On the Outside: The Best Wood for Exteriors

By Turko Semmes

Everyone loves the look and feel of wood, but when used outside there are many challenges with its long-term care and durability. After 35 years in the Central Coast construction business, I have observed and utilized many different kinds of wood.

There are several attributes that should be taken into consideration when choosing a wood species for outside use. These are finish, cost, durability, maintenance, appearance, and harvesting. The placement of wood on your building project will determine what species you should choose.

If the wood will be used in overhangs or under protected patios – places that aren’t exposed to weather – then lumber that isn’t naturally durable could be used. But, it’s not preferred. I’d like to discuss wood that is exposed to the elements, specifically siding and decks.

For siding, the most successful material I’ve seen has been All-Heart Redwood or Western Red Cedar. Cypress and Yellow Cedar (a wood that smells like pencils), is used less and only somewhat successfully. In general, wood with a tight grain, from larger trees holds up better. Wood procured from younger, wide-grain trees is not as durable.

By using wood that’s harvested in a sustainable manner, then handled and applied properly, your deck or siding can be enjoyed for many years.

To keep the wood from cupping (when the wood swells and pushes the board edges up), make sure it has been milled with little or no heart center. (Request FOHC – Free of Heart Center.) A clear wood material will hold up better than wood with knots, but I have seen siding with small tight knots age well for over 30 years. (Request STK – Select Tight Knot.)

After you choose the type and quality of lumber, a protective coating is very important. To insure that your siding will last and hold its appearance, a protective finish should be applied to all four sides with two coats before installation. Apply a sealer to the end cuts, finishing up with a third coat after installation. If you are using paint, prime it first with oil and then you can use latex paint after that. Wood siding will require periodic re-coating. On the south and west sides this could be as often as every other year.

Decking requires the most attention as it will be walked upon and touched directly. It also gets the most intense direct weather and sun. For years, Redwood has been the standard for decks, but the quality of most lumberyard redwood has diminished. However, through local sources such as Pacific Coast Lumber we are able to access higher quality redwood trees grown in the Santa Cruz Mountains that are being harvested sustainably.

With decking, like siding, wood-type and milling makes a big difference. It is important to get All-Heart material for deck applications. The same milling and specifications as siding also apply. However, I do not recommend applying finish coatings to wood decking. Let the material weather to its natural color and annual maintenance will be all you need. If you do coat, follow the same installation methods outlined above for siding.

There are many fossil-fueled produced alternatives for exterior applications. However, it should be remembered that wood is the most renewable of them all. If harvested in a sustainable manner, then handled and applied properly, even in the harshest conditions, your deck or siding can be enjoyed for many years.

Contact Semmes and Co. Builders, Inc. for your building or remodeling project.