Patent Application
20090056240
This invention relates to a sliding roof seam construction to accommodate differential expansion of adjacent metal panels.
A typical metal roof construction includes an array of metal purlins laid across structural beams. The purlins and beams are referred to below as the “substructure” of the roof. Most purlins have a “C” or “Z” cross-section with upper and lower flanges at either edge of a central web. “Z”-shaped members are popular because they have the advantage of being nestable. The roof substructure supports an array of interlocked metal roof panels, often with a layer of insulation beneath the panels. The roof panels are laid perpendicularly across the purlins so that, on a ridge roof, the panels extend from the ridge to the eave. Normally, the panels are fixed to the eave, and are supported in a way that lets them expand and contract lengthwise, yet prevents them from being lifted off the purlins by high winds. Widthwise expansion is not normally a problem, because the panels are typically corrugated; however, lengthwise expansion cycles can be considerable, inasmuch as ambient temperatures vary annually by as much as 100° F. The upper extreme is augmented by solar heating, which causes the to roof expand and contract considerably, even at constant ambient temperature, as the sun rises, sets and is hidden by clouds. For these reasons, roof panels must be connected to the substructure in a way that permits the panels to move considerably in the lengthwise direction. Usually the panels are fixed to the substructure at the eaves, and are permitted to expand toward the roof ridge, where their ends are covered loosely by a cap.
In a standard warehouse-style building with a rectangular footprint, the panels are all the same length, and as the panels are laid, their overlapped edges are tightly folded over to form a weather-proof structure. Various specialized roof seaming machines exist for this purpose. Panels of equal length expand and contract in unison as thermal variations occur.
When a roof has an inside corner, however, panels of one length are laid adjacent panels of a substantially different length, extending from eaves at different distances from the ridge. Such a roof is illustrated in
An object of the present invention is to allow a construction in which adjacent roof panels of different lengths, or having offset anchoring eaves or different coefficients of thermal expansion, can be securely held on the roof without seaming the overlapping edges those panels.
This object is achieved by a sliding roof seam construction as described below.
In the accompanying drawings,
A portion of a roof seam embodying the invention is illustrated in
In the drawings, portions of two roof panels 10 and 10′ of different lengths are shown secured to respective eaves E1, E2 (
As
The expansion bracket assembly 30, best seen in
Two slots 50, 52 (
To stabilize the bracket assembly for ease of handling, a nylon centering pin 60 is inserted at the factory through aligned holes which are formed, respectively, as the center of each of the elements.
During installation, an expansion bracket assembly is placed across each of the purlins with the bottom flange of the center element overlapping the top flange of the purlin. A fastener such as a self-drilling and self-tapping screw is driven through the overlapped flanges to secure the assembly to the purlin. The nylon centering pin, which prevents the wing brackets from shifting about during installation need not be removed by the installer. It shears off after installation, when thermal effects shift the roof panels with respect to one another.
Once the expansion bracket assemblies 30 have been installed along the shear line, the roof panels are placed on the roof, with their complementary edges 26, 28 overlapped in the usual way to form a seam. All roof joints except those along the shear line are folded together to form seams. Those on the shear line are left undeformed so that relative sliding movement can occur.
To connect the roof panels to the bracket, suitable fasteners 62 are driven through the raised side portions of the roof panels and the oblique webs of the wing brackets, where they overlap. The fasteners may be self-drilling, self-tapping screws. The screws are tightened sufficiently to prevent any movement between the panels and the underlying brackets.
If left unsealed, the joint along the shear line might provide a site for entry of cold air, rain water, dust or insects. To prevent leakage and to keep foreign material out of the joint, a cover 70 is installed over the undeformed joint. The cover includes a flexible seal 72, for example a silicone membrane, which is secured to the respective side portions of the roof panels by a continuous adhesive sealant strip 74 (
Details of the elements of the invention may vary. For example, the choice of materials, metal gauges, and the exact location and nature of the fasteners and pins which interconnect the various parts are a matter of design choice. Also, the invention might be used to compensate for differential expansion in a construction where panels made of different materials were laid side-by-side. Since the invention is subject to modifications and variations, it is intended that the foregoing description and the accompanying drawings shall be interpreted as only illustrative of the invention defined by the following claims.
