Sometimes referred to as I-beams, are structural, load-carrying products. I-joists are typically available in long lengths and because they are very lightweight can be easily handled at the jobsite without the need for costly handling equipment. Their "I" configuration provides high bending strength and stiffness characteristics. The top and bottom flange material for I-joists is typically dimension lumber or laminated veneer lumber; the web material is OSB or plywood. Prefabricated wood I-joists are used extensively in residential construction for both floor and roof framing and are among the fastest growing of the glued engineered wood products.
Structural composite panels (the APA tradename is COM-PLY) consist of veneer faces bonded to a wood-base core material, such as OSB. Composite panels are manufactured in three- or five-layer arrangements. A three-layer panel has a wood fiber core and a veneer face and back, while a five-layer panel also has a veneer crossband in the center. When manufactured in a one-step pressing operation, voids in the veneers are filled automatically by the particles or strands as the panel is pressed in the bonding process. Typical composite panel applications include sheathing, siding and industrial applications.
Most greenhouses have frames of wood or aluminum. Wood will lose no significant heat through the frame. Over time the wood fades unless you keep it painted or finished, and it may rot or warp. Aluminum frames retain shape well, won't corrode, and are often color-coated. Some heat is lost through the aluminum.
Glued Laminated Timber or Glulam is an engineered stress-rated product created by bonding together individual pieces of lumber having a thickness of two inches or less. Individual pieces of lumber are end-joined together to create long lengths referred to as laminations. These laminations are then face-bonded together to create the finished product. Glulam is also among the most versatile of the engineered wood products. It can be shaped into forms ranging from straight beams to complex curved members, and is used in a wide variety of residential and nonresidential building construction applications, including headers, floor girders, ridge beams and purlins, cantilever beam systems, arches, domes and exposed applications such as bridges, marinas and utility structures.
Laminated Veneer Lumber: also known as LVL is the most widely used of the structural composite lumber products. It is produced by bonding thin wood veneers together in a large billet so that the grain of all veneers is parallel to the long direction. The LVL billet is then sawn to desired dimensions depending on the construction application. Some of the products many uses are for headers and beams, hip and valley rafters, scaffold planking, and the flange material for prefabricated wood I-joists.
Oriented Strand Board or OSB consists of wood strands bonded with adhesives to form a mat. Like the veneer in plywood, these mats are layered and oriented for maximum strength, stiffness and stability. The individual strands are typically three to four inches long. OSB is widely used as construction sheathing, as the web material for wood I-joists, as the structural skins of structural insulated panels (SIPs), and in a growing number of other applications.
The original engineered wood, plywood consists of veneers arranged in perpendicular layers. The layers consist of veneer plies laminated with the grain running in the same direction. There are always an odd number of layers, with the grain of the face layers typically oriented parallel to the long dimension of the panel. It is the cross-laminated lay-up of veneer that gives plywood its excellent strength, stiffness and dimensional stability. In addition to a variety of sheathing, siding, sanded and concrete form grades, many manufacturers can produce custom lay-ups for specialized applications.
An easy way to estimate how much a stack of plywood will weigh is to figure about 25 lbs. per 1/4 in. of thickness. For example, one 4x8-ft. sheet of 1/4-in. plywood will weigh about 25 lbs., 1/2-in. about 50 lbs., and 3/4-in. about 75 lbs. This can help you decide how many trips you need to make to get a stack home, or whether you should have it delivered.