Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
Ask a Question or Search InspectAPedia
InspectAPedia ® Home
STRUCTURAL INSPECTIONS & DEFECTS
ARCHITECTURE & BUILDING COMPONENT ID
CHIMNEY INSPECTION DIAGNOSIS REPAIR
COLUMNS & POSTS, DEFECTS
CONNECTORS, FASTENERS, TIES
DECK & PORCH CONSTRUCTION
DEFINITIONS of Mobile Home, Doublewide, Modular, Panelized
DEFINITIONS of ENGINEERED WOOD OSB LVL etc
DISASTER BUILDING INSPECTION & REPAIR
EARTHQUAKE DAMAGED FOUNDATIONS
FIRE DAMAGE vs MOLD DAMAGE
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FOOTING & FOUNDATION DRAINS
FOUNDATION CRACKS & DAMAGE GUIDE
FRAMING DAMAGE, INSPECTION, REPAIR
GRADING, DRAINAGE & SITE WORK
HOUSE PARTS, DEFINITIONS
INSECT INFESTATION / DAMAGE
KIT HOMES, Aladdin, Sears, Wards, Others
LOG HOME GUIDE
MOBILE HOMES, DOUBLEWIDES, TRAILERS
MODULAR HOME CONSTRUCTION
MOISTURE CONTROL in BUILDINGS
PORCH CONSTRUCTION & SCREENING
PRE-CUT & KIT HOMES
RETAINING WALL DESIGNS, TYPES, DAMAGE
ROT, FUNGUS, INSECT DAMAGE
SINKHOLES, WARNING SIGNS
STAIRS, RAILINGS, LANDINGS, RAMPS
STRAW BALE CONSTRUCTION
STRESS SKIN INSULATED PANELS
STRUCTURAL WOOD ASSESSMENT
TIMBER FRAMING, ROT
TRUSSES, Floor & Roof
WATER ENTRY in BUILDINGS
This article defines and illustrates the properties of OSB sheathing. This article series describes wood products used in construction including engineered lumber, OSB, and Plywood products.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
"OSB" or Oriented Strand Board wood products is similar to LVL and PSL, but OSB is produced in sheets (typically 4' x 8' in size) and is constructed of shorter strands of wood or even (in the case of 4' x 8' sheets) wood chips that may be roughly rectangular in shape.
Our page to photo shows OSB oriented strand board used for roof decking, and at left our photograph shows OSB subflooring.
Developed in the 1980's, oriented strand board is an engineered wood product in which strands and flakes of wood are cut from straight, low-knot small-diameter logs, usually aspen or white birch.
The wood strands and flakes of OSB are glued (or "bonded") together with a phenol-formaldehyde resin binder (forming a waterproof glue), heated (to at least 120 degF), and are compressed and flattened using pressure. Other chemical binders may be used in OSB products, and the OSB sheathing surface may have a wax coating to improve water resistance of the product.
Our photographs of OSB "plywood" below illustrate that the wood fragments glued together under heat and pressure are deliberately oriented randomly to produce greater strength than would be achieved if these small individual fragments were all oriented in the same direction
Our second OSB sheathing photo (above right) shows fire retardant treated plywood roof sheathing (photo-left) and OSB roof decking (photo-right) sheathing the roof of a multi-unit condominium building.
Properties of OSB Panels & OSB Sheathing Ratings, Markings, Lumber Stamps
In an OSB panel the two exterior surface layers of wood strands are oriented parallel to the long axis of the panel. In the interior OSB panel layer or "core layer" strands are oriented either randomly or across the short axis of the OSB panel. In overall thickness the ratio of face panels to core panel ranges from 40:60 to 60:40.
According to the Universite Laval and also Timberco, the dimensions of wood strands used in OSB are specified in industry standards; most producers of OSB use a combination of strands that are up to 6" long and 1" wide or from another source, 19-40 mm in width and 90 to 100mm in length.
OSB is a modern wood product that developed from earlier 1970's "waferboard" product. In 1990 the Structural Board Association was formed. By 1996 there were 38 OSB producers in North America. But unlike waferboard whose composite wood chips were place randomly, an oriented strand board product is made from wood chips that are deliberately oriented with respect to one another to provide greater strength.
As a result, modern OSB products are rated at the same strength as plywood products. OSB roofing panels are available with a perforated (breathable) foil radiant barrier affixed to the pane's interior surface.
Type Variations of OSB Specialty OSB Sheathing Products
At below-left you can see an Oriented Strand Board whose composing wood fragments are longer than the more rectangular wood chips from our OSB pictures above. Still the strands are oriented randomly for strength.
At above right is a cedar OSB product used in construction of cedar-lined closets, a less costly alternative to solid wood cedar planks traditionally used for that purpose.
Mold Growth on OSB Oriented Strand Board Products
Our moldy OSB roof and attic gable end wall sheathing photo (left) illustrates that as with most other wood products, if left exposed in a damp or wet environment, some species of mold will grow readily on this material.
Listing submissions are welcome from websites whose content, services, or products are appropriate for our readers. To provide your link exchange information and our link exchange policy see InspectAPedia.com - Directory Listing & Link Exchange Instructions There are no listing fees & no conflicts of interest. We reserve the right to list or not list individuals or companies and to provide notice of consumer compliments or complaints.
The design and content found at InspectAPedia.com® are © Copyright protected, All Rights Reserved. Contents of this website may not be copied in any form. Our main website topics listed at page top or at Related Topics provide in-depth, un-biased, expert information on building defect inspection, diagnosis, & repair.
Frequently Asked Questions (FAQs) about OSB - oriented strand board sheathing used in construction of building walls, roofs, floors
Use the search box below to ask a question or to search the InspectApedia.com website.
Ask a Question or Enter Search Terms in the InspectApedia search box just below.
Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.