POST a QUESTION or READ FAQs about fiberboard building sheathing: how to identify fiberboard products, fiberboard uses, fiberboard, Celotex, Homasote, Insulite & other brands, fiberboard ingredients, does fiberboard contain asbestos?
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
What are the ingredients in fiberboard insulating sheathing or wall, ceiling, or roof sheathing used on or in buildings:
Ingredients of fiberboard sheathing.
This article series describes and provides photographs that aid in identifying various insulating board sheathing materials used on building walls and roofs, such as Homasote, Celotex, Insulite, and Masonite insulating board sheathing products.
The range of materials used to produce plant-based boards and "lumber" used in construction is broad, including bagasse (sugar cane fibers), bark, flax, grass, hemp, jute, peanut shells, reeds, sawdust, straw, and wood pulp tailings or byproducts. In 1955 the US FPL reported:
Wood fiber is the most common material used in the manufacture of insulating fiberboard.
Two large companies use bagasse, while another company's board is composed mostly of waste paper. Flax shives are used to some extent by one manufacturer.
[Click to enlarge any image]
There has been a variety of techniques to produce, bond, and give desirable properties (waterproofing, vermin proofing, rigidity, structural strength, sound and heat insulating properties) to fiberboard products, in general the boards are made from a mixture of ingredients that are pressed or rolled, and bonded using asphalt, clay, decxtrin, paraffin wax, plaster, urea formaldehyde resin, or other binders.
Carbon black is used by some manufacturers in very small quantities (about 1%).
Our photo (above left, provided by a reader) illustrates use of fiberboard sheathing beneath a brick veneer wall. The demolition was performed during building renovations.
As we explain at FIBERBOARD SHEATHING, the home page for this topic, originally, Homasote® produced sanded "agasote" sheets used in the roofs of passenger railroad cars, moving, in 1915, to automobile roofs, and in 1916 to construction products. Homasote was widely used for military barracks in both WWI and WWII and is still promoted for sound resistant sheathing and other applications.
Celotex®, Homasote®, Thermafiber®, and similar insulating building sheathing board products are still sold as a lower cost alternative to plywood or OSB for building sheathing.
This fiberboard sheathing product is used as structural paneling, insulation, concrete pouring forms, and expansion joints.
Fiberboard sheets or lumber have been produced in three densities for different applications:
Low density (soft and relatively thick (e.g. 7/16")) used for insulating sheathing or soundproofing
Medium density (Medex, Medite)
High density (Masonite, Upson board, Marinite, and some Homasote products)
There both non-structural and structural fiberboard panels that did not require this additional bracing have been produced. Some fiberboard sheathing products can claim adequate structural shear strength, particularly if the proper nails and nail pattern are used.
Other contemporary producers of fiberboard building sheathing besides Homasote™, and Masonite™ include International Bildrite (Bildrite structural), Georgia Pacific (Stedi-R & Stedi-R-structural), Knight Celotex (Celotex premium insulating), and Temple Inland (Temple fiber brace).
Fiberboard sheathing, also called black board, gray board, or buffalo board sheathing in some areas, is a fibrous material impregnated by (or in some cases coated with) a stabilizer and water repellant - asphalt on early versions of this material that we have found.
While it's not easy to find and identify this material on a building wall unless indoor or outdoor demolition is being performed, you can spot the product in building attics on the gable-end walls.
The R-value of fiberboard sheathing is higher than plywood, gypsum board, etc, and is rated at about R 2.4 per inch (or about R 1.2 in more typical half-inch thickness with which it is applied. The board also reduces sound transmission into buildings.
MSDS data for fiberboard insulating sheathing products gives ingredients
In sum these are benign products for the most part, though wood dust particles from any wood material can be a potential hazard. For the specifics of your fiberboard siding you'll want to consult the MSDS of the particular product.
A review of the patents and product description for Celotex insulating lumber products shows that asbestos was not among the product's ingredients.
In "Insulite Co. vs. Reserve Supply Co", a 1932 lawsuit, relevant patents and ingredients are described, including a composition of plaster of paris, cement, or other like substance, combined with hair, wood fiber, sawdust, wool, wood shavings, excelsior, straw, or similar substances. (Asbestos was not cited in the product description. )
Homasote 440 ingredients - quoting: Cellulose based material containing
1 to 2% paraffin wax, CAS 8002-74-2, and less than 0.1% copper base pesticide, CAS 39290-85-2. The product contains no known hazardous or
Knight-Celotex Fiberboard™ ingredients - MSDS (Marrero Plant), MSDS No. 00040-85F, 4/19/2002, trade name Premium Fiberboard Insulating Sheathing, Manufactured Home USB, Coated 1 & 6 Sided, lists the following ingredients:
Cellulose (<= 96%), Starch (<= 10%), Paraffin Wax (<= 2%), Carbon Black (<= 0.5%), Clay (<= 2%), and Lamination Adhesive (<= 3.5%). Original source: anoziraworks.com/uploads/Celotex_Fiber_board.pdf
StructoDek® high density roof insulation ingredients: laminated board & coated 1 & 6-sided, MSDS: 001-86F, 4/12/2005, Knight-Celotex LLC, Northfield IL Tel: 800-596-9699 lists these ingredients:
Cellulose (<95%), Starch (<9%), clay (1%), Carbon Black (1%), Wax (1%), Laminating Adhesive (< 3.5%). Original source: usply.com/downloads/other/msds-structodek.pdf
Structodek High Density Fiberboard Roof Insulation is defined by OSHA (29 CFR Part 1910) as an "Article". A manufactured item which is formed to a specific shape or design during manufacture which does not release or otherwise result in exposure to a hazardous chemical under normal conditions of use.
Sturdy-Brace High Density Fiberboard ingredients: produced by Blue Ridge™ Fiberboard - MSDS: "Hazardous Components":
Wood Fiber*. [In other words, Asbestos is not present].
Watch out: Wood dust is listed by the IARC as a human carcinogen (Group 1).
Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
Ask a Question or Search InspectApedia
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
 Homasote® Company, 932 Lower Ferry Road, West Trenton, NJ 08628-0240 Tel: 800-257-9491 Ext 1332, or from outside the U.S. call 609-883-3300. Website: http://www.homasote.com/ , Email: Sales@homasote.com.
Thanks to Homasote CEO Warren Flicker for technical review and comment on this article.
Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: firstname.lastname@example.org
 Celotex Corporation, PO Box 31602, Tampa FL 33631, with offices in Atlanta, Chicago, Cincinnati, Dallas, Oakland and Philadelphia, and plants in six U.S. States is headquartered in Tampa, FL. Celotex is a national manufacturer of residential and commercial building materials. Website: www.celotex.com Tel: 800-CELOTEX
"Insulation Selector Guide", Celotex Corporation, web search 6/29/12, original source: http://www.silvercote.com/PDF/ThermaxInsulSelectorGuide.pdf, [copy on file as CelotexThermaxInsulSelectorGuide.pdf ]
"Celotex Blue Ridge Fiberboard", SturdyBrace®, produced by Blue Ridge Fiberboard Inc., 250 Celotex Dr., Danville VA 24541, product literature, web search 6/29/2012, original source: blueridgefiberboard.com/pages/sturdybrace.php, [Copy on file as Celotex_BlueRidge_SturdyBrace.pdf].
MSDS: original source: blueridgefiberboard.com/pages/sturdybrace/pdfs/SturdyBrace-msds-br.pdf
"Guide Specifications: SturdyBrace® Structural Fiberboard Wall Sheathing", 6/29/12, original source: blueridgefiberboard.com/pages/sturdybrace.php [Copy on file as SturdyBrace-guidespecs.pdf]
 Douglas Leen, Petersburg AK 99833, contributed the photograph of insulating board scraps from roof insulation removed from a building. Dr. Leen provides such a wide range of services, collectables, and historical information about the Northwest that a succinct description is difficult: flying dentist goes anywhere, antique forestry posters, historic campers, the tugboat Katahdin, in Alaska, Washington, and Wyoming. Mr. Leen can be contacted at email@example.com or at 907-518-0335
 Georgia Pacific: information about DensGlas gypsum board building sheathing can be found at the company's website at gp.com/build/product.aspx?pid=4674
 Pittsburgh Press, "Yesterday - in costly homes alone, Today even the simplest home can have this hidden comfort", The Pittsburgh Press, 19 April 1925, classified ads section. Web search 6/22/12, [Copy on file as Celotex_Ad_023_PP.jpg and more]
 pending research
Patents pertaining to building insulation & insulating board, Celotex & Insulating Board type products
"Sound absorbing board for walls and ceilings", Patent No. 1,554,180, issued to W.S. Trader, September 15,1925, first disclosed a wallboard constructed from "Celotex", a felted mass of strong bagasse fibers, so compacted as to be capable of use as an artificial lumber in that it can be sawed and nailed, and has sufficient strength in many cases to be substituted for lumber. That same patent mentions "Insulite", a building board made from wood pulp tailings and which likewise has a porous fibrous body portion and which is possessed of considerable strength so that the same can be nailed, etc. Celotex was preferred as an insulating material because its internal cells produce a sound-deadening insulating effect.
"Method and apparatus for drying moving material", Treadway B. Munroe et als, assigned to Dahlberg & Co., U.S. Patent No. 1,598,980, 7 September 1926, described a method and apparatus for drying sheets of artificial heat insulating lumber, known on the market as Celotex, improving the original process.
"Reenforced composition board", Treadway B. Munroe et als, U.S. Patent No. 1,578,344, 30 March 1926
"Insulating Structural Board", U.S. Patent 2,159,300, Armen H. Tashjian et als, assigned to William B. Miller, Lakewood OH, 23 May 1939, describes insulating structural boards of laminated construction for use as roof or floor slabs, and refers to "Standard insulating fiber boards, such as "Celotex", "Masonite", "Insulite", etc. that had excellent insulating properties but have relatively slight structural strength in flexure or bending under load, hence are not and cannot be used as structural slabs for load sustaining purposes, as roof or floor slabs, for example. [Adding structural strength ran into the problem of reducing the insulating value of the product.]
"Sound-absorbing chamber", Treadway B. Munroe et als, U.S. Patent No. 1,705,778, 19 March 1929 (using Celotex to construct a sound deadening chamber.
"Method of and apparatus for drying moving material", U.S. Patent 2,376,612, Carl G. Muench, New Orleans, assigned to Celotex Corporation, described a method and apparatus for drying sheets of artificial heat insulating lumber, preferably formed by the felting of bagasse fiber along with other materials necessary to make a satisfactory structural fiber board. 22 May 1945
"Sound-absorbing board for walls and ceilings," U.S. Patent 1,554,180, Sept. 15, 1925, Wilber S. Trader, assignor to Dahlberg & Company, Chicago IL. described an interior-use sound insulating product.
 "Insulite Co. v. Reserve Supply Co.," 60F.2d 433 (1932), Circuit Court of Appeals, Eighth Circuit, July 26, 1932. Web Search t/23/12. Quoting:
Rabbeted joints in material to which plaster or other material is applied are found in the Jones patent, No. 886,813. In this patent the composition is made up of plaster of paris, cement, or other like substance, combined with hair, wood fiber, sawdust, wool, wood shavings, excelsior, straw, or similar substances. The length of the lath covers three joists instead of four. The boards are arranged in staggered relation to each other and the joints are shiplapped. The specification states that after the boards or blocks are placed in position they may be covered with wallpaper or other similar material, which, of course, would include plaster.
"Machine for perforating Insulite Boards", U.S. Patent No. 1,306,283, Patented 10 June 1919, John K. Shaw, inventor from Minneapolis MN, describes improvements for machines for perforating Insulite Boards.
"Before you Build write for this mailing piece and a sample of Insulite", [advertisement], The Literary Digest, 13 September 1940.
 Museum of Fine Arts, Boston, web search 6/22/12, original source: http://cameo.mfa.org/browse/record.asp?subkey=3644 [Copy on file as MFAB_Fiberboard.pdf]
 "Separating the Fiber of Wood", A.S. Lyman, U.S. Patent No. 21,077, 3 August 1858
 Standards pertaining to fiberboard insulating sheathing:
ASTM C 208-95 (2001) – Standard Specification for Cellulosic Fiber Insulating Board. Type IV Grade 2 (Structural Wall Sheathing).
ASTM C 846-94 (2003) – Application of Cellulosic Fiber Insulating Board for Wall Sheathing.
ASTM D 1554 - Definitions of terms Relating to Wood Based Fiber and Particle Panel Materials.
ASTM E-72 (1997)- Standard Method for Conducting Strength Tests of Panels for Building Construction.
ANSI /AHA - A194.1, Cellulosic Fiberboard.
U.S. Department of Commerce: PS57-73, Cellulosic Fiber Insulating Board
A.F.A. (2003): Fiberboard Sheathing test results
 "Properties of insulating fiberboard sheathing",
Forest Products Laboratory (U.S.)
Luxford, R. F. (Ronald Floyd), 1889 (1960), original report 1955, citation:hdl.handle.net/1957/2489, web search 6/29/12, original source: http://ir.library.oregonstate.edu/xmlui/handle/1957/2489
Design of Wood Structures - ASD, Donald E. Breyer, Kenneth Fridley, Kelly Cobeen, David Pollock, McGraw Hill, 2003, ISBN-10: 0071379320, ISBN-13: 978-0071379328
This book is an update of a long-established text dating from at least 1988 (DJF); Quoting: This book is gives a good grasp of seismic design for wood structures. Many of the examples especially near the end are good practice for the California PE Special Seismic Exam design questions. It gives a good grasp of how seismic forces move through a building and how to calculate those forces at various locations.THE CLASSIC TEXT ON WOOD DESIGN UPDATED TO INCLUDE THE LATEST CODES AND DATA. Reflects the most recent provisions of the 2003 International Building Code and 2001 National Design Specification for Wood Construction. Continuing the sterling standard set by earlier editions, this indispensable reference clearly explains the best wood design techniques for the safe handling of gravity and lateral loads. Carefully revised and updated to include the new 2003 International Building Code, ASCE 7-02 Minimum Design Loads for Buildings and Other Structures, the 2001 National Design Specification for Wood Construction, and the most recent Allowable Stress Design.
Diagnosing & Repairing House Structure Problems, Edgar O. Seaquist, McGraw Hill, 1980 ISBN 0-07-056013-7 (obsolete, incomplete, missing most diagnosis steps, but very good reading; out of print but used copies are available at Amazon.com, and reprints are available from some inspection tool suppliers). Ed Seaquist was among the first speakers invited to a series of educational conferences organized by D Friedman for ASHI, the American Society of Home Inspectors, where the topic of inspecting the in-service condition of building structures was first addressed.
Defects and Deterioration in Buildings: A Practical Guide to the Science and Technology of Material Failure, Barry Richardson, Spon Press; 2d Ed (2001), ISBN-10: 041925210X, ISBN-13: 978-0419252108. Quoting: A professional reference designed to assist surveyors, engineers, architects and contractors in diagnosing existing problems and avoiding them in new buildings. Fully revised and updated, this edition, in new clearer format, covers developments in building defects, and problems such as sick building syndrome. Well liked for its mixture of theory and practice the new edition will complement Hinks and Cook's student textbook on defects at the practitioner level.
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: firstname.lastname@example.org. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones