Safe Deck Details

By Frank G. Ross

For many people the latter part of winter is when they plan spring and summer projects around the house and yard.  For example, you may be planning may be a new deck.  If so, there are some things you should know, especially if the deck is to homeowner built.

According to researchers at the Wood Materials and Engineering Laboratory at Washington State University, “The deck is the most dangerous part of a house, with more injuries and loss of life than any other part of the home structure.”  Their research showed that more injuries can be connected to failed decks than to all other wood building components and load situations combined (except for hurricanes and tornadoes).

One reason is that many do-it-yourselfers see a deck as a relatively easy project that they can tackle themselves without consulting a professional.  The WMEL research team is currently developing design guidelines for making residential decks safer.  Their recommendations include careful staggering of lag screws or bolts to attach a deck to the house according to prescribed exact distances for the bolt spacing. They also recommend structural supports near the house.

Another consideration is the type of wood and fasteners used to build the deck.  Three years ago on January 1, 2004, two newer types of pressure treated wood replaced the older type known as Chromated Copper Arsenate.  The newer types (Alkaline Copper Quaternary and Copper Azole) are far more corrosive to common building fasteners such as joist hangers, nails and aluminum flashing just to name a few. 

The electro galvanized fasteners and hangers that were in use prior to 2004 are still available in building yards and hardware stores.  However, the newer treated wood requires hot-dipped galvanized or stainless steel fasteners and hangers.  Additionally, stainless steel hangers must be used with stainless steel fasteners, not hot-dipped galvanized fasteners. 

Previously, aluminum was the choice for flashing at the ledger joist (the joist where the deck joins the house), but with the newer wood, flashing must be copper, rubber or plastic to minimize the effects of corrosion.

A further concern with the new treated woods is that both types have two varieties, one is rated for ground contact, and the other is rated for above ground use only.  A deck may incorporate both varieties, but they should not be used interchangeably.

So in summary, in order for a deck to be built to last, the builder must consider not only the design of the deck, but also the structural components.  And as always, if you are unsure about any part of the project, consult or hire a professional.

For more information on decks, check out the following sources:

Fairfax County, Virginia, has an excellent Website that gives recommended deck construction details. Go to www.fairfaxcounty.gov/dpwes/publications/decks

The WSU Wood Materials Engineering Laboratory is a leader in the development and testing of wood-plastic composite materials, which are gaining popularity for residential decks and rails. The lab has developed an excellent source of information. Visit www.wpcinfo.org

The North American Deck and Railing Association at www.nadra.org is another good source of information on decks.

Frank Ross is a Certified Utah Home Inspector for Pillar to Post Professional Home Inspection and a full member of the National Association of Certified Home Inspectors and a member in good standing with the Utah Better Business Bureau.  Readers may contact Mr. Ross at (435) 867-6400 or frank.ross@pillartopost.com or www.pillarposthomeinspection.com