Construction & Renovations on Buildings with Fiberboard Sheathing
FAQs about repairing, remodeling, or adding on to buildings where wall or roof sheathing is an Beaverboard, Celotex, Homasote, Insulite
SHEATHING FIBERBOARD CONSTRUCTION - CONTENTS: how to repair, add-on-to or remodel buildings at which an insulating board sheathing product was use on exterior walls or roof or on the building interior walls and ceiligns.
POST a QUESTION or READ FAQs about buildings at which an insulating board sheathing product was use on exterior walls or roof or on the building interior walls and ceiligns.
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
Building on or remodeling structures where insulating board sheathing products were used. This article provides questions & answers about procedures to repair, remodel, extend, or add-on to buildings where an insulating board sheathing product was use on exterior walls or roof or on the building interior walls and ceilings.
Construction & Renovation at Buildings with Fiberboard Insulating Sheathing
Question: uninsulated buildng, no vapor barrier, just fiberboard
(Mar 3, 2014) Re-posting without link (image to be added to article & comments above) derek terveer said:
[Click to enlarge any image]
House: 1983 twin home in Minneapolis suburb.
Exterior wall between floors (9" vertical) has no fiberglass insulation or vapor barrier and thus the fiberboard sheathing is exposed to internal air and vapor. Total area is approximately 30 sq ft. We get temps down to -15F in the winter.
See diagram given here.
1) Is this common construction 'technique' from the 80's?
2) I am concerned about water damage from condensing water vapor.
3) I am concerned about heat loss.
4) What is the standard mitigation technique and cost?
5) Is this worth worrying about?
Derek I agree that continuing the housewrap over the band joist is a better practice
In Steve Bliss's Best Practices article series provided at InspectApedia we argue for housewrap over the band joist not because of air penetration through the joist itself (nonsense!) but because of possible leaks at the framing connections & interfaces; I'd prefer to see housewrap over the rim joist or band joist, and indoors we'd insulate on the interior side of that framing member to avoid a cold band of heat loss around the home.
Yes, the method you described was widely used if not the absolute most energy efficient. A thermal scan of the building exterior would get us past arm-waving and on to an actual assessment of the heat loss at your building from this feature and might also point out other heat loss points of greater concern.
Regarding improvements: it'd be a costly deal to R&R siding just to add housewrap over this feature, but insulating from the interior is likely to be worthwhile; if you used foam insulation that'd also address air leakage.
Reader Follow-up Query: fire code on fire resistance
(Apr 18, 2014) derek terveer said:
I see this article states "If the boards are exposed in an occupied space, fire codes will require that a fire resistant finish surface such as drywall be installed."
In my case, I have noticed that there is exposed fiberboard in an empty chimney chase (outside the living space), with a piece of foam over a portion of it (because the original builder didn't insulate the wall covered by the chimney chase).
1) Does the entire exposed area of fiberboard on the wall adjoining the living space inside the (empty) chimney chase have to be covered with a fire resistant surface? There is a lot of it and it would be quite difficult to reach - requiring a ladder built up within the chase itself.
2) Does any kind of fire resistant surface have to be installed over the foam that has been screwed on to the outside of the fiberboard?
The chimney chase has a sheet steel cap.
Derek, thanks for the interesting fiberboard v fire exposure question. As the interior of a chimney chase is not occupied space, different construction guidelines apply. But it would make sense to check with your local building department about the allowable materials for a chimney chaseway and while you're at it, as you're describing exposed foam therein, mention that as well, and finally, check the requirements for fire blocking in the chimney chase against how yours was constructed.
The thing that I'm afraid of is that the city may make me firerock the entire inside of the chimney chase, which would be an awful lot of work. It is pretty constricted space inside and I'd probably have to end up building a temporary work platform of some kind inside the narrow chimney chase. There were a number of things in this house that were not built to code, even back in the 80s (1984), so I don't know if the original builders (long bankrupt) were cheating on this or if it was allowed by code at the time.
As a compromise, I'm thinking of screwing a sheet of decorator drywall (3/8") on top of the foam to retard ignition (165F, I believe) and fire promotion. It should never get that hot in the chimney chase so it is mostly to retard oxygen and promotion.
would test the worry about what the city might make you do against the loss against which the codes are trying to assure. In my experience people who approach code enforcement officials asking for help often find officials cooperative and happy to find an acceptable solution to the concern. Doing a half-baked job that might fool someone later into thinking that the proper installation was made could be very dangerous in several regards.
Start by finding the answer to the question.
Question: Why do I only see fiberboard insulating sheathing on older homes? How do I deal with post-fire and smoke odors?
I have a home that was damaged by smoke and water and has fiberboard wall sheathing. There is an issue as to the affect of smoke and water on this product. It seems to be porous and susceptible to the water and smoke. How would the front side of this product be cleaned and dried out.
Why is this product not as popular as before.? I only see it on homes 30 years plus - Blaine Jelus 11/17/2011
Reply: Standard post-fire odor control sealants
Regarding the shift away from using fiberboard sheathing in homes, I have not yet found an authoritative account but I can offer several probable explanations:
First it should be noted that bagasse (sugar cane) based insulating fiberboard sheathing continues to be produced in the U.S. at least by Celotex Inc., as you will read in our Celotex section of the article above. It appears that a common contemporary (2012) application of this product is in the construction of mobile homes. Product literature for Blue Ridge Fiberboard describes Celotex SturdyBrace® for use in wood frame construction as well..
A 1955 U.S. FPL report offers the early history of growth in the use of insulating fiberboard sheathing and is quoted in the article above. By 1950 the product was used extensively in some areas of the U.S.
I believe that rising energy costs that came in several waves after the 1950's and especially beginning in the Arab oil crisis in the 1970's led people to focus on much higher levels of building insulation in the attics and walls of typical wood frame residential buildings than the less than R-2 provided by 1/2-inch insulating fiberboard sheathing used alone (as it was at first).
So a combination of plywood (later OSB) structural sheathing and the placement of usually 3 1/2" fiberglas batts in 2x4 walls or 6" batts in 2x6 walls gave both structural stiffness and a much higher level of insulation (R11 to R19 as opposed to about R2-3). There was less incentive then to continue to use fiberboard as the primary building sheathing.
However some producers, including Celotex, have continued to produce newer insulating board products including those made of open or closed cell foam covered by a paper or foil surface, for example Celotex XR-4000 or Celotex CG-5000 foil-faced polyisocyanurate foam board. These products are still lighter than fiberboard and offer still higher R-values.
Blaine: Fiberboard insulating sheathing does not, in my field experience, pose more of an odor or smoke absorption problem than other wood-based building materials or even drywall.
Regarding post-fire deodorizing of a building that used fiberboard wall sheathing, at fire jobs I've inspected, regardless of the building materials used to construct wood framed walls (plywood, OSB, wood studs, or wood fiberboard insulation) in areas of smoke and fire odor problems the contractors often conclude by coating the wall cavity with a paint intended as an odor sealant - this step prevents persistent odors that may linger and annoy building occupants after the finish surfaces have been replaced.
Question: Should I remove Georgia Pacific fiberboard sheathing when re-siding my home?
Hello, I am having new vinyl siding put on my home. This GP Sheathing was underneath. Do you recommend leaving it and residing the house or pulling it off and putting newer material up? It was built in 1982. Thank you! - Robert 8/17/11
I'm not sure why you'd need to remove old sheathing boards when installing siding, but if you did so you may find that you need to install plywood or OSB or another wall sheathing product in its place. Provided the original sheathing was un-damaged, you're not gaining anything that I can see.
Question: how do I repair a small hole in fiberboard sheathing
How do I repair a 2 inch hole in celotex? - Jerry 7/30/12
If the wall cavity is open to access you can add insulation of just about any sort: fiberglass, foam, or even a scrap of celotex or similar fiberboard insulation. Frankly, if the wall is insulated and that exact spot in the fiberboard sheathing is not required as a nail base for siding, just repair the exterior siding and you should be fine. You can leave the fiberboard alone.
Question: how do I install flanged replacement windows on a fiberboard sheathed building?
Can flanged replacement windows be installed over 1970's era fiber board sheathing? using the same general installation method that is used if the exterior were sheathed with plywood or OSB? - Walt 9/17/2012
Walt, it should be fine as long as there is framing to nail to on all sides, and flashed against leaks. If not you'll need to frame in or fir out a rough opening for your windows to fit the replacement unit.
Question: fiberboard sheathing used behind brick veneer wall gets wet - is that OK?
I have fiberboard installed behind the brick veener of my house. Both faces are black, but the middle of it has the natural fiberboard color. The fiberboard start at the top of the brick veener wall (1 1/2 inch air gap) and stop at the foundation in front of the sill plate. If some rain goes behind the brick, does the fiberboard will resist over the long term? I was surprised to realize that at a specific section of the sill plate, there were some signs of past water infiltrations. - Phillipe C. 10/31/12
Fiberboard is generally treated with a moisture repellent and can tolerate a rare wetting event but in my opinion was not designed for frequent wetting. It is common for a brick veneer wall to be constructed with a drainage plane behind the brick. Be sure that the weep openings at the bottom of the veneer wall are open so that you don't accumulate water (inviting insects into the structure).
Question: Can I glue carpet on to Fir-tex carpet board underlayment?
I have a floor underlaymet band name "fir-tex carpet board" can I glue down carpet to it? and if so what is the process? thank you - V. Tedesco 11/8/2012
Low density fiberboard will not bond well to carpet adhesive, and some LDF fiberboard coatings using wax may prevent adhesion at all. Harder fiberboard products, uncoated, may accept carpet mastic applied with a notched trowel ok.
Question: does insulating fiberboard meet the 2009 IRC/UBC requirement?
(Dec 10, 2012) Anonymous said:
We have a insul board installed on the exterior walls of our 1 story house. We are addting a second floor additon. Will the insul board meet the 2009 IRC/UBC requirements?
Insulating board sheathing is code-approved provided that the structure has the requisite bracing. Since final construction code approvals are the authority of the local building department, that's whom you should ask - as there may be local codes that pertain.
Question: found black exterior sheathing on 1974 home - thinking I should replace it with OSB?
(Mar 27, 2014) Charles said:
I have recently discovered that my home built in 1974 has black fiberboard exterior sheating, when I pulled off some of the pink fiberglass insulation, I noticed that there was quite a bit of mositure, as I am redoing the whole house, this was the same in the kitchen and bathroom. So basically the fiberglass insulation facing the fiberboard as well as the fiberboard facing the inside of the house is wet, even frozen in some spots. After removing the insulation overnight, the fiberbaord dried up in the spots that I pulled off the insulation. I have aluminum siding and plan on residing the house with vinyl in the summer or early spring, I am thinking I should replace the fiberboard with OSB? Any thoughts on this issue.
Unless the fiberboard actually absorbed water, can't be dried, and / or is damaged, replacing it is not likely to be cost effective nor necessary. Unless there is a serious mold problem I'd leave the sheathing in place.
THese products were treated to resist moisture uptake, so perhaps the moisture you see is on the surface.
Instead, focus first on where that moisture came from.
If there are leaks in the exterior wall you'll still have a problem.
If the problem was leaks inside the wall - say from plumbing - those need to be repaired.
If the problem was (as is likely) the absence of a working vapor barrier or more likely, air leaks into and out of the wall, those are what need to be addressed when repairing the building.
Question: can we dispose of fiberboard by using it as mulch?
Is Celotex recyclable? We just removed some and I wondered if it could just be broken up on the ground like mulch or does it have chemicals in it. - Karen Bradshaw 7/25/11
Reply: fiberboard sheathing or insulating boards are not recommended as yard mulch
Karen the recycle-ability of fiberboard sheathing products like Celotex or Homasote is an interesting one. These products that are made principally of wood fibers or other plant fibers and a binder and are usually disposed of as construction debris. The properties of insulating fiberboard sheathing were thoroughly described by the U.S. Forest Products Laboratory in a 1955 report as well as in original and current manufacturer's product literature and MSDS sheets.
But watch out: trying to break up any fiberboard product into small mulch like fragments risks creating an irritating or problematic dust hazard for eyes and respiration.
I'm unsure how well the binder or coating chemicals are bonded to the material (some products used paraffin), but I wouldn't use this product for mulch in any case. Some newer insulating boards may contain plastics and some older ones appear to contain bituminous coatings or binders. You will find that the treatments used to make these insulating boards moisture resistant and to impart stiffness also mean that they will not break down or bio-degrade as a yard mulch.
Reader Question: how do I apply stone veneer to fiber board sheathing?
6/19/2014 Amy VonArx said:
What are the spec's for putting stone veneer on fiber board sheeting? Do I have to cover with OSB or plywood sheeting first? My house was built in 1964 and has this on it. I want to stone veneer the front porch area.
Amy, masonry veneer walls are typically supported by a structural ledger of steel, or by a foundation wall, and are also secured by mechanical connections to the building structural wall. There are also requirements for moisture barriers, weep or drain openings, and other derails.
Search InspectAPedia for or see these articles (by clicking on the links below)
No FAQs have been posted for this page. 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.
 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.
Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program. 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 Home Reference Book, a reference & inspection report product for building owners & inspectors. 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.
The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
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.
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
Wikipedia provided background information about some topics discussed at this website provided this citation is also found in the same article along with a " retrieved on" date. NOTE: because Wikipedia entries are fluid and can be amended in real time, we cite the retrieval date of Wikipedia citations and we do not assert that the information found there is necessarily authoritative.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
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.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.