Fiberboard sheathing © Daniel Friedman at InspectApedia.comAsbestos in Fiberboard Building Sheathing & Insulating Board

  • 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?

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Asbestos content of fiberboard sheathing products:

Asbestos hazards for fiberboard panels, sheathing, insulating board & ceiling coverings or tiles. Does or did Celotex® fiberboard or or Georgia Pacific® fiberboard or Homasote® or other fiberboard and insulating board products contain asbestos?

This article addresses worries about asbestos in fiberboard insulating sheathing - a question that comes up during building demolition and renovation.

The short answer is "no" but the history is interesting. We include research citations and testing lab referrals for concerned readers.

Fiberboard sheathing and Insulating Board products that were cellulose-based and that are discussed here include these brands and names: Beaverboard, Blackboard, Brownboard, Celotex insulating lumber, Georgia Pacific insulating board, Gold Bond insulating board panels, Homasote, Insulite, Nu-Wood Sta-Rite, and others.

This article series describes and provides photographs that aid in identifying various insulating board & fiberboard sheathing materials used on building walls and roofs, such as Homasote, Celotex, Insulite, and Masonite insulating board sheathing products. Here we provide fiberboard product names and we describe the components, properties, and applications of various fiberboard, hardboard, and insulating board or sound deadening board products.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Is there Asbestos Content in Insulating Board Products: Beaverboard, Celotex, Gold Bond, Homasote, Insulite, Nu_Wood?

Fiberboard insulation fragments used under bowling alley lanes (C) InspectApediaArticle Index - Insulating Board & Sheathing Board Products Asbestos Content

Is there Asbestos in Beaverboard?

6/25/2014 Sara said:

Does Beaver Board contain asbestos? I am cleaning out my grandmothers home and her basement has a Beaverboard ceiling. The home is approximately 65 years old but not sure how long the tiles have been in the basement


No, BEAVERBOARD is a wood fiber product not an asbestos-product. See BEAVERBOARD Identification for details.

Does blackboard sheathing, fiberboard, Homasote, Celotex dark or black insulating board contain asbestos?

Reader Question: Could my Georgia Pacific regular sheathing PS 57 and ASTM C 208 black board fiberboard sheathed house contain asbestos?

(Dec 15, 2012) Lisa said:

i live in a BISF house the interior walls are some kind of board they look like fibre board and are a light brown some are more grey..could they contain asbestos?

(Aug 8, 2015) Sue S said:
Doing some remodeling and we found this under the drywall - Georgia Pacific regular sheathing PS 57 and ASTM C 208 black board. Do you know if this product contains asbestos or a wood product?

Reply: Fiberboard sheathing is a wood product.


Fiberboard sheathing is normally a cellulosic product - that is, made from wood fibers. Here is what Georgia Pacific says - retrieved today from their site:

Georgia-Pacific regular fiberboard sheathing is certified and labeled by an ICC-ES recognized agency as meeting the requirements in ASTM C208, the Standard Specification for Cellulosic Insulating Board.

Similarly, ASTM C 208 is a standard for cellulosic (wood fiber) boards from which we excerpt:

This specification covers the principal cellulosic fiber insulating board types, grades, and sizes. Insulating board covered by this specification consists of six types: Types I, II (Grades 1 and 2), III (Grades 1 and 2), IV (Grades 1 and 2), V, and VI.

Cellulosic fiber insulating board shall be manufactured from refined or partially refined ligno-cellulosic (wood or cane) fibers, by felting or molding process, into homogeneous panels. The insulating board shall conform to the physical properties specified.

Hemp based fiberboard illustrated at THC Magazine at

Fiberboard panels are also constructed using hemp, as we illustrate above, touted by THC a hemp enthusiast magazine. As the article sports a silly pseudonym we haven't cited the author more directly. The magazine's email:

Also see CANEBOARD PANELS - separate article, and to identify this material

Reader Question: Well I am curious about the black board?

Well I am curious about the black board? Our house was built in 1962 and I need to drill through the black board to run electrical! Some of it is super brittle and falling apart anyway.

Was any of that stuff made with asbestos? What are chances it has asbestos in it? - Brett 9/4/2011

I was tearing off parts an outside wall connected to the garage to add insulation to the wall, after removing the plywood and tar paper I ran into Celotex fiber/black board.

I have a picture of it to upload if at all possible, but what I can see is that it is black fiber board with Celotex in yellow writing with patent pend. underneath the logo.

The house was built in 1950 and I am concerned this product actually may contain asbestos. Is there any way you can confirm or deny this or point me in the right direction to find out. - Jon T. 11/5/2011

Reply: Asbestos is not an ingredient in fiberboard insulating sheathing. See the product description & MSDS information above

Brett and Jon: it's easy to drill through "black board" Homasote or Celotex type building insulating sheathing. Generally the product is made from wood fibers, not asbestos - See the insulating board MSDS data sheet quotations in the FAQ discussion just above.

Though I've heard rumor, not fact, claiming that some fiberboard insulating sheathing products contained asbestos, I have been unable to find an authoritative source that confirmed that worry for any of those products.

Take a look at the insulating board MSDS data in the FAQ above about yard mulch and you'll see clear statements from the manufacturers on this matter.

Reader comment:

I only have to drill small hole to run wiring! Some of it's already crumbling and brittle! It's black on outside looks like wood inside. I too have not been able to find anything confirming or not confirming this concern! I'm stuck with new electrical to run and deciding if this is health issue or or not. Thank you again - Brett


Sounds as if the risk is nil, Brett. In addition to the comment we made above (wood fibers are not asbestos), you can minimize dust release by moistening the drilling area a bit. It's unlikely that there would be a measurable hazard from drilling a single wire-sized hole.

Too, if you have a generic objection to even small amounts of dust from any building material, you have the option of HEPA vacuuming during and after drilling to keep the dust out of the air.

See IDENTIFY Celotex® Insulating Board and Fiberboard Products

Is this a brown insulation board? I worry that it contains asbestos.

Fiberboard insulation used under bowling alley lane (C) InspectAPedia - ACReader Question: does the brown insulating board found under bowling alley lane material contain asbestos?

I am writing to you because I found your website after realizing I may have been handling asbestos-containing materials for the past year or so without knowing.

I don't know how it didn't occur to me sooner, but now I'm really scared and don't know where to turn for help.

I'm a teacher in NYC and, unrelated to my teaching, about a year ago I started working with old bowling lane flooring.

On the underside of bowling lane floors there is a fiberboard type material I believed was used for sound dampening.

I've handled and ripped off this material so many times without once thinking what it was- I think I was told it was Homasote and harmless.

Since many of these bowling lanes were installed many years ago, it worried me even more. Now I'm not so sure what it is and scared at the thought of what it could be.

I've spent the last few hours panicked at the computer searching for information, trying not to show my wife how scared I am.

If there is any way you could call me or share any information, I would be so grateful.

Bowling alley lane fiberboard insulation (C) InspectApedia ACYour website seems like the work of a very knowledgeable expert in this area so I'm turning to you for some advice. Attached below is a photo of some of the material- it is the black strips of material stapled to the black underside of the wooden board on the left.

Again, thank you in advance for any information you can offer. Feel free to call any time of day or night.

Thank you for taking the time to speak with me yesterday. I really appreciate your advice and insight into my situation. I attached a link below to a bunch of photos of this material that was attached to the back of three different pieces of the bowling lane.

There are just strips of this material attached with staples to the underside every few feet of the bowling lane. Some is black on the outside, some is white, and some is just like a brown cardboard color-- it all looks fairly similar on the inside.

If you can let me know what you think ASAP, that would be great- I know you told me not to be, but I am really worried about all this- I've been a mess all week at school.

Also, if you have those names or contact info for anyone who might be willing to test this material for me, that would also be incredibly helpful. I can't thank you enough for your help with this- feel free to call or email me back with any information. - A.S. 11/5/2013

Reply: The material looks like and probably is a wood fiber insulating board - not asbestos-containing. But protect yourself from demolition dust.

Fiberboard insulation fragments used under bowling alley lanes (C) InspectApediaThe material I can see in your online photos is almost certainly wood fiber based Homasote type insulating board. That is not an asbestos product. You can see more examples of this product


If nevertheless you want to have as sample of the material tested for asbestos content, the cost is usually minor - about $50. U.S. You can use any certified asbestos testing laboratory - and can find one via help given


As we discussed by telephone, you should, however protect yourself from breathing dust during any demolition project.

While the material you are working with was sandwiched between other building materials: bowling alley lane surfacing and the subflooring atop the floor structure - a location where it was rather protected unless the building flooded. In that location I speculate the material would be less likely to be contaminated by other exposures.

Nevertheless, breathing high levels fine dust particles that can be released into the air by the disassembly or demolishing of building is a health risk. Ultra fine particles, down in the 1u range are probably low in dust from fiberboard sheathing, but of course I don't know what else is in the environment where you are working.

To be ultra safe while working you'd wear a HEPA-rated dust mask. At a very minimum I recommend you wear a paper N-95 dust mask as well as other appropriate protection (eyes, hands) when disassembling and demolishing these materials.

If you decide to have a section of the material tested for asbestos, I would choose a piece of the insulating board that has that white skin or coating - to check that those products were not made with a facing of asbestos paper.

The history of fiberboard insulating products is interesting in that while the product itself is not an asbestos-based material, there were some questions of cross contamination with asbestos because of the manufacturing location of some brands.

However to date, except for Kollman (1975) I have not found scholarly studies nor other information that confirmed that wood fiberboard based insulating board did actually contain asbestos.


Reader Question: I was worried it contains asbestos but just looks too dark to be to me

Brown insulation board and roof leak (C) Daniel Friedman Ben KohlbeckI know you guys know a lot about asbestos containing products and just wanted advice on a wood like fibre board I found in a cellar, I was worried it contains asbestos but just looks too dark to be to me and more like other wood fibre boards you discuss on your website.

Any views would be appreciated. Picture attached! (feel free to republish as you like). - B.K. 06/29/2012


A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem - in the case of your photo it looks as if that area has been quite wet for some time - nice mushrooms growing - watch out for rotted ceiling joists or rafters.

It appears that the original ceiling was a brown fiberboard product that was later covered by drywall - visible in the left side of your picture. Your home is an old one - the roof sheathing boards visible where the ceiling has collapsed in from leaks were cut with a machine-operated pit saw.

Depending on the building's location, that could be a structure built before 1900.

Fiberboard products have been around in the U.S. since about 1858, though they were not widely used until the 1940's.

The brownboard in your (not so sharp) photo looks to me like a wood fiber product.

Depending on the age of the building and its location (in the U.S. ?)  that ceiling could have been originally installed using an insulating fiberboard from any of fourteen manufacturers, so there are indeed variations in both original color, and in color after wetting and age.

Can you tell me the thickness of the material? Insulating fiberboard's were usually 15/32" thick, with a few 1/2" thick; Hardboard such as some Masonite products can be 1/4? or thinner, and are hard. In your photo the board looks thicker than that, but the way it is tearing left me to consider a hardboard product.

I'd be glad for you to send me about 2 sq. in. in a clean ziplok bag, so that I can examine it in the lab (pro-bono, no fee). Unfortunately though I won't be able to examine it closely until our lab returns to the U.S. in January.

Question: What is Celotex Insulating Lumber? Do insulating board products contain asbestos?

Celotex insulating lumber

I have a home built in 1940 that used a brown fiber board called "Celotex Insulating Lumber" looks like is was designed to be used as sheathing and lath.

Made in either Chicago on Louisiana. Anyone familiar with this? Or know if it contained asbestos? - Dan Theisen 1/30/12


Dan, Celotex, a Chicago company, has been a producer of a wide variety of insulating sheathing boards for a long time and the company continues to produce modern insulating board products as well.

Celotex Insulating Lumber was introduced by the Celotex corporation in 1922, making it

"... possible for the first time to build a completely insulated house practically without extra cost". [8]

Our illustration (left) shows Celotex insulating lumber on the exterior of a Lebanon PA home.

There was some question, not substantiated by any research I could find, that because some wood fiber board products may have been made at the same site where asbestos-containing materials had been used, that there may have been some cross contamination; that theory has not been supported.

Checks & MSDS Citations for Asbestos Content in Fiberboard Insulation

A review of the patents and product description for Celotex insulating lumber products shows that asbestos was not among the product's ingredients.

See IDENTIFY Celotex® Insulating Board and Fiberboard Products.

For more about Celotex sheathing and products see CELOTEX HISTORY & PRODUCTS.


see FIBERBOARD SHEATHING MSDS for details about the ingredients or constituents of fiberboard sheathing products. They vary but ther're basically cellulose, bonder, and waterproofing.

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. )[11]

Watch out: ** Wood dust is listed by the IARC as a human carcinogen (Group 1).

In other words, the dose makes the poison for all substances.

Really?: we have read a few accounts indicating that while asbestos was not an ingredient in fiberboard insulating sheet products, some of these products may have been manufactured at or near facilities previously used to process asbestos materials.

The question of cross-contamination arose but I have not yet found a report of actual asbestos contamination in fiberboard from that source (nor others).

Does Gold Bond Insulating Board (IB) Contain Asbestos?

Gold bond wood fiber insulating board (C) HR Reader question: does this Gold Bond brown or black insulating board contain asbestos?

These photos are of insulating board found n the electric cupboard.

I would appreciate any feedback on this board, I'd not really noticed it until the renovations when I'd started seeing articles on building materials , but now I've realized it's exposed in the door well and my son has been crawling around there I'm pretty worried!

Many thanks - Anonymous by private email 2017/09/19

Reply: Probably not

Wood-based or cellulose-based insulating board like the product we show here would not be expected to contain asbestos unless by accidental cross-contamination by having been made at the same location where asbestos products were being manufactured.

The Gold Bond IB shown above looks like a wood-fibre based insulating board, typically covered with an asphalt or wax coating to improve its moisture resistance.

It should not be shedding much material of any kind unless it's being sawn or chopped or demolished.

I note the brown wood fibers where the black coating has been lost or worn away (red arrow in photo just above) where I see light material between two insulating board panels I am guessing that is the surface of a stud or of some other material.

Gold bond wood fiber insulating board (C) HR However at ASBESTOS PRODUCING COMPANIES where you will find National Gypsum in that alphabetic list, we discuss a number of Gold Bond™ products, all produced by National Gypsum, that did indeed contain asbestos.

Those were principally gypsum-based or cement-asbestos based materials.

National Gypsum, who made Gold Bond products, did produce other asbestos-containing gypsum based (plasterboard) products and also asbestos-containing cement-board products as well as other asbestos products such as some coatings.

See IDENTIFY National Gypsum Gold Bond® Brand Insulating Board

General information about wood or cellulose based insulating board products is


The use of asbestos in gypsum panels or "drywall" panels (plasterboard) is discussed

at ASBESTOS in DRYWALL and also


Reader follow-up: plan to test Gold Bond insulating board for asbestos

Very much appreciate the info! It is comforting to know it is wood based, I have been worrying since I saw that big Gold Bond logo on it and Googled the company. I actually sent a sample off to pro lab to be tested yesterday so I will update you when I get the results, perhaps it will reassure another of your readers.

I couldn't find much info on their insulation board online. In the door well on the same wall. I had mentioned there are several layers of exposed drywall/plasterboard (I'm assuming), likely old, so I will definitely treat that with caution, and look into it before demolition.

Again, thank you for the info and I'll keep you updated! - Anon 2017/09/21

Reader follow-up: results of lab-test for asbestos in Gold Bond fiberboard sheathing - negative

2017/12/06 reader anon updated us on the tests she had performed for asbestos content in Gold Bond brand fiberboard.

... sorry I am so long getting back to you! Lab results came back as 90% cellulose and 10% Bitumen, a relief! Thanks for your help with this, - Anonymous by private email

How to Distinguish Cellulose or Fiberboard IB from Plaster or Gypsum or Cement-Board Products that are More-Likely to Contain Asbestos

To distinguish between gypsum-based or plaster-based panels or cement-asbestos panels that may have contained asbestos (or are known to have contained asbestos) and cellulose or wood fiber board, look for a hard white or gray core in your insulating board or sheathing board panels.

If your panels are brown or tan cellulose-like fibers throughout, often with a waxy or dark asphalt surface coating (added for water resistance) those are a cellulose product, not a plaster or asbestos cement product.


see FIBERBOARD SHEATHING MSDS about the ingredients or constituents of fiberboard sheathing products.

See SHEATHING, GYPSUM BOARD for a separate description of gypsum or plaster based wall sheathing board.

Does or Did Homasote® Contain Asbestos

No, not according to the company nor in research that we cite at the Homasote® article given just below.

Homasote® company history, current product list, product composition & contact information are


Do Nu-Wood Sta-Rite Cellulose ceiling tiles contain asbestos?

Nu_Wood Sta-Rite cellulose ceiling tile (C) InspectAPedia

Reader Question: 2015/11/30 Leslie said:

I've been poking around the net trying to find out about tiles in a 1960 Maine lake house that fortunately still has the box in the attic Nu-Wood Stay-Lite cellulose fiber ceiling tiles 40-004 class d

This question was posted originally at ASBESTOS CEILING TILES

Reply: cellulose is not asbestos but there were asbestos warnings for workers at several Nuwood processing mills.

Nu-Wood Interiors catalog pages (C) InspectApedia[Click to enlarge any image] Shown here: Nu-Wood products catalog pages from 1936.

Leslie, the Sta-Lite cellulose ceiling tile photo that you posted is self-described as a 12" x 24" painted-bevel cellulose product #40-004 - that's wood fibers not asbestos. These products are classified as low-density fiberboard. Quoting the U.S. FPL,

Fiberboard is a generic name for construction panels made of wood or vegetable fibers. (Wilson 2007).

Here is how the manufacturer itself described Nu-Wood panels:

Made of clean wood fiber, this new wall and ceiling treatment consists of specially designed and accurately fitting tile, plank and wainscot units, in large, easy-to-handle sheets. A high degree of insulation value is built into these Nu-Wood products. 

The image you contributed will be added here to assist other readers and to invite further comment that may give us more information. Thank you.

I'd be grateful if you'd take another look at the box for any other labels or markings. Please also use our page bottom CONTACT link to email photos of both sides of the ceiling tiles themselves as well as an installed ceiling if one is present in your home.

Nu-Wood is described by the U.S. Forest Service Technology & Development Program as a cellulose (wood-based) fiberboard product that was produced as early as 1938 including brand names Masonite, Nu-Wood, Du-X and Fir-Tex.

Those early products were not ceiling tiles but rather wood-fiber hardboard or softboard sheets used as a finish material or as a lath or base for plaster walls and ceilings.

Related products included other familiar brand names beaverboard, caneboard, Celotex, Homasote, Insulite, Masonite, Gold Bond, National Gypsum, Nu-Wood, and Upson Board are described by links given at the MORE READING section of this article.

These include principally wood-based or cellulose or plant-based products not asbestos products except for plaster or gypsum based wall sheathing.

However for some of these wood-based or cellulose products, cross contamination with asbestos did occur. See our NU-WOOD discussion just below for an example.

It is noteworthy that these products indeed included some ceiling products and installations as the U.S. Forest Products lab has documented, illustrating a fiberboard ceiling in a ranger station. Excerpting from the US FPL document cited below we include that image here:

Fiberboard ceiling panel, US FPL excerpted from a number of asbestos and mesothelioma information sources point out that some fabrication plants that at one time processed asbestos materials also processed wood-fiber products and thus there were hazards of cross-contamination and worker exposure to asbestos in those locations.

None of those references that I have read (this is not an exhaustive research) confirmed asbestos hazards in the cellulose products themselves, even though such is technically possible. An example follows:

Watch out: further research is needed to confirm the relationship between Nuwood and Nu-Wood ceiling products but we have found a warning issued by the Minnesota State Health Department cautioning that workers were exposed to airborne asbestos fibers when working in three Nuwood production areas at the Cloquet plant in Minnesota between 1958 and 1974.

Excerpts and the document reference are given below.

Asbestos was used at the Conwed Corporation (Wood Conversion Company) plant in Cloquet, Minnesota, in making ceiling tiles and other products from 1958 through 1974. Mixing, sawing, grinding, and other processes used in making these products created asbestos-containing dusts that were inhaled by many workers.

This is how most workers were exposed to asbestos.

Asbestos was used at the Cloquet plant in the manufacturing process during the years 1958-1974, and this is when the greatest number of workers were exposed. It is possible, however, that some workers were exposed to asbestos outside this time period.

For example, workers involved with maintenance and repair of equipment that had asbestos insulation, such as steam pipes and boilers, may have been exposed to asbestos before or after this time period.  

We do not have information on actual levels of asbestos in the plant air. Asbestos dust levels probably varied at different locations and at different times. Overall, people who worked in the following departments probably had more exposure to asbestos than other workers:

People who worked in the dustiest jobs for the longest periods of time would have had the most exposure to asbestos.

Anyone who worked at Conwed's Cloquet plant at any time during the years 1958-1974 may have been exposed to asbestos-containing dusts. Company records and other sources of information show that nearly 6,000 workers were employed for some period of time during those years.

The Minnesota Department of Health has been working for several years to identify and locate all former Conwed workers employed during those years.

Several types of asbestos from different suppliers were used at different times at Conwed during the 1958-1974 time period. Although all types of asbestos can cause asbestosis and lung cancer, the risk of mesothelioma may depend on the type of asbestos.

Conwed has not provided the State with information about the types and amounts of asbestos used during different years.

Most workers wore their work clothes home or took them home for washing. Asbestos-containing dusts could have been carried into the home on the workers' clothing, shoes, or hair.

Any exposure to family members in the home would be small compared to exposures in the plant. The risk of disease from these household exposures would be very small.

Watch out: Court documents assert that some Conwed ceiling tiles and/or some Simpson ceiling tiles and other products contained asbestos. (Wagner v. Bondex, Simpson, & Conwed, 2012). See SIMPSON CEILING TILES for details.

Research: Asbestos found in Nu-Wood, Wood Conversion Company, Bondex, Simpson Timber products

Coarse Random-Oriented Wood Strand Fiberboard

Question: are these asbestos-based panels?

Fiberboard panel, random long fibers (C) CE Fiberboard panel, random long fibers (C) CE

I'm hoping you can tell me what these panels are and whether they have asbestos in them.

I just purchased them as a cheap way to put up a partition wall at the family cottage and the next day it hit me like a bolt that they might have asbestos!

The panels are 4' x 8' and heavy as all get out! The seller was an older gentleman who said his uncle gave them to him & that he's had them in his garage for over 40 years.

I've attached pictures. #143018 is a side view. #143034 is a corner that is damaged and gives a better view of the materials (shredded). They were originally white but someone painted them grey.

Thanks so much for your help! - Anonymous by private email 2018/02/15

Fiberboard panel, random long fibers (C) CE Fiberboard panel, random long fibers (C) CE

Reply: not likely

Without a lab analysis I cannot say absolutely that an unknown product is asbestos-free, but your photos look to me like a relatively modern wood product, a coarse, random-orientd wood- strand fiberboard product.

If these panels are truly 40 years old that would have them produced in 1978 when asbestos was still used in some building products. But with a few exceptions, principally from cross-contamination, 100% cellulose, non-cementious, wood-based fiberboard products do not contain asbestos.

Watch out: if the binding material in your panels is cementious I think these are a cement fiberboard product such as the strand-reinforced cement board produced by Architonic and shown just below. Such cement products might indeed contain asbestos, depending on when and where they were produced.

Cement fiberboard by Architonic at

Above: wood fibre-reinforced cement board panels describe by the Architonic, a UK source of buidling products who insists on keeping the actual product manufacturer and identity a secret, Architonic ID: 1184351, prompting us to decline to cite the Archi tonic website directly.

Savolit wood fibre panel at

Other readers: see this similar-looking but light-weight panel product [shown above] found by our correspondent above: Savolit Wood Wool Building Panel | SKANDA Acoustics Ltd, Savolit, a lightweight wood wool building panel for external cladding, internal lining, base board for plastering, carrier board for render and internal partition walls.

These panels are listed by SKANDA Acoustics Ltd 67 Clywedog Road North, Wrexham Industrial Estate, Wrexham, LL13 9XN U.K., Tel: 01978 664255

You can see a catalog of these products by type and properties at DEFINITIONS, ENGINEERED WOOD HDF LDF LVL MDF MDO OSB

OSB panel structure, Lindquist patent 1995 at InspectApedia.comMore-modern coarse wood-strand or wood-fibre fiberboard products (popularly "OSB" or oriented strand board) use larger chips of wood either in a random pattern or oriented specifically for strength, and are seen in more-recent patents like

Wood-based or cellulose-based fiberboard products are not asbestos-containing products (normally) and have been in use in the U.S. since the early 20th century, as you will see in

References on Possible Asbestos Contaminants in Fiberboard Insulation Products

Some interesting citations pertinent to the question include both articles and patents that I include below

Asbestos Content in Gypsum-core Homasote exterior sheathing (gypsum board) product from 1940s.

Gypsum board wall sheathing © Daniel Friedman at InspectApedia.comWas there a Homasote product used in the early 1940s on the exterior of houses that looks like sheet rock? How long does this last for?

If it is still on the house, could it contain asbestos and/or contain mold due to lack of sunlight?

Was there "code" at some point that would have forced individuals who were to replace vinyl siding on the house over these boards to replace with proper products after a certain date? Thank you, K.B.C.

Reply: Properties of Homasote® type fiberboard compared with gypsum-based exterior wall & roof sheathing boards

A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with sheathing, leaks, and mold or asbestos sources in buildings - the concerns you expressed. That said, here are some things to consider:

Homasote® fiberboard sheathing is a wood fiber product, not a gypsum or plasterboard product. However there were indeed gypsum-based sheathing board products used on buildings both as wall sheathing (under siding and over studs) as well as roof sheathing.

Please see HOMASOTE HISTORY & PRODUCTS to read the ingredients of Homasote® panels: principally recycled newspaper.

Some Gypsum board and plaster board products indeed contain asbestos as does some joint compound

Watch out: Indeed some gypsum--based drywall products did contain asbestos into the 1980's. I have not, however, tested nor seen test results specifically for exterior wall sheathing using that material. I suggest sending a small sample, a square inch would be plenty, to a certified asbestos testing lab - the cost should be $10 - $50. U.S. Do let me know what you find as the results will be helpful to other readers.

Even when gypsum board or plaster board did not itself contain asbestos, some joint compounds did contain that material right up into the 1980's. But used as an exterior sheathing, at the buildings I've seen, there was no top coating of joint compound and tape on this type of sheathing board (as there would be on drywall used for interior wall coverings).

Asbestos in FlintKote Insulating Sheathing Board?

FlintKote building products including roofing, sheathing, insulation at InspectApedia.comReader Question: does FlintKote Stalward Sheathing contain asbestos?

2018/03/15 jessi said:

Does stalwart sheathing contain asbestos

Illustration: FlintKote building products, Life Magazine, 25 April, 1960. [Click to enlarge any image]

Reply: Stalwart Sheathing, by FlintKote was principally a cellulose product but its coatings might contain asbestos


FlinkKote's Stalwart Sheating was a cellulose-based insulating sheathing board widely used in the 1960's in North America.

From what I've been able to find the fiberboard was impregnated with asphalt and perhaps other water-resistant materials such as waxes, and often surfaced with asphalt-impregnated paper or "felt".

Some asphalt-impregnated felts contained asbestos. Generally cellulose board products did not except where cross-contaminated by having been manufactured at a facility that also handled asbestos.

FlintKote building products including roofing, sheathing, insulation at InspectApedia.comAn exception MIGHT be found in some FlintKote products including insulating sheathing that were coated with a bituminous layer that included vermiculite, as you'll read in the patent disclosures below. The potential for asbestos in these products is that some vermiculite contains asbestos.

The history and ingredients in FlintKote insulating sheathing can be found, at least partially, in patent disclosures assigned to FlintKote

This much-later patent citation

Asbestos was used in other FlintKote products including the company's ThermalKote a water resistant siding, and in fire-resistant products:


Note that some Vermiculite contains asbestos.

The company prodcued roofing products containing asbestos and also asbestos-cement shingle siding.

These patents assigned to FlintKote give more details of the history and constituents of FlintKote insulating sheathing



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