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Resource Conservation – The nitty-gritty of the back yard fence

November 24, 2009

A fence is rebuilt by deconstruction--salvaging pickets and rails--with new construction sometimes overtaking the old. Each salvaged board was power-washed, trimmed at both ends, and individually painted on all surfaces. Photographed from neighbor's yard.

Building for 5 years, or the next real estate move, needs only cardboard.  Building for a lifetime requires design, sound construction principles, and is a craft from which everyone will benefit. 

I have been building and watching wood fences deteriorate for 50 years.  My observations and resulting conclusions regarding this basic feature of society has helped mold much of my philosophy in resource conservation. 

I rebuilt my home’s “back yard” fence this past summer.  The project was done to analyze my career-long fence specifications, and to test my philosophy of optimizing resources conservation.  A third test developed as I launched the project: physical and mental resolve to complete the project based upon the above objectives.  An in-depth, detailed, guide for construction is in draft now, to be posted in the future.

A cedar fence will never last as long as it takes to grow and replace the wood used in its construction, but it will be close.

A wood fence from cedar grown, cut and finished within one-hundred miles of my fence to reduce the energy costs associated with distribution has a limited useful life.  How one designs, builds, maintains, and reuses the material will determine how long the construction survives, and how well resources are conserved.

A heartwood cedar post with an ideal (expected) in-ground life of 20 years has to be cut from a tree of a minimum 50 years age, and usually a tree over 100 years old in order to overcome growth flaws that reduce the life expectancy. 

Sapwood of cedar, the first 12 or more annual rings under the bark, has little more durability than its Fir cousins with a 5-year in-ground life expectancy. Most of a cedar picket–the fence board–consists of sapwood. If suitably protected from end-grain exposure and painted, a picket can be expected to be useable for 40 to 50 years.

Once mold and fungus enters cedar, deterioration is rapid. In another project I salvaged a 2×4 cedar deck. At the time, I estimated that over three-quarters of the wood could be reused. The wood was stored incorrectly. It was stacked flat so it remained constantly damp or wet. When I needed more rail and cap material for the fence, I found most of the old decking wood to be rotten, and could only use about a third of the boards—after two years being stacked.

I can extend a fence’s useful life by protecting the wood from decay–and, reusing wood when it needs to be rebuilt.

We can delay deterioration by protecting wood with paints or artificial preservatives; using wood with natural preservatives (cedar); cleaning it of algae, mold and repainting (maintenance); and by design–using construction techniques that avoid an environment conducive to introduction and growth of biological agents that break down its structure. 

I reused most of the original cedar (90 %) when rebuilding my fence. The original fence stood for 24 years.  Salvaging the cedar pickets was difficult, time-consuming, and required several extra steps beyond new construction to have useable boards. Salvage was a big test of my resolve to extend the useful life of the boards to 45 or 50 years.

This was close to meeting the harvest cycle, however, and was the most rewarding aspect of doing the construction myself—and suffering through all the physical effort.  I don’t count on the next person rebuilding the fence to go to the trouble of reusing the pickets, but believe most could be serviceable if salvaged.

A word of caution: Do not expect a contractor to reprocess old fence boards.  The cost in labor alone is probably four times what a new cut board costs.  I had plenty of time to calculate the costs while pulling nails, power washing, trimming the boards to final length, and painting them. Dismantling, and nailing the pickets required a little more concentration for those specific tasks.  A contractor can only be expected to trash the old and build with new material.

All of the pressure treated rails were cleaned and reused. The rails will live through this reincarnation, and probably another.  Only a few cedar rails were structurally sound for reuse.  They would have fared better if painted. I hope they will survive until the next rebuild.

The fence pickets float over a concrete curb with a 2-inch air space to prevent decay of wood in ground contact. Also, the top end-grain of the pickets is covered by a 2×4 cap rail. All the recycled pickets were trimmed of rotten end sections; 3 – 4″ at the exposed top and 3 – 8″ at the bottom that were buried in or touching ground.

A fence is only as good as the post supporting it.

The whole rebuild was initiated due to rotten fence posts.  Posts are processed from fir species harvested at 45 to 75 years growth. The posts (new and old) were 4×4 pressure treaded fir, and advertised for 30 years life—I found a readable end-tag encased in the concrete footing of one bad post, in the only footing I removed.  A cedar post costs four times more than pressure treated, is cut from an older log, and may (very iffy may) last 20 years.

All the destructive rot occurred within 2 inches of the ground surface, although decay extended several inches. The soil at the footing provided a constantly moist environment for decay to thrive. The first post failed at 21 years, and wobbled three more. To accentuate the concern for decay, all the old posts were removed at the concrete footing surface by cold chiseling the wood to one-half-inch in the flats, and up to one-inch depth at corners. When pushing on the posts they all sheared off at the scored line, with little effort. The wood was damaged by decay interior to the treatment zone near the ground line.

Due to environmental concerns with the original preservative components, the chemicals in pressure treated wood were changed about 2001. No one knows the durability of pressure treated wood produced currently. I slopped copper based preservative onto 30 – 36 inches of the base of 23 pressure treated posts, and have my fingers crossed in hopes they will support the fence another 25 years.

Hardware and what was new

All the old hardware and what I could recover of nails was put in recycle, or repaired and reused. I reused the gate springs and a few rail clips.  All but one of the old footings were left in place, as artifacts. For years my fence and the side neighbor’s lived six inches apart. He agreed and I recycled his for the additional 30 feet I extended mine. His posts and most of the cedar rails are in my hazard waste pile.

I bought new pressure treated posts; new fence hardware—nails, clips, and gate hinges—and bagged (pre-mix) concrete. Concrete has a finished strength of 2500 to 3000 psi.  Soil only has about 1500, so the concrete was cut with one-third to fifty percent soil and dirty gravel.  28 pier blocks from the old deck, and about 75 linear feet of new 4x8x16 HCMU (hollow core masonry units) caps comprise the curb.

Four new pressure treated 2×4’s finished the project’s required rails. I went through about 10 gallons of gas pressure washing all the recycled wood–bless the neighborhood’s tolerance. 9 gallons of latex paint to protect all the wood surfaces was the single costliest material, at $23 per gallon.  A half-gallon of copper based preservative I had on hand from old projects was used.  I wore out one new pair of leather gloves; and replaced a box of mixed size Band-Aids for cuts and scrapes.  I simply swore over hammering fingers and other body parts and snacked on aspirin; and lost my belly hangover–15 pounds.  In lousy health, I still have more stamina than my son who is half my age.

Politics

I won’t get into the environmental politics here of chemically preserving wood, other than this one statement: Using only naturally durable wood (cedar) for ground contact in the Pacific Northwest is an environmental travesty that only exposes the ignorance of those who insist on its use.  A cedar fence identifying a mapped wetland will only survive, at most, a third as long as the resource destroyed to build it.  Who is being environmentally unconscionable?

One thing our environmental constituents must address and have not is disposal of painted and preservative treated wood.  I have a 2009 edition of the Washington State Hazardous Waste Directory—its 64 pages of rules and contacts.  One paragraph identifies pressure treated wood as a hazardous waste. Disposal is excluded from all standard recycling at this date. 25% and more of the Home Depot’s dimensional lumber racks is pressure treated wood.  Three recyclers are listed.  Only one takes pressure treated wood, even though the company excludes it in its print.

Conclusion

My fence project is complete, except for disposal of two yards of old pressure treated wood and painted cedar. I can probably use most of the posts in another project, but the scraps at about a half yard won’t remain in a pile looking for legal disposal in whatever-future-year.  And, I consider myself more environmentally conscious than the average citizen.

This is the last fence I will build.  Of course, I said the same thing twenty-eight years ago. I seriously doubt I will be alive in 25 years, but the next owner of my home will inherit a well made fence.  This is not just pride.  Building for the future is a basic tenet of conservation.

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