WO2009062298A1

WO2009062298A1 - Architectural pavements in elevated exterior deck applications

Info

Publication number: WO2009062298A1
Application number: PCT/CA2008/001993
Authority: WO
Inventors: John R. Naccarato; Joseph A. Severini
Original assignee: Casata Technologies Inc.
Priority date: 2007-11-13
Filing date: 2008-11-13
Publication date: 2009-05-22
Also published as: EP2225424B1; CA2705832C; EP2225424A4; CA2705832A1; EP2225424A1

Abstract

A joist for assembly with like joists to provide a deck assembly, the joist having a web portion and a deck portion extending orthogonally from the web portion and defining a generally planar surface, the deck portion having a shelf section formed by an offset at the intersection of the web portion and deck portion to lie below the general planar surface of the deck portion, an offset at a distal edge of the deck portion to provide a tail, the offsets being relatively dimensioned such that when a tail of one joist is supported on the shelf section of an adjacent joist, the deck portions lie in a common plane.

Description

TITLE: ARCHITECTURAL PAVEMENTS IN ELEVATED EXTERIOR DECK APPLICATIONS FIELD OF THE INVENTION

[0001] The present invention relates to the use of exterior architectural pavements. More particularly this invention relates to the use of architectural pavements in elevated exterior deck applications.

DESCRIPTION OF THE PRIOR ART

[0002] Exterior paving systems for pedestrian use are those which are intended to present a pleasing lower-maintenance architectural decorative surface. Architectural pavements (hereinafter referred to as "pavers") may be selected from pre-cast concrete, stone, porcelain tile, concrete or stone slabs or the like; or recycled rubber pavers, wood tiles, plastic wood composite tiles or the like designed for use with pedestrian traffic, and are required to perform through weather environments ranging from freezing and thawing, to earthquakes and tremors. Architectural pavements are available in a variety of plan form shapes and a variety of thicknesses.

[0003] Concrete pavers are generally units that can be lifted and placed with one hand and whose surface doesn't exceed 100 square inches. These units can be used in pedestrian and vehicular applications. Concrete pavers for pedestrian or terrace applications range in thickness from 1.5 inches (40 mm) to 2.375 inches (60 mm) thick.

[0004] Pre-cast concrete paving slabs range in nominal size from 10 x 10 in. (250 x 250 mm) to 36 x 36 in. (910 x 910 mm). Like pavers, concrete paving slabs can be manufactured with a variety of colors, special aggregates, and architectural finishes to enhance their appearance. Paving slabs generally range in thickness from 1.5 inches to 2 inches (40 to 50 mm) and thicker units are also applied to roofs. Some applicable industry standards require a minimum average flexural (bending) strength of 650 psi (4.5 MPa), freeze-thaw durability when exposed to de-icing salts, and conformance to dimensional tolerances. Flexural (rather than compressive strength) is used to assess unit strength since the larger slabs are exposed to bending and cracking. Compressive strength is excluded from the standard because it is not a true measure of the performance of the concrete. Thinner slabs will break in bending more readily than thicker ones.

[0005] Thin pavers may be manufactured with varying flexural strength, and generally have a minimum compressive strength of 5,000 pounds per square inch, and a minimum characteristic breaking load of 1125 pounds force. The pavers may be contiguously located in an immediate pattern that may be interlocked to prevent the ability of a paver to move independently from its neighbors.

[0006] Dimension stone is natural stone or rock that has been selected and fabricated (i.e., trimmed, cut, drilled, ground, or other) to specific sizes or shapes. Color, texture and pattern, and surface finish of the stone are also normal requirements. The principal rock types are granite, limestone, marble, travertine, quartz-based stone (sandstone, quartzite) and slate. Other varieties of dimension stone that are normally considered to be special minor types include alabaster (massive gypsum), soapstone (massive talc), serpentine and various products fashioned from natural stone. Tile is a thin modular stone unit, commonly 12 in. square (30.5 cm) and 3/8 in. (9.5mm) thick. Other popular sizes are 15 in. square (38 cm), 18 in. square (46 cm), and 24 in. square (61 cm); these will usually be thicker than the 12 in. square.

[0007] Porcelain tiles are ceramic tiles with a water absorption rate of generally less than 0.5 percent that are used to cover floors. They can either be unglazed or glazed and range in varying patterns and thickness from .250 inches to .625 inches. Generally, ceramic, porcelain, or stone tile can be installed over suitable substrates, in exterior locations, including mortar beds over concrete slabs and directly to concrete slabs. These substrates must be structurally sound, meet deflection requirements, and meet on-plane requirements. In addition, exterior tile work demands attention to mandatory expansion joints, moisture considerations, and thermal demands.

[0008] Recylced rubber pavers are non-rigid more common as an architectural surface finish generally for on-grade applications where the loads can be transferred to the ground. In general, pavers incorporating recycled rubber tires comprise preparing a rubber crumb by mechanically or cryogenically shredding disposed rubber tires, adding a binding agent or adhesive, adding a colorant, and thereafter forming the paver by the application of heat and pressure in a mode. It has been generally not advisable to install a recycled rubber paver in an elevated deck application with a wood substructure, due to the negative affects of trapping moisture between the rubber pavers and wood substructure, including mold growth and wood rot. In addition, recycled rubber pavers used in pedeatrian applications are not capable of spanning open areas between joists and supporting vertical loads. [0009] Other non-rigid pavers include wooden tiles and boards assembled or adhered onto a tile backer such as a mesh or plastic grid. These tiles are not self-supporting and require a structural sub-floor to support the load between joist spans. Their use is not advisable in an elevated deck application with wood subfloor and structure, due to the negative affects of trapping moisture between the tiles and wood substructure, including including mold growth and wood rot. One very common area for mold growth and other moisture-related problems to begin is any place in which two or more pieces of wood are fitted together with the potential threat of water getting in between them.

[0010] In the past deck or terrace applications using architectural pavers were usually constructed by placing the pavers on-grade using a compacted base with a setting bed, using a base of reinforced concrete, or in direct contact with an under-surface such as a roof. For on- grade applications, pavers are usually supported from beneath by a base of natural or compacted sand, gravel or the like that may be either rigid or somewhat yielding, and a setting bed laid on the base and supporting the pavers. The joints between pavers are then grouted so that the entire system is rigid. Disadvantages with this arrangement arise due to random cracks of the pavers and/or the base from flexural forces exerted from above or exerted vertically from below as by sub-base instability, quakes or tremors, or horizontally by movement due to thermal or moisture expansion and contraction. Also, the entry of surface water into these systems causes pavers to heave due to freeze-thaw cycling, wash-out, breakup, and eventual deterioration of the deck support structure and/or water-proofing membrane over occupied areas below. The high cost of replacement, levelling and aligning the pavers as well as repairs to the waterproofing is an ongoing maintenance problem.

[0011] A second procedure requires the use of relatively thicker pavers which are placed on or laid on a bed or base of sand that permits each individual paver to "float". Movement will then occur between pavers rather than through them. This method, however, requires the use of relatively thick pavers which have the necessary strength to prevent breaking under foot or other adverse forces mentioned above.

[0012] Alternatively, United States Patent 7,244,076 issued July 17, 2007 to Whitson discloses a method for installing paving blocks comprising preparing an area on-grade to be paved to a desired grade, and then applying a preformed, load-bearing sheet of material such as extruded polystyrene to be placed on the prepared area. Pavers are then laid in a desired pattern on the sheet of material. The disadvantage with the Whitson is that is not suitable for use on an above-grade or elevated deck application with spaced beams, as the load-bearing sheet of material requires complete contact with the on- grade area in order to perform.

[0013] For rooftop terrace applications, paver pedestal systems have been designed to elevate architectural deck surfaces to. separate and provide a drainage space between pavers and the waterproofed supporting structure below. However, in this case, the paver must be of sufficient strength to provide sufficient support for loads carried, as well as the load of the paver between pedestals. This requirement is generally addressed by increasing the thickness of the paver, which increases cost and weight. An additional disadvantage is that these pedestals systems require installation by professional installers with specialized skills, tools and equipment.

[0014] In a general elevated deck application, the site is first prepared to remove any grass or weeds from the measured area to form a level working space. The foundation is next installed, with some installations calling for footings below the frost line (to avoid heaving during freeze and thaw cycles) for piers or posts, and others allowing piers to sit on top of deck blocks and float on grade. The number of piers and pier spacing is determined by local building codes. A decision is made to either connect the deck to an existing structure such as a house, or to have it free-standing. Beams that are properly sized to distribute the load from the deck surface to the foundation are then installed. The size and maximum span of the beams between posts are determined based on the structural loading conditions and legislated building regulations. Longitudinal joists are then installed perpendicular to the beam with the joist edge resting on the beam, and generally spaced from 12 to 16 inches apart. The final major step is cutting the decking boards themselves and screwing them to the tops of the joists in a staggered pattern so that the seams don't all line up. The materials used for the substructure and joist are generally selected from softwood species impregnated with a wood preservative. Various fastening means for each structural element are generally provided in the prior art, and include screws, nuts, and bolts as appropriate for the circumstances.

[0015] It is not advisable to install architectural pavements in an elevated deck application directly on top of a wood substructure due to the structural limitations of traditional wood substructures and the negative aspects of trapping moisture between the paver and wood decking increasing susceptibility to wood rot. Another known elevated deck application involves laying a fibreglass grating system on top of an existing wood substructure, and thereafter setting stones or pavers with and without the use of an adhesive. The disadvantage of this system includes its relatively higher cost of the fibreglass grating compared to the present invention, as well as the limited dimensions of the grating system and the specialized skills and tools required to adapt the system to varying deck designs. In addition, the system is limited in structural performance to the performance of existing wood sub-structures which may not be suitable for increased loading associated with paver applications.

[0016] It is seen from the prior art that these methods can require some technical knowledge or expertise and are generally time-consuming. As a result, a professional installation is generally required. In many cases, however, the consumer desires to perform the installation as a "do-it-yourself project to reduce the total cost of the project.

[0017] Therefore, there is a need to simplify methods of installing pavers in deck or terrace applications to permit installation by non-professionals with limited or no technical knowledge, without sacrificing the structural integrity of the installation.

OBJECTS OF THE INVENTION

[0018] Accordingly, a principal object of the present invention is to provide an elevated deck system that obviates or mitigates the above disadvantages.

SUMMARY OF THE INVENTION

[0019] According to the present invention there is provided a joist for assembly with like joists to provide a deck assembly. The joist has a web portion and a deck portion extending orthogonally from the web portion. The deck portion has a shelf section formed by an offset at the intersection of the web portion and deck portion to lie below the general planar surface of the deck portion. The distal edge of the deck portion is offset to provide a tail. The offsets are relatively dimensioned such that when a tail of one joist is supported on the shelf section of an adjacent joist, the deck portions lie in a common plane. In a nested configuration, the continuous longitudinal offsets provide increased sectional rigidity which contributes to limit vertical deflections and resist crippling under loading conditions, and achieves a structural efficiency that is not achievable with a single piece structural element of similar thickness.

[0020] Preferably, ribs are formed in the web portion and deck portion and extend laterally relative to the longitudinal axis of the joist.

[0021] As a further preference, the shelf section is wider than the tail to facilitate adjustment of one joist relative to another. [0022] In a preferred embodiment, a flange is formed at the free edge of the web portion and extends orthogonal to the web portion. The flange may extend either away from the deck portion or in the same direction.

[0023] By providing a deck assembly from the joists, a paving system employing thin pavers may be installed on the deck portions which is especially useful for an elevated deck or the like. The pavers can be removed without affecting the substructure to facilitate replacement with an alternative decking finish and decking appearance.

[0024] Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.

[0025] According to a further aspect of the present invention, there is provided an elevated deck architectural paver system and a method of architectural paving which overcomes the disadvantages of prior systems and methods, by utilizing a generally continuous structural metal diaphragm that is installed on top of a supporting joist and beam substructure, and which provides both longitudinal and transverse support for architectural pavements. The structural metal diaphragm has a first shelf section formed longitudinally by an offset and generally centered on a joist position underneath and lies below the general planar surface of the deck portion. The distal edge of the structural metal diaphragm is offset to provide a tail. The next metal diaphragm is then positioned with its tail resting on the shelf section of the preceding diaphragm. The wider shelf section allows the tail to be adjusted along the length of the diaphragm to maintain the required alignment between the diaphragms and provides for flexibility of alignment and pitch during assembly of the diaphragms to accommodate variability and dimensional inaccuracies of structures in an as-built condition. In a nested configuration, the continuous longitudinal offsets provide increased sectional rigidity which contributes to limit vertical deflections and resist crippling under loading conditions, and achieves a structural efficiency that is not achievable with a single piece structural element of similar thickness. These continuous longitudinal offsets are recessed into the plane of the deck portion to allow for nesting and fastening while maintaining a singe horizontal datum surface on which to apply stone pavers, tiles, or the like on a common datum surface and minimize rocking, splitting or cracking of stones or pavers due to an uneven surface or the projection of the fastener heads above the datum surface. The diaphragm may be manufactured at any length and at a width between from 12 inches to 48 inches with corresponding shelf sections at regularly spaced intervals of at least 12 inches, and preferably 16 inches.

[0026] Alternatively the structural metal diaphragm may comprise an integral longitudinal web portion, an integral deck portion, and integral ribs to stiffen the web and /or deck portions. The web portion is designed to primarily resist vertical bending longitudinally along the joist; whereas the deck portion and stiffeners are designed to primarily resist vertical bending between adjacent joists. The generally continuous structural metal diaphragm may be assembled from modular structural metal joists that are adapted for nested engagement with another adjacent joist using fastening means and overlapping longitudinal edges.

[0027] The modular structural diaphragm can be rapidly and securely placed in new construction or over an existing substructure to provide a generally continuous structural diaphragm to support architectural pavers. The continuous structural diaphragm may be fabricated at different material thicknesses, where the selection of material thickness and dimensions of the joist, are dependent on achieving minimum structural performance for static and dynamic loading, deflection, and flexural strength of the architectural pavements.

[0028] The modular structural diaphragm material may be selected from a flat-rolled steel having a thickness of between 0.030 and 0.138 inches with 0.056 to 0.080 inches preferred and coated to prevent or retard corrosion, such as with zinc, aluminum zinc or organic coatings. Preferably a zinc coating is applied using the hot dipped galvanized process. Galvanised zinc coating thickness may vary depending on location in use, but is generally within the range of 0.6-2.35 ounces per square foot applied (i.e.G60 to G235), (i.e.G60 to G235), and preferably 0.9 ounces per square foot, (i.e.G90). Where the modular structural diaphragm material is steel, it should have material yield strength from at least 33ksi, preferably at least 50ksi. The integral joist element and integral deck stiffeners may be designed for maximum section modulus at a given material thickness and material properties for steel to achieve design criteria for longitudinal deflection. In addition, there may be provided a plurality of web stiffeners at repeating individual or group intervals along the web portion of the joist to improve the structural performance of the joist and increase resistance to the web crippling.

[0029] The material thickness of each modular element remains constant to within normal production tolerances. The particular design of offsets, web portion, web ribs, the transverse ribs, and deck portion are designed to satisfy structural conditions due to static and dynamic loading in accordance with local building regulations, including the maximum vertical displacement across the particular element; and maximum permissible slopes, moments, stresses, and shear forces for the particular element. In addition, the layout of the web portion, ribs, and deck portion relative to each other may be designed to limit the maximum permissible span of any individual paver over any single element. The maximum displacement of any element is limited to at most L/360, and preferably L/480, where L is the length of the span of the particular element between supports.

[0030] The supporting substructure may be assembled using traditional methods from softwood with preservative treatments, or from alternative materials such as aluminium or steel (including hot rolled steel sections or sections cold formed from corrosion resistant flat rolled steel). The specific design and dimensions of the substructure are dependent on the loading characteristics of the deck application, but may comprise traditional dimensional treated lumber, I-beam, c-channel, or box sections.

[0031] In another aspect of the present invention, an underlayment may be positioned between the metal diaphragm and the pavers to assist with cushioning, and water drainage. The thin pavers may be either placed in a floating arrangement on top of the structural metal diaphragm with or without the underlayment, or adhered to the metal diaphragm with a suitable mortar or adhesive.

[0032] In a preferred embodiment of the present invention, floating architectural pavers in combination with the present invention should have a minimum weight of 15 pounds per square foot, a minimum flexural strength of 580 pounds per square inch ("psi) when tested per ASTM C-293, and minimum breaking force of 1125 pounds. Depending on the mass density of the pavers, such pavers with these attributes would have a minimum thickness of 1.25 inches per square foot for concrete pavers, and 1.00 inch per square foot for most dimension stone tiles.

[0033] As the thickness of the paver is decreased, then there is a requirement for increased flexural strength of the paver to prevent cracking and breaking, as well as the use in combination with adhesives or mortar to prevent wind uplift. The use of an underlayment or adhesive is based on the dimensions of the paver, paver weight per square foot, flexural strength of the paver to support loading and prevent cracking, and applicable building codes and regulations (including standards relating to wind uplift forces).

[0034] In a further embodiment a raised deck system utilizes pavers with integral "feet" allowing water to pass beneath without obstruction.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which: -

[0036] FIG. 1 is a three-dimensional rendering of a deck system with a modular structural diaphragm with integral joist, deck, and deck stiffener.

[0037] FIG. 2 is a section view of a deck system with a modular structural diaphragm with integral deck and deck stiffener, adapted to an existing wood substructure.

[0038] FIG. 3 is a section view rendering of a deck system with a modular structural diaphragm with integral joist, deck, and deck stiffener.

[0039] FIG. 4 is a section view rendering of a deck system with a modular structural diaphragm with integral joist, deck, and deck stiffener.

[0040] FIG. 5 is a section view rendering of a deck system with a modular structural diaphragm with integral joist, deck, and deck stiffener.

[0041] Figure 6 is a perspective view on an enlarged scale of the deck assembly shown in figures 1 to 5

[0042] Figure 7 is an end view on an enlarged scale of a deck assembly of figure 6,

[0043] Figure 8 is an enlarged view of figure 7 showing in greater detail the connection between adjacent joists

[0044] Figure 9 is a section on the line IX-IX of figure 6 [0045] Figure 10 is a plan view of the deck assembly of figure 6 on an enlarged scale.

[0046] Figure 11 is a side elevation of a stair assembly

[0047] Figure 12 is an enlarged view of a section of the stair assembly of figure 11,

[0048] Figure 13 is a side elevation of a stairway using the assembly of figure 11 ,

[0049] Figure 14 is a side elevation similar to figure 11 of an alternative embodiment of stair assembly.

[0050] Similar numerals refer to similar parts throughout the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] Turning now descriptively to the drawings, as can be seen in FIG. 1 to 5, a modular structural diaphragm 201 that functions as a joist comprises an integral longitudinal vertical web 202, an integral horizontal deck portion 203, and integral ribs 210 with weep holes 211 to allow drainage of accumulated water. The joist 201 is adapted for nested engagement with another adjacent joist 201 to which it is connected using a mechanical fastening means or equivalent 244. A plurality of modular structural diaphragms 201 therefore are assembled contiguously in the longitudinal direction to provide a deck assembly 200. Each of the joists 201 is positioned on top of structural beams 60 connected by fastening means 65 to structural posts 70 connected by fastening means 75 in a foundation system 80. The deck assembly 200 may support first a membrane or adhesive 90 upon which are positioned the pavers 100 in a floating or adhered pattern. The pavers 100 are laid over the deck assembly 200 to provide a tight, relatively high strength deck that is highly decorative and relatively impervious to the elements and wear. Edge restraints 110 around interlocking pavers are provided hold together the pavers and sand, enabling the system to remain interlocked.

[0052] As can be seen in FIG. 2, a modular structural diaphragm 10 with integral deck element 30 and integral ribs 40, adapted to an existing wood joist sub-structure 65, positioned on top of structural beams 60. In this embodiment, the web portion is truncated and incorporated in to a longitudinal offsets running along both edges of the joist. The integral rib 40 has weep holes 45 to allow drainage of accumulated water. The modular structural diaphragm is adapted for nested engagement with another adjacent modular element 10 and connected in a vertical fashion using a mechanical, adhesive fastening means or equivalent combination thereof 50 into the wood joist sub-structure 65. The structural diaphragm 10 may support first a membrane or adhesive 90 upon which are positioned the pavers 100 in a floating or adhered pattern to provide a tight, relatively high strength deck that is highly decorative and relatively impervious to the elements and wear. Edge restraints 110 around interlocking pavers are provided hold together the pavers and sand, enabling the system to remain interlocked.

[0053] In the embodiment of Figure 3, a vertical web portion is incorporated and the longitudinal offset is formed as a channel inset from the edge. In the embodiment of Figure 4, and underlayment is placed between the pavers and deck portion. In the embodiment of Figure 5, the distal edge is downturned to be parallel to the web portion and secured by fasteners in shear.

[0054] The modular structural diaphragm can be rapidly and securely placed in new construction or over an existing substructure to provide a generally continuous structural diaphragm to support architectural pavers. The continuous structural diaphragm may be fabricated at different material thicknesses, and with or without stiffeners in the transverse direction. The selection of material thickness, integral joist element, and transverse stiffener is dependent on achieving minimum structural performance for static and dynamic loading, deflection, and flexural strength of the architectural pavements.

[0055] The modular structural diaphragm material may be selected from a flat-rolled steel having a corrosion resistant coating, with a substrate thickness in the range from 0.030 to 0.138 inches, and material yield strength from at least 33ksi, and preferably 50ksi. The integral joist element 20 may be designed for maximum section modulus at a given material thickness and material properties for steel, to achieve design criteria for longitudinal deflection.

[0056] The arrangement of the structural diaphragm or joist 201 may best be seen in figures 6 to 12 in the context of a deck assembly and reference will therefore be made to the terminology conventionally used in such construction..

[0057] As can best be seen in figure 6 and 7, two different profiles of joists 201 are used in the deck assembly 200, a main joist indicated at 201a and an end joist indicated at 201b. Both joists 201 have a web portion 202 to extend generally vertically and a deck portion 203 that extends generally horizontally from the web portion 202 for engagement with an adjacent joist. Each of the web portions and deck portions has inwardly directed ribs, 210, formed at spaced intervals along the respective portions. Each of the ribs 210 extends laterally relative to the length of the joist 201 and generally has a part circular cross section, indicated at 212, as seen in figure 9, and a part spherical end section indicated at 214, as seen in figure 9. The ribs 210 thus merge smoothly with the generally planar deck portion and web portion whilst providing local stiffening. A drainage hole 211 is provided in each of the ribs 210 of the deck portion to prevent accumulation of water.

[0058] At the intersection of the deck portion 203 and web portion 202, the deck portion 203 is jogged inwardly to provide an offset shelf section 216 running along the length of the joist 201. The shelf section 216 is set below the upper surface of the deck portion 203 to provide support for the distal edge 218 of the deck portion 203 of an adjacent joist 201.

[0059] As can be seen in figure 8, the distal edge 218 of the deck portion 203 is itself jogged to provide an offset tail 220 along the distal edge 218. The offset of the shelf section 216 is greater than the offset of the tail 220 by the thickness of the material used in the deck portion 203, so that when the tail 220 rests on the shelf, the deck portions 203 of adjacent joists 10 are level with one another. The shelf section 216 is also wider than the tail 220 to accommodate relative adjustment between the joists 10, as described more fully below.

[0060] The lower edge of the web portion 202 terminates in a flange 230 that extends generally perpendicular to the web portion 202. In the case of the main joist 210a, the flange 230 extends outwardly, i.e. in the opposite direction to the deck portion 203, whereas in the end joist 201b, the flange 230 extends inwardly in the same direction as the deck portion 203. The flange 230 terminates in an upstanding return 232 to impart stiffness to the flange. Small holes may be located at intervals longitudinally along the flange 230 to provide for adequate drainage of accumulated or shedding water.

[0061] To assemble the joists 210 on the beams to form a deck assembly 200, an edge strip 234 is first secured to the beams at one side. The edge strip 234 has a vertical web 236 with a flange 238 at its lower edge and a ledge 240 at its upper edge. The spacing between the flange 238 and ledge 240 corresponds to the distance from the underside of the flange 230 to the underside of the tail 220 of a j oist 201. If a particulate material such as sand or gravel is to be placed on the deck assembly 200, the edge restraints may be integrally formed with edge strip 234 as an upstanding wall 242 beyond the ledge 240. This is integrally formed by folding the web 236 back on itself. Fasteners 244 are inserted through the flange 238 of the edge strip 234 in to the beams to hold the edge strip 234 in place. The fasteners 244 may be self piercing, or holes may be formed in the flange 238 at suitable increments to allow the fastener 244 to be inserted.

[0062] With the edge strip 234 in situ, a main joist 201 a is positioned with the tail 220 resting on the ledge 240. The tail 220 may be secured to the ledge 240 with fasteners 246 and the joist 201a is secured to the beam by further fasteners 244 passing through the flange 230. The out-turned flange 230 of the main joist 201a facilitates the insertion of the fasteners 244 as the flange 230 is exposed and allows the fasteners 244 to be easily inserted. It will also be appreciated that the offset of the tail 200 from the deck portion 203 allows the fasteners 246 used to secure it to the ledge 240 to be flush with or below the general level of the deck portion 203.

[0063] The next joist 201 is then positioned with its tail 220 resting on the shelf section 216 of the preceding joist 201. The wider shelf section 216 allows the tail 220 to be adjusted along the length of the joist to maintain the required alignment between the joists 10 and provides for flexibility of alignment and pitch during assembly of the joists 10 to accommodate variability and dimensional inaccuracies of structures in an as-built condition. Normally, such an alignment is parallel to one another, but in some circumstances the joists 10 may be farmed relative to each other to provide an arcuate surface in plan. With the joists positioned, fasteners 246 are inserted through the tail 220 and shelf section 216, and fasteners 244 inserted through the flange 230 in to the supporting beam.

[0064] Further main joists 1 Oa are connected side by side in a similar manner to complete the required extent of the deck assembly. At each connection, the tail 220 is supported on the shelf section 216 of the preceding joist and secured with fasteners 246.

[0065] At the opposite side of the deck assembly 200, an end joist 201b is used so that the flange 230 is directed inwardly relative to the deck portion 203 and a flush end face is maintained. Access to the interior of the flange 230 is available to place fasteners 244, or alternatively the fasteners may be inserted diagonally through the web portion 202 and flange 230. If a retaining edge is required, an angle piece 248 may be secured to the shelf section 216.

[0066] With the deck assembly 200 complete, the surface may be clad with the requisite covering. The deck assembly is formed from modular structural diaphragms that can be rapidly and securely placed in new construction or over an existing substructure to provide a generally continuous structural diaphragm to support a variety of coverings such as architectural pavers 100. The selection of material thickness, and other dimensions is dependent on achieving minimum structural performance for static and dynamic loading, deflection, and flexural strength of the architectural pavements.

[0067] The modular structural diaphragm material may be selected from a flat-rolled steel having a corrosion resistant coating. Where the modular structural diaphragm material is steel, it should have material yield strength from at least 33ksi, preferably at least 50ksi; and substrate thickness from at least 0.030 inches, preferably from 0.056 to 0.080 inches. The integral webs and integral ribs may be designed for maximum section modulus at a given material thickness and material properties for steel to achieve design criteria for longitudinal deflection.

[0068] The material thickness of each modular element remains constant to within normal production tolerances. The particular design of the joist, web stiffener, transverse stiffener, and deck element are selected to satisfy structural conditions due to static and dynamic loading in accordance with local building regulations, including the maximum vertical displacement across the particular element; and maximum permissible slopes, moments, stresses, and shear forces for the particular element. In addition, the layout of the joist, the transverse stiffener, and deck element relative to each other may be designed to limit the maximum permissible span of any individual paver over any single element. Typically, the maximum displacement of any element is limited to at most L/360, and preferably L/480, where L is the length of the span of the particular joist between supports.

[0069] Where individual pavers 100 are used, an underlayment 90 may be positioned between the metal diaphragm and the pavers to assist with cushioning, and water drainage. The thin pavers may be either placed in a floating arrangement on top of the structural metal diaphragm with or without the underlayment, or adhered to the metal diaphragm with a suitable mortar or adhesive.

[0070] In a preferred embodiment, floating architectural pavers 100 have a minimum weight of 15 pounds per square foot, a minimum flexural strength of 580 pounds per square inch ("psi) when tested per ASTM C-293, and minimum breaking force of 1125 pounds. Depending on the mass density of the pavers, such pavers with these attributes would have a minimum thickness of 1.25 inches per square foot for concrete pavers, and 1.00 inch per square foot for most dimension stone tiles.

[0071] As the thickness of the paver is decreased, then there is a requirement for increased flexural strength of the paver to prevent cracking and breaking, as well as the use in combination with adhesives or mortar to prevent wind uplift. The use of an underlayment or adhesive is based on the dimensions of the paver, paver weight per square foot, flexural strength of the paver to support loading and prevent cracking, and applicable building codes and regulations (including standards relating to wind uplift forces). If preferred, pavers with integral "feet" may be used to allow water to pass beneath without obstruction.

[0072] A suitable form of main joist 201a intended for residential installations and conforming to the Ontario Building Code has an overall height of the web portion 202 of 51/2 (5.5) inches and an overall width of the deck portion of 113/4 (11.75) inches. The flange 230 has a width of 1.9 inches. The shelf section 216 has a width of 15/8 (1.625) inches and that of the tail 220 9/16 inch. The ribs 210 in the deck portion have a length along the major access of the rib 210 of 7 inches, starting 2 inches from the intersection of the web portion and deck portion, and a minimum depth of Vi inch to provide a width of 1 inch. The ribs 210 in the web portion 202 are centred on the web portion and have a length of 4.5 inches and a minimum depth of 0.460 inches for a width of 0.92 inches. The ribs 210 repeat at intervals of three inches.

[0073] The material conforms to ASTM A653 and has a nominal substrate thickness of 0.056 inches. The offset of the shelf section from the main deck portion is !4 inch, and that of the tail 220 correspondingly reduced by the thickness of the material.

[0074] This configuration of joist 201 is sufficient to support a covering of pavers when placed on beams at eight foot centres.

[0075] More generally, the preferred dimensions provide for a continuous offset of the shelf section to provide a 0.25" recess beneath the common surface to accommodate most screw fastener heads. The shelf section is from 1 inch to 2 inches, preferably 1.625 inches. The tail 220 forming the free edge may be as large 1 inch to 2 inches, preferably 1 inch. In nested arrangement, the tail may be laterally adjusted up to 1 inch on each end of a mating shelf section of an adjacent joist to accommodate variations of dimensions of as-built structures. This avoids the tedious work of precisely fitting the joists 10 to conform with as- built structures, such as a perimeter wall. [0076] The configuration of joist 201 may also be adapted to provide stairs, as illustrated in figure 10 to 13. Traditional wood stairs in a straight configuration from one floor to the next requires around 280 saw cuts and can easily take a single highly skilled carpenter 4-6 hours to complete. Even existing prefab stairs require skilled trades to complete the installation of the pre-fabricated stair in the field.

[0077] In building a set of stairs, the homeowner has limited choices with respect to materials and dimensions. Prefabricated concrete stairs are limited in width, rise and run due to fixed tooling and manufacturing methods, and are susceptible to cracking during transport and installation. Prefabricated and site-built concrete stairs are expensive and are susceptible to spalling and wear from environmental factors. Prefabricated steel stairs are also expensive and limited in width, rise and run dimensions due to fixed tooling and manufacturing methods, and require specialised tools and skills to install.

[0078] As shown in figures 11 to 13, use of the joist arrangement provides a modular system that allows the stair system to be assembled quickly and easily. Referring to figures 10 to 12, a stair assembly 300 is formed from a series of joists 301, connected to one another. The profile of each joist 301 is similar to that of the deck assembly 200 described above, with a web portion 302 and a deck or tread portion 303. The tread portion 303 has a shelf structure 316 formed at the intersection of the web portion 302 and tread portion 303 and a tail 320 on the distal edge 318. Ribs 310 are formed in each of the web portion and tread portion having a similar configuration to those used in the joists 10. A flange 330 is inturned, as in the end joist 201b.

[0079] As best seen in figure 12, the tail 320 has an upturned flange 321 that extends at right angles to the tail 320 along the length of the joists 301. The flange 321 serves as an attachment surface to connect adjacent joists 301 in stepped manner.

[0080] As can be seen in figure 10, the flange 321 of the lower joist 301 is connected to the lower edge of the web portion 302 by fasteners 344. The vertical face of the flange 321 provides for connection of the two joists while at the same time permitting limited vertical adjustment of the exposed face of the web portion 302 to determine the rise of the steps preferably from between 5.5 to 7.5 inches. Similar connections are made with successive joists until the required number of treads is obtained. Thereafter, as shown in figure 13, the stair assembly is fastened via side plates 350 to stringers, 352 and surfaces finishes 354 can be attached to the tread portions 303. The stringers may be made of a material and dimensions suitable for the structural performance desired such as with wood or metal , and are preferably made from cold formed steel tubing that has cross section dimensions of 2 inches by 6 inches and is 0.080 inches thick and coated to prevent or retard corrosion, such as with zinc, aluminum zinc or organic coatings. Preferably a zinc coating is applied using the hot dipped galvanized process. Galvanised zinc coating thickness may vary depending on location in use, but is generally within the range of 0.6-2.35 ounces per square foot applied (i.e.G60 to G235), and preferably 0.6 ounces per square foot, (i.e.G60).

[0081] The joists 301 are preferably made from cold formed steel having a thickness of between 0.040 and .0138 inches with .056 to .080 inches preferred and coated to prevent or retard corrosion, such as with zinc, aluminum zinc or organic coatings. Preferably a zinc coating is applied using the hot dipped galvanized process. Galvanised zinc coating thickness may vary depending on location in use, but is generally within the range of 0.6-2.35 ounces per square foot applied (i.e.G60 to G235), (i.e.G60 to G235), and preferably 0.9 ounces per square foot, (i.e.G90).

[0082] This stair assembly 300 is secured using galvanized steel brackets and fasteners to at least two stair stringers preferably made from galvanized steel tube with dimensions 2 inches by 6 inches by length. The number of stair stringers required is dependent on loading conditions to be satisfied and the width selection of the stairs. The actual spacing between stringers is variable, but is preferably between 30-48 inches apart. The bracket may be made from galvanized steel in standard C-sections known and available in the art preferably with dimensions of 2 inches by 4 inches and is 0.080 inches thick .

[0083] The ribs 310 provide increased structure and stability to the stair assembly, depending on loading conditions. The ribs are generally semi circular in cross section for improved rigidity and are formed contiguously into the web portion 302 to increase the resistance to deflections, web crippling strength of the section and increase the lateral- torsional strength. The ribs 310 also provides a means to balance material flow between the first web and the lateral ribbing of the deck or tread portion during manufacturing to control acceptable flatness and camber of the deck or tread portion and straightness of the first web.

[0084] The continuous longitudinal shelf sections 316 and 320 are recessed into the plane of the tread portion to allow for fastening to brackets while maintaining a singe horizontal datum surface on which to apply stone pavers, tiles, or the like on a common datum surface and minimize rocking, splitting or cracking of stones or pavers due to an uneven surface or the projection of the fastener heads above the datum surface.

[0085] The shelf section also provides increased sectional rigidity which contributes to limit vertical deflections and resist crippling under loading conditions, and achieves a structural efficiency that is not achievable with a single piece structural element of similar thickness.

[0086] An alternative arrangement is shown in figure 14 where the web portion 302 is extended and formed without the flange 310. Knockouts are generally provided in the web portion to allow adjustability without interference with the stringers. The vertical adjustability is therefore increased whilst still providing attachment surfaces between the adjacent joists.

[0087] To achieve a stair with a enhanced variable run capability, the joist 301 may be manufactured without the vertical flange 301 and the tail 320 increased. Multiple joists may be combined to achieve a large run dimension in the stair tread.The tail 320 provides for lateral adjustment to accommodate variability and dimensional inaccuracies of structures in an as-built condition. This arrangement also allows for variable pitch nesting to create a curved stair surface.

[0088] It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.

Claims

What we claim is:-

1. A joist for assembly with like joists to provide a deck assembly, said joist having a web portion and a deck portion extending orthogonally from the web portion and defining a generally planar surface, said deck portion having a shelf section formed by an offset at the intersection of the web portion and deck portion to lie below the general planar surface of the deck portion, an offset at a distal edge of the deck portion to provide a tail, said offsets being relatively dimensioned such that when a tail of one joist is supported on the shelf section of an adjacent joist, the deck portions lie in a common plane.

2. A joist assembly according to claim 1 wherein ribs are formed in at least one of the web portion and deck portion and extend laterally relative to the longitudinal axis of the joist.

3. A joist assembly according to claim 2 wherein ribs are formed in each of said web portion and deck portion.

4. A joist assembly according to claim 2 or 3 wherein said ribs are recessed from said generally planar surface.

5. A joist assembly according to claim 4 wherein said ribs are part circular in cross section.

6. A joist according to any preceding claim wherein said shelf section is wider than the tail to facilitate adjustment of one joist relative to another.

7. A joist according to any preceding claim wherein a flange is formed at the free edge of the web portion and extends orthogonal to the web portion.

8. A joist according to claim 7 wherein said flange extends in a direction opposite to said deck portion.

9. A joist according to claim 8 wherein said flange extends in the same direction as said deck portion.

10. A joist according to any one of claims 7 to 9 wherein said flange terminates in a return extending generally perpendicular to the flange to impart stiffness thereto.

11. A deck assembly having a plurality of joists extending side by side and connected to one another, each of said joists having a web portion and a deck portion extending orthogonally from the web portion and defining a generally planar surface, said deck portion having a shelf section formed by an offset at the intersection of the web portion and deck portion to lie below the general planar surface of the deck portion, an offset at a distal edge of the deck portion to provide a tail, said joists being connected to one another by placing a tail of one joist over a shelf section of another, said offsets being relatively dimensioned such that when a tail of one joist is supported on the shelf section of an adjacent joist, the deck portions lie in a common plane.

12. A joist assembly according to claim 11 wherein ribs are formed in at least one of the web portion and deck portion and extend laterally relative to the longitudinal axis of the joist.

13. A joist assembly according to claim 12 wherein ribs are formed in each of said web portion and deck portion.

14. A joist assembly according to claim 12 or 13 wherein said ribs are recessed from said generally planar surface.

15. A joist assembly according to claim 14 wherein said ribs are part circular in cross section.

16. A joist according to any one of claims 11 to 15 wherein said shelf section is wider than the tail to facilitate adjustment of one joist relative to another.

17. A joist according to any one of claims 11 to 16 wherein a flange is formed at the free edge of the web portion and extends orthogonal to the web portion.

18. A joist according to claim 17 wherein said flange extends in a direction opposite to said deck portion.

19. A joist according to claim 18 wherein said flange extends in the same direction as said deck portion.

20. A joist according to any one of claims 17 to 19 wherein said flange terminates in a return extending generally perpendicular to the flange to impart stiffness thereto.

21. A stair assembly having a plurality of joists connected edge to edge in stepped array, each of said joists having a web portion and a deck portion extending orthogonally from the web portion and defining a generally planar surface, said deck portion having a shelf section formed by an offset at the intersection of the web portion and deck portion to lie below the general planar surface of the deck portion, and an offset at a distal edge of the deck portion to provide a tail, a web portion of one of said joists being connected to a tail of one another of said joists to connect said joists in a stepped array.

22. A stair assembly according to claim 21 wherein a flange is formed on said tail to project above said tail and said web portion is connected to said flange.

23. A stair assembly according to claim 22 wherein ribs are formed in at least one of said web portions and said deck portions to increase stiffness thereof.