Patent Publication Number: US-9890590-B2

Title: Building roof safety assembly having a barrier and ladder restraint

Description:
FIELD 
     This disclosure relates to roof safety assemblies, and more particularly, to a safety assembly for placement on a building roof to prevent workers from falling from that roof and to prevent tipping of ladders used by those workers to access that roof. 
     BACKGROUND 
     Workers working on building roofs risk serious injury or even death in the event of a fall from that roof or in the event of tipping of a ladder used to access that roof. As such, many jurisdictions impose workplace safety rules to govern conditions for accessing and working on roofs. For example, in Ontario, Canada, regulations enacted under the Occupational Health and Safety Act require guard rails to be installed on a building roof, if the building roof does not have a parapet of sufficient height to prevent workers from falling off. Those regulations also require the use of devices to secure the top ends of ladders used for roof access, to prevent falls caused by accidental tipping of those ladders. Similar requirements exist in other jurisdictions. 
     Various ways of erecting guard rails on roofs are known. For example, guard rails may be erected using support posts bolted or otherwise securely planted into roofs. It is also known to erect guard rails using support posts that are each attached to a heavy weight. However, while guard rails protect workers from falls while they are on a roof, they do nothing to protect workers from falls while they are ascending or descending on ladders used to access that roof. Thus, any ladder used to access that roof must be separately secured, as required by safety regulations. 
     Accordingly, there is a need for improved roof safety apparatuses. 
     SUMMARY 
     According to an aspect of the present disclosure, there is provided a safety assembly for placement on a roof of a building, near an edge of the roof. The safety assembly includes a ladder restraint having an opening to receive a ladder that provides access to the roof. The opening is sized to restrict left and right sideways movement of the ladder when received therethrough. The safety assembly also includes an upstanding barrier that extends on left and right sides of the ladder restraint to block falls by a user. The safety assembly also includes a counterweight interconnected with the ladder restraint and the upstanding barrier and disposed to prevent forward tipping of the upstanding barrier by the user, and to prevent sideways tipping of the ladder during use by the user, when the safety assembly is placed on the roof and the ladder is received through the ladder restraint. 
     According to another aspect of the present disclosure, there is provided a method of providing access to a roof of a building. The method includes providing a ladder restraint attached to a counterweight, the ladder restraint having an opening to receive a ladder for accessing the roof, the opening sized to restrict left and right sideways movement of the ladder when received therethrough; receiving the ladder through the ladder restraint; and counteracting lateral forces on the ladder during use by a user, by way of the counterweight, to prevent the forces from tipping the ladder. 
     According to yet another aspect of the present disclosure, there is provided a kit for assembling a roof safety assembly, to be placed on a roof of a building near its edge. The kit includes a ladder restraint having an opening for receiving a ladder, the opening sized to restrict left and right sideways movement of the ladder when the ladder is received through the opening; a barrier to block falls by a user; and a counterweight, for interconnection with the barrier and the ladder restraint, that prevents forward tipping of the barrier by the user when the counterweight is interconnected with the barrier, and prevents sideways tipping of the ladder during use by the user, when the counterweight is interconnected with the ladder restraint and the ladder is received through the ladder restraint. 
     Other features will become apparent from the drawings in conjunction with the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the figures which illustrate example embodiments, 
         FIG. 1  is a rear perspective view of a roof safety assembly, exemplary of an embodiment; 
         FIG. 2  is a front elevation view of the roof safety assembly of  FIG. 1 ; 
         FIG. 3  is a rear perspective view of a fitting used to interconnect guard rail members of the roof safety assembly of  FIG. 1 ; 
         FIG. 4  is a rear perspective view of another fitting used to interconnect guard rail members of the roof safety assembly of  FIG. 1 ; 
         FIG. 5  is a rear perspective view of a fitting used to mount a ladder restraint of the roof safety assembly of  FIG. 1 ; 
         FIGS. 6A, 6B, 6C and 6D  are each front elevation views of a ladder restraint of the roof safety assembly of  FIG. 1 , exemplary of four embodiments, respectively; 
         FIG. 7  is a right elevation view of the roof safety assembly of  FIG. 1 ; 
         FIG. 8  is a top plan view of the roof safety assembly of  FIG. 1 ; 
         FIG. 9  is a top plan view of the roof safety assembly of  FIG. 1  with its weighted elements exposed; 
         FIG. 10  is a is a rear perspective view of a roof safety assembly, exemplary of another embodiment; 
         FIG. 11  is a is a rear perspective view of a roof safety assembly, exemplary of yet another embodiment; 
         FIG. 12  is a rear perspective view of the roof safety assembly of  FIG. 1  during operation; and 
         FIG. 13  is a right elevation view of the roof safety assembly of  FIG. 1  during operation. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  depicts a roof safety assembly  10 , exemplary of an embodiment. As will become apparent, roof safety assembly  10 , when placed on a substantially flat or gently sloping building roof near an edge of that roof, protects workers from falls from that roof, and also protects workers from falls caused by accidental tipping of a ladder used to access that roof. As such, roof safety assembly  10  may be placed on building roofs that otherwise lack fall protection features or require existing safety features to be supplemented, to protect workers who work on and access those roofs. 
     Roof safety assembly  10  includes a ladder restraint  12  having an opening  14  for receiving a ladder. A ladder received through opening  14  is secured from accidental tipping, as detailed below. Roof safety assembly  10  also includes upstanding barriers  16 A and  16 B for blocking falls by a worker. Barriers  16 A and  16 B are erected to extend on either side of ladder restraint  12 , along at least one edge of roof safety assembly  10 . Roof safety assembly  10  also includes base  18  that supports roof safety assembly  10  on a roof, and provides a flat working surface. As will be detailed below, base  18  includes a counterweight that both prevents a worker from tipping barriers  16 A and  16 B towards a roof edge, and prevents sideways tipping of a ladder secured by ladder restraint  12  while a worker uses that ladder. 
     As noted, roof safety assembly  10  includes upstanding barriers  16 A and  16 B to block falls, e.g., by a worker on base  18 . As such, upstanding barriers  16 A and  16 B are fixedly mounted to base  18 , and are sized to extend along one side of base  18  at a height sufficient to block passage of a worker. The height of each of barriers  16 A and  16 B in the depicted embodiment is approximately 3½ feet. However, as will be appreciated, this height may be changed in other embodiments to suit particular roof setting and/or suit particular safety requirements, which may vary from jurisdiction to jurisdiction. 
     In the depicted embodiment, barriers  16 A and  16 B each take the form of guard rails. However, in other embodiments, one or both of barriers  16 A and  16 B may be replaced with fences, walls, or any combination of fences, walls, rails, or the like, suitable to block passage of a worker. 
     As depicted in  FIG. 2 , barrier  16 A includes a top horizontal rail member  20 A and a mid horizontal rail member  22 A that extend along the length of barrier  16 A. Horizontal rail members  20 A and  22 A are attached to posts  24 A,  26 A and  28 A using a plurality of 90-degree cross-over fittings  40  (e.g., as shown in  FIG. 3 ). Barrier  16 A extends from an end proximate ladder restraint  12  to an opposite end terminated by a left-handed D-return formed by attaching vertical rail member  30 A to horizontal rail members  20 A and  22 A using two 90-degree elbow fittings  42  (e.g., as shown in  FIG. 4 ). Each of posts  24 A,  26 A, and  28 A are respectively attached to base  18  using three socketed flanges  46 . 
     Barrier  16 B extends on the side of ladder restraint  12  opposite barrier  16 A. In the depicted embodiment, barrier  16 B is symmetrical to barrier  16 A about a vertical plane that bisects ladder restraint  12 . Similar to barrier  16 A, barrier  16 B includes a top horizontal rail member  20 B and a mid horizontal rail member  22 B that extend along the length of barrier  16 B. Horizontal rail members  20 B and  22 B are attached to posts  24 B,  26 B and  28 B using a plurality of 90-degree cross-over fittings  40 . 
     The end of barrier  16 B opposite ladder restraint  12  is terminated by a right-handed D-return formed by attaching vertical rail member  30 B to horizontal rail members  20 B and  22 B using two 90-degree elbow fittings  42 . 
     In the depicted embodiment, each of the rail members and posts of barriers  16 A and  16 B are substantially cylindrical in shape. In other embodiments, these rail members and/or posts could have other shapes providing structural strength sufficient to meet safety requirements. 
     As best seen in  FIG. 3 , a 90-degree cross-over fitting  40  includes two hollow cylindrical portions  50  and  52 , oriented at right angles to each other. Cylindrical portion  50  has an inner diameter complementary to the diameter of horizontal rail member  20 A/B and  22 A/B, while cylindrical portion  52  has an inner diameter complementary to the diameter of posts  24 A/B,  26 A/B and  28 A/B. By way of example,  FIG. 3  illustrates the use of a 90-degree cross-over fitting  40  to attach horizontal rail member  20 A to post  28 A. As depicted, horizontal rail member  20 A is inserted through cylindrical portion  50  and fastened therein using a grub screw  54 . Meanwhile, post  28 A is inserted through cylindrical portion  52  and fastened therein using another grub screw  54 . 
     Each grub screw  54  may be a conventional grub screw, and may be formed from case-hardened steel or a like material. Each grub screw  54  includes a socket such as, for example, a hexagon socket to permit tightening/loosening by a conventional hexagonal key. 
     The use of 90-degree cross-over fitting  40  elsewhere in roof safety assembly  10  follows the example shown in  FIG. 3 , and is not further detailed herein. 
     As best seen in  FIG. 4 , a 90-degree elbow fitting  40  includes two socketed portions  56  and  58 , oriented at right angles to each other. Socketed portion  58  has an inner socket diameter complementary to the diameter of vertical rail members  30 A/B, while socketed portion  56  has an inner socket diameter complementary to the diameter of horizontal rail member  20 A/B and  22 A/B. By way of example,  FIG. 4  illustrates the use of a 90-degree elbow fitting  40  to attach horizontal rail member  20 A to vertical rail member  30 A. As depicted, horizontal rail member  20 A is inserted into socketed portion  56  and fastened therein using a grub screw  54 , while vertical rail member  30 A is inserted into socketed portion  58  and fastened therein using another grub screw  54 . 
     The use of 90-degree elbow fitting  40  elsewhere in roof safety assembly  10  follows the example shown in  FIG. 4  and is not further detailed herein. 
     Upstanding barriers  16 A and  16 B are spaced to provide a gap therebetween to allow ingress/egress by a worker using a ladder positioned proximate to that gap, and to mount ladder restraint  12  for securing that ladder. As such, barriers  16 A and  16 B are spaced to provide a gap of sufficient width to allow a worker to step off the ladder received in ladder restraint  12  on to base  18 , and to allow a worker to climb on to on to the ladder from base  18 . In the depicted embodiment, the gap between barriers  16 A and  16 B is approximately 5 feet in width, but this width may be adjusted in other embodiments to suit particular roof settings and particular safety requirements. 
     Further, in the depicted embodiment, ladder restraint  12  is mounted centrally between barriers  16 A and  16 B such that a worker may ingress/egress from either the left side or the right side of a ladder received in ladder restraint  12 . Conveniently, workers may elect to ingress/egress from one side or the other based on their handedness. In other embodiments, ladder restraint  12  may be mounted to be next to barrier  16 A or  16 B, and thus allow workers to ingress/egress on only one side (i.e., the left side or the right side) of a ladder received in ladder restraint  12 . 
     As depicted, the gap between  16 A and  16 B is bridged by a horizontal bar  32  for mounting ladder restraint  12 . In the depicted embodiment, horizontal bar  32  is substantially cylindrical in shape. Horizontal bar  32  is attached to post  24 A of barrier  16 A and to post  24 B of barrier  16 B using two 90-degree cross-over fittings  40 , in a manner similar to that shown in  FIG. 3 . 
     In some embodiments, horizontal bar  32  may be mounted at a height that allows a ladder to be rested against bar  32  without contacting the edge of a roof, the edge of roof parapet, and/or roof fixtures such as, e.g., an eavestrough. Conveniently, this prevents those edge and/or fixtures from being damaged by a ladder rested thereagainst, or otherwise makes contact therewith. Similarly, resting a ladder against roof features that would not provide stable support for a ladder, such as, e.g., curved edges or canted edges of roofs or parapets may be avoided. In other embodiments, horizontal bar  32  may be mounted at a height that allows a ladder received in ladder restraint  12  to be rested on the edge of a roof or roof parapet. 
     Ladder restraint  12  of roof safety assembly  10  is used to secure a ladder used to access a building roof. Ladder restraint  12  is shaped to define an opening  14  for receiving a ladder, with opening  14  sized to secure a ladder received therethrough. In particular, opening  14  is sized to restrict left and right sideways movement of a ladder received therethrough. Ladder restraint  12  may, for example, comprise two parallel posts spaced to provide opening  14 . In some embodiments, ladder restraint  12  may be shaped to encircle a ladder at least partially, to prevent the ladder from tipping backwards out of opening  14 . Ladder restraint  12  may also be shaped to encircle a ladder completely, e.g., ladder restraint  12  may be U-shaped or hoop-shaped, or the like. In the depicted embodiment, ladder restraint  12  is shown to be formed from separate components, but ladder restraint  12  could also be formed as a unitary body in other embodiments. 
     As depicted in  FIG. 6A , ladder restraint  12  is formed using posts  34 A and  34 B and bar  36 , each of which is substantially cylindrical in shape. Specifically, ladder restraint  12  is formed by attaching bar  36  to posts  34 A and  34 B using two 90-degree elbow fittings  42 , in a manner similar to that shown in  FIG. 4 . 
     Ladder restraint  12  is mounted to horizontal bar  32  by attaching posts  34 A and  34 B to horizontal bar  32  using respective tee fittings  44 . As best seen in  FIG. 5 , a tee fitting  40  includes a hollow cylindrical portion  60  oriented at a right angle to socketed portion  62 . Cylindrical portion  60  has an inner diameter complementary to the diameter of horizontal bar  32 , while socketed portion  62  has an inner socket diameter complementary to the diameter of posts  34 A/B. As depicted, horizontal bar  32  is inserted through cylindrical portion  60  and fastened therein using a grub screw  54 , while post  34 A is inserted into socketed portion  62  and fastened therein using another grub screw  54 . The opposite end of horizontal bar  32  is secured to post  34 B using another tee fitting  40 , in a similar manner. 
     Once ladder restraint  12  is mounted, posts  34 A/B, bar  36  and bar  32  define opening  14  for receiving a ladder therethrough. As such, post  34 A and  34 B are spaced far enough apart to make opening  14  wide enough to receive a ladder. At the same time, posts  34 A and  34 B are spaced close enough together to restrict left and right sideways movement of that ladder when it is received through opening  14 . In the depicted embodiment, posts  34 A and  34 B are spaced to make opening  14  approximately 21 inches wide. However, in other embodiments, posts  34 A and  34 B may be spaced closer together or farther apart to accommodate ladders of different widths, and may vary according to regulations governing the width of ladders used in particular jurisdictions. 
     As will be appreciated, when a ladder is received through opening  14  of ladder restraint  12 , bar  36  that extends along the top of opening  14  serves to prevent the ladder from tipping backwards out of opening  14 . 
       FIG. 6B  depicts ladder restraint  112 , according to an embodiment in which bar  36  of ladder restraint  12  is omitted. Such an embodiment may be suitable for use in settings where backwards tipping of a ladder is not a concern. Omitting bar  36  allows a ladder to be lowered into the opening of the ladder restraint from above the ladder restraint. This facilitates ready placement of a ladder into the opening of the ladder restraint, even in settings where view of the opening from the ground is partly or fully occluded, e.g., by obstructions below a roof parapet. In such embodiments, the two 90-degree elbow fittings  42  used to attach posts  34 A and  34 B to bar  36  may be replaced with plugs  38  to terminate the top ends of posts  34 A and  34 B. 
       FIG. 6C  depicts ladder restraint  212 , according to a yet another embodiment. Like ladder restraint  112  ( FIG. 6B ), ladder restraint  212  does not include bar  36  of ladder restraint  12 . However, as depicted, ladder restraint  212  includes a bar  37  that extends between posts  34 A and  34 B. Bar  37  is mounted to posts  34 A and  34 B using respective tee fittings  44  at a height that allows a ladder to be rested against bar  37  without contacting the edge of a roof, the edge of roof parapet, roof fixtures that might be damaged such as, e.g., eavestroughs, and/or roof features that would not provide stable support for a ladder such as, e.g., curved edges or canted edges. As will be appreciated, bar  37  is mounted at a height sufficiently below the top ends of posts  34 A and  34 B to allow a ladder to be securely retained between posts  34 A and  34 B. 
       FIG. 6D  depicts ladder restraint  312 , according to yet another embodiment. As depicted, ladder restraint  312  includes both bar  37 , which provides a support against which a ladder may be rested, and bar  36 , which prevents the ladder from tipping backwards out of ladder restraint  312 . 
     As best seen in  FIG. 7 , ladder restraint  12  is mounted on horizontal bar  32  to extend away from barriers  16 A/B, such that, when roof safety assembly  10  is placed on a roof near an edge of that roof, ladder restraint  12  extends in a direction towards that edge. Further, ladder restraint  12  is mounted on horizontal bar  32  at an angle offset from upstanding barriers  16 A/B. In the depicted embodiment, this angle is approximately 45°. In other embodiments, ladder restraint  12  may be mounted on horizontal bar  32  with this angle at 0°, i.e., such that ladder restraint  12  is parallel to upstanding barriers  16 A/B. In yet other embodiments, this angle may be between 0° and 90°, and may be selected to accommodate roofs of different heights, as well as roof parapets of different heights and widths. Mounting ladder restraint  12  at such an angle facilitates ready insertion of a ladder through opening  14  of ladder restraint  12  during operation. 
     In some embodiments, ladder restraint  12  may be mounted directly to base  18 , such that horizontal bar  32  may be omitted. 
     The bottom end of each of posts  24 A/B,  26 A/B, and  28 A/B is inserted into a corresponding socketed flange  46  to attach the posts to base  18 . The posts are secured to socketed flanges  46 , e.g., using grub screws. Socketed flanges  46  are in turn secured to elongate support members  64 A/B,  66 A/B, and  68 A/B of base  18  ( FIG. 8 ), e.g., also using grub screws. As depicted, in this way, each of posts  24 A/B,  26 A/B, and  28 A/B is attached to a corresponding one of elongate support members  64 A/B,  66 A/B and  68 A/B. The bottom end of each socked flanges  46  includes a spread plate  48  for distributing the weight of roof safety assembly  10 , including the weight of barriers  16 A and  16 B, over an area of a roof under the spread plate  48 , when roof safety assembly  10  is placed on that roof. Conveniently, use of spread plates  48  helps to prevent the roof from being damaged by point loads. In the depicted embodiment, spread plate  48  is a rectangular plate approximately 6″×12″ in size. However, in other embodiments, the size and shape of spread plate  48  may be changed. 
     Together, barriers  16 A and  16 B and the gap therebetween span the length of base  18 , with the D-returns at the far ends of barriers  16 A and  16 B extending slightly past the right and left edges of base  18 . In the depicted embodiment, the total span of barrier  16 A and  16 B and the gap therebetween is approximately 20 feet. However, the span of barriers  16 A/ 16 B may be increased by extending horizontal bars  20 A/B and  22 A/B. Further, additional posts alike to posts  24 A/B- 28 A/B may be added to support the extended horizontal bars. Conversely, the span of barriers  16 A/B may be decreased by shortening horizontal bars  20 A/B and  22 A/B, and removing one or more of posts  24 A/B- 28 A/B as necessary. The heights of each of barriers  16 A and  16 B may be changed in other embodiments by increasing or decreasing the lengths of post  24 A/B- 28 A/B. 
     Each of the rails members and post forming barriers  16 A/B, each of the bars and posts forming ladder restraint  12 , as well as horizontal mounting bar  36 , may be hollow tubing or solid bars formed from metal such as iron, steel, aluminum, or the like. These components may be formed by casting. For resistance to rusting, components formed from stainless steel, aluminum or galvanized metal may be used. In some embodiments, these components may be made from high-stiffness plastics such as, for example, fiberglass-reinforced plastic. Such plastic components may be formed from conventional, molding or extrusion/pultrusion processes. Some or all of these components may be sized to have a diameter/width suitable for gripping, e.g., approximately 1-2 inches. 
     Fittings and flanges of roof safety assembly  10 , described above, may be formed from materials similar to the rail members, bars and posts, such as, for example, cast iron or cast aluminum, or any other suitable alloy or stiff plastic. 
     Although grub screws are used to interconnect components of roof safety assembly  10  in the depicted embodiment, other ways to fasten these components may be used in other embodiments. For example, components (e.g., a rail member and a fitting) may be fastened together using bolts, rivets, pins, etc. In some embodiments, rail members may be fastened to fittings by way of crimping. In yet other embodiments, rail members may fastened to other rail members directly (e.g., by welding) such that some or all of the fittings may be avoided. Yet other suitable ways to interconnect components of roof safety assembly  10  will be readily apparent to those skilled in the art. 
     Further, although barrier  16 A and  16 B are terminated by respective D-returns in the depicted embodiment, in other embodiments, one or both of barriers  16 A and  16 B may simply be terminated by plugs inserted into the ends of horizontal rail members  20 A/B and  22 A/B. In yet other embodiments, one or both of barriers  16 A and  16 B may be terminated by flanges suitable for affixing barrier  16 A/ 16 B to a wall. 
     As noted, roof safety assembly  10  includes base  18  to support roof safety assembly  10  on a roof and to provide a flat working surface. Further, base  18  includes a counterweight that prevents upstanding barriers  16 A/ 16 B from being tipped towards a roof edge by a worker, and also prevents sideways tipping of a ladder received in ladder restraint  12  while a worker is using the ladder. To this end, base  18  includes a plurality of weighted elements that have sufficient mass and that are positioned to provide this counterweight, as detailed below. 
     Base  18  includes a plurality of elongate support members  64 A/B,  66 A/B, and  68 A/B, which extend from barriers  16 A/ 16 B towards the back of roof safety assembly  10 . Collectively, elongate support members  64 A/B,  66 A/B, and  68 A/B serve to support roof safety assembly  10  on a roof surface. 
     As depicted in  FIGS. 1 and 8 , the top surface of base  18  is covered with four panels  70  and a panel  72 . Panels  70  and  72  are substantially rectangular in shape and rest in between elongate support members  64 A/B,  66 A/B, and  68 A/B on recessed support rails extending along those elongate support members, as detailed below. Panels  70  and  72  and elongate support members  64 A/B,  66 A/B, and  68 A/B collectively form a substantially flat working surface, on which workers can walk. 
     Panels  70  and  72  may be formed from stiff plastic, such as, for example, fiberglass-reinforced plastic, formed from conventional molding or extrusion/pultrusion processes. As depicted, panels  70  and  72  may be perforated to form a grating. This reduces the weight of panels  70  and  72 , facilitates water and snow run-off, and may improve traction. Conveniently, snow that falls through the grating may rest directly on the roof instead of accumulating on roof safety assembly  100 . This may reduce localized loading of the roof by roof safety assembly  100 , e.g., at spreader plates  48 . In some embodiments, panels  70  and  72  may be formed from materials adapted to prevent slipping. In some embodiments, panels  70  and  72  may be formed from UV-protected materials adapted to prevent UV degradation. In the depicted embodiment, panels  70  and  72  are approximately 1 inch thick. In other embodiments, the thickness of panels  70  and  72  be increased or decreased. In some embodiments, panels  70  and  72  may, for example, be Fibergrate™ molded plastic grating distributed by Fibergrate Canada of Ontario, Canada. 
       FIG. 9  depicts roof safety assembly  10  with panels  70  and  72  removed. Removal of  70  and  72  exposes the aforementioned support rails extending along elongate support members  64 A/B,  66 A/B, and  68 A/B, namely, support rails  74  which extend along right side of each of the support members and support rails  76  which extend along the left side of the support members. Support rails  74  and  76  are recessed from the top surface of support members  64 A/B,  66 A/B, and  68 A/B at a depth corresponding to the thickness of panels  70  and  72  (e.g., 1 or more inches), and extend along substantially the entire length of elongate support members  64 A/B,  66 A/B, and  68 A/B. 
       FIG. 9  also depicts four weighted elements  78  and a weighted element  80  disposed at the rear of base  18 . Weighted elements  78  and  80  are substantially rectangular in shape, and are sized to fit between support members  64 A/B,  66 A/B, and  68 A/B, where they are supported by support rails  74  and  76 . In some embodiments, weighted elements  78  and  80  may be securely fastened to support rails  74  and  76  and/or support members  64 A/B,  66 A/B, and  68 A/B. 
     Weighted elements  78  and  80  are formed from material substantially heavier than panels  70  and  72 . In the depicted embodiment, each of weighted elements  78  and  80  is formed from metal plates. Collectively, weighted elements  78  and  80  form a counterweight that serves to prevent tipping of upstanding barriers  16 A/ 16 B towards a roof edge by a worker. As will be appreciated, the tipping point of upstanding barriers  16 A/ 16 B is located at their base, along the forward edge of roof safety assembly  10 . Thus, forming a counterweight at the rear of roof safety assembly  10  at a set distance from this tipping point creates a load moment that is proportional to this distance and the mass of the counterweight, which counteracts loads created by tipping of upstanding barriers  16 A/ 16 B by a worker. Conveniently, weighted elements  78  and  80  also serve to prevent tipping of a ladder away from a roof when that ladder is received in ladder restraint  12 . 
     At the same time, the counterweight formed from weighted elements  78  and  80  also serves counteract lateral forces on a ladder to prevent sideways tipping of the ladder while a worker is using it, e.g., as caused by weight or movement of a worker on the ladder, slipping of the ladder along a building edge or parapet, unstable or uneven ladder footing, improper placement of a ladder against a building wall, wind, etc. In this situation, the tipping point is located at ladder restraint  12 . Thus, forming a counterweight having portions located laterally away from ladder restraint  12  to its left and right sides creates load moments that are proportional to the left/right lateral distance between ladder restraint  12  and those portions of the counterweight. This counteracts loads created by left or right sideways tipping of a ladder secured in ladder restraint  12 . 
     Conveniently, providing a counterweight as shown allows roof safety assembly  10  to be installed on a roof by merely placing roof safety assembly  10  on the roof. As such, there is no need to drill into or otherwise penetrate the roof, which may breach the roof&#39;s waterproofing membrane or otherwise damage the roof. 
     Further, forming a counterweight that extends along substantially the entire length of roof safety assembly  10 , as depicted, serves to distribute the downward load of the counterweight over a larger roof area. This reduces localized loads on the roof, which may be desirable if the roof is not designed to support loads substantially beyond normal snow loads. 
     Although the depicted embodiment includes a counterweight formed from metal plates, other suitable weighted elements may also be used. For example, the weighted elements need not be formed from metal, but may be formed from other materials, such as concrete, stone, ceramic, sand, rubber, plastic, or the like, or combinations thereof. In some embodiments, the weighted elements may be formed from recycled materials, such as, e.g., recycled rubber, plastic, or the like. Yet other materials having density suitable for forming weighted elements will be readily apparent to those skilled in the art. Further, the number of weighted elements could vary, so long as the total mass of the weighted elements is sufficient to serve as a counterweight, as described above. 
     This total mass of the weighted elements may be varied to suit particular roof settings and particular safety requirements, and may also be varied based on the distance of the counterweight to the above-discussed tipping points. In the depicted embodiment, the four weighted elements  78  and weighted element  80  have a combined mass of approximately 115 kg. 
     Of course, the total mass of weighted elements  78  and  80  should be selected taking into account the mass of other components of roof safety assembly  10  which may also function as part of the counterweight, such as, for example, panels  70  and  72 , and elongate support members  64 A/B,  66 A/B, and  68 A/B. 
       FIG. 10  depicts roof safety assembly  100 , according to another embodiment, with base  18  replaced with base  118 . As depicted, in this embodiment, the top surface of base  118  is partly covered with four panels  92  and a panel  94 . Unlike panels  70  and  72  of base  18 , panels  92  and  94  of base  118  do not extend from barriers  16 A/ 16 B all the way to the back edge of the base. Rather, panels  92  and  94  terminate near the back of base  118  where panels  92  and  94  meet a row of weighted elements  90 . Panels  92  and  94  may be alike to panels  70  and  72  in other aspects, e.g., panels  92  and  94  may be formed from the same materials as panels  70  and  72 , as discussed above. 
     Like weighted elements  78  and  80  of roof safety assembly  10 , weighted elements  90  are supported by support rails  74  and  76 . Weighted elements  90  are also supported by additional support members (not shown) which extend perpendicularly to support rails  74  and  76  underneath weighted elements  90  and are attached to elongate support members  64 A/B,  66 A/B, and  68 A/B. 
     Unlike weighted elements  78  and  80  of roof safety assembly  10 , weighted elements  90  are not covered by panels. Rather, weighted elements  90  are coplanar with panels  92  and  94 ; weight elements  90  and panels  92 / 94  collectively form a substantially planar working surface, on which workers can walk. As such, weighted elements  90  have a substantially flat top surface and are adapted to support workers thereon. Further, weighted elements  90  are formed from material substantially heavier than panels  92  and  94 . In the depicted embodiment, each weighted element  90  is a concrete paving slab. In other embodiments, these concrete paving slabs may be replaced with other suitable weighted elements. 
     Further, unlike weighted elements  78  and  80  of roof safety assembly  10 , which are contained in the space within base  18  below panels  70  and  72 , weighted elements  90  of roof safety assembly  100  extend to the top surface of base  118 . As such, weighted elements  90  of roof safety assembly  100  can be larger, and therefore more massive than weighted elements  78  and  80  of roof safety assembly  10 . In the depicted embodiment, each of the concrete paving slabs used as a weighted element  90  has a mass of approximately 20 kg. Accordingly, the combined mass of the eleven concrete paving slabs of roof safety assembly  100  is approximately 220 kg, which is approximately twice the total mass of the weighted elements of roof safety assembly  10 . 
     As will be appreciated, weighted elements  90  of roof safety assembly  100  form a counterweight that functions in substantially the same manner as the counterweight discussed above for roof safety assembly  10 . As before, the counterweight formed from weighted elements  90  is located at a distance behind barriers  16 A/ 16 B and ladder restraint  12 , and thereby prevents tipping of barriers  16 A/ 16 B off of a roof and tipping of a ladder secured in ladder restraint  12  away from the roof. Further, as before, this counterweight extends laterally to the left and right of ladder restraint, and thereby prevents left and right sideways tipping of a ladder secured in ladder restraint  12 . 
       FIG. 11  depicts roof safety assembly  200 , according to a further embodiment, with base  18 / 118  replaced with base  218 . As depicted, in this embodiment, the top surface of base  218  is substantially covered with weighted elements  90 , arranged to form a substantially planar working surface, on which workers can walk. As such, the panels of safety assemblies  10  and  100  may be omitted. 
     As in roof safety assembly  100 , weighted elements  90  of roof safety assembly  200  are supported by support rails  74  and  76 . They are also supported by additional support members (not shown) which extend perpendicularly to support rails  74  and  76  underneath weighted elements  90  and are attached to elongate support members  64 A/B,  66 A/B, and  68 A/B. 
     In the depicted embodiment, each weighted elements  90  of roof safety assembly  200  is a concrete paving slab, having a mass of approximately 20 kg. The combined mass of weighted elements  90  of roof safety assembly  200  is therefore approximately 660 kg. As such, roof safety assembly  200  may be used in situations calling for additional counterweight. 
     In yet other embodiments, elongate support members  64 A/B,  66 A/B, and  68 A/B may, by themselves, have sufficient mass to form the counterweight described above. To this end, elongate support members  64 A/B,  66 A/B, and  68 A/B may be made formed from or include any of the materials described above for forming weighted elements. In such embodiments, no additional weighted elements are required. 
       FIGS. 12 and 13  depict roof safety assembly  10  in operation. As depicted, roof safety assembly  10  is assembled on roof  300  of a building near an edge  302  to protect falls by a worker working on or accessing roof  300 . In particular, base  18  is placed on roof  300 , and ladder restraint  12  and barriers  16 A/B are attached to base  18 . As depicted, barriers  16 A/B extend substantially parallel to edge  302  on left and right sides of ladder restraint  12 . As worker  500  moves on top of base  18 , the counterweight of base  18  prevents worker  500  from tipping barriers  16 A/B off roof  300 . Thus, roof safety assembly  100  protects worker  500  from falling off of roof  300 . 
     Further, as depicted, a portable ladder  400  is used to access roof  300 . Ladder  400  is received through opening  14  of ladder restraint  12 . Meanwhile, ladder  400  is erected to rest against the building at edge  302 , at an angle of approximately 75° from vertical in accordance with conventional safety practices. With ladder  400  received through opening  14 , the counterweight of base  18  prevents ladder  400  from tipping while worker  500  is using it. In this way, roof safety assembly  100  protects worker  500  from falling when using ladder  400  to access roof  300 . 
     Conveniently, ladder restraint  12  may be adapted in the field to suit particular roof and roof parapet configurations. For example, the position of ladder restraint  12  may be adjusted up or down by changing the height at which horizontal bar  32  is attached to posts  34 A and  34 B. Further, the angle at which ladder restraint  12  is offset from upstanding barriers  16 A/B may be adjusted by changing the angle at which tee fittings  44  are secured to horizontal mounting bar  32 . The position and the angle of ladder restraint  12  may be adjusted to allow ladder restraint  12  to receive a ladder, while accommodating roofs of different heights, as well as roof parapets of different heights and widths. Furthermore, the height of horizontal bar  32  may be adjusted in the field such that a ladder may be rested against it. Similarly, ladder restraint  12  could be modified in the field to include a bar  37  ( FIGS. 6C / 6 D) mounted to posts  34 A and  34 B at a height to allow a ladder to be rested against bar  37 . In these ways, a ladder received in ladder restraint  12  may be offset from a roof edge, a parapet edge, roof fixtures, and/or a roof features, as desired. 
     Conveniently, embodiments of the roof safety assembly described herein allow portable ladders such as, e.g., a conventional extension ladder, to be used to access a roof, even when safety regulations require the tops ends of ladders to be secured prior to use. Accordingly, certain drawbacks associated with installation of permanent ladders may be avoided, such as, for example, vulnerability of permanent ladders to vandalism or weather damage, and the risk of unauthorized access to roofs. Further, use of portable ladders leaned at an angle, as provided herein, also avoids the need to comply with government safety regulations that specifically govern the use of vertical ladders. 
     Conveniently, the modular design of embodiments of the roof safety assembly facilitates ready transport of components to and from building roofs, and assembly and disassembly in situ. As such, embodiments of the roof safety assembly may be distributed in the form of kits, with components of the roof safety assembly unassembled or partially assembled. Such kits may be assembled on a roof of a building to provide a roof safety assembly for use in manners described herein. 
     Of course, the above described embodiments are intended to be illustrative only and in no way limiting. The described embodiments are susceptible to many modifications of form, arrangement of parts, details and order of operation. The invention, rather, is intended to encompass all such modification within its scope, as defined by the claims.