Have you ever looked around and wondered why the siding on old barns lasts so long and seems to hold paint until the pigment has totally faded, while at the same time the paint on your house is falling off and the trim is rotting only a few years after replacement – must be the paint or inferior wood; most likely, it is neither of those issues. The primary reason natural siding and trim materials last so long on old, un-insulated buildings is that they are well vented on all sides.

When wood is well ventilated it generally stays dry with a moisture content of less than 19 percent. Under these ideal conditions, siding and trim will not support wood decay fungi (which requires moisture of 20-25 percent). Unfortunately, standard and accepted residential building practices over the past 40 years have generally disregarded this important fact that wood likes to stay dry.

The unfortunate fact is all siding and trim installations can leak, and moisture can get trapped in the very tight space between the siding or trim and the building paper and plywood behind it. This trapped moisture can come from inside or outside the building, from leaks, or even from moist air from normal household activities. When liquid moisture gets trapped in wood, the moisture content goes up and decay fungi grow.

“Nonsense,” you say,  “my parent’s house was built in the 70s and there hasn’t been much rot and the paint looks pretty good.” This could be, and the likely reason is another culprit in this rotten wood, paint peeling mystery. Older homes are generally less “tight” than homes built today. The down side to this is older homes tend to be more drafty; the upside is they also move more air through the walls which allows drying. Homes in recent years, built with plastic sheeting behind the sheetrock and building paper of some sort behind the siding, really don’t allow much air to move inside a wall or behind siding. While you have improved the insulating value of the wall you have greatly reduced its potential to dry out once wet; wet wood leads to rot and decay.

And what about the peeling paint? Paint is nearly vapor impermeable, in other words, water in either liquid or vapor form will not easily pass through it; this is what you want after all. The problem comes when moisture is trapped behind siding, as explained above, with no place to go and no way to dry out. Once that moisture reaches the backside of the paint it has no place to go. Eventually accumulated moisture will literally pop the paint off of the house, sometimes in sheets. Repeated paint jobs produce no better results. Preparation and proper product are also critical in the painting process, but if it is coming off in sheets, it is likely moisture.  So what do you do about this?

RAIN SCREEN APPLICATION:

A rain screen is simply a technique of creating a space between your siding and your building’s weather resistant barrier. The purpose of the space is to drain accumulated water and to allow airflow to improve the drying process.

All of the natural wood and wood-composite products on the market today will perform much better when vented with a rain screen application. There are many products to choose from that vary in price and durability. Ask your builder what products are the best for your project or stop by one of our four locations to speak to our building materials experts for more information about siding & trim options and proper installation techniques.

 CONSIDER THIS:

  • Many of your siding and trim product choices will require maintenance on average of every 5 years; re-painting or re-staining.
  • All of these products will perform much better if they are vented using a rain screen application (see detail).
  • If you are replacing rotted siding or trim, or if you are struggling to keep paint on the side of your house, you will continue to get rotted siding, trim and peeling paint if you don’t create a proper air channel or rain screen. The problem is not the product, but the application.
  • The process of creating a rain screen in new construction is complicated. The process of creating a rain screen in a renovation is even more complicated. Ask your builder what is right for your or stop by our store just ask.
  • Overhangs are a siding and trim’s best friend; the bigger, the better.
  • Gutter systems are a close second.
  • Hard surfaces like steps, patios and decks cause water to splash back on the skirt boards, siding and doors. Start the clock, these will be the first areas to look tired, lose finishes and eventually start to fall apart.
  • Make sure water from the roof is directed away from the sidewall. We sell inexpensive diverters that do the job.
  • Use only Stainless Steel Fasteners with Cedar and we
    recommend Cortex Screws for PVC applications- see us for details.
Peeling Paint
Red House Roof
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