Lap joint roof assembly

A lap joint structure for adjoining panels of a sheet metal roofing assembly permits shifting of the joint panels longitudinally and transversely with respect to the joint as caused by thermally induced expansion and contraction, as well as providing a securely anchored connection of the panels to the roof substrate. Two adjacent panels are rigidly connected to one another, an underlying cleat is rigidly connected to the roof substrate, and the two joined panels are securely connected to the cleat with clearance allowed for thermally induced movements of the panels across the substrate.

The present invention pertains to the art of sheet metal roofing 
assemblies, and particularly to the structure of a lap joint between 
adjoining sheet metal roofing panels. 
BACKGROUND OF THE INVENTION 
Sheet metal panels are commonly used as components of commercial roofing 
structures. An assembly of sheet metal panels is fastened together to form 
a generally flat cover over a roof substrate which may comprise a 
framework of wood or metal joists, a plywood surface supported on an 
underlying framework of joists, poured concrete, or the like. Various 
types of joints are used to fasten the panels into a strong and watertight 
cover assembly. Standing seam joints comprise a folded connection between 
adjacent panels which extends vertically upwardly from the panels along 
the length of the joint. A novel standing seam joint structure is the 
subject of another patent application of the present inventor. This 
application pertains to a lap joint which has a primarily horizontal 
configuration across the joined panels. 
A common lap joint structure is that used to assemble the traditional flat 
lock roof. A flat lock roof panel has edge sections folded back over the 
main section of the panel to form hemmed edges. The hems are left slightly 
open to permit hooked engagement with the oppositely facing hem of an 
adjacent panel to form a joint defined by the overlapping hem sections. 
The joints are soldered to provide a watertight seal. Although used 
consistently for many years, this type of joint structure has several 
problems. For example, the engaged hem sections, when considered in cross 
section, comprise four layers of sheet metal material which must be 
thoroughly heated from above to create conditions wherein the molten 
solder will be drawn into the joint sufficiently to provide a reliable 
watertight seal. The soldering portion of the assembly process is thus 
time consuming and skillfully demanding. Soldering problems also arise 
where the sheet metal panels are nailed or otherwise fastened to the 
underlying substrate since those punctures through the sheet metal 
material must be sealed against water. Furthermore, sealing the joints 
with solder results in a rigid connection between adjoining panels which 
cannot yield to the strenuous forces induced by thermal expansion and 
contraction and which may in turn cause buckling of the sheet metal 
material or breakage of the soldered seal. 
Another disadvantage of the traditional flat lock roof joint structure is 
the difficulty of assembling the panels in an orderly layout along planned 
lines without accumulating substantial deviations between successively 
joined edges. This problem is best overcome by assembling a staggered 
array of panels having a practical size limit of 20.times.28 inches. As 
the number of joints multiplies with the number of panels, construction of 
a flat lock roof of any substantial size can become a disproportionately 
demanding portion of a commercial construction project. 
Another type of lap joint structure for a sheet metal roofing assembly may 
be referred to as a flat lock joint with cleats. Such a joint comprises a 
row of cleats extending along the length of the joint. The cleats are each 
nailed or otherwise securely anchored to the roof substrate and include 
cleat hems interposed between the interlocking hem sections of the sheet 
metal panels to hold the panels down against the roof substrate. Since the 
panels are not nailed directly to the underlying substrate but instead are 
anchored thereto by means of the cleat, this joint structure is superior 
to the above-described flat lock joint structure which is prone to leak 
where the anchoring nails perforate the sheet metal panels. However, the 
overlapping hem sections must still be soldered, and positioning of the 
cleat hems between the interlocking panel hems brings the number of sheet 
metal layers which must be thoroughly heated to a total of six. The skill, 
time, and consequent cost of providing a water tight soldered seal along 
the entire length of the joint are thereby greatly increased. Furthermore, 
the panels and cleats are rigidly interconnected through the joint 
structure and cannot yield to the stress imposed by thermal expansion and 
contraction of the sheet metal material. 
A third type of lap joint structure for a sheet metal roofing assembly 
consists merely of overlapping panel edges riveted and soldered together. 
Although this is the strongest type of joint, it, too, suffers from 
several disadvantages. A simple overlap between panel edges does not 
accommodate the use of cleats to anchor the panel assembly to the roof 
substrate, whereby the panels must be anchored by means of nails or other 
fasteners perforating the panels. Nails not only present an unsightly 
appearance with frequent damage from hammer blows to the surrounding sheet 
metal material, but also cause imperfect perforations which are difficult 
to seal with solder, and their use may be prohibitively labor intensive on 
a large project. Sheet metal screws are likely to be used more commonly 
than nails since they may be quickly and easily inserted by means of an 
automatic driving tool. However, the drilling action of the automatic tool 
tends to shred the sheet metal material to raise a burr at each 
perforation which both disrupts the level contour of the panels and 
increases the difficulty of sealing the perforation with solder. Again, 
the rigidly anchored assembly cannot accommodate thermally induced 
movement of the panels. 
Methods of constructing known joints for sheet metal roofing assemblies are 
correspondingly troublesome. Great difficulty is experienced in 
maintaining adjacent sheets in alignment with a planned layout. 
The prior art is thus seen to fail to provide a joint structure for a sheet 
metal roofing assembly which can easily be soldered without a great deal 
of time and skill, which accommodates thermally induced movement of the 
sheet metal panels, and which can be securely anchored to the roof 
substrate without unsightly and leak-prone perforations through the 
panels. 
SUMMARY OF THE INVENTION 
The present invention overcomes the above-described disadvantages and 
others and provides a lap joint structure for a sheet metal roofing 
assembly which securely anchors the sheet metal panels to the roof 
substrate with provision for thermally induced movements of the panels and 
without leaks, as well as an efficient and simplified method of installing 
the joint structure. 
In accordance with a principal feature of the invention, there is provided 
an elongated joint structure for a roofing assembly covering a roof 
substrate, the joint structure comprising cleat means extending 
longitudinally along the joint structure to define first and second 
transverse directions across the joint. The cleat means has cleat hook 
means and is rigidly anchored to the roof substrate. A first panel is 
provided with a first edge extending along the joint structure, a first 
major section extending from the first edge in the first transverse 
direction across the joint, and panel hook means associated with the first 
edge. The panel hook means is engaged with the cleat hook means to 
restrain the first panel from movement away from the cleat means in the 
first transverse direction across the joint. A second panel is provided 
with a cover section overlying the cleat hook means and engaged panel hook 
means, a second major section extending from the cover section in the 
second transverse direction from the joint, and an attachment section 
extending from the cover section in the first transverse direction. The 
attachment section of the second panel is rigidly attached to the first 
major section of the first panel. In this arrangement, the first and 
second panels are rigidly attached to one another and are securely 
anchored to the roof substrate through the cleat. In advantageous 
distinction to the prior art, the panels are not rigidly anchored to the 
roof substrate, either directly or through the cleat. A slight amount of 
clearance where the panel hook means engages the cleat hook means thereby 
permits a slight amount of transverse movement of the joined panels 
together across the cleat. The invention thus accommodates thermally 
induced strains in the roofing assembly. 
In accordance with a more specific feature of the invention, a joint 
structure as defined above is provided wherein the attachment section of 
the second panel has a second edge overlying the first major section of 
the first panel, with those sections being soldered together. Only two 
layers of panel material must be heated to create conditions wherein the 
molten solder will be drawn inwardly between the panel sections being 
soldered. An additional specific feature in this respect is the provision 
of means for blocking the flow of liquid solder in the first transverse 
direction away from the second edge of the second panel in order to 
maintain control of the molten solder and to provide a neat finished 
appearance. The preferred means for blocking the flow of liquid solder 
away from the soldered edge is a raised rib in the first panel extending 
parallel to and closely spaced from the second edge of the second panel. 
Further regarding soldering of the first and second panels, the panels may 
advantageously be composed of Terne Coated Stainless Steel, a product of 
Follansbee Steel Corporation, assignee of the present patent application. 
Terne Coated Stainless Steel bears a surface layer of solder material 
which melts appropriately upon heating to eliminate the necessity of 
externally applied solder and the labor and material costs associated 
therewith. 
In accordance with another specific feature of the invention, in addition 
to the provision of solder to attach the panels and to seal the joint, pop 
rivets are provided to rigidly connect the major section of the first 
panel to the overlying attachment section of the second panel. Pop rivets 
will securely connect the panel sections without anchoring them to the 
roof substrate. As discussed above, the connected panels are anchored to 
the roof substrate through the cleat in a manner to permit thermally 
induced movement of the connected panels transversely across the joint and 
the substrate. 
Yet another specific feature of the invention provides the cleat means in 
the form of an elongated sheet metal cleat extending longitudinally in the 
direction of the joint. This advantageously facilitates installation of 
the joint in a straight line without the need for precise and skillful 
alignment of a plurality of individual cleats spaced along the joint line. 
In accordance with another principal feature of the invention, there is 
provided a method of constructing an elongated joint between panel 
components of a roofing assembly covering a roof substrate. The method 
comprises the steps of providing components including a first panel having 
panel hook means defining a longitudinal direction and first and second 
opposing transverse directions with respect to the joint when the first 
panel is in a first assembled position; a cleat adapted to be rigidly 
anchored to the roof substrate and having cleat hook means for engagement 
with the panel hook means to restrain the first panel from movement from 
the cleat in the first transverse direction; and a second panel having an 
attachment section. The first panel is placed in the first assembled 
position, the cleat hook means are engaged with the panel hook means, and 
the cleat is rigidly anchored to the roof substrate. The second panel is 
placed in a second assembled position overlying the cleat with the 
attachment section thereof overlying the first panel, and the attachment 
section is then rigidly attached to the first panel. This results in a 
joint which includes a rigid connection between the panels, a rigid 
anchored connection between the cleat and the roof substrate, and a secure 
attachment of the panels to the substrate through the cleat which is 
transversely shiftable across the joint and substrate in response to 
thermally induced stresses in the panel material. 
In accordance with a specific feature of the method, the panels in the 
assembled positions are first releasably anchored to the roof substrate at 
a base anchoring point to hold the panels steady against longitudinal or 
transverse movement out of position. The panels are then more easily 
rigidly attached together in the proper alignment. The releasable 
anchoring step is preferred to comprise the specific steps of punching a 
hole into the substrate through the overlapping panel sections and 
inserting a releasable locator pin into the hole. A second hole may be 
punched to provide a supplemental releasable anchoring point, preferably 
at a position longitudinally spaced along the joint from the base 
anchoring point, for insertion of a supplemental releasable locator pin. 
This would restrain the panels from horizontal rotation about the locator 
pin in the base anchoring hole and would thereby more completely hold the 
panels in aligned positions. Rigid connection of the overlapped panel 
sections by means of pop rivets and sealing of the joint with solder would 
then follow with subsequent removal of the releasable locator pins and 
sealing of the respective locator holes with solder. 
Specific features of the method pertain to the riveting step. Use of a 
punching tool to drive the holes in which the pop rivets are inserted 
provides an indentation in the sheet metal panels to effectively 
countersink the pop rivets and avoid a disruptive burr in the material as 
caused by prior art screw threading methods. Importantly, setting of the 
pop rivets in a countersunk manner contributes to pooling of the solder 
thereafter applied to seal the punctures. 
The principal object of the present invention is to provide a lap joint 
structure for adjoining sheet metal roofing panels which can accommodate 
thermally induced expansion and contraction of the panels while securely 
anchoring the panels to the roof substrate along planned lines. 
Another object of the invention is to provide a securely sealed joint 
structure for adjoining sheet metal roofing panels which can be 
efficiently and easily installed without a great deal of expertise. 
A further object of the invention is to provide a method of constructing a 
joint between adjoining sheet metal roofing panels which is more effective 
and less skillfully demanding than prior methods. 
Yet another object of the present invention is to provide a lap joint for a 
sheet metal roofing assembly and a method of constructing the joint which 
enables the use of the elongated adjacent panels extending in planned 
lines from the eave to the ridge of the roof assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings wherein the showings are for the purpose of 
illustrating a preferred embodiment of the invention and not for the 
purpose of limiting the invention, in FIGS. 1 and 2 there is shown a roof 
assembly R covering a wooden roof substrate S and including a joint 
structure J in accordance with the invention. The roof assembly R 
comprises adjacent elongated panels P extending from the eave 12 to the 
ridge 14, with an adjacent pair of panels, such as panels 16 and 18 shown 
in FIG. 2, being joined by the joint structure J. The joint structure J is 
likewise elongated to extend longitudinally between the joined panels 16 
and 18 and to define transverse right and left hand directions r and 1 
thereacross. More specifically, the joint structure J comprises a right 
hand or first panel 16, a left hand or second panel 18, and a cleat 20. 
The first panel 16 includes a major portion 22 and a hook or hem section 
24. The hem section 24 includes a first free edge 26 and is folded back 
over the major portion 22 to define a folded terminal edge 28 and an open 
hem pocket 30. A first attachment section 32 of the major portion 22 is 
defined adjacent the open hem pocket 30. 
The cleat 20 is preferred to comprise an elongated component extending 
longitudinally in the direction of the joint structure J and is formed 
into substantially parallel sections including a base section 34, an 
intermediate section 36, and a hook section 38 arranged with respect to 
the intermediate section 36 to define an open cleat pocket 40. A cleat 
space 41 is defined between the free edge 42 of the hook section 38 and 
the base section 34 as shown in FIG. 2. The cleat 20 takes an assembled 
position with the hook section 38 received within the open hem pocket 30 
of the first panel 16, and with the hem section 24 of the first panel 16 
likewise received within the open cleat pocket 40 as shown in FIG. 2. The 
first panel 16 is thereby restrained from movement away from the cleat 20 
in the right hand direction r. Slight clearance spaces 43 and 44 are 
preferably provided between the innermost ends of the open pockets 30 and 
40 and the free edges 42 and 26 of the sections 38 and 24 respectively 
received therein. The base section 34 of the cleat 20 is rigidly anchored 
to the substrate S by means of nails 46. 
The second panel 18 comprises a second attachment section 48 overlying the 
first attachment section 32 of the first panel 16 and including a second 
free edge 50; a second major portion 52 generally co-planer with the 
second attachment section 48 and extending from the joint structure S in 
the left hand direction 1 atop the roof substrate S; and a cover section 
54 extending between the second attachment section 48 and the second major 
portion 52 out of the plane of those components to overlie the cleat 20 
and the hem section 24 of the first panel 16. Angularly disposed 
transition portions 55 and 57 of the cover section 54 provide strength. A 
rigid attachment between the second attachment section 48 of the second 
panel 18 and the first attachment section 32 of the first panel 16 is made 
by means of pop rivets 56 and solder 58. 
It is to be understood that the elongated panels P typically have a left 
hand sided formed as the left hand side of the first panel 16 shown in 
FIGS. 2 and 3, and an opposite right hand side formed as the right hand 
side of the second panel 18 as shown in order to provide successive joint 
structures J between successive adjacent panels P. Furthermore, one 
longitudinal end of a panel P may have a narrower width than the other end 
to fit into a curved roof structure. 
The joint structure J as thusfar defined securely anchors the roof assembly 
R to the substrate S yet fully accommodates thermally induced strains in 
any direction across the roof assembly R. This feature of the invention is 
provided by the novel arrangement wherein the two joined panels 16 and 18 
are rigidly connected only to one another and not to the cleat 20 or the 
underlying substrate S. In contrast to the prior art lap joint structure 
known as a flat lock joint with cleats as shown in FIG. 6 to have a rigid 
soldered connection between the joined panels and the cleats, the joint 
structure J in accordance with the present invention, enables the joined 
panels 16 and 18 to shift together in the right and left hand directions r 
and l as permitted by the clearance spaces 43 and 44 and the cleat space 
41. Movement in the longitudinal direction of the joint structure S is 
also permitted as needed by the arrangement where the hem pocket 30 and 
the cleat pocket 40 are open with respect to the sections 38 and 24 
respectively received therein. The same structural advantages of the 
present invention are obtained over the prior art lap joint structure 
shown in FIG. 7 which also has a rigid connection between the joined 
panels and the underlying substrate. 
A method of constructing the joint structure J is also provided in 
accordance with the present invention. The cleat 20 is placed in the 
assembled position described above with the hook section 38 received 
within the hem pocket 30 of the first panel 16, and the base section 34 of 
the cleat 20 is then rigidly anchored to the substrate S by means of nails 
46 or other suitable rigid fasteners such as screws or the like. Use of an 
elongated cleat 20, preferably co-extensive with the elongated joint 
structure J, as opposed to a row of spaced cleats as indicated in FIG. 6 
greatly simplifies this initial step in the construction process. The 
second panel 18 is then placed in position with the second attachment 
section 48 overlapping the first attachment section 32 of the first panel 
16 as shown in FIG. 2 such that the cover section 54 overlies the cleat 20 
and the engaged hem section 24. A rigid connection between the panels 16 
and 18 is then made in accordance with the sequence of steps illustrated 
in FIGS. 4A through 4F. 
In FIGS. 4A and 4B a punching tool 60 is shown to drive a hole 62 into the 
substrate S through the first and second attachment sections 32 and 48 of 
the first and second panels 16 and 18 with the effect of producing a 
slight depression 64 in those sections of the panels about the hole 62. In 
FIGS. 4C and 4D a locator pin 66 is shown to be loosely inserted into the 
hole 62 as a temporary anchor for the panels 16 and 18 in order to hold 
them in their assembled positions before a permanent rigid connection is 
made therebetween. One or more of these anchoring arrangements may be made 
as required since a single temporary anchor will restrain the panels 16 
and 18 from lateral movements across the joint structure J, but a second 
anchor spaced longitudinally from the first may be required to restrain 
the panels from rotation about the first anchor. Placement of a releasable 
anchor at each opposite end of the elongated joint structure J, when the 
panels are placed in proper alignment, would thus be an efficient means of 
holding the panels in line. With the panels 16 and 18 thus releasably held 
in line, a plurality of pop rivets 56 are installed in a generally 
staggered array along the longitudinal extent of the overlapping 
attachment sections 32 and 48 as shown in FIGS. 2 and 3. 
An important feature of the invention arises in the use of pop rivets as 
illustrated in FIGS. 4E and 4F wherein it is shown that the depression 64 
caused by use of the driving tool 60 enables the heads 68 of the pop 
rivets 56 to rest in a somewhat countersunk position with respect to the 
overlapping panel sections 32 and 48. In the case of a wooden substrate S 
as shown in FIGS. 4F and 2A, or another substrate which would similarly 
yield under the impact force of the driving tool 60, the depression 64 
would further provide clearance between the substrate and the panel 
sections for expansion of the rivet shaft into the position wherein it 
holds the two Joined panel sections together. These particular steps of 
the present method provide a distinct advantage over prior art methods 
using sheet metal screws which tend to raise a burr beneath the 
overlapping panel sections to disrupt the level contour of the completed 
roof assembly, and which do not countersink the screw heads to provide a 
relatively smooth surface. 
Following installation of the pop rivets as described above, the 
overlapping panel sections 32 and 48 are sealed together with solder. The 
present invention also provides several advantages over the prior art in 
the soldering step. In distinction to the prior art configuration shown in 
FIG. 6 wherein six overlapping layers of sheet metal material must be 
thoroughly heated by a soldering iron in order to create conditions 
required for a thorough application of molten solder, only the two 
overlapping attachment sections 32 and 48 of the first and second panels 
16 and 18 need to be heated in accordance with the present invention. This 
not only reduces the operator skill, time, and consequent cost of the 
soldering operation, but also greatly reduces the risk that an incomplete 
seal will be made. As shown in FIG. 2A, a spot of solder may be provided 
atop each rivet head 68 in order to provide a thoroughly complete seal as 
well as a smooth finished appearance. 
Another beneficial feature of the invention is the provision of means for 
containing the molten solder at a region closely adjacent the second free 
edge 50 of the second panel 18 where it overlaps the first panel 16. This 
means is preferred to take the form of a raised rib 70 extending along the 
major portion 22 of the first panel 16 parallel to and closely spaced from 
the second free edge 50 as shown in FIGS. 2 and 3. The raised rib 70 acts 
as a dam for containment of molten solder which might otherwise flow 
outwardly from the second free edge 50 onto the major portion 22 of the 
first panel 16. 
An additional feature of the invention regarding soldering is the use of 
Terne Coated Stainless Steel, a product of Follansbee Steel Corp. Terne 
Coated Stainless Steel is pretinned to bear a surface coating of solder 
material 72 as shown in FIG. 5. Use of Terne Coated Stainless Steel 
insures complete application of molten solder between the overlapping 
panel sections as shown in FIG. 3. In accordance with the present 
invention, the sheet metal panels may bear a partial surface coating of 
solder material 74 or a complete surface coating of solder material 72 as 
shown in FIG. 5. 
The invention has been described with reference to the preferred 
embodiment. It will be appreciated that modifications or alterations which 
would not deviate from the present invention will occur to others upon 
their reading and understanding of this specification. For example, in 
FIG. 8 there is shown an alternate joint structure J including an 
alternate cleat 80 and an alternate first panel 90. The alternate cleat 80 
comprises a base section 82 and a hook section 84 folded back over the 
base section 82 in the left hand direction l as shown. The alternate first 
panel 90 includes a major portion 92 with an attachment section 94 and a 
raised rib 96; an intermediate section 98 spaced above the plane of the 
attachment section 94 and extending tberefrom in the left hand direction 
l, and a hem section 100 folded back beneath the intermediate section 98 
to define a hem pocket open to the right hand direction r as shown. This 
arrangement enables placement and anchoring of the alternate cleat 80 to 
the substrate S before placement of the alternate first panel 90 in its 
assembled position with respect to the cleat 80, whereby all of the cleats 
may first be installed along established lines to thereafter avoid precise 
attention to alignment upon installation of each of the panels to be 
engaged therewith. Also, an alternate second panel 102 is shown in FIG. 8 
to have a cover section 104 and a generally distinct major portion 106 
which is permitted to descend to the level of the substrate S from the 
cover section 104 without a sharp transition section on that side. In this 
respect, both transition sections 55 and 57 of the cover section 54 
described above could be omitted but are employed in the preferred 
embodiment to impart strength to the cover section and to insure 
overlapping contact of the adjacent attachment section over the first 
panel. It is intended that all such modifications and alternate 
arrangements be included insofar as they come within the scope of the 
dependent claims or the equivalence thereof.