the issues you might face with different trim products. Some should be avoided completely, while others require care to be certain the paint properly adheres to the trim’s surface.

As the saying goes, an ounce of prevention is worth a pound of cure. Making sure your paint adheres properly will save you the cost of having to scrape and repaint at some point in the future.

Vinyl Trim is Temperature Sensitive

Exterior vinyl trim is a difficult material to paint because the product expands and contracts quite a bit due to changes in temperature across the seasons. Unless an expensive, resilient, premium paint product is used, this expansion and contraction will eventually cause the paint to lose adhesion, split, and peel away from the trim’s surface. Depending on the local climate it still may not be fully effective. For this reason, vinyl trim may not be the best option for exterior painted trim.

Don’t Mix Oil and Latex Paints and Primers

To get the best results you should always match your paint and primer. If you’re using a later-based exterior paint, then you should use a latex primer. An oil-based paint should be paired with an oil-based primer. This is critical to guarantee proper adhesion.

Latex paint can be applied directly over oil-based paint as long as the surface is properly roughed and cleaned first. However, you also should never apply an oil-based paint over latex paint without first applying a good quality oil-based primer. Oil-based paint is much stiffer than latex when it dries. If you paint it directly over latex it creates a hard shell which can crack when the more flexible latex below shifts.

Avoid Low-Quality Wood Trim

Preservative-treated, primed wood trim is an excellent choice for exterior applications, but purchasing a lower-quality product can cause problems. Manufacturers of cheap wood trim save money where they can, and that often translates to a thin, patchy primer application.

Good primer coverage is critical on raw wood for proper paint adhesion. If your trim doesn’t have a thick enough coating to fully seal the wood, or if the coverage is incomplete leaving the trim mostly bare in spots, you’ll almost certainly wind up with a ruined paint finish. You can fix this by applying your own primer first before painting, but that’s an extra step that increases the cost and length of the project. It’s better to spend the extra money to purchase high-quality treated exterior trim like that produced by Belco Forest Products. Our trim features six mils of premium latex primer evenly distributed across the surface to guarantee strong top-coat adhesion. Starting with better materials doesn’t cost more upfront, but the time and money saved by avoiding messy and expensive fixes necessitated by poor paint adhesion will more truly save time and money in the long run. Not more money, just better product.

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