BUILDING MATERIAL
All materials are processed so they are suited for building. Some are composites of different materials which are designed to be used as well as or better than natural materials. Construction materials include:
1. Sawed wood
2. Plywood
3. Particle board, had board, and waffer board.
4. Wood and non wood materials for flooring and shingles.
5. Steel and aluminum.
6. Concrete.
7. Adhesives and sealers.
8. Gypsum board and fibrous manufactured ceiling tiles.
Lumber is the name given to products of the sawmill and includes;
1.Boards used for flooring, sheathing, paneling, and trim.
2.Dimension lumber is used for sills, plates and for studs.
3.Timbers are used for posts, beams and heavy stringers.
4. Numerous specialty items.
Carpenters should have a good working knowledge of how to recognise and use lumber.They must be familiar with the different grades and sizes as well as other details that apply to lumber selection and use.
Carpenters should also know something about its growth, structure and characteristics.
Tiny strands of cellulose make up the cell walls. The cells are held together with a natural cement called LIGNIN.
This cellular structure makes it possible to drive nails and screws into the wood. It also accounts for the light weight, low heat transmition, and sound absorbsion qualities of wood.
The growing parts of a tree are;
1. The tips of the roots.
2. Leaves.
3.A layer of cells just inside of the bark called the CAMBIUM.
Water absorbsion by the roots travels through the sapwood to the leaves, here it is combined with carbon dioxide from the air. Through the miracle of photosynthesis, sunlight changes these elements to a food known as carbohydrates. The sap carries this food to the various parts of th tree.
New cells are formed in the cambium layer.The inside area of the layer is called XYLEM. It develpoes new wood cells while the outside area , known as PHLOEM, developes cells that form the bark.
In the spring, trees grow rapidly and the cells produced are large and thin walled. As growth slows down during the summer months, the cells produced are smaller, thicker walled, and appear darker in color.
These annual growth rings are largely responsible for the grain patterns that are seen in the surface of boards cut from the log.
Sapwood is located inside the cambium layer. It contains living cells and may be several inches or more in thickness. Sapwood carries the sap to the leaves. The heartwood of the tree is formed as the sapwood becomes inactive. Usually it turns darker in color because of the presents of gums and resins. In some woods such as hemlock, spruce, and basswood, there is little or no difference in appearance.
Sapwood is as strong and heavy as heartwood but is not as durable when exposed to weather.
This clasification is somewhat confusing because some hardwood trees produce a softer wood than some of the so-called soft wood trees.
Several of the more common softwoods and hardwoods are listed below;
SOFTWOODS HARDWOODS
Douglas Fir Basswood
Southern Pine Willow
Western Larch American Elm
Hemlock Mahogany
White Fir Sweet Gum
Spruce White Ash
Ponderosa Pine Beech
Western Red Cedar Birch
Redwood Cherry
Cypress Maple
White Pine Oak
Sugar Pine Walnut
A number of hardwoods have large pores in the cellular structure and are called “OPEN GRAIN WOODS.” They require special or additional operations during finishing.
Different kinds of wood will vary also in weight, strength, workability, color, texture, grain pattern and odor.
Several of the softwoods used in construction work are simular in appearance. Considerable experience is required to make accurate identification.
Availibility of different species (kinds) of lumber varies from one part of the country to another. This is especially true of framing lumber which is expensive to transport long distances. It is usually more economical to select building materials found in the area.
This method produces less waste. also , more desirablegrain patterns are possible.
Lumber can also be cut so the annular rings form an angle of more than 45 deg. with the surface of the board. This method is called EDGE GRAIN if it is softwood, and QUARTER SAWED if it is hardwood.
It is more difficult and expensive to use this method. However, it produces lumber that swells and shrinks less across its width and is not likely to warp.
Lumber used for framing and outside finish should be dried to a moisture content of 15 per cent. Most cabinet and furniture makers prefer wood that has been dried to a moisture content of 7 to 10 percent.
The amount of moisture or moisture content (M.C.) in wood is given as a percentage of the oven dry weight.
To determine the moisture content,a sample is first weighed. Then it is put in an oven and dried at a temprature of 212 degrees F. The drying is continued until the wood no longer loses weight. the sample is then weighed again and this oven-dry weight is subtracted from the initial weight, the difference is then divided by the oven dried weight to determind the moisture content percentage of that sample.
Moisture contained in the cell cavities is called free water. That in the cell walls is called bound water. As the wood is dried, moisture first leaves the cell caities. When the cells are empty but, the cell walls are still full of moisture, the wood has reached a point or condition called the FIBER SATURATION POINT. For most woods this is about 30 percent.
The fiber saturation point is important because wood does not start to shrink until this point is reached. As the moisture content drops below 30 percent, moisture is removed from the cell walls and they shrink.
Wood shrinks most along the direction of the annual rings(tangentially) and about one half as much across these rings. There is little shrinkage in the length.
As wood takes on moisture, it swells in the same proportion as the shrinkage that took place.
Ideally, a wood structure should be framed with lumber at an M.C. equal to that we have in service. This is not practical. Lumber with such a low moisture content is seldom available and would likely gain moisture during construction.
Standar practice is to use lumber with a moisture content of around 15 to 19 percent. In heated areas or structures it will eventually reach a level of about 8 percent. However, this will vary in different area of the country.
Carpenter understand that some shrinkage is inevitable. They make allowances where it will affect the structure. The first and by far the greatest change in moisture content will occur during the first year after construction, particularly during the first heating sason.
When “green” lumber with more than 20 percent M.C. will cause shrinkage of excessive amounts. Warping, plaster and drywall cracks, nail pops, squeaky floors, and other difficulties will be almost impossible to prevent.
Lumber is kiln dried by placing it in a large oven where the temperature an humidity can be controlled. When the green lumber is first placed into the kiln, steam is used to keep the humidity high. The temperature, meanwhile, is kept low. Gradually the temperature is raised while the humidity is reduced. Fans keep th air constantly moving around the wood.
Bundles of lumber may carry a stamp to indicate that they are kiln dried (K.D.) and the letters (P.K.D.) means that they are partially kiln dried as they were first air dried to a certain M.C., then placed into the kiln.
Some of the defects include:
1. KNOTS caused by an imbedded branch or limb. They generally are considered to be strength reducing.
To what extent depends on their size, type and location.
2. SPLITS AND CHECKS seperations of the wood fibers which run along the grain and across the annular growth rings. They usually occur at the ends of a board that has been unevenly seasoned.
3. SHAKES seperations along the grain and between the annular growth rings. Shakes are likely to occur only in species with abrupt change from spring to summer growth.
4. PITCH POCKETS cavities that contain or have contained pitch in solid or liquid form.
5 HONEYCOMBING seperation of the wood fiber inside the tree. it may not be visible on the board’s surface.
6. WANE the presents of bark or the absence of wood along the edge of a board. It forms a bevel and reduces the width of a board.
7. BLUE STAIN discoloration caused by a mold like fungus. though objectional for appearance in some grades of lumber, it has little or no effect on strength.
8. DECAY disintegration of wood fibers due to wood fibers due to fungi. Early stages of decay may be difficult to recognise. In advanced stages wood it soft, spungy, and crumbles easily.
9. HOLES caused by handling equipment or boring insects and worms. These will lower the lumber grade.
10. WARP any variation from true or plane surface. Warp may include any one or combination of the following: Cup, bow, crook and twist.
The sawmill would actually have a 2″ x 4″ size as it came from the saw. After it is dressed, ( run through a planer) it will be 1 1/2″ x 3 1/2″ in size actually. So don’t be confused or think you are getting ripped off by the lumber yard.
Buying lumber at a saw mill you will ask for the load or amount you are wanting to buy, will be sold to you in board feet and by quarters in other words a board foot is a board that is 4/4 x 12″ x 12″ or 1″ by 12″ square.
The formula for finding board feet is the nominal thickness in inches x width in inches and length in feet and divide by 12. An example is: 2″ x 8″ x 12 ‘ =192, divided by 12 = 16 Board feet in that board.
Detailed rules are developed and applied by the various associations of lumber producers- Western Wood Products Association, Southern Forrest Products Association, California Redwood Association, and similar groups. These agencies publish grading rules for the species of lumber produced in there regions. They also have qualified personnel who supervise grading standards at sawmills.
Basic classifications of softwood grading include boards, diminsion, and timbers.
Another classification called FACTORY and SHOP LUMBER is graded primarily for manufacturing purposes.
It is used by millwork plants in the fabrication of windows, doors, moldings, and other trim items.
The carpenter must understand that quality construction does not require that all lumber be of the best grade.
Today, lumber is graded for specific uses. In given structure, several grades may be appropriate. The key to good economical construction is the proper use of the lowest grade suitable for the purpose.
Following are grade listings of softwood lumber;
APPEARANCE GRADES
B& Better (IWP_SUPREME)
C SELECT (IWP_CHOICE)
D SELECT (IWP_ GUALITY)
FINISH
Superior
Prime
E
PANELING
Clear (any select or finish grade)
No. 2 COMMON SELECTED FOR KNOTTY PANELING
No 3 COMMON SELECTED FOR KNOTTY PANELING
SIDING
Superior
Prime
BOARDS SHEATHING
No.1 Common (IWP_ Colonial) Select merchantable
No.2 Common (IWP_Sterling) Construction
No.3 Common (IWP_Standard) Standard
No.4 Common (IWP_Utility) Utility
The lower grade is SELECTS and permits pieces 4″ wide by 6′ long. A still lower grade is No. 1 COMMON. Lumber in this group is expected to yield 66 2/3 percent clear cuttings.
The number of board feet in a piece is obtained by multiplying the nominal thickness in inches by the nominal width in inches and the length in feet, then divide the answer by twelve. Lumber less than a n inch is figured as one inch.
Standard size pieces can be quickly calculated by visualizing the board feet included. For example:: a board i x 12 and 10 ft long will contain 10 board feet. If it were only 6″ wide it would contain 5 board feet.
If the priginal board were 2 in. thick it would contain 20 board feet.
The following formula can be applied to any size piece where the total length is given in feet;
BD. FT. = No, PCS. x T x W x L/ 12
Example 21 x 2 x 4 x 12′ = 2016 /12 = 168 BD. FT.
1. As plywood where thin sheets are laminated to various thicknesses.
2. As composite plywood where veneer faces are bonded to different kinds of wood cores.
3. As nonveneered panels including wafer board, particle board, and oriented strand board.
The outer plies are called FACES or front face and back. the nexed layers under these are called CROSS-BANDS and the other inside layer or layers are called the CORE. A thin plywood would have two faces and one core.
There are two basic types of plywood;
1. EXTERIOR plywood is constructed by gluing together a number of layers(plies) with water proof glues.
It can be used for siding, concrete forms, and other constructions where it will be exposed to the weather or excessive moisture.
2. INTERIOR plywood which is made in thicknesses of 1/8 in. to more than 1in. with common sizes being 1/4, 3/8, 1/2, 5/8 and 3/4 in. A standard panel measures 4′ wide by 8′ long. Smaller size panels are available in hardwoods.
1. As plywood where thin sheets are laminated to various thicknesses.
2. As composite plywood where veneer faces are glued to different kinds of wood cores.
3. As non veneered panels including waferboard, particle board, and oriented strand board.
There are two basic types of plywood;
1. EXTERIOR plywood which is bonded with water proof glues. It can be used for siding , concrete forms, and other constructions where it will be exposed to the weather or excessive moisture.
2. INTERIOR plywood which is bonded with glues that are not waterproof. It is used for cabinets and other inside construction where the moisture content of the panels will not exceed 20 percent.
Plywood is made in thicknesses of 1/8″ to more than 1″ with the common sizes being 1/4, 3/8, 1/2, 5/8, and 3/4 inch. A standard panel size is 4′ wide by 8′ long. Smaller sizes are available in hardwoods.
Many softwood species are used in making plywood.
1. A grade lettering system may be used to idicate the quality of the veneer used on the face and back of the panel. The letters and their meaning are given below;
A Smooth, paintable. Not more than 18 neatly repairs, boat, sled or router type, and parallel to grain, permitted. May be used for natural finish in less demanding applications.
B Solid surface. Shims, circular repair plugs, and tight knots to 1 inch across grain permitted. Some minor splits permitted.
C PLUGGED Improved C veneer with splits, limited to 1/8 inch width and knot holes and borer holes limited to 1/4 by 1/2 inch. Admits some broken grain.
C Tigh knots to 1 1/2 inch. Knotholes to 1 inch across the grain and some 1 1/2 inch if total width of knots and knotholes is within specified limits. Synthetic or wood repairs. Discoloration and sanding defects that do not impair strength permitted. Limited splits allowed. Stitching permitted.
D Knots and knotholes 2 1/2 inch width across grain and 1/2 inch larger within specified limits. Limited splits allowed. Stitching permitted. Limited to interior. Exposure 1 and Exposure 2 panels.
2. A name indicating the panel’s intended use or “performance rating.”
The APA (American Plywood Association) has a ridgid testing program based upon PS 1/74, mills which are members of the association may use this official grade-trademark. It is stamped on each piece of plywood.
A typical stamp for an engineered grade of plywood is shown as follows;
span rating—————————–32/16 —-1/2 inch ——–thickness
durability ——————————–EXPOPSURE 1
classification
000 ———————Mill number
National
Research Board ——————————NRB – 108
Report Number
—————————–
The above is a typical stamp, found on the back of plywood.
The span rating shows a pair of numbers seperated by a slash mark (/). The number on the left shows the maximum recommended span in inches when the plywood is used for roof decking (sheathing). The right hand number applies to span when the plywood is used for subflooring. The rating applies only when the sheet is placed the long dimension across three or more supports. Generally, the longer the larger the span the greater the panels stiffness.
1. Exterior type which has 100 percent water-proof glueline.
2. Interior type with highly moisture resistant glueline.
However, panels can be manufactured in three exposure durablilty classifications:
1. Exterioir
2. Exposure 1.
3. Exposure 2.
Panels marked ” exterior ” can be used oputdoors and may be continually exposed to weather and moisture.
Panels marked ” exposure 1″ can withstand moisture during extended periods but should be used indoors.
Panels marked “exposure 2 ” can be used in protected locations.
They may be subjected to some water leakage or high humidity but, generally, should be protected from weather.
Most plywood is manufactured with waterproof exterior glue. However, interior panels may be manufactured with intermediae or interior glue.
For either softwood or hardwood plywood, it is common practice to designate in a general way the grade by a symbol, G2S means good two sides. G1S means good one side.
In addition to the various kinds, types and grades, hardwood plywood is made with different core constructions.
The most common are the veneer core and the lumber core. VENEER cores are the least expensive. they are fairly stable and warp resistant. LUMBER cores are easier to cut, the edges are better for shaping and finishing, and they hold nails and screws better. Plywood is also manufactured with a particle core. It is made by gluing veneers directly to a particle board surface.
In cabinet work, hardboard and particle board, serve as appropriate materials for drawer bottoms and concealed panels in cases, cabinets and chests. they are manufactured by many different companies and sold under various trade names.
Tempered hardboard is impregnated (filled) with oils and resins. These materials make it harder, slightly heavier, more water resistant, and darker in appearance. Hardboard is manufactured with one side smooth (S1S) or two sides smooth (S2S). It is available in thickness from 1/12th in. to 5/16 in. The most common thicknesses are 1/8, 3/16, and 1/4 in. Panels are 4 ft wide and come in standard lengths of 8,10,12 and 16 ft.
Wide use is made of particle board as a base for veneersd and laminates. It is important material in the construction of counter tops, cabinetsdrawers and shelving, many types of folding and sliding doors, room dividers and a variety of other built- ins.
It is popular because of its smooth, grain free surface and its stability. Its surfac qualities make it a popular choice as a base for laminates. Doors made of it do not warp and require little adjustment following instalation.
Particle board is available in thickness ranging from 1/4 in. to 1 7/16 in. The most common panel size is 4 x 8 f.
These flakes are bonded together under heat and pressure with phenolic resin, a waterproof adhesive. Both sides of waferoard have the same texture surface. this surface has a natural slickness which can be minimized by special treatments. The density of waferboard is about 40 lb. per cu. ft. Standard panel size is 4 x 8 ft. in a thickness range from 1/4 to 3/4 in.
The degree of protection depends on the effectiveness of the chemical and how thoroughly it penetrates the material. Millwork plants employ extensive treatment processes in the manufacture of such items as door frames and window units.
There are two general classes of wood preservatives:
1. Oils, such as petroleum solutions of pentachlorophenol. ( penta- chloro- phenol)
2. Certain salt that can be desolved in water. When selecting a preservative you should consider its effectiveness in protecting the wood as well as any side effects that may result. Some products produce discoloration of painted surfaces or objectionable odors.
A number of commercial preservatives are available for on- the- job application. Study the manufacturer’s directions and recommendations. Some contain toxic or flammable chemicals.
Piles of framing lumber and sheathing should be laid on level skids or timbers to keep them off the ground.
Be sure all pieces are well supported and are lying straight.
Cover the material with canvas or water proof paper. Polyetholene film provides a watertight covering.
If moisture absorption is likely, cut steel banding on panel materials to prevent edge damage when fibers expand.
Keep coverings open and away from the sides and bottom of lumber stacks to promote good ventilation. Too tight coverings ancourage mold growth. Also it is advisable to land the lumber on high ground when possible as a low spot could become flooded if a heavy rain should occur.
Exterior finish materials, door frames, and window units should not be delivered until the structure is partially enclosed and the roof surfaced. In cold weather, the entire structure should be enclosed and heated before interior finish and cabinetwork are delivered and stored.
When finish lumber is received at a higher or lower moisture content than it will attain in the structure, it should be open stacked with wood strips between so air can circulate freely around ach piece.
Plywood, especially the ine hardwoods, must be handled with care. Sanded faces become soiled and scarred if not protected. In storing they should be laid flat, with the back side up on the top panel. This will protect the face side of said panel.
1. Gypsum lath.
2. Wallboard and sheathing.
3. Insulation boards and blankets.
4.Shingles of asphalt or fiber glass, metal, an tile.
5. Metal flashin materials.
6. Caulking materials.
7. Resilient flooring materials and carpeting.
Metal studs are another example of a non wood material. Originally designed for commercial and industrial construction, there use is now extended to residential construction.
A typical stud consists of a metal channel with openings through which electrical and plumbing can be installed.
These are attached to the top and bottom channels with screws or clips. Wall surface materials is attached with self drilling drywall screws. Some web-type studs have a metal edge into which nails can be driven. Metal srud systems are usually designed for nonload bearing walls and partitions.
The common nail has a heavy cross section and is designed for rough framing. The thinner box nail is used for toe nailing in frame construction and securing sheathing. The casing nail is the same weight as the box nail, but has a small conical head. It is used in finish carpentry work to attach door and window casings and other wood trim. Finishing nails and brads are quite similar and have the thinnest cross section and the smallest head.
The nail unit size is called a “penny” and is abreviated with the lower cased letter “d”. It indicates the length of the nail. A 2d is 1 in. long, a 6d nail is 2 in. long, a 16 d is 3 1/2 in. long and so forth.
Each is designed for a special purpose and the annular or spiral threads greatly increase the holding power.
Some nails have special coatings of zinc, cement, or resin.Coating of such materials increase the holding power. Nails are made from such materials as iron, steel, copper, aluminum, and stainless steel.
Wood screws have greater holding power than nails and are often used for interior construction and cabinet work. Their size is determined by the length and diameter (guage number). Screw ar classified according to the shape of the head, surface finish, and the material from which they are made.
Wood screws are available in lengths from 1/4 to 6 in., and in gauge numbers from 0 to 24. The gauge number can vary for a given length of screw. For example, a 3/4 in. screw is available in gauge numbers of 4 through 12.
The number 4 has a thin body, while the 12 screw has a large diameter.
From one gauge number to the next, the size of the wood screw changes by 13 thousandths (.013) of an inch.
Most wood screws used today are made of mild steel with a zinc chromate finish. They are labeled as F.H. (flat head), P.H. ( Pan head), R.H. (round head), O.H. (Oval head), and can be driven with a standard screwdriver, a phillips head screwdriver or any other driving bit designed to fit the given screw.
Wood screws are usually priced and sold by the box and each box contains 100 screws. However one can purchase screws in small quanities.
Additional fasteners the carpenter will find useful include lag screws, hanger boalts, carriage bolts, corrugated fasteners, and metal splines.
POLYVINYL RESIN EMULSION GLUE ( generally called polyvinyl or white glue) is excellent for interior construction. It comes ready to use in plastic squeeze bottles, and is easily applied.
This glue sets up rapidly, does not discolor or stain the wood or dull tools, and holds wood parts securely.
Polyvinyl glue hardens when its moisture is removed through absorbsion or through evaporation. I t is not water proof and therefore is not suitable for assemblies that will be subject to high humidies or moisture.
The vinyl-acetate materials used in the glue are thermoplastic. Under heat they will soften. They should not be used in areas where the temperature may rise above 165 degrees F.
UREA-FORMALDEHYDE RESIN GLUS (usually called urea resin) is available in powder form and when mixed with water into a smooth paste and contains the hardening agent or catalyst.
Urea resin is moisture resistant, dries to a light brown color, and holds wood securely. It hardens through chemical action when water is added and sets at room temperature in 4 to 8 hours. an example is the gorilla glue on the market.
CONTACT CEMENT is applied to each surface and when completely dry to the touch is ready to apply.
the surfaces are then pressed together and the bonding is immediately. The pieces must be carefully be aligned over the area it is to be placed as it will not move once it comes into contact with the other surface.
Contact cement is made with a neoprene rubber base and is an excellent adhesive for applying plastic laminates or joining parts that cannot be clamped together easily. It works well for applying thin veneer strips to plywood edges and can also be used to join combinations of wood, cloth, leather, rubber, and plastics.
Contact cement usually contains volatile, flammablesolvents. the work area where it is applied must be well ventilated.
CASIEN GLUE is made from milk curd, hydrated lime, and sodium hydroxide. It is supplied in powder form and is mixed in cold water for use. After mixing it should be allowed to set for about 15 minutes before it is applied. It is classified as a water resistant glue.
Casien glue is use for structural laminating and works well with wood that has a high humidity or moisture content. It has good joint filling qualities and is, therefore, often used on materialsthat have not been carfully surfaced.
Casein is used for gluing oily woods such as teak, padouk, and lemon wood. Its main disadvantage is that it stains wood, especially such species as oak, maple, and redwood, and has an abrasive effect on tool edges.
One application method consists of placing several gobs on the surface of the material and then pressing the material unit firmly in place. This causes the mastic to spread over a wide area. Some mastics are sperad over the surface with a toothed trowel , while still others are designed for a caulking gun.
Mastics are usually packaged in metal containers or gun cartridges ready for application.
Always read and follow the directions from the manufacturer.
This completes chapter one.
