US2167208A - Floor or roof construction - Google Patents

Description

July 25, 1939. M. G. HILPERT FLOOR OR ROOF CONSTRUCTION Fi-led Feb. 5, 1937 -4 Sheets-Sheet 1 0000 0000000000 IW o iObovtvOrfto.

Me ier GeaH/ZPGWL July 25, 1939. M, Q HlLPE'RT 2,167,208

FLOOR 0R ROOF CONSTRUCTION Filed Feb. 3, 1937 -l 4 Sheets-Sheet 2 Meier. Gol faerf `luly 25, w39c M. G. HILPERT FLOOR OR ROOF CONSTRUCTION Filed Feb. s, 1937 4 sheets-sheet 3 Mei/e GGILH-perl;

, July 25, 1939. M. G.`H|| PERT FLOOR 0R ROOF CONSTRUCTION Filed Feb. 3, 1957 4 Sheets-Sheetl 4 l Mierbmfligpert,

Patented July 25, 1939 UNITED STATES PATENT OFFICE 18y Claims.

This invention relates to improvements in floor and roof structures of the type which include steel beams to support the principal loadings, and has particular reference to the construction intermediate of and about said beams.

One important object of the invention is to provide a strong, light-Weight oor or roof construction intermediate of and about the principal load supporting steel beams thereof, which construction materially assists said beams in carryving live loads and serves to reinforce said beams against deflections. j

Another important object of the invention is to provide a floor or roof construction intermediate of and aboutlthe principal load supporting steel beams thereof, which construction serves eifectively to fire-proof said beams and may readily be made to meet the nre-proofing requirements of 'various different building codes.

2g Another important object of the linvention is to provide a floor or roof construction intermeiiiate of and about the principal load supporting -beams thereof, which construction includes a major number of isolated air spacesf of major size consistent with the depth or thickness and required strength of the floor or roof, affording', in themselves, effective vthermal and sound insulation and being designed to accommodate bulk or other insulating material to afford additional insulation in any desired case.

Another important object of the invention ls to provide ajoor or roof construction intermediatefof and about the principal load supporting beams thereof, whichconstruction is cheap and easy to produce and may be produced either in situ, or, in major part, as low cost pre-fabricated units capable of rapid and easy installation in a building structure.

With the foregoing and various other objects and purposes in View, which will become more fully apparent as the nature of the invention is better understood, the same consists in the various novel features of construction, combination and arrangement as will be hereinafter more fully described, illustrated in the accompanying drawings and defined in the appended claims.

In the drawings, wherein like characters of reference denote corresponding parts in related Views:

Figure l is a top plan View illustrating an in situ embodiment of the present licor or roof construction, parts being broken away to show the underlying construction.

Figure 2 is a longitudinal section through the 5s construction shown in Fiel.

Figure 3 is a transverse section through the construction shown in Fig. 1.

Figure 4 is a detailperspective view illustrating a beam carried reinforcement for bonding in the plastic material adjacent tothe beam.

Figure 5 isa View similar to Fig. 4 `illustrating an alternative form of beam carried reinforcement. y y

Figure 6 is a side elevation of the reinforcement means for one of the joists.

Figures 7, 8 and 9 are detail sectional views illustrating alternative forms of beams specially designed to be used with the present pre-fabriecated construction intermediate and about the same. 16

Figure l0 is a View similar to Fig. l illustrating an embodiment of the invention in'which the construction intermediate the principal load supe porting beams is comprised mainly by pre-formedV elements.

Figure 11 is a longitudinal section through the construction shown in Fig. 10.

Figure 12 is a transverse section on the line I2-I2 of Fig. 10.

Figure 13 is a detail longitudinal section illustrating an alternative form of end piece which may be used in the pre-formed elements; and

Figures 14 and 15 are views similar to Figs. 12 and 11 respectively, illustrating anl alternative form of joist which may be used in lieu of the joists illustrated in Figs. 1 to 12.

Figure 16 is a perspective view of the improved unit of construction. l

In modern building structures having steel frames it is usual to provide steel floor and roof 3.5 beams to support the' principal floor and roof loadings. Usually these beams are ofthe I-beam type and extend horizontally,A or substantially horizontally, in parallel, spaced relationship between columns or walll beams to vwhich they are secured at their ends. The accompanying drawings illustrate a pair of such beams, designated as I0, I D, disposed horizontally in spaced, parallel relationship. However, as will' later become apparent, it is not necessary that said beams be disposed either horizontally or parallel, as the present floor or roof construction is readily capable of being formed between them whether they slope or are inclined to the horizontal and whether they are or are not disposed parallel to each other.

In carrying out the present invention there are provided a suitable number of reinforced concrete joists Il to extend between the beams l0. These joists Il are preformed either at the building site or at any other suitable location,

and each includes a concrete body of preferably vertically elongated, rectangular shape in cross section having embedded therein a suitable reinforcing steel frame comprising, for example, an angle iron tension member I2 disposed near the bottom of the joist and extending longitudinally thereof, a compression member I3 in the form of a rod or the like disposed near the top of the joist and extending longitudinally thereof, and a plurality of upright rods or the like Il connecting the members I2 and I3 at points suitably spaced therealong. Conveniently, certain of the uprights I4 may be extended laterally at their lower ends through holes formed in the upright flange of the tension member I2 and may be Welded to said tension member, and near their upper ends may be welded to the compression member I3. However, any or all of said uprights I4 may be secured to the members I2 and I3 in any other suitable or desired manner. Moreover, all or some of said uprights extend short distances above the top of theeompleted joist and some may extend below the bottom of the completed joist for purposes which will later appear.

The joists I I obviously are capable of easy and economical production, either singly or in pluralities, in suitable forms or molds. They are formed with downwardly and outwardly inclined ends and with upwardly and outwardly inclined bottoms adjacent to their ends so that when they are subsequently disposed between the beams Il) with their ends resting upon the laterally extending bottom ilanges of said beams in accordance with the invention, their bottom faces are disposed flush, or substantially flush, with the bottom faces of said beams andspaces for the reception of concrete, aerocrete Yor the like are formed between their ends and the webs of said beams. In producing said joists suitably symmetrical openings I5 are formed Ytherethrough to accommodate conduits for Aelectrical wiring or the like when the joists are embodied in a building.

According to the in situ embodiment of the invention illustrated in Figs. 1 to 3, a series of the joists II are placed between the beams I in suitably spaced apart, preferably parallel relationship and are covered by expanded metal lath or similar material I6 which extends across the tops of the spaces between said joists. At its sides this material I6 is extended downwardly, as indicated at Il, over the downwardly and outwardly inclined ends of the joists II and across the spaces between the joists to points such that, when concrete or the like is poured between the webs of the beams I0 and the metal lath, the concrete or the like will spread out over the bottom flanges of the beams and to either side of the joists and, upon hardening, will ireproof the lower flanges of the beams and serve at the same time to fix the joists inspaced relationship. The upper ends of the uprights I4 extend through the material I6 and some of them are bent downwardly upon said material to hold it securely in place.

Beneath the joists II and the beams II) is arranged a ceiling reinforcement in the form of relatively light weight metal ceiling lath I8 or other suitable material which extends 'across the bottoms of the spaces between said joists and beams and is secured thereto in any suitable manner, as, for example, by means of tie wires I9 or by having bent upwardly Vther'eagainst the lower ends of such of the uprights I4 as extend below the joists.

After the joists I I have been placed in position between the beams IU and the materials I6 and I8 have been placed in the positions described relative to said joists and beams, flooring or roofing concrete, Haydite cr the like, designated as 25J, is poured into the spaces between the beams I and the downturned side portions of the material IS, and also over the top of the material I6 and over the tops of the beams Ill to any suitable or desired depth, some of the concrete, Haydite or the like flowing over the bottom anges of the beams I and thus fireprooflng said bottom flanges and fixing the joints in place as previously stated. Previously, or at any desired time, suitable ceiling forming material, such as plasterboard or preferably a plaster mortar, designated as 2|, is applied to the lath or similar material I8. Thus, there is formed a floor or roof construction of hollow or cellular form having sound and thermal insulating qualities in itself and which may have been additionally insulated, had that been desi-red, by placing bulk insulation or insulation of any other desired type within the air spaces or cells thereof prior to covering said air spaces or cells b-y the material I6. Moreover, due to the beams I!! being completely encased by the materials 2-0 and 2l, they Vare effectively reproofed and may be fire-proofed to any desired extent in conformity with any given building code simply by varying the thicknesses of the materials 20, ZI. Furthermore, the material 26, when set and bonded to the joists I I by the uprights I4 and the material I6, not only serves to prevent lateral deflections of thebeams I0, but provides, in itself, an effective concrete T-beam cooperating withthe beams I0 to provide a composite beam which is exceptionally 'eifective to sustain loads to which the floor or roof may be subjected. Also, it is obvious that by having-the top portions of some or all of the uprights I4 bent over into the flooring or roofing material 2B, the necessary bonds are provided to make effective composite T-beams -of the joists and the flooring o-r roof-lng 26. Furthermore, since the ends of the joists are firmly embedded in the material 20 and consequently are rigid with respect to the beams I0, it is evident that said joists in conjunction with the material 2l! will carry additional loads due to the arch actions from the bottom flanges of the beams I0 through the joists and the material 2D. Also, since the material 20 ows to either side of the ends ofthe joists and thereby stays the joists against Ylateral movement, the entire construction, panel by panel between beams IIl and subpanel by sub-panel between joists, becomes one integral construction capable of supporting heavier loads for the materials used than if the beams and joists operated singly.

While it is not essential that the beams I0 have top elements in addition to their top flanges for embedment in the material 20 to reinforce said beams, it is, nevertheless, desirable to provide vsaid beams with such elements. In this connection, Figs. 3, 4 and 5 illustrate that crimped rods 22 are welded to and extend from the webs of the beams Ill upwardly and outwardly across the edges of the top flanges of said beams, to which flanges they also are welded, and that said rods have welded thereto, outwardly of the outer edges of the top flanges of said beams,'other rods 23 extending longitudinally of said beams for embedment in the material 20 and for cooperation with the rods 22 to reinforce the said beams by bonding with the material 2D encasing the top portions of said beams and making composite T-beams thereof. Alternatively, and

as illustrated in Fig. 4 of the drawings, each beam I0 may be provided with a single crimped rod 22a disposed flatly on top thereof and welded thereto and having extending beyond the edges of the top ange of the beam portions 221 to which are welded rods 23 similar to the rods 23. In fact, the beams I0 may carry any suitable means at their tops in addition to their top anges for embedment in the material to reinforce said beams. Similarly, instead of applying a mortar or plastic material 2| to the lath I8 and allowing said material to set, a plasterboard or pre-formed slabs of any suitable ceiling material may be employed and may be secured in place in any desired manner, as, for example, by nailing the same to the joists Il,

' it being pointed out inthis connection that the base of the concrete material comprising said joists and also the flooring or roong 20 may be cinders or the like permitting the driving of nails into the same and affording good sound insulating qualities. In any event, the ceiling material 2l for in situ placement preferably has either a plaster base or is in the form of a good commercial plasterboard so that any finishing coat, or coats, of plaster will eiectively adhere thereto.

Tne embodiment of the invention illustrated in Figs. 1 to 3 is particularly adaptable to rapid and 'economical construction because successive beams I0 may be placed and supported in their final permanent positions preparatory to construction of the floor proper between them. On the other hand, in some cases it may not readily be possible to operatively position the joists I I between a pair of the beams l0, particularly if thel lowering the other end of the joist,or the other side of the slab skeleton, as the case may be, into engagement with the bottom flange of the other beam. In this connection, Fig. '7 illustrates that the top flange of eachbeam I0 may be` removed,

I either entirely or in part, at one side of the web of the beam, thereby to permit the joists Il, as embodied in a pre-formed slab skeleton, to readily be lowered into position in the manner stated to rest upon the bottom flanges of said beams. As

. an alternative construction,- Fig. 8 illustrates that the beams I0 may be of vinverted T-shape in section and may have narrow compression members at their topsl formed by Welding rods 24 against opposite side faces of their webs. figure also suggests that an equivalentbeam may be formed by only partially removing the top flanges of an I-beam or ,by recessing either or both top flanges at a point or points of least moment, to permit the joists first to be lowered onto the beam bottom anges and then to be slid along said bottom flanges to desired final positions. As a further alternative construction, Fig. 9 illustrates that the beams I0 may be formed each from a channel section 25 having an angle 26 welded to its bottom to provide a bottom tension member of inverted T-shape, and further having a rod 21 welded to the top thereof for cooperation with the top flange to provide a compression member. Other beam constructions, of which the foregoing merely are examples, obvious- Thisl ly may be devised to aiord necessary strength and to permit the joists to be assembled therewith in the manner stated. Alternatively, the joists and lath materials if placed insitu, or prefabricated skeleton units, may be placed at one end on the bottom ilange of beam I and this intermediate construction may be supported on horses resting on the floor construction below and the adjacent floor beam l0 may then be swung into its final position with its bottom flange below the said intermediate construction at its other end, after which said joists or units may be lowered permanently onto the bottom flange of the last placed beam I0.

As previously indicated, the present floor or roof' construction intermediate the beams l0 may be comprised in major part by pre-formed slab skeletons corresponding in all essentials to the in situ slab skeletons formed by practicing the invention as described in connection with the illustration in Figs. 1 to 3. A construction embodying pre-formed slab skeletons is illustrated in Figs. 10 to 13 and will be observed to comprise a plurality of-slab skeletons disposed in end to end relationship between the beams I 0. These skeletons may be of any suitable length and are of a width determined by the spaced apart relationship ofthe vbeams lll. As shown, eachv slab skeletonr comprises any desired plurality of joists Ha which may be duplicates of the joists I l and which may be disposed in any desired spaced apart, parallel relationship. The two outermost joists of each slab skeleton are spaced inwardly from the ends of the slab skeleton and at the ends of the slab skeleton are'sheet Vmetal elements 28 having the profile or side elevational shape of the joists Hato preserve the cross-sectional shape of the slab skeleton at its ends and to cooperate with the corresponding elements at the ends of adjacent slab skeletons to provide forms for the pouring of joists between the ends of adjacent'slab skeletons. In this connection and as illustrated in Figs. 10 to 12, the elements 28 are of channel shape in cross section and have inwardly directed top and bottom ilanges. Alternatively and as illustratedl in Fig. 13, said elements may be of substantially Z-shape in cross section, each having an inwardly directed ange at its top and an outwardly directed flange at its bottom. Alternatively, said elements may be of any other suitable sectional shape. In any event, the joists l Ia and the elements 28, and the spaces between said joists and elements, are covered by expanded metal lath or the like E63 which is extended downwardly over the downwardly and outwardly inclined ends of said joists and elements and between the same may be tucked inwardly to better preserve the spacing of said joists". Similarly, the bottoms of said joists and elements, and the bottoms Yof the spaces therebetween, are covered by metal lath, wire mesh or the likeV i8a fastened in place by tie tires ille or by the uprights Ma; In addition, stays orbraces 29 extend from the tops of alternate of the joists and the elements 28 to the bottoms of the remaining joists and elements to hold the joists and the elements 28 properly'positioned and to impart rigidity to the slab skeletons.

Following fabrication of the slab skeleton they preferably are lowered into 'a thin lay-er of' liquid cement and cinders or Haydit'e which, enmeshing the wire mesh Ia and'hardening, forms the ceiling plaster base. Thus, such base, being applied underfactory conditions, will be ofY economical thickness and uniform texture for its purpose.

gil

Obviously the width of such precast plaster base must register as desired with the distance center to center of the supporting beams l and the length must be of the exact length center to center` of the formed in situ joists designated as J.

This prefabricated skeleton or unit having a solidly supported base or bottom allows of adding under factory control the required thickness of bulk or other type of insulation as indicated for the permanent position in building of said prefabricated floor unit. The insulation may be introduced through the ends between the joists under the downward extending mesh la or by f lifting a central top section of the mesh la as previously arranged for. This factory introduction of the insulation eliminates a tedious operation under the many unfavorable conditions obtaining when placing insulation between the beams at the building site and expedite erection of the building proper. This prefabricated unit allows alternates as the substitution of commercial plasterboards or the like in place of the factory cast plaster base, said board being fastened to the underside of said joists Ila and to end members 28 and, if desired, being wired to the edges of the mesh |62. Such alternates will cbviously provide the base desired for factory placing of insulation, for reproong the webs and bottom flanges of beams ll) and for the'ceiling plaster finishing coats.

In constructing a iioor or roof by employing slab skeletons as described, the slab skeletons are placed between the beams l0 in end to end relationship with the ends of the joists lla resting upon the bottom fianges of Vthe beams. In this connection, if end elements 28 as illustrated in Fig. 13 are used, the outwardly directed bottom flanges of said elements at adjacent ends of adjacent slabs are disposed in abutting relationship, thereby to close the bottoms of the spaces between the webs of said elements. On the other hand, if the elements 2B do not have outwardly directed bottom flanges, said elements are held properly spaced apart, and the spaces between them are closed at their bottoms in any suitable manner, as for example, by means of a suitable extension of aV pre-cast plaster base Yheld in place by the wire mesh la or otherwise. In any event, after placing the slab skeletons between the beams,

concrete, Haydite or the like is poured into the spaces between the elements 28 at adjacent ends of the slab skeletons, thereby forming an additional joist at the adjacent ends of each' two adjacent slab skeletons. At the same time, con crete, Haydite or the like is poured into the spaces between the beams l0 and the downwardly directed and inwardly tucked side portions of the metal lath llia and over said metal lath and said beams to a desired thickness or depthV with the same advantageous results as described in connection with Figs. 1 to 3 of the drawings. Thereafter, or previously. if desired, the ceiling finishn ing coating, or coatings, is, or are, applied. In this connection it will be understood, of course, that conduits 30 for electric wires or other purposes may be embodied in the slab skeletons either during construction of the same or at any time thereafter and that connections between said conduits may be made in the spaces between adjacent ends of the slab skeletons prior to pouring of the concrete. It will also be understood that the joists formed between the ends of adjacent skeleton sections may be reinforced in any desired manner.

It is not essential'that the joists l or Ila be of the construction heretofore described or even vof reinforced concrete construction. On the contrary, said joists may be of any suitable construction, and in this connection Figs. 14 and l5 'illustrate one alternative construction which may be especially desirable in certain installations. As illustrated' in said figures, the joists, designated generally Vas l Ib, are of all metal construction and are characterized by Webs 30 formed of rods which are crimped to provide successive V-shaped and inverted V-shaped formations as viewed in siderelevation. Such of said j oists as are intended to be used intermediate the ends of pre-formed slab skeletons preferably have top and bottom compression and tension members, respectively, each of which is comprised by two pieces of angle iron 3| disposed to opposite sides of the web 3G, respectively, and welded to the apices of the V- shaped formations of saidv web. On the other hand, such of said joists as are intended to be used at the ends of preformed slab skeletons may have top and bottom compression and tension members, respectively, each comprised by a single piece of angle iron at the inner side of the web of theAjoist. Alternatively, the bottom member may be comprised by two pieces of angle iron and the top member by only a single piece of angle iron atv the inner side of the web; 0r, the top member maybe comprised by a single piece of angle iron at the inner side of the top of the web and the bottom member may be comprised by a single piece of angle iron at the outer side of the bottom of the web. In this connection it is apparent that in any case where the bottom member consists of or includes a piece of angle iron at the outer side of the web, the outwardly directed anges of adjacent slab skeletons cooperate to close the bottomY of the space between the slab skeletons. Obviously the joists illustrated in Figs. 13 and 14 may be used either individually in the manner described in connection with the `joists i! of Figs. l to 3, or in forming slab skeletons of the character described in connection with Figs. 7 to 13. As shown, said joists are longer at their bottoms than at their tops. and when embodied in slab skeletons the metal lath' or the like itl covering them and the spaces therebetween extends downH wardly over their ends as at 32 and also over their sides, as at 33. In other respects said slabs and slab skeletons. and floors or roofs embodying the same are, or may be, of the same construction set forth in connection with Figs. l to 3 and 7 to 13.

Any of the joists may be formed so that when they are seated at their ends on the bottom flanges of the beam Ill their top and bottom faces may be disposed at any desired levels relative to the top and the bottom faces of said beams. Moreover, in any case where the bottoms of the .ioists are disposed at elevations such that a ceiling coating of normal thickness applied thereto does not eifectivelycover the bottoms of the beams l0, the said bottoms of said beams may be covered and effectively fireproofed byV a stepped ceiling formation as illustrated in Fig 14 and including, for example, a plank 34 of suitable insulating material, such as gypsum, wired or otherwise secured against the bottom of each beam.

Without further description it is thought that the features and advantages of the invention will vbe readily apparent to those skilled in the art,

and it will of course be understood that changes in the form, proportion and minor details of construction may be resorted to, without departing from the spirit of the invention and scope of the appended claims.

I claim:

l. In a building structure, spaced floor or roof beams, joists extending between said beams, a plastic material supporting sheeting covering said joists and the spaces therebetween and partly covering the ends of said joists and the spaces between such ends, and plastic material disposed over said beams and said sheetingand extending downwardly between the ends of said joists and the webs of said beams and `providing in cooperation with said beams and joists a composite beam structure. v

2.` In a building structure, spaced floor or roof beams having webs and bottom flanges, joists extending between said beams and resting at their ends on the bottom anges thereof, the ends of said joists being spaced from the webs of said beams, a plastic material supporting sheeting covering said joists and the spaces therebetween and extending downwardly over portions of the ends of said joists and over portions of the spaces between the ends of said joists, and plastic material covering said sheeting and said beams and extending into the spaces between the webs of the beams and the downwardly extending portions of said sheeting.

3. In a building structure, spaced iioor or roof beams having webs and bottom anges, joists extending between said beams and resting at their ends on the bottom flanges thereof, the ends of said joists being downwardly and outwardly inclined, a plastic material supporting sheeting covering said joists and the spaces therebetween and extending downwardly over portions of the ends of Y said joists and over portions of the spaces between the ends of said joists., and plastic material covering said sheeting and said beams and extending into the spaces between the webs of the beams and the downwardly extending portions of said sheeting.

4. In ar building structure, spaced floor or roof beams having laterally extending top and bottom compression and tension members, respectively, joists extending between said beams and supported thereon, a plastic material supporting sheeting extending over said joists and over the spaces therebetween, and partly covering the ends of said joists and the spaces between such ends, the side marginal portions of said sheeting being directed beneath the top compression members of said beams in spaced relationship thereto, and plastic material covering said beams and said sheeting and extending into the spaces between the top compression members of said beams and the underlying marginal portions of said sheeting.

5. In a building structure, spaced floor or roof beams having laterally extending top and bottom compression and tension members, respectively, joists of reinforced concrete extending between said beams and supported thereon, a plastic material supporting sheeting extending over said and extending into the spaces between the top compression members of said beams and the underlying marginal portions of said sheeting and having the aforesaid parts of the joist reinforcements embedded therein.

6. In a building structure, spaced oor or roof beams having webs and bottom flanges, joists extending between said beams and resting at their ends on the bottom flanges thereof, the ends of said joists being spaced from the webs of said beams, a plastic material supporting sheeting covering said joists and the spaces therebetween and extending downwardly over portions of the ends of said joists and over portions of the spaces between the ends of said joists, and plastic material covering said sheeting and said beams and extending into the spaces between the webs of the beams and the downwardly extending portions of said sheeting and downwardly over the bottom flanges of said beams.

7. The combination as set forth in claim 6 including ceiling lath material secured against the bottoms of the joists and extending across the bottoms of the spaces therebetween, and plastic ceiling material extending across the bottoms of the beams and the joists and across the bottoms of the spaces between said beams and joists and having said ceiling lath material embedded therein.

8. 'Ihe combination as set forth in claim 6 including ceiling material extending across the bottoms of the spaces between the beams and the joists and cooperating with the plastic Inaterial covering said spaces to provide a hollow or cellular floor or roof structure.

9. The combination as set forth in claim 5 in which ceiling lath `and ceiling material extend across the bottoms of the spaces between the beams and the joists, and in which some of the joist reinforcements extend below the joists and serve to fasten the ceiling lath to the joists.

l0. The combination as set forth in claim 2 in which the beams have top Aflanges and in which additional flange `members and composite beam bonds for the plastic material are carried by and extend laterally from the top flanges of the beams and are embedded in the plastic material.

11,. A pre-fabricated unit for the reinforcement of floors, roofs and the like formed from plastic material, said unit comprising laterally spaced joists, and foraminous metal attached to said joists and extending across the space between the tops of said joists and downwardly across the upper portions of the spaces between the ends of said joists.

l2. A pre-fabricated unit for the reinforcement of floors, roofs and the like vformed from plastic material, said unit comprising laterally spaced joists, and upper and lower sheets of foraminous metal attached to the tops and the bottoms of said joists and extending respectively across the spaces between the tops and the ybottoms of said joists, the vend portions of the upper sheet extending downwardly across the spaces between the upper portions of the ends of the joists.

13. AA pre-fabricated unit for the reinforcement of hoors, roofs and the like formed from plastic material, said unit comprising laterally spaced joists the tops of which are shorterthan their bottoms, and metal lath extending across the tops and ends of said joists and across the space between the tops and partly across the space between the ends of said joists and fastened to said joists.

14. A pre-fabricated unit for the reinforcement of floors, roofs and the like formed from plastic material, said unit comprising at least one joist intermediate the ends of the unit, sheet metal members at the ends of the unit having the side elevational shape lof the joist, and metal lath material extending over saidv joist and said members and over `the spaces therebetween'.

15,7A pre-fabricated unit as set forth in claim 14 in which the sheet metal members at the ends of the unit Ihave' outwardly directed bottom anges for cooperation with the companion flanges of adjacent units to close the bottoms of the spaces between the end members of adjacent units. s

16. A pre-fabricated unit for the reinforcement of oors, roofs and the like formed from plastic material, said unit comprising a plurality of spaced, parallel josts having downwardly and outwardly inclined ends, and metal lath material extending across the tops of said josts and across aictgao

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