Why is it that decks, our Great Northwest get away place, only last a decade or so? Roof structures are commonly made of wood and they can last for centuries so why not decks? Chemically pressure treated roof rafters, trusses, joist, planks or plywood aren’t commonly used, why don’t they rot? How does one build a deck once right? 

What causes wood to rot? Rot is the breaking down of an organic mass. Wood rot is natural. Wood, moisture, oxygen and warmth are all simultaneously required for rot to occur, limit the degree of wood’s exposure to one or more of these components and rot slows. Take away one of these components and wood rot stops.

WHAT ABOUT THE NEW PLASTIC OR ENGINEERED LUMBERS?

Besides not having a history, let’s look at the facts, the top of the deck is not the primary reason for most deck failures. The surface boards are readily available for oiling, staining, or treatment to keep them from immediate decay. Any twisted, broken or rotted lumber is replaceable with little problem. Even when meticulous care is provided to the deck top the backbone of the deck is neglected. The backbone fails due to the wood structure’s supports and fasteners getting wet. They hold moisture where they are jointed and go through freeze and thaw cycles. Joist and beams left to nature rot or loose hold of fasteners due to the fasteners rusting, lumber’s interior rot or because of the treated soft lumber’s poor holding power. Deck failures occur when the deck becomes unstable or unable to support a load, not because it looks ugly or its getting too costly to maintain. Plastic lumber does nothing to increase the life of the supporting structure, therefore, it is not the fix one would hope.

WHAT ABOUT TREATED LUMBERS?

Over the years as our deck lumber quality and longevity diminished, people have sought deck-tops requiring less maintenance. 

Chemically-treated materials have become common place in the deck market. Improvements to these lumbers have been made, incising, and pressure provide a means to maximize chemical treatment saturation but do not insure 100% penetration of the lumber thus the inner core is commonly still untreated. The harder, stronger woods do not absorb liquids very well, if at all. Therefore, the stronger wood products are not treated and softer wood lumbers are. Softer woods have less structural strength and fastener holding power allowing screws or nails to lose their hold. 

Fasteners penetrate the wood to the inner core allowing water to infiltrate the untreated areas. The sun bakes the deck’s wood surface causing ever widening cracks, which in turn allow deeper moisture penetration. Freeze thaw cycles widen surface splits while attacking and breaking down the wood surrounding the deck fasteners which causes even more moisture retention, ice breakdown, fastener breakdown and finally rot damage. Furthermore, the chemicals themselves may promote fastener, joist hanger and sway strapping corrosion. Indeed most common metals used in conjunction with the deck need some type of chemical or natural shield. The lumber joints, whether butted, sistered or laid together, remains wet for days allowing further breakdown, diminishing the deck integrity until finally, complete structural failure occurs. 

Treated docks fail and that proof is everywhere, just take a drive to any water’s edge and look. No, treated lumber only addresses the decay and insect infestation issues; therefore, it is also not the fix one would desire.

 BUILD IT ONCE RIGHT 

• Only use treated ground contact lumber where required by building code 
• Use Douglas Fir framing lumber when possible 
• Slope the top surface ¼ inch per foot to allow water run-off 
• Use ¾ in CCX or better Cross Banded end blocked or tongue and grove plywood 
• Acclimate all lumber and plywood before installing 
• Glue and screw the deck plywood 
• Provide plenty of ventilation to the joist and underlying lumber
• Verify factory authorized installation company 
• Keep all the fasteners and hangers from getting wet 
• Keep the supporting structure from getting wet
• Use a proven waterproof product 
• Verify factory training installer program 
• Complete a moisture survey (nonpenetrating) of the perimeter and deck field every two years 
• Maintain siding, window, door and post caulking or sealant 
• Recover or replace membrane surface at serviceable life end 

Duradek Ltd. deck systems comply fully with the “Build It Once Right” qualifications. Having been protecting sundecks, roofdecks, walkways and porches, including their structures, for thirty years, Duradek also has the proof.

Duradek Northwest has the oldest, largest and most experienced local waterproof vinyl deck authorized installer network available. Duradek membranes are thermal plastic, this means they can not peel or flake and need no coating to maintain their warranty. Deck failures can mean much more than just replacing your deck, they are connected to your home or building and rot does not know the difference or have boundaries. For complete information on successful deck construction, call Duradek Northwest @ 1.800.442.9215 or visit our web site at www.duradeknorthwest.com.