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

FungiInsectsWoodpeckers Marine borers

Temperature

Food

Water

Oxygen(air)

Biotic Requirements

Water (>20% MC but really 30 % or the fsp)

Moderate Temperature (32° to 100°F)

OxygenFood

Wood & Water16

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 withBound Water

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Wood & Water17

Free water is liquid water that fills wood’s void spaces and affects only

Thermal conductivity

Mass

Free Water

Free Water

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Wood & Water18

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)

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Wood & Water19

Temp. °FRelative Humidity %

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

EMC of wood at various temperature and humidity values

Temperature & Humidity

04/20/23

BacteriaRemove pit membranes

Degrade extractives

Digest cell walls (Tunneling)

Can be important in submerged wood

Fungi

Fungal Spores are Everywhere

Fungal TypesMolds/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 AntsSocial 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

SubterraneanWet woodDry wood

Light colored, small to large insect Straight antenna Unrestricted waistReproductives have wings of equal length

Dampwood termitesRequire very wet wood

Colonies small (several thousand workers)

Confined to Pacific NW and Florida)

Dampwood Termites

Subterranean TermitesRequire 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

http://www.utoronto.ca/forest/termite/termite.htm.

http://www.utoronto.ca/forest/termite/termite.htm

http://www.utoronto.ca/forest/termite/micqueen.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.longpestcontrol.com/termites.html http://www.longpestcontrol.com/termites.html

http://www.ent.orst.edu/urban/Termites.htmlhttp://www.utoronto.ca/forest/termite/ret_dam.htm

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/insect_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/Lab‑05/Shipworms_1/shipworms_1.htm

http://bioweb.uwlax.edu/zoolab/Table_of_Contents/Lab‑05/Shipworms_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 ProtectionFire 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-TraditionalModification

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

RealityWood has high energy and many

organisms have evolved to utilize it. Unless you deny a requirement or alter the substrate, something will eventually attack.