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Understanding the Basics of Wood, Furniture Specification and Construction Techniques
Written by Robert Lyons with assistance from Terri Scanlon
Purchasing furniture for the residence hall environment can be both confusing and complicated to the lay person managing a housing operation. Many housing staff in purchasing positions are not skilled woodworkers or builders, and must rely on a wide variety of furniture vendors, who each provide their own unique features and options. Considerations when selecting furniture should involve quality of materials (wood) and construction methods, along with the individual needs of the students on your campus (which to name a few could be aesthetic, space considerations, storage, size of computer equipment, requirements due to the Americans with Disabilities Act).
This article, although informative, will not turn the reader into an expert overnight. It will however, give you knowledge as to terminology, and good insight into the process of selecting furniture for the residence halls, using basic information presented at a layman's level.
Natural vs. Man Made Products
Natural Wood has been time-tested though the years, as the primary material for furniture construction. Wood is available in many species, and a large emphasis in recent years on reforestation has allowed it to serve as a viable and renewable resource.
Hardwood vs. softwood terminology is perhaps one of the most misunderstood concepts in regards to wood. Although most people assume that hard and soft refers to the overall strength of the wood, it in fact refers to the botanical grouping and structural differences of the wood species. In most species however, hardwoods (ash, oak, and maple, cherry) are more durable than softwoods (pine or poplar). Hardwoods for the most part offer greater choices in respect to natural finish, graining, texture and durability. Hardwoods are generally more expensive than softwoods, due to supply and workability (i.e. hardwoods are more challenging to work with).
Description of Wood Types
Oak: Although over 60 different species exist, oak is separated into two main varieties: white and red (also known as black oak). Oak is heavy, durable, and light in color with coarse texture and highly visible grain. Of all of the hardwoods, oak is the most predominantly used.
Maple is a hard resistant wood, so strong in fact that is often used in the floors of bowling alley lanes. It has a fine texture and even grain. Rock and sugar maple are the most common of the maple species.
Pine is a softwood, white or pale yellow in color. It is light in weight, and resists shrinking and swelling. Consideration should be given to the type of pine selected if it is to be used in residence hall furniture construction, as pine tends to be less durable and joints in pine furniture do not hold up as well as joints in hardwood furniture. Southern Yellow Pine is durable, although not as hard as oak or maple. Southern pine is strong enough to be used as flooring however. It is less costly in general than other hardwoods.
Ash is a hardwood that resembles oak, due to its predominant grain. White ash is the largest of the ash species, and is used most predominantly in commercial furniture production. Ash is a hard, heavy wood. In comparing ash to other hardwoods, it is often less expensive.
Poplar is a stable softwood, resistant to warping and shrinkage. It is often used in the construction of the internal components of wood furniture. Due to its light color and limited grain, it could be considered less attractive than other woods. Poplar is equal in strength to southern yellow pine, however southern yellow pine is more attractive as a finished product.
Man Made Products: In addition to solid wood construction, solid wood is sometimes combined with man made wood products, (such as plywood) in the construction of furniture. Plywood is basically a laminated material that is made of thin sheets of wood that are bonded together in layers to form strong, stable boards. Plywood is strong and stable because the sheets of wood are glued together with the grains of alternating sheets placed at 90-degree angles to one another. This process produces a strong, warp resistant product. Due to its wide range of adaptability (large sheets and many choices of thickness), plywood has unlimited uses in the furniture construction field.
Plywood is manufactured in both exterior and interior grades. The manufacturer grades plywood at the mill. This grading system rates the overall appearance of the outside sheets of wood, and does not refer to the structural strength of the board. A-grade plywood is rated as the best quality, due to the overall excellent condition of the outside of the plywood board. D-Grade plywood is of the least quality, due to its appearance being negatively impacted by knots, holes, splits and discoloration.
Plywood comes in 3-ply, 5-ply and 7-ply sheets. The "ply" in plywood refers to the number of layers of wood that has been glued together, which forms the thickness of the board. As an example, 3-ply refers to 3 layers of wood, 5-ply to 5 layers of wood, and 7-ply to 7 layers of wood. 7-ply sheets are usually considered hardwood, because the outside plys of wood are typically hardwood. 7-ply plywood is used frequently in furniture construction, with very good results.
Veneers are very thin finished plys of wood, typically of a high quality wood product. that are glued to plywood or a lesser quality wood product (potentially poplar as an example). Veneers are used as a way to reduce cost in furniture construction, because a lesser quality wood is used underneath the veneer. Veneers are typically used in the construction of large doors perhaps for wardrobes, because the process of veneer on plywood or other wood reduces the possibility of warping. The disadvantages of veneers deal with the thinness of a veneer top and the difficulties in repairing scratches. Veneers are susceptible to moisture damage, which will cause the veneer to lift off the base product, which is known as delamination.
Joint Construction Techniques
Joining sections of wood together refers to the process by which sections of wood are joined together to form stable, self supporting units. These techniques, which have evolved from early Egyptian times, are designed to lock and hold pieces of wood together. In most cases, strong glue and sometimes screws and metal supports are used on the joint to enhance its overall strength. Strong jointing allows a piece of furniture to withstand movement and sudden impact (not that that would happen in a residence hall), along with normal wear and tear through normal use. The method of joining furniture pieces together can extend the life of a piece of furniture considerably, so this is an important consideration.
A wide variety of joining options can be used. Two basic types of joining furniture pieces together are defined as follows:
Butted Joints: Butted joints are made when 2 pieces of wood are formed together with the use of dowels and glue.
Doweled joints have in many instances replaced mortise and tenon joints because they have the advantage of making an invisible, strong, and quickly made joint. In a doweled joint, wooden pins are glued into holes at right angles to joint surfaces. Dowels are strongest when made by splitting a straight-grained hard wood. The important item in doweled joints is that the dowels and holes are an excellent fit, and the dowels enter the wood not less than 1 1/4 inch on either side of the joint line. Doweled joints are not as strong as interlocking joints, as more surface contact is available in interlocking joints.
Interlocking Joints: Interlocking joints such as dovetail and mortise and tenon, offer high levels of strength and durability.
Dovetails are triangular shaped projections on one piece of wood that fit into similar shaped slots on a second piece of wood. Dovetails, along with being used in interior frame construction, are used in the construction of drawers widely used in securing drawer fronts to sides. The strength of dovetails is enhanced by the addition of excellent quality wood glue.
Mortise and tenon joints consist of the tenon, which is a rectangular projection, which fits into a mortise, or a similarly shaped hole. Mortise and tenon construction is sometimes enhanced through the addition of metal fasteners (screws and brads), that are added after the mortise and tenon joint has been set in glue.
Edging:
Edging is the process by which the raw edges or end grain of the plywood are finished. Edgings can be selected in a variety of shapes, ranging from flat, to bullnosed, to beveled. Flat edging creates a 90-degree corner on the edge, while beveled edges have a 45-degree angle. Bullnosed edges are tapered and rounded. The three main types of edging used in finishing furniture are T-moldings, hardwoods, and laminates:
T-moldings are pre-finished colored plastic materials (such as PVC as an example) that are extruded at a factory. Extrusion involves plastic in a liquid form, which is dyed so that the entire product is solid in color that is available in a choice of colors. After coloration, the extruded T-molding is formed into a t-shape. The T-molding is then inserted into a 1/16th-inch groove, and tapped firmly into place to seal and finish the raw edge. T-moldings are durable because once the T-molding is inserted and tapped, it becomes an integral part of the finished furniture piece. Compared to a laminate edge, T-moldings are more susceptible to nicks or gouges than a laminated edge and similar to damage as would occur to a hardwood edge.
Hard wood strips are sometimes used to finish the edges of plywood. Hardwood strips should be attached by a tongue and groove system, which when glued makes for a very durable edging on wood furniture. Of the 3 possible edging types in this article, hardwood edges provide perhaps the most aesthetically pleasing overall finish. With hardwood edging, the possibility of finish failure from normal use over time is possible.
Laminated Edging: A laminate is a highly durable product, which comes in sheets, and is cemented/glued onto the frame of a piece of furniture to finish the piece. Laminates come in all wood patterns reflecting the grain and shade of the wood furniture piece. Laminates are susceptible to damage by high heat when scorched, and when damaged they typically require replacement, as repair is difficult and not aesthetically pleasing when completed. Laminated edging is typically more costly than T-molding, less expensive than hardwood edging, however more durable than both.
Finishes: Furniture finishing products are used to enhance the overall strength and beauty of a piece of furniture. Typically, wood products are stained, sanded, and top coated for the following reasons:
Applying stain brings out the grain and color of the wood
Protection from environmental factors such as sunlight and air
Protection from scratches and chemical/water stains
Sealing can prevent changes in wood moisture content which can cause warping, shrinkage, and splitting
A good quality wood finish is smooth and rich in color, with edges free from drips, runs, or streaks.
Durability is also a consideration when finishing wood. Synthetic finishes such as polyurethane are resistant to heat, moisture, chemicals and abrasion. Although they provide a strong finish to wood, they are more difficult to repair if damaged. Lacquers are quick drying products, which are usually sprayed onto furniture in thin layers. Lacquers are durable, clear, and easy to repair. Alcohol, shoe polish, and nail polish remover, along with high heat can damage furniture with lacquer finishes. A superfinish refers to a finish that is applied to furniture that makes the surface unusually resistant to environmental factors. Superfinishes protect wood from water stains, damage from chemicals such as bleach, finger nail polish and alcohol, problems caused by excessive heat, and damage from abrasion and impact.
A few final thoughts
With the multitude of products available on the market, a great deal of research should be done when making a furniture selection for your campus. The ability to go beyond the advice of the furniture representative is critical in evaluating whether you are obtaining a durable, high quality product that will last and maintain itself in a quality fashion. It is important to note that sometimes a few extra dollars spent can mean more years of durability and product satisfaction.
As a member of our local school board construction and advisory committee, I am reminded of a time that I spent working with our school superintendent in selecting a new classroom chair. We were in an upstairs room with 2 furniture vendors, when one vendor said, 'you know I could take my sample chair and throw it right out the window and it wouldn't be hurt a bit'. Much to our surprise, the second vendor picked up the chair threw it out the window, and it smashed into many pieces. The moral of this story is to let the buyer beware. Although I am not advocating that you pursue this practice to test the durability of furniture that you may select, I am recommending that you not believe everything that you hear, and that as an informed consumer you make educated decisions that will result in the purchase of quality products.
About the Authors
Robert "Bob" Lyons has been working with wood as a carpenter and furniture maker for over 40 years. He describes himself as "self-taught", having acquired much of his knowledge through reading books and trade journals. He is currently retired, and continues to explore his interest in wood, spending part of his time operating a small sawmill that he purchased with his neighbor. Bob says that his exposure to the workings of his sawmill has greatly enhanced his understanding of wood species and their characteristics. In his own words, "There is no greater satisfaction than to take a log, saw it into a rough board, plane it down and make a product with pride that is useful and functional for many years." He currently operates a small wood shop where he makes and repairs furniture and wood items.
Terri Scanlon has worked as a housing professional for 18 years, serving in the Chief Housing Officer role for over 8 years. She has 12 years experience working in various positions supervising renovations, maintenance operations, housekeeping and grounds. She is currently serving in the position of Managing Director for ResLife.Net.