Q-We are in the process of building a new home that will have redwood siding and trim. We are going to paint the new house. The painting contractor mentioned in her quotation that all of the exterior siding, trim, and other wood should be backprimed. What is backpriming? Is it necessary and/or worthwhile?
A-As long as you feel that her quotation is in order, give her the job. She is one of the few painters I know of who really is on top of her game. Backpriming is absolutely necessary on redwood. It is also an excellent idea for any exterior wood siding or trim.
Backpriming is really a very simple procedure. It means painting the back side and all other hidden edges of a piece of wood. Just think of it as a basic form of plastic shrink-wrapping. Very few painters take the time to do this extremely important step. However, it is not always the painters’ fault. Builders must allow the painters sufficient time and space to perform this task before installation of the wood by the carpenters.
Backpriming can dramatically extend the life of the initial and all subsequent paint jobs. For this reason alone, it should be seriously considered. Backpriming extends the life of a paint job by virtually eliminating the possibilities of paint peeling and blistering.
Here is how it works. Water, for the most part, can easily enter and exit wood. That’s how the water from the soil gets up to the leaves while a tree is alive. However, this property is a negative when the wood is on your house.
Under normal atmospheric conditions, water wants to evaporate. That is why people hang clothes up to dry. This same thing will happen to a wet piece of wood. If the wood does not have a coating on it, it really isn’t a problem. However, if something gets in the way of the water that is trying to evaporate, the water vapor will simply push it out of the way. This effect can be dramatic with highly flexible latex paints. Evaporation can create a high enough vapor pressure behind the surface of the paint so as to create a bubble not unlike that of bubble gum.
Paints are simply coatings. Many are sold on the basis of their effectiveness in protecting wood from water and the elements. The trick is to use this technology to your advantage. By applying paint to an entire piece of wood, you make it extremely difficult for water to enter the wood in the first place. This process is not as difficult as it sounds.
An advantage to backpriming is that it can be done on the ground and very quickly. If you plan your work, have the weather on your side, and have plenty of room, it goes very quickly. Simply set up some sawhorses or a large painting platform and get out the roller or spray equipment. However, glide a brush over the side of each piece that will be exposed to the weather. This will give it the texture of a hand-brushed application.
I also recommend applying the second coat on the ground as well. By doing this, the painter usually only has to set ladders and scaffolding one time. This is safer and quicker. Finally, don’t forget to leave a brush and some paint for the carpenters. Every time they cut a piece of wood, the cut edge must be sealed. These cuts usually expose the wood’s end grain. End grain is the easiest and fastest way for water to enter wood. If this end grain is not sealed, all of your work and effort will be wasted.
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Have questions about the remodeling process? Write to Tim Carter, c/o The Chicago Tribune, P.O. Box 36352, Cincinnati, Ohio 45236-0352. Questions will be answered only in the column.
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