Materials 3.1

Silviculture

• (Fajardo, 1993) is the science of growing timber crops of valuable variety for commercial purposes 

• Stand Tending

• Harvesting

• Regeneration

Timber Forest Cycle

Wood

the most common building material

Wood

is the fibrous substance which composes the trunk and branches of a tree that lies between the pith and the bark 

• Strong 

• Durable 

• Light in weight 

• Easy to work on 

• With natural artistic beauty

Properties of Wood

1. Wood is stronger than other materials in proportion to weight

2. Easily worked on with tools and fabricated into many shapes, sizes and designs 

3. Excellent non-conductor of heat

4. Its grains and appearance is conducive to artistic and architectural design

5. Abundant in many shapes, color, sizes and is a renewable resource

6. Small wood members can be used as connectors in trusses, spans, towers, etc. 

7. Does not deteriorate in value if properly handled and protected

8. Not readily affected by changing styles 

9. Has a prompt resale value 

10. Not seriously affected by heat, cold or climate 

Advantages of Wood 

• Strength 

• Weight

• Hardness

• Cleavability

• flexibility/Toughness 

• Durability

Physical Properties of Wood 

Strength

the ability of wood to resist stress and strain

Weight

heavy woods are strong while light woods are weak 

Hardness

resistance to indentation or cutting across the grain 

Cleavability

the resistance of wood to cleavage along the grain

Flexibility/toughness

the strength, shock resistance and pliability of wood 

Durability

the ability to resist decay

• There is no direct relation between the physical and mechanical properties of wood and its durability. 

• However, there is a relation between the color of the heartwood and its durability

• The darker the heartwood, the more durableis the wood

Relationship between Physical, Mechanical Properties and Durability

• Mode of Growth 

• Density

• Leaves

• Color of the Wood

• Grain of Wood

• Nature of wood surface when sawed

Classification of Wood 

• exogenous

• indogenous

(2) Mode of Growth 

Exogenous

outward growing tress which are preferred for lumbering

Indogenous

inside growing trees which are less preferred for lumbering since its center core is soft and brittle 

• Softwood

• hardwood

types of density

Softwood

also known as the conifers or evergreen

Hardwood

generally deciduous and with broad leaves

1. Needle-shaped 

2. Broad-shaped

types of Leaves

1. White 

2. Yellow 

3. Orange 

4. Red 

5. Brown 

6. Black

Color of the Wood

1. Straight grain 

2. Cross grain 

3. Fine grain 

4. Coarse grain

Grain of Wood

1. Plain 

2. Grained 

3. Marked 

Nature of wood surface when sawed

• Logging

• Sawing

• Lumbering

Preparation of Wood

Logging

the harvesting of mature trees 

• Felling

• Skidding

• Bucking

Logging Operations

Felling

cutting of the mature tree 

Skidding

transporting the felled logs from the forest to the sawmill

Bucking

the process of sawing the entire log into smaller pieces

• Axe

• Saw 

• and Wedges

In the old days, all the cutting and bucking operations were done using:

• Lower labor cost 

• Greater production 

• Time element 

Nowadays, the cutting of trees are done using powered machine cutters and chain saws due to the following advantages:

Lumbering

involves all the operations in the preparation of wood for commercial purposes

Sawing

the cutting of a log into small pieces using a saw

• Two-man logging rip saw 

• Power band saw

Two types of Saw

• Plain Sawn

• Quarter Sawn

• Rift Sawn

• Live Sawn

Manner of Log Sawing

Lumber

the resulting wood pieces after a log has been sawed or sliced into boards, planks, sticks, etc. for commercial purposes

Rough Lumber

unplaned or undressed lumber 

Surfaced/Dressed Lumber

a planed lumber having at least one smooth side

• Rough Lumber

• Surfaced/Dressed Lumber

• S2S

• S4S

Lumber Surface Classification

• Slab

• Timber

• Plank

• Board

• Flitch

Types / Forms of Lumber

Surfaced/Dressed Lumber

a planed lumber having at least one smooth side

S2S and S4S

 a planed or dressed lumber of which the number connotes the smooth side. Hence S2S is smooth on two sides while S4S is smooth on four sides. 

Slab

a kind of rough lumber cut tangent to the annual rings of wood running the full length of the log and containing at least one flat surface

Timber

a piece of lumber 5 inches or larger in its smallest dimension

Plank

a wide piece of lumber 2-5 inches thick

Board

a piece of lumber less than 1 ½ inches thick and at least 4 inches wide

Flitch

a thick piece of lumber 

Defect

any irregularity found in wood

• Wood Defects due to Abnormal Growth

• Wood Defects due to Deterioration

Defects in Wood

• Shakes

• Knots

Wood Defects due to Abnormal Growth

• heart shakes

• ring shakes

• wind/cup shakes

• star shakes

shakes

• dead/decayed knots

• live knots

knots

knots

usually occurs at the starting point of a branch

Heart shakes

radical cracks originating from the heart of the log.

Ring shakes

 when cup shakes cover the entire, they are known as ____________

Wind/Cup shakes

cracks/breaks across the annual rings at the timber during its growth caused by excessive bending by wind 

Star shakes

composed of several heart shakes radiating from the center of the log in a star-like manner

• dry rot

• wet rot

Wood Defects due to Deterioration

Dry rot

 the presence of little moisture (<20%) is seasoned woods invites fungi to grow and cause dry rot 

Wet rot

caused by a relatively high moisture saturation (>20%) in woods. Tales place during the growth of the tree or after the wood is assembled 

• constitute about 1/3 to more than 2/3 of its weight 

After cutting, trees still contain moisture in their cells. The water contained in a freshly cut wood:

preserve the lumber from shrinkage or decay

The moisture has to be expelled out thoroughly to:

Seasoning

the process of the removal of this moisture content from lumber

• Natural or Air Seasoning

• Artificial Seasoning

Methods in Seasoning Lumber 

Natural or Air Seasoning

 considered as one of the best method in seasoning lumber. The lumber is piled horizontally or at a slanting position outdoors 

Artificial seasoning

the lumber is stacked inside a drying kiln and subjected to steam and hot air under pressure

• Forced air drying

• Kiln drying

• Radio frequency dielectric drying

Artificial Methods in Seasoning Lumber

Forced air drying 

 electrical fans are used to booster the circulation of air in the preparation for kiln drying

Kiln Drying

the lumber is dried in a special room where temperature, humidity and air circulation is controlled

Radio frequency dielectric drying

a fast method in drying lumber using radio frequency dielectric heat

constantly dry or continuously submerged in water

Wood does not decay naturally through age nor will it decay as long as it is kept _________________ or _____________________

good seasoning

The essential requirement in achieving a successful preservation of wood is ________________

• External processing

• Internal processing

Methods in Wood Preservation

External Processing

the wood is coated with preservative chemicals (solignum, tar, used engine oil, etc.) by brush, spray or immersion that penetrate the fibers. 

Internal Processing

the wood is impregnated with a chemical preservative at a specific pressure in order to permeate into the wood thoroughly

thickness (inches) x width (inches) x length (foot)

Measuring Wood (Lumber)

Board foot (bdft)

the volume of a piece of wood 12 inches wide, 1 inch thick, and 12 inches long. It is equal to 144 in³

Formula in determining the value of the board foot of a single piece of lumber:

Formula in determining the value of the board foot of several pieces (n) of lumber:

Formula in determining the value of the board foot of a log (Doyle Log Rule):

Manufactured boards

are made of wood but does not appear in their natural state.

Manufactured boards

This type of building material can be classified as a type of lumber as they are by-products in the manufacture of lumber. 

• Plywood 

• Hardwood

• Particle board

Types of Manufactured Board

Plywood

is made of an odd number of veneer sheets glued together with the grains running at right angle to each other.

Veneer Sheets

It refers to thin slices of wood, usually thinner than 3 (1/8 inch). It is obtained either by “peeling” the trunk of a tree or by slicing large rectangular blocks of wood. 

Plywood

is also light in weight but strong enough that a screw or nail can be driven close to the edges without danger of splitting. 

• soft plywood

• hardwood plywood

• exterior or marine plywood

different types of plywood:

Soft plywood

the most common for structural use

Hardwood plywood

used for paneling and finishing where usually only one face is hard finished

Exterior or Marine plywood

made for external use, sometime used for construction of boats

Hardwood

hardboard or pressed wood is made from wood chips which are exploded into fibers under steam of high pressure. The lining in the wood itself binds pressed wood together with no filters or artificial adhesives applied. Pressed wood is equally strong in all directions but very brittle. Its color varies from light to dark brown.