Wood Deterioration and its Prevention Wood Losses 10 % of all wood cut in the U.S. replaces wood that has failed in service Biotic vs Abiotic Abiotic: Non-living agents Heat: (>150 F)(Fire) hemicellulose>cellulose>lignin Chemicals: Strong bases, strong acids, salts Mechanical: impacts, erosion Sunlight: UV weathering attacks lignin Biotic Agents Fungi Insects Woodpeckers Marine borers Water Oxygen (air) Temperature Food Biotic Requirements Water (>20% MC but really 30 % or the fsp) Moderate Temperature (32° to 100°F) Oxygen Food Where is the Water in Wood? Occurs in two locations: Within cell lumen Liquid Free Water Liquid Called free water Cell Wall with Bound Water Within the cell wall Captured in cell wall matrix Called bound water 16 Wood & Water 5/15/2011 Free Water Free water is liquid water that fills wood’s void spaces and affects only Thermal Free Water conductivity Mass 17 Wood & Water 5/15/2011 Equilibrium Moisture Content The Equilibrium Moisture Content (EMC) is the MC of wood when it is in equilibrium with the environment’s temperature and humidity. From Haygreen & Bowyer (1989) 18 Wood & Water 5/15/2011 Temperature & Humidity EMC of wood at various temperature and humidity values Relative Humidity % Temp. °F 30% 60% 90% 30° 6.3 11.3 21.0 70° 6.2 11.0 20.5 90° 5.9 10.5 19.8 130° 5.2 9.4 18.2 19 Wood & Water 5/15/2011 Bacteria Remove pit membranes Degrade extractives Digest cell walls (Tunneling) Can be important in submerged wood Fungi Fungal Spores are Everywhere Fungal Types Molds/Stain Fungi Soft rot fungi Brown rot fungi White rot fungi Green Fungal Hyphae in Wood Blue Stain http://www.forestry.ubc.ca/brchline/98sept/page4.html Mold on sapwood Mold Species 250 to 300,000 species 45 species on Douglas-fir sapwood lumber in the first 6 weeks Decay Fungus Fruiting Body Brown Rot White Rot Damage by True Dry rot Fungus Example of Decay Fungus in Culture Soft Rot on a Utility Pole Southern pine Southern pine with soft rot Soft Rot on a Eucalyptus pole Decay Effects Reduced bending strength Reduced acoustic/insulation value Increased permeability Increased water absorption Wood Destroying Insects Carpenter ants Termites Beetles Bark/Ambrosia Metallic wood borers Long-horned borers Powderpost beetles Carpenter Ants Social insects (Queen/workers) Use wood for shelter Forage for food outside nest Attack softer woods Colonies <100,000 workers Carpenter ant Worker Carpenter ant Frass Carpenter Ant Damage Termites Social Insects Types Subterranean Wet wood Dry wood Light colored, small to large insect Straight antenna Unrestricted waist Reproductives have wings of equal length Dampwood termites Require very wet wood Colonies small (several thousand workers) Confined to Pacific NW and Florida) Dampwood Termites Subterranean Termites Require soil contact Large colonies (1 to 5 million) Produce mud-tubes Subterranean termite Workers Termite mud-tube up concrete wall Wood Deterioration Wood destroying Insects http://www.utoronto.ca/forest/termite/micqueen.htm Termites http://www.utoronto.ca/forest/termite/ter mite.htm. http://www.utoronto.ca/forest/termite/termite.htm Drywood Termites Attack very dry wood (<13 % MC) Confined to Pacific SW Attack wood above ground Wood Deterioration Wood destroying Insects Termite Damage http://www.ent.orst.edu/urban/Termites.html http://www.utoronto.ca/forest/termite/ret_dam.htm http://www.longpestcontrol.com/termites.html http://www.longpestcontrol.com/termites.html Termite vs Carpenter Ant Reproductives Beetles-Coleoptera Bark beetles Ambrosia beetles Long horned beetles Metallic wood borers Powderpost beetles Wood Deterioration Wood destroying Insects Ambrosia Beetle Wood Deterioration Wood destroying Insects Ambrosia Beetle Damage in a Peeler Core Beetles-Coleoptera Golden buprestid Eggs deposited in green wood Adults leave elliptical holes when they emerge Very long life cycle Buprestid gallery with decay Beetles-Coleoptera Long horned Borers Have long antennae Larva produce round tunnels Most have 1-2 year life cycles Most do not attack finished wood farm4.static.flickr.com/3113/2847107680_8e229 Powderpost Beetles Attack dry sapwood Especially destructive to museum pieces or seldom used furniture Evidenced by fine powder and small emergence holes http://www.cfr.washington.edu/classes.fm.324/images/ins ect_galleries/dcp00044.jpg http://www.ces.ncsu.edu/depts/ent/notes/Urban/ppb-wif.htm Woodpeckers Excavate galleries to find insects (ants, beetle larvae), create roosts, and nests Damage opens wood to water, fungi and insects www.wunderground.com/.../n/NorthLight/284.jpg Woodpecker Damage Marine Borers Require Salt water Types Shipworms (Teredo/Bankia) Limnoria (gribbles) Pholads Shipworms (Teredo) Mollusks Larva borrow into wood leaving only very small entrance hole Filter feed through entrance hole Can reach ¾“ diameter hole that is 1-5 feet long http://bioweb.uwlax.edu/zoolab/Table_of_Contents/L http://bioweb.uwlax.edu/zoolab/Table_of_Contents/Lab-05/Ship ab-05/Shipworms_1/shipworms_1.htm worms_1/Shipworms_1a/shipworms_1a.htm Shipworm Head Internal Shipworm Damage X-ray of wood showing shipworm tunnels Pholads Mollusks ¼“ entrance hole Grows 1-2.5 inch diameter Weakens pilings outer shell Tend to be more tropical http://membres.lycos.fr/mattauer0001/rivage2.jpg Pholads Limnoria (Gribbles) Small crustacean Live in surface borrows for protection Wave action erodes weakened wood- producing an hourglass shape Can attack even creosote treated wood http://www.ffp.csiro.au/wft/wpc/fig1_2.jpg Limnoria damage at tide line Preventing Deterioration Building Issues -Less air circulation -Less durable materials -Changes in design -HVAC Systems -Indoor plumbing Prevention Methods Keep wood dry Coat wood Alter wood/moisture relationships Poison wood (natural or artificial) Keep Wood Dry Avoid soil contact Long roof overhangs Gutters Caulking and paint Ventilation Remove vegetation Durable Heartwoods Natural Durability Heartwood only Varies with age and height Varies from tree to tree Second growth can have reduced decay resistance Artificial Protection Fire protection Water repellency UV protection Improve physical properties Improve appearance Biological protection Protection Strategies Create barriers Chemically alter substrate Bulk cells to alter wood/moisture relationship Apply toxins Wood Orientation Sapwood is more permeable Non-Traditional Modification Thermal Treatment Bulking (glycol) Smoking Silanes Barrier Treatments Metal, concrete, plastic , or fiberglass coatings Paint films Water repellents Wood Bulking Polyethylene glycol Silanes Resins/Methacrylates Waxes Treat Wood End Tag Preservatives Creosote* Pentachlorophenol* Inorganic arsenicals* Copper/organic biocides Totally carbon based Goal of Treatment Create a shell of protection sufficient to support a design load or a barrier that protects the interior Wood Protection Myths Charring protects Salt protects Silanes protect Harvesting time matters Coatings completely protect Reality Wood has high energy and many organisms have evolved to utilize it. Unless you deny a requirement or alter the substrate, something will eventually attack.
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