Mesh roof facing system

A roofing system includes a strong nonmetallic mesh fabric placed loosely over an array of purlins, and secured fast at the periphery of the roof. The fabric, which serves to support roof insulation between the purlins, also has sufficient strength to protect workers laying the insulation, or roofing panels over the insulation, as well as those on the ground below, in case of an accident.

BACKGROUND OF THE INVENTION 
This invention relates to building construction, and particularly to a mesh 
roof system for buildings, especially metal buildings with insulated 
roofs. 
Expanded metal, metal screen, and other types of mesh have been proposed 
previously for use in constructing walls and ceilings of buildings. In 
some cases, such as in U.S. Pat. No. 4,522,004, cementitious material or 
plaster is applied over the mesh. Mesh has also been used to support or 
retain insulating material, an in U.S. Pat. No. 2,148,281. 
In U.S. Pat. No. 3,506,746, a net supported by poles serves as a support 
for receiving plaster of the like, which hardens to form a structure in 
which door, windows and the like are subsequently cut. U.S. Pat. No. 
545,301 describes a method of constructing an arched roof by applying 
concrete or cement to a corrugated wire mesh supported by structural 
beams. 
U.S. Pat. No. 4,557,092 describes an insulating blanket having a strong 
scrim layer attached to its fiber barrier, to resist falling objects. It 
has been found difficult, however, to create joints of sufficient strength 
in such material to prevent heavy objects from falling through. 
Finally, flexible materials have been used to support ceiling insulation in 
a dropped ceiling construction, as shown in U.S. Pat. No. 3,791,089. 
None of the above patents adequately addresses the problem of worker 
safety; nor does the known prior art provide a simple, durable and 
attractive way of retaining glass fiber blanket insulation on the roof of 
a metal building. We re-address safety and structural considerations with 
this invention, and simultaneously provide aesthetic and functional 
advantages over prior roof insulation retention methods. 
We are particularly concerned with construction worker safety. 
Unfortunately, injuries occur from time to time during roof construction, 
either to workmen who fall from the roof, or those below, from dropped 
objects. It is therefore standard and required practice to provide safety 
netting or other sheet material below roof installers to protect them and 
those below, and/or to require workers to be tied or tethered to the 
structure. 
Dropped tools are a another problem; the safety netting designed to catch 
falling workmen is generally of a sufficiently large mesh (e.g., six inch 
mesh) to allow small tools, bolts, fasteners, and other construction 
materials to pass through. Conventional practice is to deploy a separate, 
smaller mesh debris net below the safety netting, to catch such articles. 
Furthermore, required safety practices are sometimes violated. For example, 
if a required tether is not applied, or while it is being moved, the 
workman and those below him are at risk. It would be better to have a 
restraint that could not be avoided, and did not require a positive action 
to be effective. That is, a restraint analogous to an automobile air bag 
is preferred over one analogous to a seat belt, since the former cannot be 
avoided. 
We have found that a very simple, attractive and durable insulated roof can 
be constructed with a strong mesh fabric that reduces the likelihood and 
severity of construction accidents resulting from falling objects, and 
also forms a permanent part of the roof. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide an improved mesh roof facing 
system comprising a plurality of transverse beams, an array of spaced, 
parallel purlins each extending orthogonal to the beams, and a plurality 
of roof panels laid across and supported by the purlins. The improvement 
comprises a nonmetallic mesh extending over and supported by a plurality 
of the purlins, beneath the roof panels. Insulating material is preferably 
included as well, supported from below by the mesh, between the mesh and 
the roof panels. The purlins may be Z-channel metal members, bar joists, 
trusses (see FIG. 6), or wooden joists. 
It is particularly preferred that the mesh be strong enough, when secured 
over the purlins, to support a substantial weight dropped upon it between 
purlins, and that the mesh be applied loosely, so that it sags 
substantially between the purlins, to improved its loading capability and 
to provide room under the roofing panels for a substantial thickness of 
insulation.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
As shown in FIGS. 1 and 2, a building embodying the invention has a frame 
10 composed of plural pairs of vertical structural members 12, each pair 
of members being interconnected at their upper ends by a transverse 
structural beam 14. The transverse beams support an array of parallel 
purlins 16, each extending orthogonal to the transverse beams along the 
length of the building. The purlins are equally spaced, for example at 
five foot intervals. As shown in FIG. 3, the purlins may be Z-section 
members formed from sheet metal. Their exposed ends at either end of the 
building are capped by gable angles 18. Eave struts 20 are provided at the 
edges of the roof, each extending parallel to the purlins; the eaves are 
preferably C section members whose open sides face toward the center of 
the roof. 
FIGS. 2 and 3 show a mesh material 30 laid loosely across the roof, 
directly over the purlins. By "loosely", we mean that, when loaded with 
insulation, the fabric forms throughs having a depth of about six inches 
to one foot, depending on the thickness of the insulation, below the level 
of the purlins. The mesh supports a blanket of insulation 32, preferably 
glass fiber batting. Finally, metal roof panels 34 are laid over the 
insulation, transverse to the length of the purlins. 
The preferred mesh material is an open polyester scrim mesh interwoven to 
form a half-inch square grid, coated with a fire retardant polyvinyl 
chloride binder. The mesh should be of sufficient strength to withstand 
the weight of a 200-300 pound man from a height of three feet above the 
plane of the purlins. A mesh material weighing 2.6 ounces per square yard, 
and meeting the strength requirements of the preceding sentence, is 
available from Bay Mills Limited, Ontario, Canada, in rolls seven to ten 
feet wide; it is identified by Bay Mills as "Bayex Product QX-2220/V". For 
standard buildings bays, thirty feet wide (the distance between beams), 
several widths of the material are spliced together edgewise with plastic 
tie straps, stitching, or other fasteners chosen to provide an 
edge-to-edge fastening strength as great as that of the material itself, 
to prevent joint failure. The edges of the material, as received from the 
manufacturer, are reinforced by a selvedge 31 (FIG. 4). The free end of 
the material is reinforced by a beaded fabric tape 33 sewn over the end, 
and newly exposed raw ends may be similarly reinforced in the field, 
optionally with reinforcing rope at the selvedge if desired. 
The mesh is sandwiched at its leading and trailing edges between a 
respective one of the eave struts and a steel strap 38 having a slight 
dihedral angle, as shown in FIG. 3. The strap is drawn against the 
structural member by self-drilling or self-tapping screws 40 applied at 
one-foot intervals. The lateral edges of the material strip may be secured 
to the gable angle in the same manner, or by plastic ties 42 (FIG. 5) 
extending through holes in the angle 18 at intervals. 
In use, a thirty-foot wide roll 36 of mesh material, previously spliced 
from narrower rolls of material, if necessary, is positioned to one side 
of the building, with its axis parallel to the purlins, as shown in FIG. 
6. The leading edge of the material is then pulled up, over the respective 
eave strut, and across the purlins. The mesh is maintained relatively taut 
transverse to its width (i.e., along the length of the purlins), but is 
installed loosely along its own length, to form six-inch to one-foot 
troughs as mentioned above. The leading edge of the material is secured to 
the far eave strut by straps and screws as described previously. The 
lateral edges of the material are similarly affixed to the gable angle or 
transverse beam beneath, and the trailing edge is affixed to the near eave 
strut. The remaining roll material is severed, and the roll is moved a 
distance equal its width along the building, where the covering process is 
repeated. Once the entire roof has been covered with mesh, insulation is 
laid on the mesh and both are then covered with the metal roof panels. 
During these latter operations, the secured, strong mesh provides 
significant safety to workers on and below the roof. 
The added worker safety is obtained at minimal cost, since the same fabric 
that provides protection during construction also supports the insulation, 
and becomes a permanent part of the building. Since it remains in position 
for the life of the roof, it may serve to protect people from falling 
through skylights or other openings in the roof; furthermore, it protects 
the insulation layer from tears. Additionally, we have found that the mesh 
is virtually invisible against the background of glass fiber blanket 
insulation, and thus provides an innocuous support for the insulation, 
resulting in an attractive interior surface. 
While particular advantages result when the mesh is used to retain blanket 
insulation, the safety advantages are provided even with a rigid board 
insulation, such as "Thermax" (trademark of Celotex Corporation) or Butler 
Manufacturing's "CMR-24" insulation, or plywood, or even when no 
insulation at all is installed over the mesh. 
The invention of course does not protect workers from falling off the edge 
of the building, and is not represented to replace currently OSHA-approved 
devices and procedures for protecting personnel from falls, even at the 
center of the building, although it doubtless will improve safety. 
The foregoing description illustrates only one mode--the best now 
contemplated--of practicing the invention. Many changes can be made to 
details without departing from the gist of the invention claimed below. 
For example, the metal roof covering panels could be replaced by plastic, 
wood, or other panels; for this reason, we refer to the panels only as 
"weatherproof" in the claims. Also, insulating materials other than glass 
fiber blanket may prove useful. And the members referred to above as 
"purlins" could be any functionally equivalent members, including wooden 
joists, or truss-type members such as Butler Manufacturing's "Delta 
Joist". "Purlins" in the following claims is intended to cover all such 
variations. 
Another contemplated variation of the invention (see FIG. 7) is to provide 
a steel deck 50, supported by the purlins 16 on which the mesh 30 has 
previously been laid. The decking may subsequently be covered by rigid 
insulating board 52, and then topped with a weatherproof coating of felts 
54 and bitumen. 
Inasmuch as the invention is subject to these and other modifications and 
variations, it is intended that the foregoing description and the 
accompanying drawings shall be interpreted as illustrative of only one 
form of the invention, whose scope is to be measured by the following 
claims.