Gyp-rock and other gypsum or plasterboard panels used for building wall & roof sheathing:

This article describes the use and durability & history of water resistant gypsum panels used in construction of building walls & roofs.

We include advice for renovating or repairing gyp-rock sheathed buildings and a discussion of the mold resistance of this material.

Gypsum board building exterior wall sheathing - history, description, age of use

[Click to enlarge any image]

Gypsum board has been used for non-structural wall sheathing (photo above) and even roof sheathing on buildings (photo at above left).

Above is a row of 1940's buildings constructed at Stewart Air Force Base in Newburgh, New York, apparently as military housing.

Some of these structures are still in use while others (foreground) are being demolished.

Originally a brick veneer covered the structure, behind which was this black paper-covered gypsum board sheathing.

An ongoing demolition project ca 2012-2014 has removed the brick veneer from several of these buildings, leaving the gypsum-board sheathing exposed to the weather.

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Look closely at the photo above-left [click to enlarge] and you'll see that the interior wall (visible as white through the hole in the gyp-rock exterior) appears to be cement asbestos millboard.

Above, from a different but similar-aged building, also located in New York State, is the same water-repellent sheathing stamped as in compliance with ASTM Standard ASTM C79/C79M-04a.

1.1 This specification covers gypsum sheathing with a water-resistant core, which is designed to be used as a sheathing on buildings.

Note 1—Specification C 1280 contains application procedures for gypsum sheathing board.

According to ASTM, this specification was withdrawn in December 2004 and replaced by Specification C 1396/C 1396M for Gypsum Board. The standard itself does not discuss asbestos - at least not in material at the ASTM website.

See ASBESTOS in DRYWALL where we discuss this wallboard further.

Current gypsum board or wallboard standards pertinent to these products include ASTM C1278 / C1278M - 07a(2011) (fiber-reinforced gypsum board) and ASTM C1396 / C1396M - 14 (standard specification for gypsum panels).

Despite having been exposed to full weather in a northern U.S. climate for at least two years, the gypsum board sheathing on the under-demolition buildings at Stewart Field was remarkably intact except for having been smashed about by the demolition crew.

Below we include a photograph of the gypsum board sheathing in cross-section.

On buildings where gypsum board was used to cover walls or roofing (photo at left), for structural stiffness we expect to find either plywood or let-in bracing nailed at the corners of building walls.

Initial versions of this product have not performed well on buildings where they might be exposed to dampness or leaks.

We have found this material installed under asphalt roof shingles, hardboard siding, and other exterior siding materials.

Gypsum board continues to be marketed as a less costly alternative to plywood or OSB building sheathing.

These panels are intended for use under brick veneer and stucco exterior building wall finishes.

Later versions of the material are called cementious board sheathing and can be expected to have been treated with water repellant chemicals.

Producers of gypsum panels used for building sheathing and interior wall and ceiling coverings, including gypsum board products that contained asbestos include:

Georgia Pacific Co. (Densglas gold™)

US Gypsum Co. (Fiberock™)

US Gypsum Company, founded in 1901, produced a wide range of gypsum board panel and wall or ceiling products including acoustical ceiling coverings and coatings that contained asbestos between 1920 and 1978.

National Gypsum Company (Gold bond™).

National Gypsum, currently named NGC and headquartered in Charlotte, North Carolina, has manufactured building products, including gypsum wallboard since its founding in 1926.

The National Gypsum company filed for bankruptcy status in 1990, emerged from bankruptcy status in 1993, filed for bankruptcy a second time in 2002 and reorganized in 2003.

Asbestos was used in a number of National Gypsum Gold Bond™ gypsum board products produced between 1950 and 1970.

Asbestos was not used in National Gypsum gypsum-board products after that year.

See GOLD BOND IB ASBESTOS? for details about fiberboard (not drywall) products.

Also see NATIONAL GYPSUM DRYWALL ASBESTOS?

Our photo (left) shows a close up of gypsum sheathing board used on building exterior walls and on some roofs.

Georgia Pacific's DensGlas™ exterior building sheathing includes this product description: "The product features a moisture-resistant core and enhanced fiberglass mats, instead of paper facings, to resist the effects of moisture exposure during and after construction.

It is so weather-resistant that Georgia-Pacific backs it with a 12-Month Weather Exposure Limited Warranty. "

The company indicates that contemporary gypsum board sheathing such as their DensGlas™ product is intended to serve as a building " substrate behind brick, siding, EIFS, stucco and other permanent claddings."

Watch out: OPINION: unless your building is only expected to last 12-months, you should not leave gypsum board exposed to the weather.

In fact few building sheathing products are intended to be left exposed to weather. For example, OSB sheathing board also deteriorates if it is repeatedly wet.

See ASBESTOS LIST of PRODUCTS for a comprehensive list of building products that contained asbestos.

Also see ASBESTOS PRODUCING COMPANIES & TRUSTS for a most-complete list of companies that produced products containing asbestos

History of Popular Use of Gypsum Board Exterior Sheathing

We estimate that from 1942 to 1965 gypsum board was used as exterior wall sheathing on a variety of buildings, especially low-cost structures and in panelized construction as we explain along with our photographs shown below.

We also find gypsum board sheathing used on some roofs, believe it or not.

In some applications a water repellent paper was used to improve the product's durability, as we show in this wall cavity side photograph of identifying marks on gypsum board sheathing.

When gypsum board was used for exterior wall sheathing, as we show in this interior photo (above left), let-in cross bracing was required at building corners.

The white paint on the wall cavity side of the gypsum board shown in this photo was added during building renovations to address water damage and to improve water resistance.

Notice the pair of wall studs in the left hand photo? That stud pair marks the abutment of two panelized wall sections in this building. The corner panels were built flat in the panelized home factory and measure just 1/2" under 8' x 4'. Larger 8' x 8' wall panels were also produced and were used for this home.

These details permit the conclusion that this home was constructed using pre-fab exterior and interior wall panels, all clad with gypsum board that was glued to the wall studs for extra strength.

Our photo at above right shows additional bracing that was incorporated into the gypsum-clad wall panel bottom, along with an assembly wire.

Details of this panelized construction home are

at PANELIZED CONSTRUCTION

An example of a drywall/gypsum board identification number appear on this 1950's product shown at left. This is another example of gypsum board used for exterior wall sheathing.

Mold growth on the wall cavity side of drywall is common when there have been leaks into the wall cavity.

Our photo below shows mold growth on the wall cavity side of gypsum board used as exterior wall sheathing on a 1960's condominium in New York.

See SAMPLING DRYWALL for more information about mold growth on drywall and gypsum board products.

Also see MOLD-RESISTANT BUILDING PRACTICES

and  MOLD PROOF DRYWALL? You Must Be Kidding!

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The photographs above show two different gypsum board wall sheathing products that employ a textured paper surface. At right is a modern product found in a home built in the 1990's.

Question: Renovating home with GypRoc Sheathing

(Sept 9, 2012) Derek said:

I am doing a renovation on my home (built in the mid 1950's) and have come across an exterior sheathing product called Gyproc Sheathing made by a company called Gypsum, Lime and Alabastine in Canada.

It appears to be a drywall type product with a black paper coating. The entire exterior of the home is sheathed in this material. My question is whether you are familiar with this product and whether it contains asbestos.

Reply:

Yes indeed, Derek. A number of buildings used exterior wall sheathing made of a weather-resistant gypsum board, as we discuss and illustrate here.

In the photo my wrinkled hand is showing a cross section of gypsum board that was installed as exterior sheathing on military housing built at Stewart Air Force Base in Newburgh, NY in the 1940's. More about this material is in the article above.

Question: Question about Homasote sheathing from 1940s. Mold problems on gypsum board exterior building sheathing?

Was 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 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

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.

There was no building code that required building owners to replace vinyl siding over gypsum board exterior sheathing - at least not because of the material's presence. A specific building might be so severely damaged from leaks or flooding that its sheathing needed to be repaired or replaced in part or entirely.

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

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

We describe two different exterior sheathing product types

FIBERBOARD SHEATHING Sheathing Celotex Homasote & Other

SHEATHING, GYPSUM BOARD Gypsum or plaster-based ceiling or wall covering or similar products that were sometimes used as exterior wall sheathing

At FRAMING MATERIALS, AGE, TYPES we describe the history of and different types of building framing and sheathing materials.

Mold growth on gypsum board building wall sheathing?

About mold growth: the simple absence of light is not sufficient to cause problematic mold growth in building cavities. Water or high moisture would be a requirement for nearly all indoor mold contamination.

And indeed I have found mold growth on paper backer on plaster-board exterior wall sheathing, in the wall cavity in buildings where there had been leaks into those spaces.

So if your home's walls were leaky (from ice dam leaks at the eaves, from leaks around windows or doors, from wind-blown rain penetrating damaged siding, etc) then there might be problematic mold growth on those surfaces - in the previously or currently wet areas.

Whether or not this problem deserves investigation and remediation is not something one can decide without more detailed information.

See MOLD EXPERT, WHEN TO HIRE for help in deciding if in your particular case hiring a competent professional to inspect and test the building is justified.

If your home has been damaged by flooding and is built with an exterior wall covering of brick or stone veneer,

see BRICK VENEER WALL REPAIRS in FLOOD PRONE AREAS

Gypsum Board Sheathing Ingredients, Research & Patent History

• Emeron, Joseph W. GYPSUM WALL BOARD [PDF] U.S. Patent 1,439,954, issued December 26, 1922.
  Excerpt
  All gypsum wallboards of which I am aware present surfaces of cardboard. For this reason they are not waterproof and are ruined by water, since the cardboard, if wet, expands, becomes weak and flabby and tends to detach itself from the gypsum base, and thus to destroy the reinforcing effect.
  
  My invention obviates this difficulty by not using cardboard at the surface, but substituting therefor a meshed material, such as cotton gauze or perforated paper, which, being applied while the plaster is in the plastic state, permits a little gypsum to pass through the meshes or openings and thus virtually present a gypsum plaster surface, instead of a cardboard surface.
  
  At the same time the reinforcing effect is at or near the surface where it is most needed and where it will do the most good.
  
  By this form of construction and with the use of a waterproof gypsum product which has been subjected to the action of a stearic compound and to a caustic compound in the manner described and claimed in my copending application Serial Number 481,083 filed June 28, 1921, a waterproof gypsum board may be made, suitable for exterior as well as interior use.
• Georgia Pacific Corp., PAPER FACED GYPSUM PANELS SAFETY DATA SHEET [PDF] (2017) Georgia-Pacific Canada L, 350 Argyle Street North Caledonia, ON N3W 1M2 Telephone Technical Information: 800.225.6119 (M)SDS Request: 404.652.5119 e-mail MSDSREQ@GAPAC.com
  
  Note: this SDS describes the constituents of GP's ToughRock® series of gypsum board products
• King, George D., and Thomas P. Camp. WATER-RESISTANT CEMENTITIOUS PRODUCT [PDF] U.S. Patent 2,198,776, issued April 30, 1940.
  Excerpts:
  A great number of attempts have been made to render materials more Water resistant. Some attempt to obtain it by a protective coating of a waterproofing material like varnish, paint, and a number of others. However, it is difficult and expensive to obtain a protective coating that has Sufficient stamina to withstand water either in its liquid or vapor phase. In addition, the slight est break or flaw in the protective film allows wa ter to enter and permits the damage to proceed unseen and undetected until after it is too late.
  
  A more difficult, and somewhat better, way is to waterproof material integrally by the addition of water-repellent substances compatible with the physical and chemical properties of the treat ed material.
  
  It is generally customary to add wa terproofing materials in the form of an emulsion or solution, if they are of an oily, waxy or a fatty nature. Even such substances as asphalt, and others of a Solid or semi-solid nature, can be con veniently added in this manner.
  
  However, if an emulsion is used, it is necessary to break it ir reversibly, otherwise there will be a tendency to reemulsify the waterproofing agents and thereby remove them from the material. This is often rather difficult to accomplish, and uniform results are not always obtained.
  
  We have found, contrary to general belief, that paraffin or its equivalent, either natural or synthetic, such as tallow, beeswax, hydrogenated cocoanut oil, etc., when added in a solid, but finely comminuted form, and in accordance with this invention, will render the cementitious prod uct water resistant.
  
  While not as Satisfactory, we have been able to use asphalt or a mix of as phalt and paraffin.
  
  We prefer to use paraffin, since it readily melts and resolidifies, and readily penetrates the core on remelting in the board drying kiln. We prefer to melt the paraffin or its equivalent, and spray the same as a fine mist into the cementitious mass used in forming the core. The fine particles are Solidified on com ing into contact with the cement and water mass.
  
• Camp, Thomas P. WATER-RESISTANT GYPSUM PRODUCTS AND PROCESS OF MAKING U.S. Patent 2,432,963, issued December 16, 1947.
  Excerpt
  One example of past attempts to waterproof this material integrally by the addition of waterrepellent substances is that disclosed in the King and Camp United States Patent No. 2,198,776.
  
  This shows the incorporation of parafln wax, asphalt, or other fusible water-insoluble organic substances into a gypsum mix by first melting this waxy material and then dispersing such material into the wet gypsum mix by spraying the hot molten mass into the aqueous gypsum dispersion.
  
  This brings about a formation of nely dispersed solidied parain or asphalt particles which then serve to improve the water resistance of the gypsum product.
  
  While these past efforts resulted in some degree of success, there has been no waterproofing process developed in the past which was capable of causing a drastic 'increase in water-resistance by the use of only a comparatively very small amount of cheap water-proong materials.
  
  The object of my invention is to produce highly water-resistant gypsum wallboard. ...
  
  I have discovered that if a mixture of paraffin wax and asphalt, in definite proportions, say on the order of from about 5% to about 15% (dry basis), is incorporated in the form of an emulsion with a wet plastic gypsum mass, the fnished dried gypsum wallboard will possess a degree of water resistance which is greatly out of proportion to the degree of water resistance obtained if one uses these same paraffin wax and asphalt materials without emulsication.
  
  The degree of water resistance obtained by the use of a mixture of paraiiin wax and asphalt in certain proportions is very much greater than that obtained when one uses either the wax alone or the asphalt alone in emulsified form.
  
• Camp, Thomas P. "Water-repellent coating composition and method of coating." U.S. Patent 2,464,759, issued March 15, 1949.
• Camp, Thomas P. "Water-resistant gypsum products and method of making." U.S. Patent 2,526,537, issued October 17, 1950.
• Camp, Thomas P. "Process of producing water-repellent gypsum sheathing board." U.S. Patent 2,560,521, issued July 10, 1951.
• Riddell, Wallace C., and George B. Kirk. "Water repellent gypsum product and process of making same." U.S. Patent 2,597,901, issued May 27, 1952.
• Riddell, Wallace C., and George B. Kirk. "Water-repellent gypsum product." U.S. Patent 2,610,130, issued September 9, 1952.
• Selbe, Rexford L. "Water-resistant gypsum composition and emulsions for making the same." U.S. Patent 2,699,414, issued January 11, 1955.
• USG 2" SOLID ROCKLATH & PLASTER PARTITION SPECIFICATIONS [PDF] - specifications & installation details from US Gypsum's 1952 Technical Specifications Book
  Note: cites use of asbestos
  

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2022-07-29 by InspectApedia-911 (mod) - concern about ingredients in gypsum board

@Linda H.,

Thank you for the discussion.

If indeed you find supporting research for your belief that the ingredients in your drywall or gypsum board "could easily be a strong lung irritant even if they aren't disturbed" it would be most helpful to add that here.

We've not found such evidence. You'd have to be looking for gases or fumes, if you're not disturbing the material, since one wouldn't expect meaningful particle release from undisturbed gypsum board.

On 2022-07-29 by Linda H.

@InspectApedia-911, Georgia Pacific called regarding asphalt and indeed that could have been used in the water resistant wall board from 1993. If I find more identifying information, they can be more specific. That is enough information, though, to make decisions. You have a good point about their concern about litigation.

I tried to ease their fear by emphasizing that I am not critical of their product for the general public but have an unusual level of chemical sensitivity. In my case, those additives could easily be a strong lung irritant even if they aren't disturbed. I'll take it a step at a time and see what can reasonably be removed and replaced and then seal off the rest. Thank you so much for all your helpful information in this process.

On 2022-07-28 by InspectApedia-911 (mod)

@Linda H.,

Companies are understandably, if regrettably, careful about providing information - scared of litigation.

Consider that if the wallboard is intact, not being chopped, ground, sanded, sawn or otherwise made into dust, the chances that it's a source of occupant IAQ complaints are slim.

On 2022-07-28 by Linda H.

@InspectApedia-911, Thank you so much! Your response and those patents give me just the information I need. A Georgia Pacific rep confirmed that it is an interior grade board and that a wax based emulsifier could have been mixed into the paper for water resistance. I have emailed again to ask if asphalt could also have been used in 1993. They are not very forthcoming. You have to know exactly what to ask or they won't mention it.

Given my hypersensitivities, both wax and asphalt could account for the lung irritation. When I have a complete and accurate understanding of the material, I can decide whether to remove it, or seal it off. Removal has its own dust problems.

On 2022-07-26 by InspectApedia-911 (mod)

@Linda H.,

It is highly unlikely that a home built in the U.S. in 1993 would have used the older exterior-use water-resistant gypsum board products describe above on this page.

We have added some research details in the article above, describing early patents and the constituents and additives used to make early (as early as the 1920s and widely used into the 1940's - 1950s) water-resistant gypsum board. You'll see that principally the manufacturers (and inventors) used paraffin or similar waxes and sometimes a mixture that included asphalt.

The ingredients or constituents of more-recent gypsum panels such as those by Georgia Pacific are described in the SDS you'll find above on this page.

On 2022-07-26 by Linda H.

I am renovating a bathroom built in 1993. It is lined with black paper backed gypsum wallboard from Georgia Pacific. I find my lungs are very irritated by it. It could just be the dust, but I want to rule out other possibilities.

Can you tell me anything about what chemicals or additives might be used with what I assume is an exterior grade wallboard of that era? I know they did not use any biocides, but am wondering about water repellent chemicals. It is the wall to the left hand side in the picture. Thanks

On 2022-01-12 by Inspectapedia Com Moderator - how can I know the level of asbestos hazard?

@Anonymous:

With regret, nobody with any actual knowledge and sense could pretend to guess at the level of asbestos hazard nor its effects on someone for some situation about which they have not a shred of objective data.

You would need to establish

1. that asbestos was present - or other harmful dust particles were present - by objective testing
2. the level and duration of exposure
3. the health vulnerability of the people exposed

What's left without objective data is so speculative as to almost certainly be wrong.

What you can do that's reasonable is to gain some peace of mind by cleaning any clothes that haven 't been already laundered or dry cleaned, and you should discuss your health worries with your doctor.

On 2022-01-12 by Inspectapedia Com Moderator

Re-posting from private email:

Anonymous wrote:

Hi, I have a question from your article. I was exposed to dust from workers cutting for a month or 2 , millboard gypsum materials that looked exactly like the photos in your article.

It had the textured grain on the outside and inside was white fluffy powdery with white fibers in thin string stuffed out in the pieces that were cut. It was behind stucco in a wood frame building along the walls and cement stucco railings outside.

There was water damage so the workers were cutting the bottom 2-4 ft of the walls to redo it due to water damage and were cutting the gypsum board leaving it exposed. I also saw vermiculite granules all over the ground being tracked thru the carpeted hallway as they were uncovering some tiles.

The building was in Los Angeles and built in 1989 (I think I read 1987 originally).

Can you give me your opinion or any info about this? I’m worried I was exposed and wondering if I should get rid of some things exposed to the dust.

On 2021-09-29 by inspectapedia.com.moderator - how to insulate with brick veneer and gypsum board

@Fernando,,

The foam is sprayed right against the gypsum.

Closed cell foam is usually stopped just before the outer face of the wall studs (to avoid having to saw it);

Open celled foam is sprayed to completely fill the cavity and then a long bread-knife type cutter blade is used to trim it flush with the stud faces. Both yield a high-R wall and no air leaks, making for a quite and well-insulated building; (of course the ceiling insulation is critical too).

On 2021-09-29 by Fernando

@inspectapedia.com.moderator, Appreciate the response. Is it recommended to leave any sort of air gap between the gypsum and the closed cell insulation? Or is it better to apply the closed cell foam directly onto the gypsum? Thanks again for the help.

On 2021-09-29 by inspectapedia.com.moderator

@Fernando, The gypsum board looks to be in excellent shape, and based on my visual inspection I believe the cavity between the brick veneer and the gypsum board has no water or mold damage.

My main concern is insulating the cavity on the inside, behind the drywall without future moisture issues. There was originally no insulation between the drywall (appears to be original 1950’s gypsum sheetrock) and the exterior gypsum board.

Do not insulate the drainage cavity between the inner face of a brick veneer and the outer face of gypsum board used as exterior sheathing;

But you can insulate the wall cavity - the space between the cavity side of the interior drywall forming your walls and the wall cavity side of the exterior gypsum sheathing board. Renovation contractors often use a closed-cell (thus waterproof) foam in this location.

Your photo shows an ideal time to insulate with spray-foam.

More costly than fiberglass batts and IMO more air-tight.

see

FOAM SPRAY INSULATION TYPES

On 2021-09-29 by Fernando

What is the best way to insulate on the inside of the gypsum board? My house is brick veneer and has a layer of this gypsum board behind the brick. There was no insulation behind the drywall, so looking for options to avoid moisture inside the wall cavity.

On 2021-03-29 by danjoefriedman (mod)

@Mark, sorry I'm not sure what you meant by "hold vinyl cedar impressions"

But I'll make a wild guess that you're asking whether vinyl siding can be supported by exterior sheathing made of gypsum board panels.

The answer is no, no siding can be supported by fasteners that are nailed only into the gypsum sheathing itself; after all we're talking about a panel made of gypsum, surfaced with paper or asphalt-impregnated paper.

Instead your fasteners need to be driven into the wall studs or into furring strips nailed across the wall studs.

On 2021-03-29 by Mark

Will gypsum panel sheathing hold vinyl cedar impressions?

On 2020-05-09 - by (mod) -

Ken

One can add a layer of plywood sheathing before re-siding, though the added thickness may mean you end up having to build out all of the window and door trim.

It's the housewrap not the sheathing that is expected to keep water from penetrating the walls (along with, of course, proper flashing around building openings)

On 2020-05-09 by Ken

If you were to remove the vinyl siding and asbestos siding and find exterior gypsum board that has Been damaged by multiple layers of siding throughout it 60 year life ,can a 1/2 inch cox plywood be installed over the gypsum board without worrying about moister permeating from home causing another whole set of problems

On 2018-11-21 by Rob K

I was tearing off vinyl siding when I came across a gypsum type sheathing.

Black paper on both sides and a 10" large Sivler S on the inside. The house was built in 1971. So my question is have you ever heard of this and did all gypsum sheathing have asbestos or just some from this time period? I asked this on another page but can't find the comment section. thanks for our time, Rob

On 2018-07-06 - by (mod) -

A little -

see Drywall R-values at INSULATION R-VALUES & PROPERTIES

On 2018-07-06 by peteramy292@gmail.com

does gypsum board sheathing used 1n 1976 provide any insulation ie r factor

On 2017-09-25 - by (mod) -

Adding to be clear,

at the article we cite you'll see a suggestion for use of closed cell foam insulation that, properly applied, can form a waterproof barrier behind the veneer.

You're dead right that without either a perfect seal or perfect drainage plane behind the veneer we're going to see water problems again on the building.

On 2017-09-25 - by (mod) - How can you install any sheathing with proper waterproofing from the interior side of the wall?

Robert,

Your question is really important - so I appreciate seeing it.

We have discussed what is an almost identical problem on flooded buildings where fiberboard exterior sheathing is installed.

See BRICK VENEER WALL REPAIRS in FLOOD PRONE AREAS

where we describe some repair options.

I have indeed found gypsum board sheathed buildings (like ones shown on this page) that had been exposed to the weather and whose gypsum board water-resistant (not waterproof) material was in remarkably good shape.

But none of those cases involved a building whose gypsum board sheathing sat under-water for days or weeks or longer. In those cases it would be smart to remove the flood-damaged gypsum board. That's done by cutting away the gyp-board between the wall studs from the wall's interior side.

Cuts are made along the wall sill plate top, along the sides of the studs, and up to a height at least a foot above the last point of visible damage, wetting, deterioration, or mold. Then cut horizontally across the gypsum board at that height.

Inspect both sides of the gypsum board for visible mold. If you see mold on either side of the top of the last bit you cut out of the wall, working from the floor height upwards, cut another foot out and inspect again.

Continue that process until you are confident that the material that remains is intact and not soft (from water damage) and mold free (by visual inspection).

You will be leaving gypsum board between the inner face of the veneer (brick or stone) and the outer or outwards-facing surface of the wall studs. Mold that might be in those spaces will be sealed against entry into the wall cavity and building when the wall cavity has been cleaned, sanitized, dried, and re-insulated (perhaps best using closed cell spray foam).

You will see in our brick veneer wall repair article I cited above that we suggest moving weep openings higher in the wall to just above the highest anticipated flood line - typically that will be the same as the bottom edge of the gypsum board that you are leaving in the wall cavity.

Details are in the article I cited.

FEMA's suggestions reported to us here at InspectApedia have been sometimes brilliant, sometimes inconsistent and sometimes frightening or arbitrary - at least in what was reported to me.

For example, removing material from a flooded building up to an *arbitrary* height of two feet or four feet above the interior floor could be a serious error - we need to consider the actual depth to which a building was flooded as well as the actual height of damaged materials in and on the walls.

But the bottom line is that it can indeed be possible to preserve the exterior veneer wall and to repair the wall from the interior side.

If the veneer wall is slightly loose or leaning but not buckled it might be repaired by adding wall ties through the veneer to the studs.

if the veneer wall is buckled, cracked, falling, it is unsafe and is probably beyond economical repair.

Use the page top or bottom CONTACT link to send me some exterior and interior photos of the conditions of your home and we can comment further.

On 2017-09-25 by Robert Taylor

By the way, the homes mentioned below just went through the Harvey storm. The homes had about 5 feet of water in them for about 2 weeks. So, can the exterior gyp board sheathing be left in place if it is not completely disintegrated?

If a house has the "water repellent" gypsum board sheathing with brick veneer, can the sheathing be dried out and left in place? To replace it, I see no way to do this without removing the brick. Otherwise, you will not have a good waterproof membrane behind the brick.

I have recently looked at several brick veneer homes that a contractor has removed interior gypboard, insulation, and the exterior water repellent gypboard sheathing. They left the brick in place.

How can you install any sheathing with proper waterproofing from the interior side of the wall with the brick in place? This seems to be impossible to do but has been suggested by FEMA.

...

Continue reading at BRICK VENEER WALL REPAIRS in FLOOD PRONE AREAS for a discussion of repair options for brick veneer walls, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see GYPSUM BOARD SHEATHING FAQs - questions & answers posted originally at this page

Or see these

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