Homasote panels showing its characteristic gray-tan color (C) DFHomasote® Fiber Board
History, Composition, Identification of Homasote®

  • HOMASOTE HISTORY & PRODUCTS - CONTENTS: Homasote® Company history, contact information, product line.
  • 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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Homasote® fiber board company & product information:

Here we give a brief history of the Homasote® company and we describe its products. We also discuss hHow to recognize/identify Homasote® insulating fiberboard building sheathing products used as exterior wall sheathing and as interior wall & ceiling surfaces.

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, Upsonboard, Nu-Wood and other insulating board sheathing products.

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Homasote®, Fiberboard & Insulating Sheathing Board Products

Homasote 440 Sound Barrier Panel on sale at Menards (C)

Homasote® Brand Boards & Panels: Composition & Identification

At FIBERBOARD SHEATHING IDENTIFICATION we explain that Low-density fiberboard panels and products trace their origin in the U.S. to Azel Storrs Lyman's 1858 patent for separating the fiber of wood and for the manufacture of paper and other purposes. (Jester 2014).

The Agasote Millboard Co. (Trenton N.J.) was formed in 1909, and as Jester notes, by 1916 that company was producing the widely-known Homasote brand fiberboard that probably has been a century-long thorn in the side of Celotex, Insulite Nu-Wood, and Masonite.

By 1910 in the U.S. the manufacturer of fiberboard made these products available to builders and homeowners for use as a sheathing product that was used on wall exteriors, wall and ceiling interiors, and even as roof sheathing.

In my personal experience and OPINION, and despite its description as quite weather resistant, general use of low-density fiberboard roof sheathing was a bad idea.

Image above: Homasote® 440 Sound Barrier panel fiberboard illustrated on sale at a Menards Lumber & Building Supply store.

[Click to enlarge any image]

Recycled Paper Comprises Homasote® Panels & Products

Definition of Homasote®: Homasote® brand wallboard and panels used for building sheathing and historically for walls and ceilings as well as underlayments are a cellulose-based product made from re-cycled paper using water to form a slurry that under pressure is formed into panels to which small amounts of additives are given before the product is cut to desired size.

While we generally describe Homasote® as well as other fiberboard panels as a "cellulose" or "wood fiber" product, currently Homasote's products are actually produced principally from recycled or "post-consumer" paper and newspaper.

Interestingly, cardboard is separated from the paper waste stream and re-sold since according to the company the long fibers in cardboard are not compatible with Homsote® production.

Homasote's paper input is pulped and mixed with hot water to produce a gray slurry that provides the characteristic color of the final Homasote® board product line. The gray results from ink content of the recycled newsprint used in production.

Small amounts of a wax emulsion and a biocide are added to the paper slurry before that raw material is formed into forming molds that squeeze out water before the boards are dried and cut to final size.

The company informs us that Homasote® board is weather-resistant, structural, insulating, and has 2-3 x the strength of "typical light density wood fiberboards". - Retrieved & excerpted 2017/11/08, original source:

Does Homasote contain asbestos?

No, no one would not expect this product to contain asbestos and the company affirms that in comments at their own website (8 Nov 2017 see citation links below).

But some other fiberboard brand products, even though made of cellulose, may contain asbestos due to cross-contamination.

That fiberboard asbestos concern is described at SHEATHING, FIBERBOARD ASBESTOS CONTENT

Homasote® Identification: check color & texture & cross section

Homasote panels showing its characteristic gray-tan color (C) DFDespite widespread use of the word Homasote® to describe brown fibrous and soft board panels, actually Homasote is gray or in my OPINION gray-tan in color, as it's produced from post-consumer paper.

However once installed the product may have been painted or covered-over so an inspector cannot assume that she will always find the gray color without some digging into the structure.

The Homasote picture shown here is from a discontinued product previously sold at Lowes stores.

According to Homasote®,

[Homasote brand fiberboard products in] cross section would not show layers of fiber since our products, unlike other fiberboards, are not layered.

With aging our products normally have a yellowish brown tint otherwise they are gray.

In all cases, unsanded Homasote Products all have very visible patterns on the face and back side surfaces. As far as I can tell, none of the samples shown below [at Unidentified Fiberboard Products] have our mold patterns.

Each fiber is coated with a wax emulsion thus making the panel weather resistant.

In a vertical application, should the panel get wet, the water will wick out the bottom as long as it’s installed properly and elevated off the bottom surface. In a horizontal application it will react like plywood and the water should not de allowed to pond on it especially after it stops raining.

Where structural shear strength is needed by using the company's recommended ring-shanked nails in a specified nailing pattern.

Current Homasote® Products & Homasote Company Information

As of November 2017 the following are excerpted from product information provided by the Homasote Company at the address given below.

Homasote® Company History & Contact Information

The Homasote Company, originally named the Agasote Millboard Company, was founded in the U.S. in 1909 by Eugene H. Outerbridge as an "offshoot" of the Bermuda Trading Company.

The Homasote Company's original product was sanded millboard panels used to form the lining and sides of railroad carriages, later used for Vehisote, applied as automobile tops installed on Ford, Buick and other vehicles. In World War I Homasote® panels were used to construct field hospitals and military hospitals.

In 1925 the company's board products were promoted as building and insulation materials. Older readers including the author [DF] will recall finding Homasote®or Thermasote® panels on walls and ceilings in homes and other buildings.

Starting in 1939, Homasote® was among companies providing modular constructed homes, making the company one of the early modular suppliers. The company's history page notes that their first modular home project in Valajo California put up 977 houses in 73 working days. Modern modular home construction is discussed at MODULAR HOME CONSTRUCTION.

That experience and product development was no doubt behind the use of Homasote's Precision Built System of Construction to put up 5000 miliatary homes in the Norfolk Naval Shipyard in Portsmouth VA (seen by this author).

The following is excerpted from the company's About-Us web page at on 2017/11/08

... Homasote Company is the oldest manufacturer of building products made from recycled materials in the U.S., and the only manufacturer of its kind in the Americas. Our 600,000 square-foot factory complex [is in ] in New Jersey, ... Each production day we recycle (and keep out of landfills) up to 100 tons of recycled cellulose fiber.

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

Gypsum board wall sheathing (C) Daniel FriedmanWas 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.

Starting at the top of this article HOMASOTE HISTORY & PRODUCTS you will read that the ingredients of Homasote® panels are principally recycled newspaper with a small amount of a wax and a biocide.

Having inspected quite a few buildings that used this material, my OPINION is that it has proven surprisingly durable so long as it was kept dry.

Wet panel board or gypsum board material of any brand can become soft, and also one might find mold growth on the paper backing of the gypsum board.

To identify Homasote you can also see IDENTIFY Homasote® Brand Fiberboard

We also describe these two different product types in more detail:


FIBERBOARD SHEATHING - Sheathing Celotex Homasote & Other (this article)

Also see FRAMING MATERIALS, Age, Types where we describe the history of building framing and sheathing materials.

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).


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