Wood Deterioration and its Prevention

10 % of all wood cut in the U.S. replaces wood that has failed in service Wood Losses

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

Temperature Food Water Oxygen (air)

Biotic Requirements  Water (>20% MC but really 30 % or the fsp)  Moderate Temperature (32° to 100°F)  Oxygen  Food

Wood & Water 16 Occurs in two locations: Within cell lumen  Liquid  Called free water Within the cell wall  Captured in cell wall matrix  Called bound water Where is the Water in Wood? Liquid Free Water Cell Wall with Bound Water 8/20/2015

Wood & Water 17 Free water is liquid water that fills wood’s void spaces and affects only  Thermal conductivity  Mass Free Water 8/20/2015

Wood & Water 18 The Equilibrium Moisture Content (EMC) is the MC of wood when it is in equilibrium with the environment’s temperature and humidity. Equilibrium Moisture Content From Haygreen & Bowyer (1989) 8/20/2015

Wood & Water 19 Temp. °F Relative Humidity % 30%60%90% 30° ° ° ° EMC of wood at various temperature and humidity values Temperature & Humidity 8/20/2015

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

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 Termites mite.htm.

Drywood Termites Attack very dry wood (<13 % MC) Confined to Pacific SW Attack wood above ground

Wood Deterioration Wood destroying Insects Termite Damage

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/ _8e229

Powderpost Beetles  Attack dry sapwood  Especially destructive to museum pieces or seldom used furniture  Evidenced by fine powder and small emergence holes ect_galleries/dcp00044.jpg

Woodpeckers Excavate galleries to find insects (ants, beetle larvae), create roosts, and nests Damage opens wood to water, fungi and insects

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 ab ‑ 05/Shipworms_1/shipworms_1.htm ‑ 05/Ship 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 inch diameter  Weakens pilings outer shell  Tend to be more tropical

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

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.