Does Canadian drywall or "sheetrock" contain asbestos?

Questions & answers about how likely is it for asbestos to be found in Canadian gypsum board or drywall systems.

Asbestos content in Canadian Drywall, wallboard or "Sheetrock" or gypsum board & in joint compound FAQs

These questions & answers about asbestos content in Canadian drywall were posted originally

at ASBESTOS in CANADIAN DRYWALL - be sure to read that article.

...

Dry powder Even Temp Dry Gypsum insulation

Hi, I have dry gypsum powder insulation in my attic. The bags are marked as Even Temp Dry Gypsum insulation from Western Gypsum products. Would this contain Asbestos? Thanks!

 

 

Here are 2 more pics, that is all for markings. A few of these bags were left empty on top of the loose powdered gypsum that is spread between every ceiling joist to a depth of 4-6 inches. I grabbed a sample for testing. 2023-11-27 by Cody

...

Moderator reply:

@Cody,

Please find your photo, question, and our research results so far now at

ASBESTOS in CANADIAN DRYWALL

in the section

WESTERN GYPSUM PRODUCTS LTD. ASBESTOS?

https://inspectapedia.com/hazmat/Asbestos-in-Canadian-Drywall.php#WesternGypsum

where we'll add what additional photos you can post as well as what else our research finds.

Can you confirm just what we're looking at: is this a bag of dry gypsum or an actual wall or attic insulating batt?

More reply: Walite dry powder insulation

@Cody,

Continuing

Another brand of dry powder insulation that was probably sold in Bates Valve Bags or an equivalent was Walite, described as "A High Grade Diatomite, sound and vermin and fire proof, for insulation."

The instructions on that product bag read:

For insulation: pour dry two inches thick over ceiling.

For concrete: add 3 to 5 pounds to one bag of cement.

Ideal in plaster or stucco work.

Deer Park Natural Pigments Corp., 1323 N. Cedar Street, Spoken Wash. "Ask Your Dealer".

Notice that the ingredient in Diatomite or diatomaceous earth, used here as an insulating powder, is not gypsum but rather diatomite - a powdered material made from sedimentary rock that in turn was composed of fossilized skeletal remains of aquatic algaes - diatoms.

Diatomaceous earth or diatomite was used in a range of applications including filtering and medical.
- source: Zahajská, Petra, Sophie Opfergelt, Sherilyn C. Fritz, Johanna Stadmark, and Daniel J. Conley. "What is diatomite?." Quaternary Research 96 (2020): 48-52.

Really? In my OPINON the idea of using either of these powdered substances, gypsum or diatomite, as building ceiling or wall insulation runs the risk of generating a gooey or cementious mess when, over the life of a building, a roof, driven rain, or plumbing leak soaks the powder.

I think that if there is a risk of asbestos it wouldn't be in Diatomite and if it's associated with gypsum in powder or wallboard form it'd be principally in joint compound used to finish joints and nail or screw heads or in some other applications, in mastic adhesive used with these products.

Really? Not entirely. At least some research reported low levels of chrysotile asbestos in gypsum-based materials:

Hu, Ruizhong, Jacob Block, Joseph A. Hriljac, Cahit Eylem, and Leonidas Petrakis. "Use of X-ray powder diffraction for determining low levels of chrysotile asbestos in gypsum-based bulk materials: sample preparation." Analytical Chemistry 68, no. 18 (1996): 3112-3120.

and in some applications, asbestos was deliberately blended with gypsum:

[Note: I think a clear example of this application was the use of asbestos/gypsum cementious paste used to insulated heating boilers and heating pipe elbows and valves - DF]

Levin, Lester. "Properties and Uses of Asbestos." Asbestos The Hazardous Fiber (2018): 27-43.
Excerpt:
… materials or with asbestos blended with cementitious materials or gypsum, other fillers,
and binders. The US Environmental Protection Agency (EPA) reported an estimated average …

Bottom line: pure gypsum is not likely to contain asbestos but a mix of asbestos and gypsum was certainly made for use in special applications such as the example I gave above.

I should add this abstract from Ruizhong Hu, et als that addresses the "how much asbestos" question:

An X-ray diffraction procedure for quantitative chrysotile asbestos analysis in a gypsum-based matrix is discussed. The procedure includes calibration standards preparation, an EDTA treatment to remove gypsum, sample milling, and X-ray diffraction analysis. The effect of each step is discussed. Morphological and crystal structural changes due to the sample preparation procedure were also characterized using techniques such as SEM, IR, NMR, and ICP. Through a statistically designed experiment, it is demonstrated that X-ray diffraction can be used as a reliable technique in gypsum-based matrices to determine chrysotile concentration from 0.25% to 2.5% with a standard deviation of 0.07%.

More reply: Portland Cement in Bates Valve Bag

@Cody and other readers:

Here we see another example of use of a Bates Valve Bag - for packaging and distributing portland cement.

The Marketing Dust article that we cited above can be seen in this copy:

Twede, Diana, and Bob Drasner. "Marketing Dust: The Effect of Packaging Technology on the Marketing of Cement and Carbon Black." In Proceedings of the Conference on Historical Analysis and Research in Marketing, vol. 16, pp. 372-377. 2013.

inspectapedia.com/hazmat/Multi-wall-Bag-History.pdf

More reply: Bates Multiwall Bag gypsum power insulation bags

@Cody,

About that nice closeup of a label on your gypsum power insulation bags in your attic and that cites Bates Multiwall Bag:

The Bates Valve Bag Company in Montreal made multiwalled (for strength) paper bags that were designed to be easily filled with dry products that could be made to flow - in this case, apparently, with gypsum powder.

We're still researching the history of the Bates Valve Bag Company but Bates Valve Bag, a Chicago company, w founded by Aldemar M. Bates, credited with inventing the multi-wall bag, probably as an aid to selling salt. Bates patented his "valve-bag" design, soon widely used for transporting numerous powdery products that previously had to be distributed in barrels or textile bags.

Twede and Drasner described Valve-Style textile bags (later made of multiple layers of paper):

The valve-bag concept, patented by “salt seller” Adelmar M. Bates in 1898, was the first solution. He first added a self-closing “comparatively small filling-aperture” in one corner of a textile bag (Figure 1).

The opening “will automatically close under the pressure of the contents when the funnel is withdrawn, and thus prevent leakage with a resistance increasing in direct ratio to the pressure of the contents thereagainst” (Bates, 1903, p. 2). He patented a machine to weigh the bag as it was filled, and established the Bates Valve Bag Co in 1901 to sell machines and license the package design.

- Twede, Diana & Bob Drasner, "Marketing Dust: The Effect of Packaging Technology on the Marketing of Cement and Carbon Black" [PDF] (2013) CHARM Proceeedings

Reader follow up:

Anyways, I had the powder tested at ALS laboratories in Saskatoon and asbestos was found to be below the detectable limit! Cellulose and other fibres were 50-75%. Please post this with the rest as some closure on the topic. Thanks

 

Does my 1958 frywall contain asbestos?

I'm currently tearing down drywall in my house and they say fireproof 1958 -1960 wondering if it contains asbestos. 2023-11-01 by Cameron

Reply:

@Cameron,

It's possible that the drywall board or the joint compound used to install it contained asbestos.

Does 1951 Stone Lath contain asbestos?

I am doing a bath room Reno, and the Plumber when installing the bath tub stopped the job, as he said he wasn't sure if the drywall material contained asbestos. The house was built in 1951.

On the back of the what looks like 2 ft. wide sheets, the manufacturer's name or product name is stamped on it. STONE LATH or STONE TONE LATH. It looks like drywall, and then a skim coat of plaster was applied on top.

Do you have any record of this product containing asbestos? 2023-06-08 by Stan Ewing

Reply:

@Stan Ewing,

Be sure to read

GYPSUM BOARD ROCK LATH SYSTEMS https://inspectapedia.com/interiors/Rock-Lath.php

Can you post a photo of the stamped text?

Westroc drywall decoding stamp

02/ 01/ 21V22
This is possibly the manufactured date of drywall by Westroc on Canada. Anyone know how to decifer? I have a few but need to know.
Thx 2023-04-08 by Tyler

Reply:

@Tyler,

I'm researching further but typically we'd decode numbers like that to a production date stamp and probably a manufacturing plant ID

2021 manufacturing year - which leaves me not confident about the decoding.

Can you help us be less speculative by telling me the building location and age and whether or not its drywall may have been newer than the building?

FYI if this is an asbestos question, we give some date bounds above on this page. Up to 1990 both drywall and joint compound in Canada may indeed contain asbestos.

Westroc also made fire-rated gypsum board sold under brand names
Aquaguard Firestop
Aquaguard Firestop C
Firestop
Firestop C

What we have on Westroc drywall is listed at

inspectapedia.com/interiors/Drywall-Identification-Stamps.php#Westroc

Common to find asbestos in joint compound

Hi, Just found this informative website. We just purchased a 44 year old bungalow (circa 1979) in Nova Scotia, Canada. The home has been vacant for almost 2 decades and is full of mold.

My husband and I plan to "gut" the home ourselves with proper protective gear (masks, p100 filters, suits), but we are wondering the probability of asbestos in either the drywall or the drywall compound.

The drywall is just regular sheet rock and is not fire-rated drywall. We plan to have it tested for asbestos as a pre- caution, but what is the likelihood that it may come back positive for asbestos?

Is it really necessary that we complete the asbestos testing? If so, where is the best place to remove a piece that will also contain the drywall compound, as well as a piece of the drywall for testing. Is taking one sample to test both compound and drywall itself sufficient? Thanks, in advance, for any advice you can offer. 2023-04-08 by Alana

Reply:

@Alana,

It would be common to find asbestos in joint compound that may have used over the taped drywalk joints as well as in the locations of screws or nails that fastened the drywall in place.

Because dust control and personal protection equipment would be about the same it would be prudent to simply treat that as an asbestos containing material.

That means damp wiping and HEPA Vacuuming as part of your clean up as well as wearing the appropriate personal protective gear.

CGC fireproof rock lath asbestos test result

I recently had some CGC Fireproof rock lath with patents ending in 1940 tested for asbestos and all 4 layers tested negative. 2023-03-23 by Stacketbitz

Reply:

@Stacketbitz,

Thank you for the CGC fireproof rock lath asbestos test result: that's helpful news for other readers.

If you're willing, please use the page top or bottom CONTACT link to get our email to send me [DF] a copy of that report so that we can document that result. Our default is to redact such documents to protect your privacy,

It would also be helpful to see photos (one per comment) of the identifying stamps you found on your CGC drywall.

Thanks again - Daniel

Canadian Gyproc

Found this plasterboard in a property built in the 1950s looking for information on this type of board. 2023-02-08 by Scott archibald

Reply:

@Scott archibald,

Sure, and thanks for the photo and Canadian Gyproc question.

We discuss Gyproc above on this page; if you don't have patience to read the whole article, at the start of the page you'll find these two direct links:

ASBESTOS in CANADIAN DOMTAR GYPROC DRYWALL?

ASBESTOS in CANADIAN GYPSUM LIME & ALABASTINE GLA DRYWALL - GYPROC

1970s drywall made in Canada might contain asbestos

We are renovating an office space and we'd like to remove a partition wall but needed to investigate it first. We removed the drywall and discovered it was a 2-layer wall. We remove both and discovered the inner one was made 1975.

We are concerned that such wall might contain asbestos. Pictures attached. Thanks! 2022-11-08 by Marito

Reply:

@Marito,

You are correct, as you can read above on this page. 1970s drywall made in Canada might contain asbestos.

CGC logo with the Fireproof designation

I have the same CGC logo with the Fireproof designation on it, but it appears that the two layers are both made up of white gypsum and not a beige layer along with a white layer. Were these boards put up in two layers during installation?

I'm cautiously hopeful that because both layers are white I don't have any asbestos. 2022-08-10 by Michael

Reply:

@Michael,

Thanks, that's a helpful question.

Can you post a sharp photo of a visible edge of the CGC board?

I agree that there were at least sometimes non-asbestos versions of these products.

Follow up:

@InspectApedia-911,
Dylan posted results from a test that shows two types of material being analyzed, white and grey. His results came back negative. The poster who has a beige layer had results come back positive.

So that is probably the big distinction between having asbestos or not.

Anyone heard of Norwest Sheathing? From a condominium built in 1981.

Has anyone heard of Norwest Sheathing? From a condominium built in 1981. The building was largely without building paper, so I am wondering if this was intended to be a water resistant product. 2022-06-28 by Kris E

Reply:

@Kris E,

Thank you so much for the Norwest Sheathing exterior gypsum board photo and question.

We're researching further to look for the history of that brand and its distribution in Canada - but at first check through our own records and articles I'm not getting far so there's more digging to be done.

I'll follow-up here.

I should add, however, that typically those exterior sheathing boards were treated in one of several ways to increase their water and moisture resistance.

Treatment may have been a wax or an asphalt coating, or something else.

2022/07/18 UPDATE: Norwest Gypsum, Seattle WA company information.

We found a listing from 1986 for Norwest Gypsum Company:

• Norwest Gypsum, 5931 East marginal Way South, Seattle Washington 98134

listed as a member of the Gypsum Association in the Gypsum Association's membership list in

• GYPSUM BOARD RECOMMENDATIONS for the USE of GYPSU BOARD in MANUFACTURED HOUSING [PDF] (November 1986) Gypsum Association, 1603 Orrington Ave., Evanston IL 60201 USA, retrieved 2022/07/18 original source: https://www.gypsum.org/wp-content/ArchivesPDFs/1980-89/Gypsum%20Board%20in%20Manufactured%20Housing%20-%201986.pdf

In the 1980s Norwest Gypsum was the second-largest producer of gypsum board in the Northwest U.S., based on the marketing study given below. (Domtar in Tacoma was the largest producer).

Watch out: some Norwest Gypsum company products may contain asbestos. The company (Norwest Gypsum Co) is included in Appendix A of the document cited below, as explained in the excerpt

• U.S. EPA, RESPONSE TO SECOND REQUEST FOR INFORMATION; LIBBY, MONTANA [PDF] (23 Feb 2000) Letter, Kenneth Lund, Holme Roberts & Owen LLP to Kelcey Land, US EPA, describing W.R. Grace's response to the Second Request for Information Regarding the Libby Asbestos site.
  
  Excerpt:
  Question 9: Provide a listing of WRG controlled (i.e. subsidiary, partner, joint venturer) companies that purchased raw (i.e. product that had not undergone exfoliation treatment) vermiculite ore from WRG that was produced at the Libby, Montana mine.

Norwest Gypsum was also marketed in British Columbia, Canada. See

• MARKETING STUDY OF BRITISH COLUMBIA'S GYPSUM IN THE PACIFIC RIM AREA OF NORTH AMERICA [PDF] (1987) Queenstake Resources Ltd., Vancouver, BC . retrieved 2022/07/18 original source: https://cmscontent.nrs.gov.bc.ca/geoscience/PublicationCatalogue/Miscellaneous/BCGS_MP-04.pdf?bcgovtm=eNewsletter
  
  Excerpts:
  There has been a strong demand for gypsum product s throughout 1985/86 and n previous years . There is every indicatio n tha t this upward trend will continue with the improved economies in the United States and Canada.
  
  Calcined gypsum i s produced by Norwest Gypsum Inc. in Seattle , and by Domtar Qypsum America Inc. at Tacoma, in Pierce County. Gypsum for calcining i n these plants i s shipped from other deposits outside the State of Washington.
  
  Another market area f r crude gypsum in the wallboard industry may be with Norwest Gypsum n Seattle , Washington. Norwest Gypsum presently imports it s gypsum supply from Mexico through Domtar and from Spain through Mineral Resource Trading Corp. However, in trying to supply Norwest Gypsum, any future producer must be careful not to undermine Domtar' s supply position , since Domtar may be a candidate for large shipments from British Columbia.
• Risk Science International (RSI). 1987. Remedial Investigation of the Norwest Gypsum Solis Waste Landfill. Prepared by RSI for Norwest Gypsum, Seattle, WA. June 1987.
• Good, Sarah, LOWER DUWAMISH WATERWAY RM 1.2-1.7 EAST (SAINT GOBAIN TO GLACIER NORTHWEST) SOURCE CONTROL ACTION PLAN FINAL REPORT [PDF] (2007) Toxics Cleanup Program Northwest Regional Office Washington State Department of Ecology Bellevue, Washington and Ecology & Environment Inc. 720 Third Avenue, Suite 1700 Seattle, WA 98104 This report is available on the Department of Ecology home page on the World Wide Web at http://www.ecy.wa.gov/programs/tcp/sites/lower_duwamish/sites/ RM_12_17_East/StGobain.html
  Excerpts:
  
  Risk Science International (RSI) conducted a remedial investigation of the solid landfill at the Norwest Gypsum facility on May 20, 1987. The site RI involved installing four groundwater monitoring wells, sampling remedial surface water and groundwater, sampling landfill core, surveying local groundwater use, and characterizing the hydrogeology of the property (RSI 1987).
  
  Ecology gave JHG a copy of the Potential Hazardous Waste Site Identification Form, dated April 13, 1990, which summarized the results of the 1987 RI as follows:
  
  1. “Soils exceeded 10 times the drinking water standards for arsenic, chromium, lead, and possibly cadmium and mercury.”
  
  2. “Groundwater samples exceeded drinking water standards for chromium, lead, and mercury” (Weston 2004).
  
  This study pertains to Certainteed Gypsym Inc., property owner in 2000, of property previously operated under the following facility names: James Hardie Gypsum, Certainteed Gypsum, Lone Star Northwest, Norwest Gypsum.
  
  The most recent property sales record listed in King County’s tax records indicates that James Hardie Gypsum (JHG) purchased tax parcel No. 1924049092 from Lone Star Northwest on May 23, 1997. The current owner of the property is listed as BPB Gypsum (King County 2008a)

Reader follow up: Norwest Sheathing gypsum board

@InspectApedia-911, Interestingly enough, I found the same brand of sheathing on another condominium in Redmond, Washington. This sheathing had building paper over it and appears to be a different color. Still can't find any information on Norwest Sheathing.

More follow up: another unidentified Canadian Drywall Product with "fibers"

@Kris E, this is from the same site but looks different. Material has some fibers.

Reply: Murphy Wall Products, Ft. Worth, TX - Murphy Drywall

@Kris E,

It would be quite helpful for questions like yours if you could tell us

- the building location: country and city

- the building age

- any guesses at age of the drywall

There is a current Murphy Wall Products company (since 2007) providing drywall materials (and paints)
Murphy Wall Products
201 NE 21st ST
Fort Worth, TX 76164

But if your MURPHY Water-Repellent board or drywall is much older it's from another source.

CGC Drywall in a 1982 home in Delta, BC, Canada

Have included photos of part of the paper from drywall in our master bathroom. Wondering if it contains asbestos?

Home was built in 1982, in Delta BC Canada. Based on previous comments, I'm guessing it does NOT contain asbestos. 2022-04-15 by Marika

Reply:

@Marika,

That's Canadian Gypsum Company gypsum board. Some older GCG drywall contains asbestos.

You'll want to read the advice above on this page. No panic needed, but don't make a dusty mess.

Follow up:

@Inspectapedia Com Moderator, thanks so very much for your reply and for the wealth of information your website provides.

Our approach will be a "controlled" removal rather than the full on dust demo, but will take all necessary precautions with respirators, etc. Keep up the great work with the website!

Reply: Canadian Gypsum Company gypsum board

@Marika,

That sounds reasonable. And thank you for the nice comments.

Canadian Gypsum Company, Sheetrock asbestos?

I started opening walls in my newly bought home's kitchen to check for load bearing when I saw Canadian Gypsum Company, Sheetrock, The fireproof gypsum wallboard. Patented 1959 1962.

I also saw an edge marking indicating CWB 109T. Patented 1958, 1959, 1961, 1962 and 1969.

It is 5/8" thick With my luck I'm guessing it has asbestos in it. But I can't find any confirmation anywhere. Anyone knows for sure? 2022-01-05 by Elliot

Reply:

@Elliot,

Please see the reader question and our reply (with added follow up by both of us) above on this page in the section titled:

Asbestos in Canadian Gypsum Co Fireproof RockLath 1958 Quebec
Question: Asbestos in Quebec home rock-lath or drywall?

Here we provide a list of steps to consider for handling your product.

Canadian Rock Lath from 1940-1944 Asbestos Test Result: Negative

I just had my piece of rocklath tested and it is stamped 1940,42,44 on the patent .

The results came back negative but I am skeptic so could someone please analyze these results. 2021-10-19 by Dylan

Reply:

@Dylan,

If your asbestos test sample was properly collected so as to accurately represent the material or product being tested, and if you use a certified asbestos test lab, and I'm not sure what additional steps you would want to take to make yourself more confident in their result.

Have you seen 2 ft. sections of modern drywall

Hi - I have a ceiling installed in my home (built in 1888 - Toronto). The ceiling has been installed 2' below the original plaster ceiling. It appears to be made of 2' drywall panels attached to 2x4 (full dimensions) ceiling framing.
When was this size/format of drywall used? What is the likelihood it contains asbestos?

2nd comment - Upon further review, the 2x4s appear to be 1.5"x2.5" but not have rounded edges. The drywall panels might be more like 18" wide. The underside of the ceiling is a decorative swirly pattern.

Looking for any insight into the age of this 2nd ceiling.

Thanks! 2021-04-21 by Nina

Reply:

@Nina,

Thanks that's an interesting question; I have not seen 2 ft. sections of modern drywall but there were certainly plasterboards sold for ceilings and walls in that size

details are at PLASTER BULGES & PILLOWS

 

Does Westrock drywall csa a82.27-m 1977 contain asbestos

does westrock drywall csa a82.27-m 1977 contain asbestos? 2021-03-26 by Rob

Reply: History of Asbestos Claims re: Canadian Westrock Company Drywall - DSA A 82.27-M 1977

@Rob,

The 1977 date on the paper strip at the edge of your Canadian drywall sets a "no older than" date for us.

We don't know if your specific drywall contains asbestos but it would be prudent to either treat it as PACM - Presumed Asbestos-Containing Material - or to have representative samples of both the drywall and joint compound tested by a certified asbestos test lab before doing any dust-creating demolition.

Note that left alone, intact, in-place and un-damaged, asbestos-containing drywall or joint compound are not at all likely to produce a detectable asbestos hazard.

Take a look at this 2019 ANNUAL REPORT from WESTROCK https://s21.q4cdn.com/975972157/files/doc_financials/2019/ar/2019-WestRock-Annual-Report.pdf

Excerpts from this 2019 report update shareholders and other interested parties in Westrock Company's previous use of asbestos in products, or asbestos in the workplace, and asbestos litigation.

Although we do not use asbestos in manufacturing our products, asbestos containing material (“ACM”) is present in some of our facilities. For those facilities where ACM is present and asbestos is subject to regulation, we have established procedures for properly managing ACM, including, but not limited to, employee training and work practices to maintain the ACM in good condition and minimize exposure. - p. 8

• our belief that the liability for environmental matters was adequately reserved at September 30, 2019; - p. 15

• our belief that we have substantial insurance coverage, subject to applicable deductibles and policy limits, with respect to asbestos claims; - p. 16

• our belief that we have valid defenses to asbestos-related personal injury claims and intend to continue to defend them vigorously, and that should the volume of asbestos-related personal injury litigation grow substantially, it is possible that we could incur significant costs resolving these cases;

• our expectation that the resolution of pending asbestos litigation and proceedings will not have a material adverse effect on results of operations, financial condition or cash flows and that in any given period or periods, it is possible that asbestos-related proceedings or matters could have a material adverse effect on our results of operations, financial condition or cash flows;

• our estimation that the exposure with respect to certain guarantees we have made could be approximately $50 million;

• our belief that our exposure related to guarantees will not have a material impact on our results of operations, financial condition or cash flows;

We have been named a defendant in asbestos-related personal injury litigation. To date, the costs resulting from the litigation, including settlement costs, have not been significant. As of September 30, 2019, there were approximately 825 such lawsuits.

We believe that we have substantial insurance coverage, subject to applicable deductibles and policy limits, with respect to asbestos claims. We also have valid defenses to these asbestosrelated personal injury claims and intend to continue to defend them vigorously.

Should the volume of litigation grow substantially, it is possible that we could incur significant costs resolving these cases.

We do not expect the resolution of pending asbestos litigation and proceedings to have a material adverse effect on our results of operations, financial condition or cash flows.

In any given period or periods, however, it is possible such proceedings or matters could have a material adverse effect on our results of operations, financial condition or cash flows. - p. 127

Westrock Industries, Ontario, drywall manufacturer Asbestos history?

Hi all,

I am wondering if this is a date stamp on this drywall? I see 1977 but don’t understand if the other numbers/letters represent the day and month and factory. Any help would be appreciated. The drywall was made by Westroc Industries in Ontario. 2021-03-10 by Lance

Mod reply: date stamps or other identifying labels on Westrock Drywall

@Lance,

The 1977 that you see on that Canadian drywall is the date of the standard CSA A 82.27-M 1977

or in more detail:
A82.27-M1977
Gypsum Board
Status: Withdrawn
SDO: CSA
Language: English
Publish date: 1977-07-01
Supersedes: A82.27-1972
Superseded by: CAN/CSA-A82.27-M91
Keywords: GYPSUM, LATHS, SAMPLES, CONSTRUCTION MATERIALS, SPECIFICATIONS, MARKING, BOARDS
ICS Codes: 91.100.10;
Standard Number: A82.27-M1977

So its presence on your drywall sets an approximate age range for that drywall in your photo - the age of the standard - telling us that your drywall was manufactured during the time that that standard was in use. That's before asbestos use ceased, but of course we need to know more about the specific Westrock drywall.

CGC ROCKLATH in 1950s - asbestos content?

What are the chances of a house from the 1950 in montreal would contain abestos in the gypsum.

We have CGC ROCKLATH.

Regard. 2021-02-23 by User 1

Reply:

@User 1, you asking important question, but unfortunately we have no data or percentages of drywall that contain asbestos.

Asbestos in drywall was common-enough that seems to me to be likely enough that it would be prudent to treat older drywall or rock lather or gypsum board as presumed to contain asbestos and to avoid making a dusty mess or demolition.

If you have no choice but to demolish the material or to do something to it that creates dust then either treat the material as presumed to contain asbestos or have a sample tested.

High probability of drywall containing asbestos?

In your opinion, does this drywall have a high probability of containing asbestos. It's rated as fireproof and as a patent date of 1944. I'm in Nova Scotia. 2020-11-15 by Mike

Reply:

Yes Mike

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