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
Called free water
Liquid Free Water
Cell Wall with
Bound Water
Within the cell wall


16
Captured in cell wall matrix
Called bound water
Wood & Water
4/8/2015
Free Water
Free water is liquid
water that fills wood’s
void spaces and affects
only
 Thermal
conductivity
 Mass
17
Wood & Water
Free Water
4/8/2015
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.
18
From Haygreen & Bowyer (1989)
Wood & Water
4/8/2015
Temperature & Humidity
EMC of wood at various
temperature and humidity values
Temp. °F
19
Relative 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
Wood & Water
4/8/2015
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
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
Ambrosia Beetle
Wood destroying Insects
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
ab-05/Shipworms_1/shipworms_1.htm
http://bioweb.uwlax.edu/zoolab/Table_of_Contents/Lab-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 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 woodproducing 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.