JUN 2 1 1943
BUILDING MATERIALS AND STRUCTURES REPORTS

On request, the Superintendent of Documents, U. S. Government Printing Office, Washington,

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The following publications in this series are available by ptirchase from the Superintendent of Documents at the prices indicated:

BMSl Research on Building Materials and Structures for Use in Low-Cost Housing 10^ BMS2 Methods of Determining the Structural Properties of Low-Cost House Constructions 10^ BMS3 SuitabiUty of Fiber Insulating Lath as a Plaster Base 10(5 BMS4 Accelerated Aging of Fiber Building Boards lOji BMS5 Structural Properties of Six Masonry Wall Constructions 15(5 BMS6 Survey of Roofing Materials in the Southeastern States 15(5 BMS7 Water Permeability of Masonry Walls . 10^ BMS8 Methods of Investigation of Surface Treatment for Corrosion Protection of Steel 10^ BMS9 Structural Properties of the Insulated Steel Construction Co.'s "Frameless-Steel" Constructions for Walls, Partitions, Floors, and Roofs 10j5 BMSIO Structural Properties of One of the "Keystone Beam Steel Floor" Constructions Sponsored by the H. H. Robertson Co 10(5 BMSll Structural Properties of the Curren Fabrihome Corporation's "Fabrihome" Constructions

for Walls and Partitions 10(5 BMS12 Structural Properties of "Steelox" Constructions for Walls, Partitions, Floors, and Roofs

Sponsored by Steel Buildings, Inc 15(5 BMS13 Properties of Some Fiber Building Boards of Current Manufacture 10^ BMS14 Indentation and Recovery of Low-Cost Floor Coverings 10^ BMS15 Structural Properties of "Wheeling Long-Span Steel Floor" Construction Sponsored by

the Wheeling Corrugating Co 10(5 BMS16 Structural Properties of a "Tilecrete" Floor Construction Sponsored by Tilecrete

Floors, Inc 10(5 BMS17 Sound Insulation of WaU and Floor Constructions 10^ Supplement to BMS17, Sound Insulation of Wall and Floor Constructions 5(5 BMS18 Structural Properties of "Pre-fab" Constructions for Walls, Partitions, and Floors Sponsored by the Harnischfeger Corporation 10(5 BMS19 Preparation and Revision of Building Codes 15^ BMS20 Structural Properties of "Twachtman" Constructions for WaUs and Floors Sponsored

by Connecticut Pre-Cast Buildings Corporation 10(5 BMS21 Structural Properties of a Concrete-Block Cavity-Wall Construction Sponsored by the National Concrete Masonry Association 10(5 BMS22 Structural Properties of "Dun-Ti-Stone" WaU Construction Sponsored by the W. E. Dunn

Manufacturing Co 10(5 EMS23 Structural Properties of a Brick Cavity-Wall Construction Sponsored by the Brick

Manufacturers Association of New York, Inc 10(5 BMS24 Structural Properties of a Reinforced-Brick Wall Construction and a Brick-Tile CavityWaU Construction Sponsored by the Structural Clay Products Institute 10(5 BMS25 Structural Properties of Conventional Wood-Frame Constructions for WaUs, Partitions,

Floors, and Roofs 15(5 BMS26 Structural Properties of "Nelson Pre-Cast Concrete Foundation" WaU Construction

Sponsored by the Nelson Cement Stone Co., Inc 10(5 BMS27 Structural Properties of "Bender Steel Home" WaU Construction Sponsored by the Bender Body Co i 100 BMS28 Backflow Prevention in Over-Rim Water Supplies 10^ BMS29 Survey of Roofing Materials in the Northeastern States 10^ BMS30 Structural Properties of a Wood-Frame Wall Construction Sponsored by the Douglas

Fir Plywood Association 10(5 BMS31 Structural Properties of "Insulite" WaU and "Insulite" Partition Constructions Sponsored by The InsuUte Co 15^

[List continued on cover page in]
UNITED STATES DEPARTMENT OF COMMERCE • Jesse H. Jones, Secretary

NATIONAL BUREAU OF STANDARDS • Lyman J. Briggs, Director

BUILDING MATERIALS

and STRUCTURES

REPORT BMS97

Experimental Dry-Wall Construction With Fiber

Insulating Board

by

CHARLES G. WEBER and ROBERT C. REICHEL

ISSUED MAY 7, 1943

The National Bureau of Standards is a fact-finding organization;

it does not "approve" any particular material or method ot construction. The technical findings in this series of reports are to be construed accordingly.

UNITED STATES GOVERNMENT PRINTING OFFICE . WASHINGTON • I943

FOR SALE BY THE SUPERINTENDENT OF DOCUMENTS, U. S. GOVERNMENT PRINTING OFFICE

WASHINGTON, D. C. • PRICE lO CENTS
Foreword

Previous reports describe the properties of fiber insulating boards

with particular reference to their suitability for use in the construction

of low-cost houses. This report contains information on methods of

application that permit a free choice of design and finish of the boards

in diy-wall construction. Difficulties which heretofore limited the

choice of wall design were eliminated in experimental walls by new

methods of fastening the boards.

Lyman J. Briggs, Director.

(II)
Experimental Dry-Wall Construction

with Fiber Insulating Board

by CHARLES G. WEBER and ROBERT C. REICHEL^

CONTENTS

Page Page

Foreword u III. Performance of wall constructions 2

I. Introduction 1 IV. Treatments of joints 5

II. Construction and testing of experimental V. Decorative treatments 6 walls 1 VI. Summary and conclusions 8

ABSTRACT

The use of fiber insulating boards for the interior sur- facing of walls and ceilings of houses has heretofore been limited with respect to choice of design or finish of the walls. The relatively high expansivity of the material with variations in the humidity of the surrounding

air has made paneling necessary because molding or batten strips were required to conceal unsightly joints. It was found possible to overcome the difficulty and

make paneling unnecessary. This was done by elimi- nating the usual nailing and substituting the use of

invisible, flexible fasteners that permit the entire sur- face of a wall or ceiling to expand and contract as a imit. Several methods of fastening the boards to obtain

this result were developed. Use of them permitted the

successful application of all of the decorative treatments normally applied to a plaster wall, without restriction as to surface design.

I. INTRODUCTION

Dry-wall construction may be defined as a type of construction that eliminates the introduction of water during the application of the

surfacing of the walls and ceilings of homes.

Its main objective is to speed and simplify construction and eliminate the drying-out period

required for the conventional plaster surfaces.

Fiber building boards have been extensively

used for this purpose for years, but certain

inherent properties of the material have greatly

restricted its utility. The expansion and contraction of fiberboards with variations in the

humidity of the surrounding air normally

caused decorative finishes to break at the joints.

The necessity of covering unsightly joints with

batten or molding strips limited the choice of wall design to paneled effects.

1 Research Associate at the National Bureau of Standards, represent- ing the Insulation Board Institute.

This investigation was made with the cooperation of the Insulation Board Institute to find

ways of overcoming the difficulties with joints

between the individual boards by new or improved methods of application of the material.

To obtain data on the problem various methods

of apph cation were used in the construction of

experimental walls, and the performance of

the wall s was observed during cycles of controlled

variations of relative humidity.

II. CONSTRUCTION AND TESTING

OF EXPERIMENTAL WALLS

The experimental walls were constructed and

tested in a chamber exected for the purpose on

the grounds of the National Bureau of Standards. This chamber was 16 by 20 feet with an

8-foot ceiling. The construction, exclusive of

the interior finish, consisted of 10-inch lap siding over ^^32-inch fiber sheathing. The studs were

spaced 16 inches on centers. The inside surfaces of the four outside walls were finished as test walls, and in addition

experimental wall sections were erected in the

chamber on wood studs. Each of these sec- tions was 8 feet wide and 7 feet 8 inches high,

as shown in figure 1 . The framework was number 1 common Douglas fir, and the studs were

spaced 16 inches on centers, with top and bottom plates nailed securely. Each frame was

stift'ened with two 1- by 4-inch diagonal braces.

The chamber was heated by an oil-burning

space heater. High humidity conditions were

obtained by circulating air over shallow pans

of warm water, and low humidities by substituting shallow pans of calcium chloride. A

516849°—43 [1]
Figure 1.

Framing used for experimental wall sections.

continuous record of the relative humidity was

kept by a recording hygrometer, which was

checl^ed daily with wet- and dry-bulb readings.

Tests were made on seventeen types of construction which differed mainly with respect to methods of fastening the insulating boards to the studs. A variety of decorative ti*eatments was used, and different types of joints were

included. The following conditions of relative

humidity were maintained, in the order given,

untU equilibrium was reached as indicated by

no further movement of the boards: 55, 85, 25,

85, 18, and 75 percent.

III. PERFOKMANCE OF WALL

CONSTRUCTIONS

The simplest method of attaching insulation

board to framing is by nails, and this is the

method most widely used in the past. Various

methods of nailing the boards securely to the

studs were used (in experimental walls) . However, in every instance, nails proved unsatisfactory for one or more reasons. The move- ment of the boards caused the surfaces to compress or tear at the nails and produced unsightly cracks at the joints, regardless of the

type of treatment. Papered walls cracked at the joints, and the nail heads showed prominently through the paper. Hence it appears

that nailing directly to studs restricts the sur- face treatment to some type of paneling in which

the nails are confined mostly to the edges and

the joints covered by the molding strips which

form the panels. Figures 2 and 3 show distortion at nail heads and cracks at the joints on

the painted surface of boards.

Pasting to the studs is another method of fastening insulating boards. This method

proved about as unsatisfactory as nailing,

except that no unsightly nail heads marred the

surface. Cracking at joints and buckling between studs occured to about the same extent

as on nailed walls, and in addition, there was a tendency for the boards to loosen from the studs

along the joints, due to movement of the boards.

This type of wall requires the covering of joints,

thereby making panel effects as essential as when the boards are nailed.

The principle of rigidly fastening boards to the studs with either nails or paste proved unsatisfactory on the experimental walls as it has

in practice because it permits the individual

boards to expand and contract as units. To

overcome this fault several methods of fastening were tried which involved the use of flexible fasteners designed to allow movement in any

direction of the entire wall surface as a unit.

This effect was obtained by two general methods

of fastening.

On wall section J, }2-inch insulation boards

4 feet by 7% feet were attached by means of concealed mechanical fasteners of a type that

[2]
Figure 2.

Distortion at nail heads on fiberboards nailed

to studs.

allowed the surface covering to move laterally,

independent of the studs, as the boards ex- panded or contracted. The fasteners were

designed to hold the boards firmly against the

studs and at the same time allow sufficient

movement laterally for normal expansivity.

The fasteners, which were designed at the

Bureau, are shown in figure 4. The fasteners,

A, were nailed to the sides of the studs as

illustrated by E, and a spreader of design B or C was placed on each as in D. The boards were

brought into contact with the fasteners in the

correct final location. Then, using a wood

block to prevent marring of the surface, and

starting with one of the fasteners on an intermediate stud, the board was driven on the

bottom row of fasteners. A temporary wood

strip was nailed over the bottom of the board to prevent loosening or shifting, and the board was driven on the remaining fasteners, working

upward one row at a time and taking the intermediate studs first. The manner in which the

Figure 3. —Unsightly cr-acks at joints between fiber- boards nailed to studs.

fastener points are spread on entering the

insulation boards is illustrated by E.

Wall section K was surfaced with K-inch

boards attached rigidly to special furring strips

that were attached to the studs by a method

that permitted lateral movement of the furring

strips on the studs. The strips were made of pressed fiberboard Ys inch in thickness, and the

insulation boards were fastened to them with

adhesive. The design of the furring strips and

method of using them are shown in figure 5. The strips were parallel to the studs and the

front surfaces covered with adhesive. The

insulation boards were then applied against the

adhesive, using temporary nailing to hold them

in place until the adhesive had set. Wall section AI was surfaced with Jo-inch insulation boards fastened securely to ordinary

1- by 2-inch wood furring strips with nails. In this instance the furring strips were fastened

to the studs with a heavy, flexible clip - of

2 Olscn Floating Wall Clips, The Patent and Licensing Corp., New

York, N. Y.

[3]
^INSULATING BOARD

A 1

FASTENERS a SPREADING DEVICES

Figure 4.Concealed, flexible fastener devised at the Bureau.

commercial manufacture. This type of construction permitted the entire surface of the

wall, consisting of the insulation boards at- tached rigidly to the furring strips, to expand

and contract as a unit by movement of the

furring strips on the studs. This was another

application of the principle used in wall section

K. The clips securing the furring strips to the

studs were countersunk into the strips so as not

to interfere with the fitting of the insulation

boards against the strips. The construction of

this wall section is shown in figure 6. The gap

between the boards near the bottom is necessary

to permit nailing the baseboard in the conventional manner without affecting the resilience of the wall surface. Wall section A^" was the same as section M

in all respects, except that /4-inch insulation

board was used instead of K-inch board.

Wall section 0 was surfaced with }^-inch in- sulation board mounted with wood furring

strips as on sections M and A'^, but cut into

sections to form two expansion joints between

the floor and ceiling. Grounds or nailing strips

equal in thickness to the combined thickness of the furring strips and the insulation board were

placed in these joints and nailed firmly to the

studs but not fastened to the furring or fiber- boards. The board was cut in widths to con- form to the lengths of the strips. Hence, the

finished wall had two horizontal joints, one

approximately 1 foot below the ceiling and the

other 4 feet below the first. These joints were

covered with a picture molding and a chair rail respectively, which were nailed to the grounds

so as to extend over the edges of the insulation

boards about }2 inch. The insulation boards were fastened to the furring strips rigidly with

concealed fasteners of commercial design, and

the furring strips were secured to the studs with

the flexible clips as in sectioxis M and A^. The

consti'uction of wall section 0 is illustrated in

figure 7. These wall sections all gave excellent results. INSULATING BOARD

1/8" PRESSED

FIBERBOARD

FURRING

STRIPS

Figure 5.-

ROOFING

NAIL

-Use of special }i-inch furring strips to form a floating wall surface.

[4]
PLm SECJIOU

FlNlSHEd CeiWN^ UIHB WOOD MOluV

?UJESICJ10K

Otatu Jype a (Jooo S-jud Clip

'"^-^Yt" lUSULAflOU BoAR.0 UaILID

fOli.R.m(j SCRIPS

-'1;—

51LL SECjm

FIWJ5HED Fl.OOR.W;.'£

Figure 6.

Method of forming floating wall surface in wall section M.

Treated joints held without any tendency to crack, and when papered or painted, the per- formance was entirely satisfactory. It is essential in this type of construction to keep the

boaids unrestricted at the edges, which should

all be concealed with trim, which may fit snugly

against the board but must not be fastened to

it. These types of construction permit unrestricted decorative treatment, as does the conventional plaster-surfaced wall, with the exception of section 0. This type requires the use

of chair rail and picture molding. It is, however, less difficult to construct than the others,

and has the advantage of concealed expansion

joints, which tend to distribute more evenly

the movements resulting from contraction and

expansion.

IV. TKEATMENTS OF JOINTS

No special types of joints are required for

resilient wall construction except where the

insulation boards are fastened directly to the

studs with flexible fasteners, as in wall section

J. In this type of construction, the joints must

have sufficient strength to hold the boards to- gether, so that the entire wall sm-face wiU

expand as a unit. In section J, a glued shiplap

joint, sanded smooth after drying, performed

satisfactorily. Other joints were made with

Swedish putty, using bucla-am tape in one type

[5]
Eu Type A uooo Sfuo Ctip

Yl IiaSULAflOU BOAR.0 fASTtWE-0

To FURft.llJQ WIfH COUCtALtD fAS^EUtR.

Figure 7.

Method of forming floating wall surface in wall section 0.

and a metal screen strip in another. These

joints are ilhistrated in figure 8. In construction where the insulation boards

are fastened rigidly to the furring strips, as in

wall sections K,AI,N, and 0, there is no strain on the joints, and they can be designed for appearance only. On these experimental walls,

joints were prepared for papering or painting by

simply sanding them smooth with a belt sander,

and excellent results were obtained. The joints

in walls that are to be painted can be filled and

sanded smooth. Swedish putty worked well

as a filler and other crack fillers will doubtless

prove satisfactory. Ordinary putty does not

work well, because the oil from the putty is absorbed too rapidly by the board. Plastic

wood dries very hard and sometimes tends to chip out on sanding.

V. DECORATIVE TREATMENTS

Due to the porous nature of the material, a

sizing or priming coat was found necessary on

all boards except the factory-decorated ones. There was a tendency, with some of the boards,

[6]
V' \ FURRING

STUD \ STRIP

FURRING

STRIP

Figure 8.

Method of forming concealed joints in fiber insulation boards.

for the surface fibers to form a fuzz on the sur- face when brushed. This was ehminated

readily by sanding the surface hghtly after the

priming coat was apphed.

The difference in texture between the surfaces

of the boards and the fillei's used in joints was a troublesome problem with painted walls. This was particulai'ly true when relatively roughsurfaced boards were used, and for some of these

boards the duplication of the board texture in

the filler was impractical. The smooth-surfaced boards gave no difficulty. Plastic paints

of casein base, and of oil base, worked satis- factorily. The latter type required a sizing

coat, but the casein type worked well on unsized

surfaces. Wallpaper and cloth-base wall coverings can

be applied with ordinary paperhanger's paste on the sized boards. No difficulty was en- countered in applying wallpaper, but no satis- factory method of removing it for a subsequent

coat has been found.

[7]
VI. SUMMARY AND CONCLUSIONS

The use of fiber insulating boards for the

surfacing of walls and ceilings in dry-wall

construction restricts the choice of surface

design and decorative fuiishes, when the boards

are nailed to the stud in the conventional manner. The restrictions can be practically eliminated

by special methods of application. These

methods embody the principle of "floating" the

wall surface, thereby permitting the entke face

of the wall to expand and contract as a unit,

independent of the frame, which should have

adequate diagonal bracing. It can be accomplished by fastening the boards from the back,

either rigidly to furring strips that are in turn

secured to the studs with floating clips, or

directly to the studs with floating clips.

The wall surface obtained with fiber insulating

boards correctly applied is practically unrestricted with respect to choice of design or

finish. It can be papered or painted or given

any other decorative treatment applicable to plaster walls if appropriate attention is given to the filling and leveling of joints.

Washington, January 25, 1943.

[8]


BUILDING MATERIALS AND STRUCTURES REPORTS

[Continued from cover page ii] BMS32 Structural Properties of Two Brick-Concrete-Block Wall Constructions and a Concrete- Block Wall Construction Sponsored by the National Concrete Masonry Association. 100 BMS33 Plastic Calking Materials 10^ BMS34 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 1 10^ BMS35 Stability of Sheathing Papers as Determined by Accelerated Aging 100 BMS36 Structural Properties of Wood-Frame Wall, Partition, Floor, and Roof Constructions with

"Red Stripe" Lath Sponsored by The Weston Paper and Manufacturing Co lOf! BMS37 Structural Properties of "Palisade Homes" Constructions for WaUs, Partitions, and

Floors, Sponsored by Palisade Homes 100 BMS38 Structural Properties of Two "Dunstone" Wall Constructions Sponsored by the W. E. Dunn Manufacturing Co 100 BMS39 Structural Properties of a Wall Construction of "Pfeifer Units" Sponsored by the Wisconsin Units Co 100 BMS40 Structural Properties of a Wall Construction of "Knap Concrete Wall Units" Sponsored

by Knap America, Inc 100 BMS41 Effect of Heating and Cooling on the Permeability of Masonry Walls 100 BMS42 Structural Properties of Wood-Frame Wall and Partition Constructions with "Celotex"

Insulating Boards Sponsored by The Celotex Corporation : 150 BMS43 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 2 100 BMS4'4 Surface Treatment of Steel Prior to Painting 100 BMS45 Air Infiltration Through Windows 100 BMS46 Structural Properties of "Scot-Bilt" Prefabricated Sheet-Steel Constructions for Walls,

Floors, and Roofs Sponsored by The Globe-Wernicke Co 100 BMS47 Structural Properties of Prefabricated Wood-Frame Constructions for WaUs, Partitions, and Floors Sponsored by American Houses, Inc 100 BMS48 Structural Properties of "Precision-Built" Frame Wall and Partition Constructions

Sponsored by the Homasote Co 100 BMS49 Metallic Roofing for Low-Cost House Construction 100 BMS50 Stability of Fiber Building Boards as Determined by Accelerated Aging 100 BMS51 Structural Properties of "Tilecrete Type A" Floor Construction Sponsored by the

Tilecrete Co 100 BMS52 Effect of Ceiling Insulation Upon Summer Comfort 100 BMS53 Structural Properties of a Masonry Wall Construction of "Munlock Dry WaU Brick"

Sponsored by the Munlock Engineering Co 100 BMS54 Effect of Soot on the Rating of an Oil-Fired Heating Boiler 100 BMS55 Effects of Wetting and Drying on the Permeability of Masonry Walls 100 BMS56 A Survey of Humidities in Residences 100 BMS57 Roofing in the United States—Results of a Questionnaire 100 BMS58 Strength of Soft-Soldered Joints in Copper Tubing 100 BMS59 Properties of Adhesives for Floor Coverings 100 BMS60 Strength, Absorption, and Resistance to Laboratory Freezing and Thawing of Building

Bricks Produced in the United States 150 BMS61 Structural Properties of Two Nonreinforced Monolithic Concrete Wall Constructions 100 BMS62 Structural Properties of a Precast Joist Concrete Floor Construction Sponsored by the Portland Cement Association 100 BMS63 Moisture Condensation in Building Walls 100 BMS64 Solar Heating of Various Surfaces 100 BMS65 Methods of Estimating Loads in Plumbing Systems 100 BMS66 Plumbing Manual 200

BMS67 Structural Properties of "Mu-Steel" Prefabricated Sheet-Steel Constructions for Walls,

Partitions, Floors, and Roofs Sponsored by Herman A. Mugler 150 BMS68 Performance Test for Floor Coverings for Use in Low-Cost Housing: Part 3 150 BMS69 Stability of Fiber Sheathing Boards as Determined by Accelerated Aging 100 BMS70 Asphalt-Prepared RoU Roofings and Shingles 150 BMS71 Fire Tests of Wood- and Metal-Framed Partitions 100 BMS72 Structural Properties of "Precision-Built, Jr." Prefabricated Wood-Frame Wall Construction Sponsored by the Homasote Co 100 BMS73 Indentation Characteristics of Floor Coverings 100 BMS74 Structural and Heat-Transfer Properties of "U. S. S. Panelbilt" Prefabricated SheetSteel Constructions for Walls, Partitions, and Roofs Sponsored by the Tennessee

Coal, Iron & Railroad Co 150 BMS75 Survey of Roofing Materials in the North Central States 150 BMS76 Effect of Outdoor Exposure on the Water Permeability of Masonry Walls 150 BMS77 Properties and Performance of Fiber Tile Boards 100 BMS78 Structural, Heat-Transfer, and Water-Permeability Properties of Five Earth-Wall Constructions 200 BMS79 Water-Distributing Systems for Buildings 150 BMS80 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 4 150 BMS81 Field Inspectors' Check List for Building Construction (cloth cover, 6 x 7K inches) 200 BMS82 Water Permeability of Walls Built of Masonry Units 20J

[List continued on cover page iv]
BUILDING MATERIALS AND STRUCTURES REPORTS

[Continued from cover page in]

BMS83 Strength of Sleeve Joints in Copper Tubing Made With Various Lead-Base Solders 10#

BMS84 Survey of Roofing Materials in the South Central States 15^ BMS85 Dimensional Changes of Floor Coverings with Changes in Relative Humidity and

Temperature 10#

BMS86 Structural, Heat-Transfer, and Water-PermeabUity Properties of "Speedbrik" Wall

Construction Sponsored by the General Shale Products Corporation 15ji BMS87 A Method for Developing Specifications for Building Construction lOjS BMS88 Recommended Building Code Requirements for New Dwelling Construction with

Special Reference to War Housing 20^ BMS89 Structural Properties of "Precision-Built, Jr." (Second Construction) Prefabricated

Wood-Frame Wall Construction, Sponsored by the Homasote Co 15^ BMS90 Structural Properties of "PHC" Prefabricated Wood-Frame Constructions for Walls,

Floors, and Roofs Sponsored by the PHC Housing Corporation 15f5 BMS91 A Glossary of Housing Terms 15^ BMS92 Fire-Resistance Classifications of Building Constructions 15^ BMS93 Accumulation of Moisture in Walls of Frame Construction During Winter Exposure 25^

BMS94 Water PermeabUitv and Weathering Resistance of Stucco-Faced, Gunite-Faced and 10^ "Knap-Concrete-Unit" Walls 10^ BMS95 Tests of Cement-Water Paints and Other Waterproofings for Unit-Masonry Walls 15^ BMS96 Properties of a Porous Concrete of Cement and Uniform-Sized Gravel 10^ BMS97 Experimental Dry-Wall Construction with Fiber Insulating Board-. 10^