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Plaster lath board © Daniel Friedman Plaster Types & Methods in Buildings
Plaster Ceilings, Plaster Walls & Plaster Type Identification in buildings

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Types of plaster walls & ceilings:nails

Here we provide a photo guide to identifying types of plaster ceilings and walls installed in buildings, using building ceilings as a photo and investigation guide.

In this article series we describe and discuss the identification and history of older interior building surface materials such plaster, plaster board, split wood lath, accordion lath, sawn lath, and expanded metal lath, Beaverboard, and Drywall - materials that were used to form the (usually) non-structural surface of building interior ceilings and walls.

Synonyms for "plaster" include stucco, render, lime plaster, cement plaster, gypsum plaster, and plaster of paris. Lime plaster is also the principal ingredient in whitewash often used on building stone walls both indoors and outside and also sometimes applied to wood surfaces.

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.

Guide to Methods & Types of Plaster Ceiling & Wall Covering Systems in buildings

Gyp lath board © D Friedman at InspectApedia.com Photo Guide to Types Interior Plaster: split wood lath, sawn wood lath, expanded metal lath, "rock lath" or plasterboard, drywall, & tainted Chinese drywall.

Our page top photo illustrates a thin plaster coating over wood lath in late 18th century home. When only a thin plaster coat was applied, as may be the case in an attic or on a basement ceiling, the wood lath strips are clearly telegraphed as the plaster dries and hardens.

Our stunning and stark photo of a thin coat of plaster on gypsum board illustrates a much later innovation for finishing building interiors. All of the modern plaster systems are discussed in this article series.

[Click to enlarge any image]

Article Series Contents

This article includes a photo guide to split wood lath, pit-sawn lath, circular blade sawn wood lath, expanded metal lath, "rock lath" or plasterboard, drywall, & tainted Chinese drywall discusses the types of plaster ceiling & wall coverings used in buildings, giving a history and description of types of materials used.

We include a description of plaster system identification and history of use of plaster, a photo guide to plaster coatings, cracks, hazards, and plaster ceiling collapse hazards & photographs.

Wood Lath Plaster Systems from 1600 A.D. to Present

Hand cut wood lath in a U.K. home, St. Weonards, Brinstone Farm, U.K. (C) Daniel FriedmanPlaster-type coatings applied over wood lath or directly onto masonry surfaces is at least 2000 years old. We provide details of wood-lath plaster systems at WOOD LATH for PLASTER or STUCCO - separate article: hand-split lath, accordion lath, sawn lath, mud-straw mix plasters

This page illustrates several generations of plaster mixtures, types of wood, metal and gypsum board lath, lath nails, drywall nails and screws and related materials used in buildings in recent-centuries.

Studying the details of plaster and its lath or other support system in a building can help determine the age of the structure.

Our photograph shows rough sawn and some hand split wood lath from Brinstone Farms in St. Weonards, Herefordshire, U.K. The lath is nailed with hand-wrought nails. This Herefordshire building and others in the area date from the early 1600s.

We name and illustrate these and discuss their periods of use below as an aid in finding out how old a building is and tracing its history. Examples:

Also see DRYWALL, FIBERBOARD, PLASTER INTERIORS where we include photographs of non-plaster interior wall and ceiling coverings including drywall, beaverboard, and paneling.

For plaster type surfaces used on building exteriors, see STUCCO WALL METHODS & INSTALLATION.

Plaster on Lath Coatings or Layers: 3-coat & 2-coat plaster systems

Mud straw plaster © D Friedman at InspectApedia.com Our plaster wall and ceiling photos below demonstrate the stages in constructing an traditional plaster on lath surface. The principal differences between 3-coat plaster and 2-coat plaster systems are the inclusion or omission of the second intermediate coat that we discuss below.

Mud Plaster

Below we illustrate the plaster ears of mud-plaster used on wood lath strips, seen from the wall cavity side.

The mud plaster in this example was simply a mud-straw mix of "plaster" base coat used in a late 18th century New York home, ca 1785.

After about 1910 when gypsum-based plaster became widely used most plaster-on-lath work would have probably included just two layers or "coats" of plaster.

Three-coat Plaster system

Three-coat plaster was applied in three layers from most-coarse to most fine.

When applied over wood lath or later, metal lath, the first coat of plaster, the brown coat or scratch coat, is pushed through openings in the lath so that when it hardens it is mechanically secured to the building wall or ceiling.

Below is a photo of the base coat of plaster viewed from the other side of a hand-split lath wall in a pre-1900 home I restored.

Hand split wood lath plaster system (C) Daniel Friedman

The base coat was very coarse and was referred to as a scratch coat or brown coat. Sometimes in attics and basements just the brown coat or scratch plaster coat was applied, which is why I was able to take the photo shown just below.

The gouges or scratches in the brown coat were made by the plasterer using a notched tool or saw-tooth-edged tool to improve the adhesion of the next coat. The first two plaster coats would each be about 3/8" thick while the final coat was quite thin, just 1/8" in thickness.

Our plaster scratch coat or "brown coat" photo (below) shows how this surface was sometimes scarified to provide better adhesion of the top coats of plaster.

However often the brown coat was simply applied roughly without gouging, as we show in this extra plaster rough coat photo [Image file].

Brown coat or scratch coat plaster (C) Daniel Friedman

The second coat of plaster in a three coat system was used to bring the surface of the finished wall forward and add thickness before applying the thinner, smoother finish coat.

Our photo at below left shows a common practice in roughly-finished attics: just a thin skim coat of plaster was applied directly to the wood lath - you can see the wood lath telegraphing through the plaster coating. Very often plaster cracking follows the lines of these lath strips.

Plaster ceiling in an attic using wood lath (C) Daniel Friedman

In a two or three-coat plaster system the final top coat was intended to be troweled smooth and typically would have included the highest lime or gypsum content of the two or three layers. Typically the top coat is just 1/8" thick.

Spray-on plaster coatings, widely used as a fireproofing in ships and buildings were more likely to include asbestos as well as rock wool, vermiculite, and fiberglass.

Asbestos was been used in other plaster preparations too. Spray-on plaster ceiling coatings beginning much later (perhaps in the 1960's [citation needed] included styrofoam or similar beads or fragments.

Using Fiberboard Sheathing as a Plaster Base

Fiberboard-gypsum plaster base sheets in a 1930's home (C) InspectApedia.com TT

Celotex and other brands of fiberboard sheathing were used both as exterior wall sheathing and as interior wall sheathing or as a base for plastering as we describe below. This fiberboard is a cellulose product, not asbestos.

Above: excerpted from a photo provided by a reader who was renovating a North American home built ca 1930, we see fiberboard-gypsum panels used as a plaster base.

[Click to enlarge any image] Fiberboard pre-laminated to gypsum was sold in sheets in several thicknesses for use as a plaster base.

Separately, fiberboard, including Celotex™ was also sold in raw fiberboard form for use as a plaster base, without pre-lamination of the fiberboard or pre-coating of it with gypsum.

These fiberboard sheets were lighter, easier to transport, and less fragile than the fiberboard-gypsum laminate product we show just above. Celotex provided detailed instructions for using their fiberboard as a plaster base. You can see those details just below on this page.

Details about the types and uses and installation instructions for fiberboard-based and fiberboard-plaster-laminate based plaster systems are at FIBERBOARD PLASTER BASE SYSTEMS.

More about fiberboard products used as exterior and interior sheathing as an insulating board is at FIBERBOARD SHEATHING IDENTIFICATION.

If you are worried about possible asbestos contamination in fiberboard sheathing or in fiberboard-gypsum laminate boards used as sheathing or as a plaster base, see SHEATHING, FIBERBOARD ASBESTOS CONTENT

 

Gypsum lath board cross section © D Friedman at InspectApedia.com

Our photo above shows a round cross section test plug we cut from a finished interior wall in an older home. Oldest materials are on the right side of the plug. From left to right we see

More Articles About Fiberboard Sheathing & Fiberboard Plaster Base

Gypsum Board Lath Sheets Used for Plaster Walls & Ceilings = Rock Lath, Plaster Lath, or Rock Lathe

Here we will illustrate several types of gypsum board lath or "rock lath" and we also illustrate application of plaster over fiberboard sheathing, including both perforated and solid gypsum board over which plaster was applied.

Perforated Gypsum Board Lath

Plaster lath board © Daniel Friedman

Our photo (above) shows perforated gypsum board panels that were used as plaster lath. Both perforated and solid gypsum board panels were sold for use as a base for finish wall and ceiling plaster.

Plasterboard with round holes punched at regular intervals substituted for the plaster scratch coat, nailed to wall studs, eliminating the wood lath requirement. A top coat of plaster was applied to the plaster board. "Ears" of oozing plaster pushed through the round holes helped hold the plaster top coat in place

Plaster lath board © Daniel FriedmanOur wall cross section cutaway photograph of gypsum board lath installed on a New York home (photo at left) shows how these walls are constructed, and you can see quite clearly the top coats of plaster that were applied over the gypsum board itself. [Click any image for an enlarged, detailed view.]

Here is another photograph of a plaster wall test cut [photo] that shows a closeup of the layers of plaster board and top coats that make up the wall surface in a 1930's-built home whose plaster-board lath included wood fiber reinforcing materials.

Contemporary gypsum lath products include GoldBond® brand gypsum board products including Kal-Kore brand plaster base panels sold by National Gypsum Corporation. Kal-Kore plaster base panels are designed as a base for veneer plaster, but these can also be used as basecoat plasters for Gypsolite, Two-Way Hardwall (National Gypsum products) or other conventional plasters.

Kal-Kore plaster base is sold in 4' and 8' widths and in 8' to 16' lengths - considerably larger than the older plaster-board lath systems shown above and just below where we describe regular rectangular bulges in plaster ceilings and walls.

Board lath and how it is applied are described in Plastering Skills, [book for sale link] F. Van Den Branden, Thomas L. Hartsell, and in US Gypsum's Gypsum Construction Handbook [book for sale link] as well as other publications. VanDenBranden/Hartsell explain the popularity of board lath as a plaster base [paraphrasing]:

Gypsum Board Lath is provided in a variety of sizes, thicknesses, and types, most commonly 3/8" x 16" x 48" in dimension, solid or perforated with 3/4" diameter round holes punched 4" o.c. to provide mechanical keys, improving adhesion and fire rating of the surface. Our photo (above) shows mortar passing through the holes in perforated board lath.

Watch out: only gypsum mortar can be applied over gypsum lath. Never apply lime mortar, portland cement, any other kind of binding agent to gypsum lath.

See PLASTER BULGES & PILLOWS. Also, perforated board lath should not be used on ceilings where it is supported only at edges, because the perforations weaken the lath.

But this is not the only type of plaster lath board or gypsum lath board found in homes. Above the product includes an insulating layer of up to 1/2" of wood or paper fiber insulating board on its innermost layer.

That layer is placed against the wall studs or in a masonry building against the masonry wall.

Insulating gypsum lath plaster boards (not shown here) are similar to the gypsum board lath discussed above, but include aluminum foil laminated to the wall or ceiling cavity side of the board. Installed with a 3/4" air space before any ensuing insulation, this material adds about the same R-value as 1/2" insulating board.

History of Sackett Board mutli-layered gypsum / paper board - the first "drywall"

Sackett Board (C) InspectApedia.com HaniacekThis photo, provided by an InspectApedia.com reader appears to be Sackett Board, first produced by Alexander Sackett, who formed the Sackett Plaster Board Co. As first produced, Sackett Board was made in 32" x 36" sheets, later in larger panels.

Soon thereafter Sackett Board was marketed by US Gypsum following USG's purchase of the Sackett Plaster Board Company in 1909.

The sale of USG's Sacket Board marked USG's entry into the gypsum board or plasterboard market.

The Geneva Illinois home where this multi-layered paper and gypsum plaster board was installed is itself dated by the owner as 1907 or 1910.

[Click to enlarge any image]

We solicit photos of similar material from our readers - you can post photos and comments at the end of this page or you can use the page top or bottom CONTACT link to send us email directly.

1888: In the U.K. the first plasterboard production facility opened in 1888. In London, Gyproc Products Ltd., produced a plaster-board that included rust-resistant metal reinforcement for use as ready-made partitions.

1890-1894: In 1890 Sackett Board was invented by Augustine Sackett (his photo is below).

Other sources give 1891 but they are incorrect insofar as Sackett's U.S. Patent for his Inside Wall Covering describing this multi-layered builders paper and gypsum plaster board was filed May 23, 1890 and granted by the U.S. Patent Office No. 520,123 on May 22, 1894.

The Sackett Wall Board company was first located in the Whitehall Building, 13-21 Battery Place, New York, NY.

To produce Sackett Board, Sackett joined forces with the Grand Rapids Plaster Company in Grand Rapids Michigan.

Sackett Board, first produced in 32 x 36" rectangles, was described as a multi-layered "wool-felt" paper and gypsum wallboard product for interior walls and ceilings.

Sackett Board was nstalled as a "ready-to-finish" surface to be intended to be finished with a layer of gypsum-based plaster.

Sackett Board before purchase by USG - at InspectApedia.com

1902: In the U.S., US Gypsum was formed in 1902 by the merger of 30 independent gypsum and plaster companies. The company's first product, Pyrobar, a gypsum-based fireproof tile, was produced in 1903.

1909 US Gypsum purchased the Sackett Plaster Board Company, (appearing as the Sackett Wall Board Co. in some advertisements) marking their entry into the gypsum board marketplace, marketing wall and ceiling panels ready to be finished with plaster.

From 1909, USG continued to market Sackett Board advertising Sackett Plaster Board as a substitute for wood lath. Early advertisements for United States Gypsum Co.'s Sackett Plaster Board cited US Gypsum, the Grand Rapids Plaster Co., and the Sackett Plaster Board Company (then owned by USG).

Sackett Board when owned by US Gypsum - early advertisement (C) InspectApedia.com

1916: By 1916 USG had simplified their Sackett Board product to use a thicker gypsum-based plasterwith single coatings of paper on the board exterior face and back (later also on edges), a predecessor to modern drywall.

That would place the multi-layered plaster board in the home above home as before1916.

1917: Some sources date the first use of the term "Sheetrock" to U.S. Gypsum's product announced the following year, 1917.

Research on the History of Drywall

Augustine Sackett at InspectApedia.com
Sackett Board patent illustration - the invention of gypsum board or drywall - at InspectApedia.com

Sackett Board advertisement before USG ownership - at InspectApedia.com

Solid Gypsum Board Lath or Rock Lath

Plaster lath board © Daniel Friedman

Solid gypsum board products: gypsum-based fire-resistant tiles were first produced by US Gypsum in 1916, a predecessor of paper-covered gypsum board used as a plaster lath base and later in lighter form as modern drywall. U.S. Gypsum, formed in 1902 by the merger of 30 independent gypsum rock and plaster manufacturers, produced Pyrobar in 1903, a gypsum-based fireproof tile.

USG's first gypsum board product was Sackett Board described just above.

Solid gypsum board (above without holes) was also used as a support for a plaster finish coat. Often this material was applied in two-foot widths - a feature that the inspector may spot by noticing scalloped ceilings and walls or even cracks that appear regularly on 24" centers.

Below: rock lath / plasterboard lath / gypsum- lath (all synonyms) in a 1940's home in Poughkeepsie, New York. [Click to enlarge any image]

Rock lath or gypsum board lath cut-out section showing cross sections of materials (C) Daniel Friedman at InspectApedia.com

While cutting an opening in the home's interior wall to provide repair access to bath tub plumbing we could see the cross section of this material showing the thick plaster applied to the wall exterior. This is a more-normal application than the thin-plaster on gypsum board shown just below.

Below: very thin-coat plaster on more-recent gypsum board.

Gyp lath board © D Friedman at InspectApedia.com

Our gyp-lath photo just above illustrates a simpler product installed on interior walls where no insulating layer was desired.

The gypsum-lath board (at left in the photo is made of gypsum covered on both sides by paper - there is no insulating board layer. You can see the very thin layer of finish-coat plaster on the right side of this gyp-lath board.

Masonry Surfaces (Brick, Stone, Concrete) as a Plaster Base

Stucco and adobe in Mexico (C) D Friedman S Goldstein

As Van Den Branden and Hartsell detail, "masonry walls are about the oldest form of plaster base known".

Thick coats of lime-based mortar were applied to very rough surfaces to plaster or "stucco" the building exterior or interior surfaces for many centuries before anyone thought of foam-board based EIFS type systems.

See SIDING EIFS & STUCCO

The authors continue to explain that because modern masonry wall exteriors are much more smooth (picture brick or concrete block walls), thinner coatings of mortar are used. The authors define three types of masonry bases for plaster, whether indoors or outside:

Our photo (above, courtesy of Steve Goldstein) shows both rough and smooth brick and adobe surfaces on buildings in Guanajuato, Mexico.

These masonry surfaces are regularly plastered or stuccoed with lime based cement mixtures and should be considered high suction masonry bases as we describe below.

  1. Low suction masonry bases for plaster: glazed tile, hard burnt brick surfaces, road or paving bricks, hard stone such as granite
  2. Medium or average "suction" masonry bases: "cinder block", concrete block, face brick, medium-hard brick, hard clay partition tile, better grades of common brick, and some softer stone surfaces.
  3. High suction masonry bases: soft common brick, soft clay partition tile, gypsum partition tile, some highly porous tile surfaces.

    For completeness one should add a fourth plaster surface type:
  4. Concrete surfaces as a plaster base: these surfaces provide special problems for plaster application and need to be specially prepared (scratched), or must be plastered using a special high-adhesive bonding plaster, or coated with a primer that is approved for bonding the plaster to the concrete

See STUCCO WALL METHODS & INSTALLATION for details about exterior stucco wall systems.

History of Invention of Gypsum Board, Perforated Board, Button Board as a Plaster Base or Plaster Lath System

Van Den Branden and Hartsell list ten gypsum board lath products, here we provide the full list

  1. Gypsum lath board - discussed above
  2. Long length insulating gypsum lath
  3. Veneer plaster gypsum lath
  4. Radiant heat gypsum lath plaster base
  5. Gypsum wallboards
  6. Gypsum backer boards
  7. Coreboard
  8. Gypsum studs
  9. Gypsum sound-deadening backer board
  10. Insulating lath board - discussed above

Patent disclosures give a general idea of the years of first popular use of gypsum board as a plaster lath base. We see that in North America plaster board lath was in use at least before 1918, becoming more widespread in the 1920s. Utzman in 1925 described "gypsum lumber" as a plaster base.

And Hicks, also in 1922, described plaster board with recesses or depressions to adapt gypsum board for use as a plaster base.

Gypsum Board & GypRoc plaster base patent research & history

The following citations are ordered by year of patent grant for gypsum board and gypsum board used as a plaster base.

Reader Question: how to recognize types of plaster board or plaster lath used in buildings

Wall test cut shows construction © D Friedman at InspectApedia.com

I am not sure if you can help. I have looked up information online and can not find any. My home was built in 1922. I have stripped wall paper that was hung in 1959. Under the paper I thought id find lath and plaster. Not so much. The look is that of sheet rock but at close inspection it is more like concrete.

Like mortar I guess. You can scrape it away and it comes off like sand. It seems thick maybe 1/2 inch. I am wondering what it is and is it dangerous. The walls are all in excellent shape with minor patch work. My grandparents lived here since it was built both lived long healthy live. But you never know. Any info would be helpful. Thanks. - B.D. 6/19/12

Reply: tips for decoding a cross-sectional cut of wall covering to disclose plaster, plasterboard, gyprock etc.

Our photo (above left) shows layers of wall finish material in a masonry block home: concrete block at left, wood insert to secure window trim (removed for the photo), a wood fiber insulating board or "beaverboard" type material, a layer of plaster, layers of finish plaster and paint, and finally at right, modern drywall

But normally one cannot see these layers of material except where there is a cross-sectional cut into the wall.

See FIBERBOARD PLASTER BASE SYSTEMS for a description of how fiberboard was used as a plastering base.

A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem material in building interiors. That said, here are some things to consider:

I'd need to see photos and perhaps a sharp photo of a test cut through the wall material to have a more confident view of how your wall was constructed but

If all that's needed are minor repairs to the finish wall surfaces and you are adding a patch not demolishing the walls, leaving the existing material in place is not itself a hazard.

Asbestos is not like a radioactive material - it does not emit harmful particles unless it is disturbed. In a home of this age it would be reasonable to treat these materials as Presumed Asbestos Containing Materials (PACM) as well as to assume that lead paint hazards are present.

Plaster Repair Methods, Resources, Standards

Loose Plaster is Unsafe, Especially Loose, Falling Plaster Ceilings

For a discussion of rectangular bulges, shadow effects, or scalloping in plaster ceilings or walls see PLASTER BULGES & PILLOWS

See PLASTER, LOOSE FALL HAZARDS for examples of bulged plaster that may be danger signs

Ingredients in Plaster Used in Buildings

This topic has been moved to PLASTER INGREDIENTS, MIX, COMPONENTS

Types of Wood Lath Used for Plaster Ceilings & Walls

Details of wood lath plaster base systems are given in this separate article: WOOD LATH for PLASTER or STUCCO

More about using saw kerf marks and other tool marks on wood to determine the age of a building can be read at SAW & AXE CUTS, TOOL MARKS, AGE

Expanded Diamond Mesh Metal Lath for Plaster Walls & Ceilings

Details about metal lath and its history are found at PLASTER LATH, METAL.

Details about exterior stucco using metal lath are at  STUCCO WALL METHODS & INSTALLATION.

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Continue reading at PLASTER INGREDIENTS, MIX, COMPONENTS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see PLASTER TYPES & METHODS FAQs - questions & answers posted originally on this page

Or see DRYWALL, FIBERBOARD, PLASTER INTERIORS - home

Or see NAILS & HARDWARE, AGE

Or see STUCCO WALL METHODS & INSTALLATION - plaster type surfaces used on building exteriors

Or see this

Article Series Contents

Suggested citation for this web page

PLASTER TYPES & METHODS in BUILDINGS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING INTERIORS

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