Millions of decks have been built in the US over the last 50 years or so. Many of the early decks were built with redwood or cedar lumber which have a natural resistance to rot and decay. Unfortunately redwood and cedar decks were very pricey and had an average life span of only 15 to 20 years. Depending on where you live and the care and maintenance of the deck some would last longer some less.
Transformation of treated lumber
In the 1970 penta treated lumber came into play because it had the advantage of a 40 year life expectancy. Some decks were built using the penta treated lumber as a decking surface however penta was not the most appealing product as it stayed oilie for a long time. The most common use for penta treated wood was the under framing with cedar as the decking and railing.
In the mid 1970s a new product called Chromated Copper Arsenate. CCA treated lumber burst on the market and soon replaced redwood and cedar as the go to product. The CCA treated lumber also had a 40 year life expectancy was 1/3 the cost of cedar and completely eliminated redwood in our market anyway. The pressure treated CCA yellow pine was readily available, cost effective, easy to use and had a pleasing appearance. CCA lumber allowed consumers to have large outdoor decks at reasonable prices and the deck boom has been going on ever since.
Unfortunately as the name implied CCA treated lumber contained arsenic as one of the main ingredients and has been discontinued for consumer use. The new product AC2 has similar properties to the CCA with out the risk to children and animals. The AC2 available from most retail out lets has lower lever of treatment for above ground use than materials for ground contact. For example the dimension lumber 2×4 etc will not be rated for ground contact and the 4×4 and larger lumber will be.
What to look for on your existing deck
Here are some of the basic points to check on the deck framing
Deck band aids are not a proper repair
- The first thing to check on an existing deck is the support posts. The American Wood Council recommends decks more than four feet above ground have 6×6 or larger posts.
- Second would be are the posts buried in the ground or do they set above grade on concrete with an approved base bracket?
- Beams should set on top of the posts and may be held in place with approved brackets.
- Rim boards attached to the house are usually secured with 1/2 inch lag bolts spaced 12 to 16 inches on center and off set so they are not on top of each other.
- Deck flashing should extend up behind the siding and over the rim board to prevent water from entering behind the rim board.
- Rim boards should not be attached to brick veneer or cantilevered floor systems.
- Joist hanger should be used and sized correctly
- Check for any rotten split or broken joists or deck boards
If you find any of the defects listed above we suggest you seek the council of a reliable deck contractor to determine what if anything should be done. Deck failures are usually do to neglected maintenance and not design. Your deck should have a good visual inspection at least once a year.
How maintain your deck
Plastic and composition decks require little more than soap and water clean up to keep them in good shape. Wood decks require a little more tender loving care.
Your wood deck should acclimate and dry out for a minimum of 6 months before any sealers or paint are applied. Sealers are available in clear, semi transparent and opaque in a multitude of colors. Remember once you add a color to the deck it will be hard if not impossible to change it so choose carefully.
for more information on decks go to The American Wood Council https://awc.org/codes-standards/publications/dca6