Many property owners ask us why there last paint job didn’t last as long as they had expected. The answer to this question is not a simple one and not because the causes aren’t know, but because there are quite a few factors that involve paint longevity. In the following post, we will explore the various reasons for fading paint and how we, the painting contractor, can help extend the life of your paint job.

Preparation

All good paint jobs begin with preparing the substrate. In the industry we use the initials CDDS – Clean, Dry, Dull, and Stable. When we have these four conditions, our paint has a good chance of adhering and functioning as it should for many years to come. I will cover why each one is important below:

Clean – this one is obvious. If the surface is dirty, the paint will adhere to the dirt and the bond is only as strong as the weakest bond in the system and dirt doesn’t typically bond too well! Any professional painter will always clean the surface before painting it. If your painter isn’t cleaning with pressure washing or similar method, they are doing you a disservice.

Dry – that a surface needs to dry might seem obvious, but some paints actually recommend that you dampen the surface first. These paints are usually masonry paints and the moisture helps extend the dry time so the paint has time to correctly bond and crosslink. A painter must always be mindful of the limitations of paint and how it was designed to be used. This information is found in the PDS (Product Data Sheet) or TDS (Technical Data Sheet) on file with the manufacturer. Wood is by far the most absorbent exterior building product. Our team carries moisture meters with them so they can ensure the wood is dry enough to paint. Painting surfaces that are too wet will cause the paint to have poor adhesion and may even damage the paint film as the moisture dilutes the paint.

Dull – it is difficult to get paint to stick to many shinny surfaces. Tile, glass, high sheen plastics, etc. are the most difficult surfaces to paint. Shinny is often achieved by creating a surface with densely packed molecules. Shinny surfaces resist absorption while dull surfaces usually readily accept water. One of the main methods of getting paint to bond to a surface is by forming a mechanical bond. The resin in paint is absorbed into the substrate and gets “keyed” into the surface. If you were to look at a surface in a very high powered microscope, you would see a very rough surface (kind of like the surface of the moon). The resin in paint fills all the voids and dries in them creating a strong bond. The second method of creating a bond is called the chemical bond. This happens when the bonding chemical either etches the surface to create a mechanical bond or softens the substrate just enough for the them to meld together. Bonding primers are a specialty product and must only be used on substrates they are designed to be use on.

Stable – this simply means that the substrate is sound. If the substrate is weak and disbonding from itself of the sub substrate, the new bond will only be as strong as the previous bond. A good example of this is paint that might look like it is adhering well, but is letting go underneath it all. New paint can sometimes stress out this bad bond and cause a more rapid disbonding. A painter must remove all unstable coatings and materials before applying the new paint or primer. We see this often on precast and CMU (concrete masonry units) buildings where water has penetrated the surface and is causing the paint to disbond from the surface. This must be removed before you paint.

Application

Application affects fading too. If paint is applied in weather that is too wet or too hot, the paint cannot properly cure. If the substate is too wet from dew, recent rain or even ambient humidity in the right circumstances, it can dilute the paint and cause uneven curing. If it is too hot and sunny, you risk the paint drying too quickly, not giving the resins the appropriate time to properly set up in the initial cure. Professional painters will follow the technical specs and will know from experience the circumstances that cause failure. One should never be too flippant about the ambient conditions when applying exterior paint!

Some substrates have special considerations too. Painting over cementitious substrates takes knowledge of the building material. Many painters skip priming on pre primed fiber cement siding and trim. This “shortcut” is almost always a mistake. The priming process at the factory often locks in high PH cement and doesn’t allow it to dissipate normally. You must pressure wash and prime fiber cement siding and trim before you paint it – even if it has been pre primed! Precast is best when you let it set for 6 months and, even then, you must prime it with a PH resistant primer. CMU needs to sit for at least 7 days (we prefer 30 days for the best results) and, even after that time frame, a good painter will use a modern block surfacer that handles high PH levels better. Even with all these precautions, we recommend waiting 48 hours before top coating to allow a good barrier to from between the substrate and the top coats. Taking shortcuts here will result in premature fade and, sometimes, early paint failure!

Finally, film build is important in exterior paint performance! Too thin and the paint will not be able to perform as it was design – too thin and the UV rays will penetrate the film too deeply and cause the paint to degrade too quickly. A good painter will take great care to control the application of paint so that the it reached the appropriate film thickness so it can perform as it was designed.

Environment

The environment the building is in matters for paint longevity. High sun and industrial environments are among the hardest on the paint film. The sun’s UV rays will break down the resins and pigments causing faster film breakdown. Industrial environments can also cause faster breakdown by speeding up the oxidation of the film if there are a lot of contaminants in the air that cause oxidation.

Quality

The quality of paint will also make a difference. Cheaper paints will have more fillers and will have a lower DFT (dry film thickness) because they are lower in solids. This is one reason you don’t want your painting contractor to water down the paint! A good quality, higher solids paint will be worth the extra cost. The resin technology in cheaper paints is also weaker and less UV or chemical resistant. Premium products will have the best resins in them and will have to prove their worth in publications like consumer reports. 

We recommend AcriShield or Permanizer from PPG, Behr e600 for commercial work and any of the upper line Behr products for a more durable finish. Sherwin Williams and Benjamin Moore also sell great product lines too.