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 THE RIGIDITY AND STRENGTH 
 Of ERAME WAEES 
 
 Revised February 1947 
 
 No. R89 
 
 tot Of 
 
 FOOT linsimy 
 
 <MM Of fLOfiiOA 
 
 UNITED STATES DEPARTMENT OF AGRICULTURE 
 
 FOREST SERVICE 
 
 FOREST PRODUCTS LABORATORY 
 
 Madison, Wisconsin 
 
 In Cooperation with the University of Wisconsin 
 
THE RIGIDITY AND STRENGTH OF FRAME WA.LLS 
 
 By 
 
 GEO. W. TRAYER, Senior Engineer 
 
 Introduction 
 
 Small frame structures have never been subjected to a thoroughgoing engineer- 
 ing analysis. The structural details of such buildings are for the most part 
 governed by precedent, tradition, and carpenters' judgment without much regard 
 for the particular requirements of a particular structure. It is true that 
 ir. principle, the superiority of certain details over others is known and 
 appreciated by good workmen and good building contractors. Convincing exper- 
 imental evidence, however, is lacking not only where the superiority of certain 
 details is known, but also where there is an uncertainty as to what is right 
 construction. Furthermore, the ultimate results of improper construction are 
 not fully appreciated. Realizing the need for such information, the Forest 
 Products Laboratory, cooperating with the National Lumber Manufacturers' 
 Association, undertook a study of construction principles and practices. A 
 series of tests was made to determine the relative resistance of different 
 types of frame wall construction to longitudinal thrust. 
 
 The purpose of the study reported here was to obtain a better understanding 
 and appreciation of the principles involved in wall construction, which tend 
 to make frame dwellings and other small frame buildings substantial structures 
 free from excessive maintenance charges. Details of construction may vary 
 in different localities, but the basic principles with which the builder 
 should be concerned are in all cases the same, A knowledge of the principles 
 discussed in this report should not only assist architects and engineers 
 but should also help prospective home owners to appreciate what they should 
 insist upon in the way of construction. 
 
 A house has comparatively few main parts. Of these parts, the ones that 
 contribute most to the rigidity of the structure as a whole are the walls. 
 Observations in numerous storm-swept areas have led to the conclusion that 
 typical lumber-sheathed walls are adequately strong for almost any condition 
 likely to arise as regards pressures perpendicular to them. Their resistance 
 to end thrust, however, is more critical both from the standpoint of wind 
 resistance and from the standpoint of keeping the building properly alined 
 over a period of years, thereby eliminating, or reducing to a large extent, 
 endless annoyances and needless maintenance costs. In order to determine 
 the amount of end thrust various types of wall construction are capable of 
 withstanding, panels, approximating in size the side of a room, were tested 
 with loads applied to the upper plate in the direction of their length. 
 
 Report No, R896 
 
Test Material and Procedure 
 
 Test Panels 
 
 Panels 9 by 14 feet were selected as representative of story heights and of 
 sufficient length to approximate practical conditions. The equipment used 
 for making vibration tests necessitated the reduction in the size of a few 
 panels to 7 foot 4 inches high by 12 feet 1-5/8 inches long. 
 
 All panel frames consisted of 2 by 4-inch upper and lower plates and 2 by 
 4-inch studs spaced 16 inches, except at the ends of the 14-foot panels 
 whore the spacing was 12 inches from the outside edge of the end post to 
 the center of the firnt stud. The end posts consisted of two 2- by 4-inch 
 pieces spaced about 3/8 inch to which a third 2 by 4 was nailed with its 
 4-inch side perpendicular to the 4-inoh sides of the other two, With the 
 outsido odges flush, this left a nailing ledge for lath. The frame was put 
 together with 16d common nails, the studs being fastened to the plates by 
 two nails through the plates into the ends of the studs « Except for the 
 end- and side-matched material, which was nominal 6-inch stock, all sheathing 
 boards were square-ed r ;ed and 8 inches wide. Sheathing and framing were of 
 No, 1 common well-seasoned Southern yellow pine, except for the panels tested 
 in a green condition, Material for the panels tested green was sawn at the 
 Laboratory direct from Southern yellow pine logs, One joint was used in 
 each course of sheathing boards, except for the short courses in finishing 
 out at the cornors with diagonal sheathing, where no joints were used. 
 
 The wood lath were 4 foot long, spaced l/4 inch and nailed with 3d nails. 
 Grounds were 3/4 inch. The plaster, which was of good quality, was mixed 
 in the proportions of 100 pounds of plaster to about 175 pounds of sand. 
 Two coats of plaster were applied and tests were made 1 week after the 
 application of the finish coat. Mixing and plastering were done by men 
 furnished by a reputable firm of local plaster contractors. 
 
 Test Procedure 
 
 The lower, or sole plate, of each panel was bolted and in some cases bolted 
 and nailed to a heavy timber which in turn was fastened to the base of the 
 Laboratory's million-pound-capacity testing machine (fig. l). The panel 
 was further anchored against thrust by a stirrup from the heavy timber 
 against which the lower plate could bear. The upper plate was also securely 
 bolted or bolted and nailed t© a heavy timber, which furnished the resistance 
 to lateral buckling always supplied to the walls by the upper floor system. 
 At the ends of each panel long horizontal pin-connected tie bars simulated 
 the alining action of cross walls, Load was applied to the upper plate in 
 a direction parallel to the length of the panel by steel cables that passed 
 around shoavos and thence up to the movable head of the testing machine. 
 The bearings for a shaft carrying these shoavos were attached to the largo 
 cast-iron standards that supported the fixed head of tho tosting machine.. 
 The application of horizontal load to the upper plate would, of course, 
 
 Report No, R896 -2- 
 
induce an overturning tendency, which normally would be prevented by the 
 upper story and roof loads. The reaction to prevent overturning in test 
 was supplied by two vertical hold-down rods, one on each side of the panel, 
 attached at one end to the base of the testing machine and at the other to 
 a bearing plate on top of the heavy timber to which the upper plate of the 
 panels were attached, 'Botween the bearing plate and the timber were placed 
 roller bearings to provide for free longitudinal movement of the panel. The 
 hold-down rods were placed about 2 feet from the ond of the 14-foot panels 
 and about 1 foot from the end of the 12-foot 1-5/8-inch panels. Load was 
 applied by raising the movable head of the testing machine at the rate of 
 0,211 inch per minute. Movement of the upper plate with respect to the lower 
 plate was observed for various increments of load. Figure 1 is a diagrammatic 
 sketch of the panel setup. The apparatus for measuring deflection consisted 
 of a vertical board securely fastened to the lower plate and extending up 
 past the upper plate. At its upper end it had a vertical slot in which was 
 stretched a fine wire. A steel scale was fastened to the upper plate or to 
 the large timber to which the upper plate was attached and deflections were 
 read by observing with a telescope the movement of the scale with rospect 
 to the wire. 
 
 Vibration tests were made by mounting a panel on a machine table having a 
 short horizontal throw. Panels were tested up to one million' cycles at 
 the rate of 110 per minute with a movement of the table which, with 750 
 pounds of dead weight distributed o.long the upper plate, produced deflections 
 in the panel of 50 to 75 percent of its deflection at elastic limit. 
 
 Discussion 
 
 The results of nearly 50 tests of large wall panels are given in tables 1 
 and 2, In table 1 are given the results for the panels without window or 
 door openings and in table 2 the results for the panels with openings, A 
 description of each panel appears in the tables together with its stiffness 
 and strength as compared with the stiffness and strength of a horizontally 
 sheathed panel without openings. In the remarks column are given the loads 
 at which the first plaster crack appeared in the plastered panels, A basic 
 load-deflection curve for horizontal sheathing 8 inches wide with two 8d 
 nails in each board at each stud crossing was obtained by averaging the 
 curves for the first four panels given in table 1 and is shown in figure 2, 
 While the four panels are of two sizes, the load for a given movement of the 
 upper plate with respect to the lower plate is about the same for eaoh size. 
 This follows from the fact that the load for a given angular distortion is 
 independent of the height and directly proportional to the length. How 
 the stiffness factor in the tables was obtained is illustrated in figure 2, 
 It is the factor by which the ordinatos of the first part of the curve for 
 any panel must be divided to reduce it to the corresponding ordinates of the 
 base curve. For example, the curve for panel No, 5 falls along the base 
 curve fairly well out to about a 1-inch deflection when the loads of the 
 panel No, 5 curve are divided by 4,3, It is to be noted that while the 
 stiffness factor given in table 1 is 4,3, the maximum load factor, which was 
 obtained by direct comparison of maximum loads, is over 8, 
 
 Report No, R896 -3* 
 
Consequently, this factor is on increasing one, Vflien the factor is a changing 
 one, a good avora ;o factor for deflections up to 1 inch, which also corresponds 
 to the factor for a l/2-inch defloction, has been taken as the stiffness factor* 
 Consider in this connection panol No. 3C. The effectiveness of its let-in 
 braces keeps increasing. At a l/lO-inch deflection tho stiffness factor is 
 about 2.0 and at 1-inch dofloction it is about 3,0, A good average figure 
 for all defloctions up to 1 inch is 2,6, which also corresponds to the factor 
 for a l/2-inch deflection. At maximum load a factor of 3,6 is finally reached. 
 On the other hand, panel No* 34 has a decreasing factor, A rood avorage valuo 
 out to a 1-inch defloction ia 4,2, whereas the maximum load factor is 3,5, 
 Thus thero are throe typos of roduced curves, one that falls directly upon the 
 base curve, one that shows a gradual increase over the base curve, and one 
 that shows a gradual drop from tho base curve, A comparison of the stiffness 
 and load factors in tables 1 and 2 will show tho tondency of any particular 
 curve. 
 
 In order to define what is meant by the maximum load in tables 1 and 2, it 
 is necessary to consider the behavior of tho various types of panels. In 
 the case of panel frames coverod with plaster on wood lath, there was a sudden 
 and pronounced drop in l*ad at a movement of the upper plate of from 3/4 of 
 an inch to 1-1/2 inches, depending upon the member, size, and arrangement of 
 the openings. The load at which this drop occurred was taken as tho maximum 
 load. In bhe case of a panel covered with both plaster and sheathing, the 
 plaster was badly cracked under distortions of less than an inch, but no 
 pronounced drop in load occurred until the upper plate had a movement of 
 from 2 to 4 inches, Tho load at '.which this drop occurred was takon as tho 
 maximum load. In the case of panels covered with sheathing only, a load was 
 reached at a distortion of from 2 to 4 inches, which either held fairly 
 constant for increasing defloctions or only fell off slightly. This load 
 was taken as the maximum load, although in the case of horizontal sheathing 
 particularly it is known that a higher maximum would bo obtained when tho 
 distortion was great enough to permit all tho boards to become tight. Tho 
 tests were not continued far enough to reach this second maximum, which has 
 no practical significance because of the enormous distortion that accompanies 
 it. Usually the tests were stopped when a load of 20,000 pounds was reached, 
 which accounts for the fact that for several panels the maximum strength 
 factor is given as over 8, 
 
 horizontal Shoathinp; (panels Without Openi ngs ) 
 
 When sheathing is applied horizontally, the principal resistance to longi- 
 tudinal thrust is due to the reaction couples of each pair of nails at tho 
 stud orossings. Some resistance, of course, is offerod by the friction 
 between the boards and studs and by the couplos sot up as the edgos of the 
 boards como in contact. The slightest shrinkage, however, almost entirely 
 eliminates the friction, and tho couples are unimportant except for relatively 
 large distortions, since relatively large movements of the uppor plato are 
 accompanied by only small changes in height. Broadly speaking, it may bo 
 said that a horizontally sheathed panel, like any other untriangulatcd 
 framework, gets its rigidity from the fixity of the joints. 
 
 Report No, R696 -4- 
 
Panels 9 feet high by 14 feet long, sheathed horizontally with square-edged, 
 nominal 1 by 6-inch boards, and nailed with two 8d common nails at each stud 
 crossing, sustained an average maximum load of 2,588 pounds applied to the 
 upper plate in a direction parallel to the length of the panel. The movement 
 of the upper plate with respect to the lower plate at maximum load was ap- 
 proximately 3 inches. 
 
 Diagonal Sheathing (Panels Without Openings ) 
 
 With the boards applied diagonally there is triangulation in the panel and 
 the nails become far more effective in offering resistance to distortion. 
 The boards may bo either in compression or in tension, according to the 
 direction of the load applied to the upper plate* ^hon the boards were in 
 tension the diagonal sheathing averaged about four times as rigid as the 
 horizontal sheathing for tho panels unpierced by openings and averaged over 
 eight times as strong. When the boards were in compression, a single test 
 showed about seven times the rigidity of horizontal sheathing and nearly eight 
 times the maximum load. 
 
 There are two things that could account for the difference in stiffness for 
 the two types t With the boards in tension, the upper and lower plates 'wero 
 pulled away in places from the heavy timber to which each was fastened, and 
 the giving of the plate was reflected in the horizontal movement of tho upper 
 plate. When the boards wero in compression, this tendency was eliminated, 
 Furthermore, the nailing at tho joint in each course was very close to tho 
 ends of the boards. With the boards in tension, these nails had slightly 
 less effectiveness than when the boards were in compression. In actual 
 practice, it is quite likely that the difference in stiffness, if any, for 
 the two types would be small. 
 
 When openings were framed into the panels, tho relations were somewhat 
 altered, since an additional factor, which has to do with the stiffness of 
 the framing around the opening, was introduced. This will be discussod later. 
 
 At the recorded maximum load, diagonal sheathing boards in compression buckled 
 as columns and carried the studs with them. 
 
 Figure 3, A, is a photograph of a diagonally sheathod test panel. The hold- 
 back stirrup is shown at the lower right-hand corner. Load was applied to 
 this panel, therefore, at the upper left-hand corner, and the boards wero in 
 tension. 
 
 Bracing (Panels Without Openings ) 
 
 In order to make horizontal sheathing more rigid, various forms of bracing 
 are used. Three types of such bracing were tried out in tho series of tosts. 
 Herringbone, or bridge bracing (fig, 3, B), cut-in between the studs about 
 midway between tho lower and upper plates, was found to increaso the stiffness 
 but little (about 30 percent), Tho maximum load was practically uninfluenced 
 
 Report No, R896 -5- 
 
by such bracing, Tho braces wore 2 by 4 inches in cross section and were 
 nailed at an angle of about 22-l/2° to tho horizontal. 
 
 Braces, 2 by 4 inches, cut-in be two en the studs on a lino (fir. 3, C) in- 
 creased the stiffness of horizontal shoathing about 60 percent and increased 
 tho strength 40 percont, Tho percentage increase is dependent upon the angle 
 that the bracing line makes with the plate. Had those braces been closer to 
 45° with tho plates, the stiffness would have been somewhat greater. As load 
 is applied at tho upper left-hand corner of the panel shown in figure 3, C, 
 the left brace is in compression and its eff ectivonoss is dependent upon tho 
 snugness of fit and the effectiveness of the nailing. The right brace is in 
 tension and the pieces therefore tend to pull away easily from the studs. It 
 is of little value in comparison with the brace in compression. 
 
 Braces lot into tho edges of the studs at an angle with the plates aro very 
 effective. Figure 3, D and E, show nominal 1 by 4 inch strips lot into the 
 studs at different angles to the plates. One brace in figure 3, D, is in 
 compression and the other in tension when a longitudinal thrust is applied 
 to tho panel. Both braces act immediately and effectively, whereas with 
 tho cut-in. bracos thore is considerable distortion before they get a good 
 bearing, .'ith braces as shown in figure 3, D, a horizontally sheathed panel 
 was two and one-half times as rigid as an unbraced panel, and with the braces 
 shown in figure 3, E, the stiffness factor was increased to about 4. Tho 
 maximum load for tho panels shown in figure 3, D and E, was about throe and 
 one-half times that for the unbraced panel. 
 
 Ilumber and 3ize of I^ails (Panels Without Openings ) 
 
 V/hon the number of nails in a horizontally sheathod panel is increased from 
 two to three at each stud crossing, thoro is no increase in the reaction 
 couples and consequently no incroaso in rigidity or strength. With four 
 nails at each crossin;, there is an incroaso in tho reaction couples of 
 approximately one-third, Thero is a slight increase in the friction between 
 shoathing boards and studs that helps to increase tho stiffness to approxi- 
 mately 40 poroent more than that for panols with either two or throe nails 
 at each stud crossi: . 
 
 With diagonal sheathing, increasing tho number of nails to three and then 
 to four at each stud crossing produced largo increases in stiffness. It 
 is questionable, however, whothor the increased stiffness is needed. 
 
 The tests indicated that bending of the nails is the predominating factor 
 in their lateral resistance to the loads applied to the panels, '/Tien 
 cither lOd or 12d nails wero used, the stiffness was about 50 percent 
 greater than whon 8d nails were used, Tho incroaso in maximum load was 
 about 40 percent. By increasing the size of nails from Cd to lOd tho 
 stiffness of a diagonally sheathod panel was incroased about 70 percont. 
 
 Renort No. R896 -6- 
 
End" and 3ide-IJatched Shoa thing (Panels Without Openings ) 
 
 It was found that the rigidity of a panol horizontally sheathed with 6-inch 
 end- and side-matched stock was the samo as that of a panel sheathed with 
 8-inch square-edge stock. This follows from the fact that although the arm 
 of tho reaction couples formed by each pair of nails is reduced, the numbor 
 of boards and henco the number of couples is increased in about the same 
 proportion. Maximum load was also found to bo the same in both cases. 
 
 Wood Lath and Plaster (panels Without Openings ) 
 
 It was found that lath and plaster producod a more rigid panel than did any 
 type of sheathing or sheathing and bracing. Furthermore, when plaster on 
 wood lath was used in conjunction with either horizontal or diagonal sheathing, 
 thore was very little increase in rigidity, but a considerable increase in 
 maxiimuu "Load- Iho load at which the first plaster crack appeared was about 
 the s^me for all ^.oos< "When the first plaster crack appeared, the upper 
 plate ha 1 move! about t?aree-oigbths of an inch with respect to the lower 
 plate,. The cracks opened iiagor.aj." 1 y across the panel as shown in figure 4, A, 
 Load was applied at the upper left-hand corner of this panel and accordingly 
 the stress or. planes parallel "co the direction of tho cracks would be a 
 tensile stress The cracks arc nuirbered in the order of their sequence. 
 
 The plaster sheet itself is extremely rigid as regards longitudinal thrust.. 
 Loads 5 however,,, come upon the f r mo and., in order for the plaster sheet to 
 be effective, must be carried orer from the frame to the plaster With wood 
 lath this is accomplished largely by the plaster keys bearing against the 
 studs , To a minor extent the loads are also carried to the lath by the 
 lath nails and thence to the plaster by friction. 
 
 Table 1 also gives tho results for a panel (No, 25) sheathed horizontally 
 with green lumber, plastered and allowed to stand 1 month. It had about 
 30 percent less rigidity than panels No, 13 and 24, which wero horizontally 
 sheathed with well-seasoned lumber. 
 
 Vibratio ns (Panels Without Openings) 
 
 Horizontally sheathed panel No 20 was vibrated 50,000 cycles with a forcod 
 throw that prqdvtsod a deflection of 50 to 75 percent of tho deflection at 
 an apparent elastic limit* Panel No, 21, similarly constructed but of green 
 lumber iC was vibrated 1 S 000^CC0 cycles after 1 month's seasoning,, Panel 
 No,. 20 showed no loss ia rigidity or strength as compared with matched 
 panel No a 19 s and the loss for panel No,, 21 is only that which would bo 
 expected after the month- s seasoning of green lumber. In fact, the loss 
 was less than that exhibitod by other tests, which are discussed later. 
 
 Report No, R896 -7- 
 
Groon Lumber (Panels V/ithout Opening g ) 
 
 Two panels horizontally shoathod and two diagonally shoathed wore made of 
 groon lumber. They wore tran allowed to season indoors for 1 month. When 
 tested thoy had about half the stiffnoss of panels made of seasoned lumber 
 and tested immediately. 
 
 Very often the sheathing on a house may be subjected to tho weather for a 
 long poriod, during which time there is considerable working of the nails 
 caused by tho altornate wetting and drying of the lumber. To simulate 
 such a condition, a horizontally sheathod panel (No. 30 in table l) was 
 
 io of seasoned lumtor and was placed outside for 30 days during a period 
 of alternate sunshine and rain. At the end of that period, it was tested 
 and showed a loss in stiffness of ab^ut 30 percent and a loss in strength 
 of about 20 percent. 
 
 Panels ith Openings 
 
 A double 28-inch window in a diagonally sheathod panel (llo. 8, table 2), 
 reduced its stiffness from a factor of about 4 to approximately 3 and the 
 strength factor from over 8 to 5. Let-in braces, arranged around a window 
 as shown in figure 3, F, gave a stiffness factor of 3 when a load was applied 
 at tho upper right-hand corner. 
 
 With a double 28-inch window and a 3 by 7-foot door framed into the panol, 
 horizontal sheathing dropped to about three-quarters of the stiffness and 
 strength of the unpierced panel. 
 
 Figure 3, G, shows a diagonally sheathed panel with a window and door in it. 
 Load was applied at the upper right-hand comer of this panel and the boards, 
 therefore, were in tension. From a factor of nearly 4, the stiffnoss dropped 
 to 1,4 with this arrangement and the strength from over 8 to 4. It was 
 still twice as rigid, ha/irovor, as a horizontally sheathed panel with tho 
 same openings . Tension in the boards that pass over the door frame tr tho 
 double window studs threw considerable bonding in window studs. This, of 
 course, roducod the stiffness of the panol as a wholo. With the positio* 
 of the door and window in the panel reversed as shown in figure 3, H, tho 
 bonding, which took place in the double door stud, oaused a still greater 
 reduction in stiffness. In this oase load was applied at tho uppor loft- 
 hand corner, Tho panel shown in figuro 3, H, had a stiffnoss factor of 
 0.8 and a strength factor of 1,3. Six-inch bevel siding applied to this 
 typo of panol with 7d box nails raised tho stiffnoss factor for tho diagonal 
 sheathing in compression te 2.0 and for that in tension to 3,3. Strength 
 
 (tars wore raised to 3,3 and 5,4, respectively. Horizontally shoathed 
 panels with lot-in braces around the window and door, arranged as shown 
 in figure 3, I, gave a stiffness factor of 1,5 and a strength factor of 2,2. 
 '..ith the siding addod, these factors were increased to 2.7 and 3,4, respec- 
 tively, which compares favorably with tho values for diagonal sheathing. 
 
 Plaster on wood lath gave a stiffnoss factor of 2,3 as tompared with 0,7 
 for horizontal sheathing, but its strength factor was only slightly moro 
 
 KoDort llo, R896 -8- 
 
than double that for horizontal sheathing. Horizontal and diagonal sheathing, 
 when used in conjunction with lath and plaster, increased the stiffness factor 
 to 2,4 and 2,8, respectively, and the strength factors to 2,2 and 4,4. Plaster 
 with horizontal sheathing and let-in braces arranged around the openings as 
 shown in figure 3, I, gave a stiffness factor of 4,1, which was greater than 
 that for the diagonal sheathing, and a strength factor of 3,6, which was some- 
 what smaller than that for the diagonal sheathing. 
 
 Due to concentration of stress at the corners of the openings, plaster cracks 
 developed at relatively small lfads as compared with the loads causing the 
 first cracks in tho unpierced panels. Instead of 10,000 to 12,000 pounds, 
 the first crack occurred between 800 to 1,500 pounds. The upper plate had 
 moved only a few hundredths of an inch when the first crack appeared, whereas 
 with tho unpierced panel this movement amounted to 3/8 inch or more. Figure 
 4, B, is a photograph of panel No* 23 taken after test. Load was applied 
 to the upper right-hand corner. 
 
 Significance 
 
 Plaster on wood lath may furnish all the rigidity necessary for most purposes 
 under normal conditions. However, as the plaster begins to crack from shrink- 
 age, settlement, or other causes, the rigidity of tho sheathing comos more 
 and more into play, thus in violent winds or earthquakes it is tho sheathing 
 that bocomes all important in preventing complete destruction. It is logical, 
 too, that slightly more resistance than is necessary to resist ordinary dis- 
 torting influences will in the long run more than pay for itself through 
 diminishing, if not entirely eliminating, neodless annoyances and frequent 
 maintenance costs that result from the structure getting out of alinement. 
 Diagonal or well-braced horizontal sheathing affords far more rigidity than 
 horizontal sheathing without bracing, Eithor diagonal or horizontal sheath- 
 ing is important from the standpoint of insulation and also assists in dis- 
 tributing concentrated loads. The amount of stiffness essential to good 
 construction is not yet known and must bo determined by experience. 
 
 The old "braced-timber" framo, which originated in Now England, had far moro 
 rigidity than was noedod porhaps, but tho hundreds of old houses still stand- 
 ing bear witness to tho fact that rigidity went hand in hand with permanence 
 Today building costs prevent the use in moderately pricod houses of the heavy 
 typo of construction omployed then, Tho modern adaptation of the braced frame 
 with its small built-up corner posts and light cornor bracing or tho present- 
 day balloon frame with tho studs carrying through for two stories represent 
 a great economy of material over the old style of braced frame* The plat- 
 form typo utilizes shorter studs but at a slightly increased expense of 
 material than tho balloon type. Good bracing and horizontal sheathing is 
 preferable for the platform type as shrinkage in tho horizontal mombors may 
 cause buckling of the shoathing if diagonal sheathing is used. Diagonal 
 sheathing or good bracing with horizontal sheathing will still give sufficient 
 rigidity with the balloon type. 
 
 Rooort No, R896 -9- 
 
Through a modorn tendency to cut costs, bracing is often omittod and 
 horizontal sheathing is used bocauso it is choapor to put on. Although 
 tho inexpensive house Is not nocossarily an unsound house, nevertheless, 
 cortain fundamental principles should be kopt in mind so that when con- 
 struction methods aro employed to roduco costs the methods will be such that 
 will result in no harm to the structuro, Furthor, tho added cost of adequate 
 bracing is so small that it can hardly bo felt in tho totil cost of tho build- 
 ing. 
 
 Comparison of Fiberboard r Yith Diagonal '.'ood Sheathing 
 
 A scries of tests was mado on frame "walls shoathod with 25/32-inch fiber- 
 board shoots, 4 by 9 feet in size, nailod to tho framo with 8d common nails 
 spacod 3 inches on centers at all vortical edgos, 6 inches on centers on 
 intermediate frame members, and approximately 5-1/3 inches on contcrs along 
 uppor and lower plates, which is tho nailing recommended by tho manufacturers. 
 The host method of applying tho fiberboard on walls with window and door 
 openings is to use sheets as wide and full-longth as possible betwoon windows 
 and doors and fill in above tho doors and windows and bolow tho windows, 
 using short 2 by 4-inch stubs whoro necessary to provido nailing along all 
 edgos of tho fioorboard. In walls without openings tho maximum number of 
 full-sized shoots probably should bo usod, togoth'or with tho nocossary 
 narrow strips to finish the covering of tho wall. 
 
 The rosults- arc compared with diagonal wood shoathing in tho following dis- 
 cussion and tablo 3, 
 
 Diagonally sheathed panels tcstod without siding tond to bend tho studs, 
 particularly at door and window oponings, and thoroby lose much of their 
 efficiency. This difficulty i3 remedied when siding is appliod ovor tho 
 diagonal shoathing, as in common building practice, Sinco tho largor sheets 
 of fiberboard do not have a tondoncy to bend tho studs undor tost loads, 
 tho fiberboard will receive only slight benefit from the application of 
 siding as compared v. r ith tho benefit rocoivod by di n gonal shoathing, Tho 
 effect of the siding on diagonal shoathing is demonstrated by the data 
 summarized in tablo 3 for walls with door and window oponings. 
 
 It may be noted from the data on diagonally-shcathod panols with and with- 
 out siding that the rigidity factor is nearly doubled and tho maximum load 
 factor more than doublod by addition of tho siding, when the sheathing is 
 strossod in compression, which, as indicated by tablo 3 is the woakor 
 dirocti on for panols with oponings. Comparison of fiberboard and diagonal 
 wood shoathing should properly bo basod on tho diagonal wood shoathing in 
 combination with sidir. jt Tho fiborbo vrd-shoathod walls with oponings had 
 
 percent tho rigidity factor and 64 porcont tho maximum load factor of 
 diagonally sheathed walls with siding, 
 
 •The dotail d rosults are given in Forost Products Laboratory report R1151 
 ontitled "Rigidity and Strongth of Framo Walls Shoathod with Fiborboard" 
 by G. E. Hock, October 1937, 
 
 Report No, R896 -10- 
 
From tho partial summary for wall panols without openings ^i v o n ^ n tabic 4, 
 it may bo oomputod that those shoathod with fiborboard had 86 porcont tho 
 rigidity factor at l/2-inch distortion, and loss than -17 percent tho maximum 
 load -actor of diagonal sheathing stressed in tension (tho weakest direction 
 for walls without openings) and without siding. 
 
 Roport Wo. R896 -11- 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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Table 3, — Comparison of strength and rigidity botwoon wood- and fiberboard- 
 shoathod wall panels with oponings 
 
 Type of sheathing 
 
 t Rigidity 
 : factor at 
 j l/2 -inch 
 : movomont 
 of upper 
 plato 
 
 Maximum 
 load 
 factor 
 
 Remarks 
 
 Horizontal wood- lot-in 
 
 braces 
 Horizontal wood 
 Fibcrboard ,,... 
 
 Diagonal wood ... 
 Do 
 
 Diagonal wood with 
 inch siding... 
 Do 
 
 6- 
 
 1.5 
 1.0 
 1.6 
 
 1.4 
 1.0 
 
 3.2 
 
 1.9 
 
 2.2 
 1.0 
 2.1 
 
 3.9 
 
 1.3 
 
 5.4 
 3.3 
 
 Roinf ore in.?: stubs — 
 
 recommended nailing. 
 Sheathing in tension. 
 Sheathing in compression. 
 
 Sheathing in tension. 
 Sheathing in compression. 
 
 Table 4, — Comparison of strength .and rigidity between wood- and f i borboard- 
 shoathod wall panels without oponings 
 
 
 : Rigidity 
 
 x Maximum 
 
 1 
 1 
 
 
 
 : factor at 
 
 5 load 1 
 
 ', 
 
 
 Type of sheathing \ 
 
 1 l/2-inch j 
 t movomont i 
 : of upper 
 : plato 
 
 \ factor 
 
 1 
 
 * * 
 
 ; 1 
 
 t 
 
 » 
 * 
 
 1 
 
 Remarks 
 
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 : 1 
 
 [ 
 
 
 braces : 
 
 1 3.4 ! 
 
 : 3,6 
 
 Avoi 
 
 *a-e of two. 
 
 
 3,0 j 
 
 3.8 ! 
 
 
 
 
 3.5 
 
 7.1 
 
 8* ! 
 
 7.8 i 
 
 She 
 She- 
 
 'thine in tension. 
 
 
 .thing in compression. 
 
 Report No, R896 
 
Hold down Rod 
 
 Applied 
 Force 
 
 Million Pound 
 Testing Machine 
 
 Test Panel 
 
 Holdback Stirrup 
 
 Testing Machine Platform 
 
 Figure 1. --Diagrammatic sketch of panel mounted for test. 
 
 tut oor\~i P 
 
2200 
 
 2000 
 
 1800 
 
 1600 
 
 « 
 
 § 
 5 
 
 I 
 
 1400 
 
 1200 
 
 1000 
 
 400 
 
 200 
 
 0.4 Ob 06 1.0 1.2 
 
 Movement of Upper Plate — Inches 
 
 Figure 2. — Basic load-deflection curve for horizontal sheathing 
 
 8 inches wide with two 8d nails in each board at 
 z u iz299 f each stud crossing. 
 
. 
 
 6 
 
 < 
 
 Figure 4. --Wood lath and plaster panels after test. 
 
UNIVERSITY OF FLORIDA 
 
 3 1262 08926 9012