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Engineered Lumber Branson MO

An I-joist is a wood version of a steel beam. Their structural performance is much better than old-fashioned dimensional lumber in Branson.

Baker-Clouse Construction Svc Llc
(417) 239-0925
146 Warehouse Rd
Branson, MO
 
Beachner Construction
(417) 339-4700
351 S Wildwood Dr
Branson, MO
 
Branco Enterprises
(417) 334-0791
483 Hatchery Rd
Branson, MO
 
Myers Building Maintenance Service
(417) 334-0511
461 Sunny Brook Dr
Branson, MO
 
Heritage Building & Construction Co
(417) 334-5001
112 Rose Oneill Dr
Branson, MO
 
Cabinet & Design Source
(417) 337-5440
566 Gretna Rd
Branson, MO
 
Baty Construction Co
(417) 334-2790
PO Box 6460
Branson, MO
 
First In And Last Out Construction
(417) 334-5499
819 State Highway 165
Branson, MO
 
Ozark Mountain Homes, Inc
(417) 699-1303
1394 Airport Road
Branson, MO
 
Cramer Construction
(417) 334-4666
111 Sandy Ln
Branson, MO
 

Engineered Lumber

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An I-joist is a wood version of a steel beam. Their structural performance is much better than old-fashioned dimensional lumber.

In the last issue John Cole presented a case for natural wood: It is nature's building material, and nothing produced in a factory will ever quite match its appeal. That being said, I went on to describe wood's defects - not defects in the living tree, but characteristics that limit sawn wood as an engineering material. In this issue, we look at engineered wood - wood-based products designed to overcome the variability of natural wood. Why Engineer Wood? Wood in its natural state consists of long, tough fibers aligned with the trunk of the tree. These fibers, individually, are remarkably strong - as strong as steel on a per-weight basis. However, the fibers are arranged in concentric growth rings that are not strongly connected.

As a result, wood is extremely strong in one direction but weak in the perpendicular direction. Craftsmen, such as boat and furniture builders, have learned to work with this limitation, but the fact remains that it is a limitation. A more serious limitation is that we are simply running out of big pieces of wood. When the first settlers arrived, the virgin forests were full of magnificent trees, many with trunks 3 and 4 feet in diameter and knot-free for lengths of 30, 40, even 60 feet. Naturally, these trees were quickly felled. Today a 12-inch-wide, knot-free pine board commands a price of $3 per foot. And the situation only gets worse; the demand for wood of all types is increasing steadily. If we could take wood apart and reassemble it in any desired geometry, we could have custom-designed wood with superior mechanical properties. And we could use every molecule of the original tree, no matter how scrawny, crooked or otherwise imperfect. That is engineered wood. FORM FOLLOWS FUNCTION Except for siding and trim, wood in construction is used for one of two primary purposes: as a framing member to support loads, or as a structural sheathing covering the frame. These two purposes demand different characteristics, so the products engineered to satisfy them assume quite different forms. Joists, Rafters and Beams Glulam, or glued laminated timber, was one of the first engineered framing products to be developed. Glulam consists of strips of lumber (boards) glued end-for-end and face-to-face.

Since a single strip contributes but a small percentage to the timber's strength, the reduction in overall timber strength due to a defect in a strip is reduced proportionally. In addition, the greatest stresses in a bending beam occur in the top-most fibers (compression) and the bottom-most fibers (tension). Taking advantage of that fact, the strongest strips are placed at top and bottom, while the weaker strips are used near the center. LVL, or laminated veneer lumber, is similar to glulam, except 1/8-inch-thick veneers are substituted for 3/4-inch-thick lumber strips, and the veneers are oriented vertically. Typically available in a thickness of 1 3/4 inches and depths from 7 1/4 to 18 inches, the product resembles ordinary framing lumber. To carry greater loads, two or three LVLs are simply bolted together on site. PSL, or parallel strand lumber, is formed of long strands of wood instead of veneers.

The strands are aligned along the direction of the beam, saturated with glue and pressed into solid timbers from 1 3/4 to 7 inches thick and 9 1/4 to 18 inches deep. LSL, or laminated strand lumber, is similar to PSL, except the wood strands are shorter in length. It is intended for less-demanding applications, such as header beams over windows, doors and garage doors. Headers generally require less strength, so weaker, faster-growing, less-expensive species, such as aspen and poplar, are used. I-joist emulates a steel I-beam. Taking advantage of the fact that compressive and tensile stresses are concentrated at the top and the bottom of a beam in bending, both consist of horizontal top and bottom chords, connected by a vertical web. In the wood I-joist, the chords are standard 2x3s, while the web is generally a sheet of oriented strand board (see OSB below). Further, since there are virtually zero stresses at the center (both of depth and length) of a beam in bending, the web is prepunched with holes for running pipes and wires.

Structural Sheathings: Floor, Wall and Roof Sheathing Plywood consists of thin veneers peeled from logs on giant lathes that are glued together. The direction of the grain alternates between veneers (plies), with the grain of both face veneers always in the panel's longer dimension. As with beams in bending, stresses are greatest at the faces, so the strongest wood is used for face plies, while lower-quality, weaker species can be used in the core. Plywood was invented by the Egyptians, who glued sawn-wood veneers together for mummy sarcophagi. Modern, weather-resistant plywoods using waterproof glues were developed in the 1960s. Today, plywood sheathing is the measure of quality in construction. OSB, oriented strand board, unlike plywood, does not require 4-by-8-foot sheets of veneer. Instead, the wood is broken down into strands measuring about 1/2 an inch by 4 inches. The strands are mixed with glue, oriented roughly in the same direction, and formed into a ply between 1/8 and 3/16 of an inch thick. The plies are then laid up in alternating directions (like plywood) and pressed into large sheets about 1/2 an inch thick. Finally the sheets are trimmed into 4-by-8-foot panels. Although extra steps are involved, using lower grades of wood results in panels with the same strength as plywood, but at roughly half the cost. OSB does have limitations, which we will touch on later. Composite is made by gluing wood face veneers over a core of OSB.

Composite panels have the same strength and appearance as plywood, but at a lower cost. Most OSB is used where it will never be seen (roof and wall sheathing), so appearance is not a factor. Composites are used more for shelving and cabinetry than for sheathing. Paper/cardboard: Once again we have the Egyptians to thank for arguably the first engineered wood product - paper. When dry, both paper and cardboard are actually stronger per weight than either plywood or OSB.

In several regions of the United States as many residential buildings are sheathed in Thermoply, a foil- and plastic-faced paper structural panel, as in OSB. Nonstructural Panels There are many other panel materials that are not intended for structural applications. Most simply don't have the strength but have one or more other desirable characteristics. Waferboard consists of chips or shavings like OSB, except the random orientation of the fibers results in decreased strength. With similar manufacturing costs, OSB has nearly replaced waferboard. Particleboard is simply coarse sawdust-like chunks of wood glued together. Without the strength of long wood fibers, the board has less strength than either plywood or OSB. Hardboard consists of finely ground wood particles steamed, glued and pressed together into an extremely tough, dense panel. Bending strength is low, however. MDF, or medium density fiberboard, is a thicker, lower-density version of hardboard, faced with waterproof paper. Its uniformity and ease in milling make it useful in furniture manufacture. STRENGTH Framing Members A beam can fail in one of two ways: bending or horizontal shear. However, except where the loads are extreme and the beam short, the vast majority of failures are in bending. Under load, the beam bends into a curve. Since the top of the beam is closer to the center of curvature (its radius is smaller), the top fibers are actually compressed. Conversely, the fibers at the bottom of the beam elongate in tension. If the value of the wood's fiber stress in bending, Fb, is insufficient, the bottom fibers will break and the beam will collapse. How do engineered timbers compare to natural wood timbers? Here are Fb values for typical sawn-wood beams and their engineered competitors: . Sawn (Douglas fir-larch, Select Structural) 1,500 pounds per square inch (psi) . Glulam (Anthony Power Beam) 3,000 psi . LVL (G-P Lam) 2,950 psi . PSL (Parallam) 2,900 psi . LSL (TimberStrand) 1,700 psi Structural Panels Structural panels are used primarily as sheathing applied over framing. When used as floor and roof sheathings, they both support loads and provide surfaces for fastening finish materials. When used as wall sheathing they support small wind loads and provide a nail base for finish sidings. In addition, however, wall sheathings provide bracing against shear of the building's wall under wind and earthquake loads. Thus two types of strength are important: bending and shear. Two numbers are important in bending. The first is the maximum uniform load a panel can support, given the spacing of the framing members it rests on.

The second is the amount of vertical deflection at the center of the span under a specified load. For example, the certifying agency for structural panels, the American Plywood Association, or APA, requires 15/32-inch OSB panels supported by framing 16 inches on-center to support a minimum of 330 pounds per square foot (now that's a party!) and deflect no more than 0.044 inches (about 3/64 of an inch) under a load of 100 psf. The APA-Grade Stamp Rather than getting bogged down in a bunch of calculations, the APA stamps approved plywood, OSB and composite "structural-rated" panels with the maximum allowed spacing of roof rafters and floor joists, as well as several other specifications. Here is how to read the APA structural-panel stamp: 1. The APA logo, certifying the panel 2. Intended use: Rated sheathing (wall or roof) Rated Sturd-I-Floor (subfloor) Structural 1 (high shear strength) 3. Panel thickness 4. Allowed framing spans for roof/floor 5.

Allowed exposure to moisture: Exterior (permanent exposure to weather) Exposure 1 (limited exposure to weather) Exposure 2 (interior, intermittent high humidity) Interior (protected interior, humidity less than 90 percent) OTHER ISSUES Moisture Moisture can affect engineered (glued) wood products in two ways. First, the strands or plies are held together with glue. If the glue is not waterproof, plies can delaminate (a common occurrence before the development of waterproof glues and APA certification in the 1960s). A delaminated panel or beam is no stronger than its individual veneers or strands, which is to say it is virtually useless. Second, if the wood fiber is exposed to moisture, its cells will absorb moisture and swell. Both plywood and OSB are fairly impervious to moisture through their faces because the layers of waterproof glue are nearly impermeable. Panel edges, however, are a different story. Here, unless treated, the wood fibers between layers of glue are exposed and can take up water easily. That is why panel edges are painted or coated and why manufacturers insist that panels cut in the field be painted. Plywood generally has either three or five plies, while OSB has roughly 50 layers of strand. OSB therefore has about 10 times as many layers of impervious glue. As a result, OSB is both slower than plywood to take up water and slower to dry out. This leads to two potential problems: 1) OSB sheathing can be a better vapor barrier than polyethylene sheeting, resulting in an inadvertent vapor barrier on the wrong (cold) side of the wall, and 2) the wet wood fiber inside the panel can rot. A less serious, but more obvious, problem with OSB is swelling of panel edges.

When OSB is exposed to moisture, the most immediate and severe swelling occurs at the panel edges. The swelling - as much as 20 percent of thickness - telegraphs through roofing. That is why many contractors will use OSB for floor and wall sheathing, but not for the roof. Fumes Engineered wood panels - particularly OSB - have taken a bad rap for their formaldehyde content. Actually, the binder resin (glue) in OSB and plywood is phenol formaldehyde, the fumes from which are so low in concentration that the U.S. Environmental Protection Agency no longer requires product testing for formaldehyde content. Except for hypersensitive individuals, the outgassing from these structural engineered wood products is a non-issue. However, according to the EPA, the composite wood sources that may cause some concern are nonstructural particleboard and MDF made with urea formaldehyde. These are products that you may find in your home as close by as your kitchen cabinets. While products made with urea formaldehyde are recognized as the most significant sources of formaldehyde emissions in homes, there are manufacturers who are committed to formaldehyde-free products. Visit www.sierrapine.com or www.rodmanindustries.com for more information. More sources: . APA - The Engineered Wood Association www.apa.org . Trus Joist MacMillan www.tjm.com . EPA Indoor Air Quality www.epa.gov/iaq/formaldehyde.html In the next issue we will look at the multiple critical functions of a building's foundation.

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