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Horizontal drywall runs (C) D Friedman Eric Galow Drywall & Plasterboard
Age, composition, tests, history

Gypsum board, plasterboard, or drywall used on building exterior or interior surfaces:

Composition and early history of drywall.

This article series discusses the identification and history of older interior building surface materials such plaster and lath, Beaverboard, and Drywall - materials that were used to form the (usually) non-structural surface of building interior ceilings and walls. Our page top photo shows hand-split wooden lath backing for a plaster interior wall.

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Drywall Composition, Ingredients, History

Sackett Board (C) InspectApedia.com Haniacek

While modern drywall or gypsum board is usually composed of a single inner layer of gypsum, sometimes reinforced with other fibres, and covered on both sides and at least two edges with paper, earlier versions of this product included Sackett Board, shown here, a wallboard comprised ofr multiple layers of gypsum and paper, generally intended to be covered by a final layer of hand-applied plaster.

Details of the earlier product are at SACKETT BOARD.

In the U.S., ASTM C11 defines gypsum board as the generic name for a family of board products consisting of a non-combustible core primarily of gypsum with a paper facing.

How is drywall made & what are the ingredients of gypsum wallboard ("drywall" or "Sheetrock™") ?

According to an ATSDR study of asbestos exposure from vermiculite and some forms of drywall, gypsum wallboard is currently (2008) manufactured in the following steps:

  1. Gypsum rock is crushed to form small pieces, dried to evaporate surface moisture, and ground;
  2. The dried gypsum is “calcined” or heated to remove excess water that is chemically bonded to the gypsum, forming what is called “stucco;”
  3. Dry additives (e.g., vermiculite, perlite, starch, fiberglass, or sugar) are mixed into the stucco depending on the properties needed in the specific product;

    Note: in special applications including the development of fire-resistant drywall, some formulations included the addition of asbestos fibres or powder.
  4. Water is added to produce a slurry;
  5. The slurry is mechanically spread over a paper backing;
  6. A top layer of paper backing is applied to form a “sandwich” with the slurry in the middle;
  7. The long, continuous sheet of wallboard moves on conveyor belts while the slurry hardens, and the sheets are cut into specified lengths;
  8. The cut boards are flipped and sent into a multi-stage kiln to dry and become hard; and
  9. The hardened wallboards are trimmed to an exact length, end-taped, stacked, and placed onto skids, ready to be shipped.

Desirable Properties for Drywall

Drywall layers (C) Daniel FriedmanExcerpting from Croce 1951

.. it is an important object of the present invention to enable the physical characteristics such as resistance to shock, nailability, flexibility, strength and similar characteristics of plaster casts to be enhanced in a simple and economical manner and in such a.way that ready workability of the set composition is attained.

Another and related object of the' invention is to accomplish this in such a way that the mixing and forming operations that must be applied to the plaster composition may be readily and easily performed.

Experiments with Inclusions in Gypsum board to Improve its Properties

Again excerpting from Croce 1951, some ingredients included in gypsum board or plasterboard reduced its strength:

In an effort to impart more desirable physical characteristics to plaster walls and wallboard, such as resistance to sudden, localized forces, many different ways or expedients have been employed.

For example, the plaster composition utilized in the making of wallboards has in many instances been made so as to incorporate a fairly large percentage of fibrous organic material such as sawdust, sisal fibers, paper pulp and the like.

Study of such prior gypsum plaster wallboard indicates that while these expedients serve to increase the nailability, certain disadvantages are encountered, and particularly it is found that the relatively high percentage of such filler or the like that must be used in such instances serves to correspondingly reduce the amount of plaster that is used, and the resulting plaster wall or wallboard possesses less strength than is desirable to resist the stresses and strains applied to such structures.

Another characteristic that is extremely desirable in plaster compositions that are used for building purposes is the workability of the resulting cast insofar as sawing or cutting may be concerned after the plaster has hardened or been put in place.

For example, normal building construction in many instances requires that an opening be cut into a plaster or plasterboard wall so that an electrical outlet box may be mounted in position, and this opening must in many instances be cut into the ceiling of a room.

In such instances it is found with conventional plaster compositions that there is a tendency for the plaster to break away from and at an angle to the line upon which the cut is to be made, and there is also a tendency for the plaster to break apart into fine dust, and this breaking and dusting, of course, is undesirable, particularly when the work is being done in a home or the like that is occupied.

Why Asbestos was Added to Plaster, Drywall, Gypsum Board

It should be observed also that in some instances asbestos has been used in plaster.

In one such use the asbestos fiber has been added to plaster primarily to improve the plaster workability or trowelling characteristics while in another instance, in the Croce Patent No. 2,526,066, such asbestos fiber was added as a means for retaining an expansive component of the plaster composition in place in the set cast. In each case the amount of asbestos was quite high, and the Water absorptive capacity of the asbestos has increased the drying time of casts thus made.

Drywall / Plasterboard Resistance to Cracking

Another important and desirable physical attribute in plaster casts, walls, and wallboard is high resistance to cracking due to settling stresses or fire, and to enable a marked improvement to be attained in respect to this important physical characteristic of plaster casts and the like is another important object of this invention.

Another and related object is to enable plaster compositions to attain such improved resistance to cracking and breaking when used in the ordinary manner to produce casts, walls, wallboard and the like.

Drywall Must Hold at Nail or Screw Fasteners

When plaster wallboard is put in place on walls or ceilings, it is secured in place by fastening elements such as nails, clips, screws or the like, and the permanence of such fastening is dependent in a large measure upon the shearing strength of the wallboard at its line of engagement with such fastening element.

This area of critical shearing strength has often constituted the point of first failure in such walls or ceilings, and it is therefore another important object to so constitute a plaster composition that plaster walls or wallboard made therefrom will exhibit a materially increased shearing strength; and a related object is to accomplish this in a simple and expeditious manner.

Reduced Fire Resistance if Wood, Sawdust, Other Organics are Added to Drywall / Plaster

... using added mixing water, with its resulting reduction in strength and increase in drying time for the casts, coupled with the further fact that the organic fibers constitute a fire hazard in a manufacturing plant, and that such organic fibers disintegrate at relatively low temperatures.

... It is well recognized that the use of plaster or plaster wallboard as a wall surfacing in buildings serves as a protection against the destructive action of fire, and many efforts have been made to increase the fire resistant or fire retardant action of gypsum plaster walls.

Such efforts have in most instances centered about the character of the lathing employed, while in another instance a heat-expansive material has been added to the plaster to compensate for heatinduced shrinkage of the plaster in the event of fire, as described in the aforesaid Croce patent.

It is another important object of the present invention to enable high-fire retardant characteristics to be attained in plaster compositions and products in an improved and simplified manher, and related object is to attain this result with the minimum of additives so as to thereby enble the maximum ratio of plaster to be used.

Advantages of Adding Fiberglass to Plasterboard or Drywall

Such disadvantages are eliminated under the present invention by affording a gypsum plaster composition which utilizes drawn textile glass fibers as a bodying and strengthening component in such a way and with such efiiciency as to be economically practical and in such a way that the mixing and forming, shaping and drying operations in respect to the mixed plaster or slurry may be readily and easily performed.

Plasterboard Resistance to Bending

At the outset it should be noted that suggestions have heretofore been made concerning the use of wool, and separation of individual fibers from the mass is quite difilcult because of the curled and interlaced or matter relationship of the fibers in the mass.

Such separation of individual fibers from the mass is also rendered difficult by reason of the relatively low physical strength characteristics of the blown fibers which bend quite easily and tend either to retain their bent form or to break at the bend.

Mechanical Tests of Drywall

Table of Croce's mechanical tests of drywall formulas and additives - at Inspectapedia.com 1951 patent

[Click to enlarge any image]

The tests included in Table I show that as co'mpared with conventional plaster wallboard as represented by board A, boards B, C and D attain a marked improvement in respect to fire resistance, while boards C and D attain satisfactory characteristics in the other tests.

Again excerpting from Croce 1951

Wallboard Whipping Test

The whipping test is one that is quite important from a practical standpoint in that it simulates a condition that is often encountered in the handling or installation of plaster wallboard.

Thus in this test the opposite ends of 4 foot by 8 foot sheet of plaster board are grasped by two men and the board is moved up and down so as to cause the central portion of the board to bow downwardly and then upwardly with what might be termed a whipping action.

In such handling, any weakness inthe board is liable to cause breakage, and by counting the number of whips or up and down movements necessary to break such a board, a munerical index is afforded which is representative of the strength characteristics of the board.

Wallboard Shock Test

The shock test was made by supporting a piece of board one foot wide and four feet long on three feet centers, and in this instance the grain of the paper extended transversely of the width of the sample.

A loading board was then placed in the center of the span and a sling arrangement was attached to the loading board.

A weight of 660 grams was then attached to the sling by means of a rope. This weight was raised up one inch and then dropped and this dropping action was repeated through progressively larger distances, the increase between drops being one inchin each instance, and this was continued until failure or breakage of the test board.

The results of this test were indicated by the number of inches of the final dropping movement of such weight.

Wallboard Furnace Test

In the furnace test the board samples were :nailed on 6-inch centers to the lower faces of joists spaced on 16-inch centers and a 4 lb. load was placed on the board midway between the joists.

The board as thus supported formed what may be termed the upper wall of the furnace and the temperature developed in the furnace was substantially 1200 to 1300 degrees F. at the end of minutes and was thereafter maintained at 1300 to 1500 degrees F.

Wallboard / Drywall / Plasterboard Nailing Test

The nailing test is performed by driving 5 penny cement coated wallboard nails into a wallboard near an open or out edge, and observing whether and to what extent the plaster core splits out or breaks.

The first such nail was driven at a point inch in from the cut edge of the board, and successive nails were driven at points located progressively close to such edge.

Wallboard / Drywall / Plasterboard Break Test

The break test was performed by cutting one paper cover of the board along a straight line entirely across the sample, and then breaking to determine whether the board would break along a straight line as is desired in use of such board.

Wallboard / Drywall / Plasterboard Hammer Blow Test

The test relating to resistance to hammer blows was performed by striking the boards near an open or cut edge and at different distances from the edge, and the quality of the board in this respect is judged by the extent to which the core shatters or flies out of such edge in response to the blows.

- (Croce 1951)

Drywall, Gypsum Board, Plaster Board, Adamant, Sackett Board, Sheetrock Early History & Dates

Drywall / Gypsum Board Composition & Testing History References

Adamant plater award issued in 1898 (C) InspectApedia.com
Above: listing of the Adamant Co. Ltd., 6 Commercial Street, Birmingham, as recipient of a bronze medal for its Adamant plaster for walls and ceiligns, in the Birmingham Exhibition, 1898 list of awards.

The Birmingham Exhibition of 1898 was a Worlds Fair organized in Birmingham, in the United Kingdom, in that year. Birmingham previously hosted a better-known worlds fair Exhibition of Industrial Arts and Manufacturers in 1949.

[Click to enlarge any image]

Illustration below: perforated multi-layer plaster board base used for plaster wall and ceiling systems, from F.L. Kane US1003754A (1911).

Kane peforated reinforced plaster board US Patent No. 1003754, from 1910 cited & discussed at InspectApedia.com

Kane Lath Attaching Device US Patent 997559 at InspectApedia.com

 

Identifying Stamps on Drywall Used for Interior Wall & Ceiling Surfaces

This discussion has moved to this separate page:

DRYWALL TYPE IDENTIFICATION STAMPS

Drywall Gypsum Board Used for Exterior Wall Sheathing

Details are now at SHEATHING, GYPSUM BOARD

Gypsum Board Lath Sheets

Plaster lath board © Daniel Friedman ... Plaster lath board © Daniel Friedman

At GYPSUM BOARD PLASTER LATH SYSTEMS - we describe the use of perforated or solid gypsum boards as plaster base: "Rock lath", including the history of use of "rock lath" or perforated gypsum board or "button board" as a plaster base or lath-substitute material.


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