Rim Board Connector Rod

Abstract

A connector for connecting an add on building structure to a rim board of an original building structure, including a connector rod including an elongated hollow intermediate portion and smaller breadth externally threaded extensions extending from ends of the hollow intermediate portion. The first externally threaded extension is a length to extend through an opening in the rim board that aligns with an opening in the ledger board, and internally threaded sockets are threaded onto the externally threaded extensions at a positions straddling the rim board at one end and a supportive member within the joists of the add on building structure at the other end for holding add on building at a desired distance from the rim board and preventing rotation of the connector rod.

Description

PRIORITY

This is a continuation-in-part of U.S. patent application Ser. No. 14/643,472 filed in the U.S. Patent and Trademark Office on Mar. 10, 2015. Applicants claim priority to U.S. Provisional Patent Application Ser. No. 61/995,770, filed in the U.S. Patent & Trademark Office on Apr. 21, 2014.

SUMMARY OF THE INVENTION

This invention concerns a method and apparatus for attaching building structures together. More particularly, this invention concerns a cantilevered connector rod with a stabilizer extension that may be used for attaching a deck, patio, porch or other add-on building structures to a rim board of an adjacent original building structure. In this invention, the end of add-on building structure opposite the original building structure is supported. And the invention also concerns methods of attaching the connector rod between the structures.

BACKGROUND OF THE INVENTION

A typical building structure may include a horizontal rim board that extends about and is supported by the foundation of the building. The floor, roof, ceiling framing, and exterior cladding of the building are referred to herein as the “original building structure”. When a deck or other add-on building structure is to be added to the exterior of the original building structure, the add-on building structure may include a ledger board that is to extend adjacent and parallel to the rim board of the original building structure. The ledger board can be mounted to and supported by the rim board of the original building structure. In this arrangement, the ledger board supports the portion of the add-on building structure that is adjacent the original building structure.

Usually both the rim board and ledger board are formed of wood and the connection of the ledger board of the add-on building structure to the rim board of the original building structure is made with dowel type connectors, typically bolts or screws. The load from the floor of the add-on building structure is transferred to its ledger board, then from the ledger board to the bolts of the bracket, then from the bolts to the rim board of the original building structure.

The exterior cladding of a typical original building structure may include, but is not limited to brick masonry, stone masonry, stucco, exterior insulating finishing system (“EIFS”), or siding. The exterior cladding usually is removed from the original building structure at the point of mounting the ledger board of the add-on building structure to the rim board of the original building structure, so the ledger board of the deck may be located close to the rim board, making contact with the wall sheathing or rim board.

In some cases, it is desirable to space the ledger board of the add-on building structure away from the supporting original building structure to avoid removing the adjacent exterior cladding of the original building structure. This may be done for water proofing reasons or to avoid supporting the exterior cladding above the ledger board.

Usually, exterior cladding of the original building structure is not intended to be a load carrying element, and recent building codes have begun to explicitly address this. If the exterior cladding is not removed and the ledger board of the add-on building structure is separated farther from the rim board of the original building structure to leave space for the exterior cladding, the connector must span farther through an unsupported gap between the two buildings. The gap may include a space or the non-structural wall cladding. This extra length of the connector and the gap weakens the strength of the connections between the buildings.

A conventional “single shear” dowel type connector, or a dowel type connector with a single failure plane, used to mount a ledger board to a rim board of joined building structures has two contact points, one at the rim board and the other at the ledger board. Pivoting of the connector bracket by the load of the add-on building applied to the connector bracket is resisted by a non-uniform compression stress distribution between the connector bracket and the wood of the rim and ledger boards. This potential failure mode is known as “mode II” in the National Design Specification for Wood Construction, as illustrated herein in FIG. 1.

When the ledger board of the add-on building structure is attached to the rim board of an original building structure and the boards are in contact with one another, or very close to one another, the length of the single shear connector extending between the rim and ledger boards is relatively short and a high shear load from the ledger board to the rim board can be transferred through the connector bracket.

But when the structures are separated by a wider unsupported gap, the length of the connector bracket extending between the rim and ledger boards must be greater and the maximum compression stress on the wood of the structures by the single shear connector becomes higher as the connector begins to pivot. The result is the add-on building structure is not supported at an acceptable level.

Prior art U.S. Patents of Jewell U.S. Pat. No. 4,953,339 and Eldeen U.S. Pat. No. 7,254,926, and Smith Patent Application Publication 2014/0215956 A1 disclose devices that span through a pre-assembled structure to a rim board with an unsupported gap there between. However, none of the known prior art could be easily installed as a retrofit in an application where the ledger board and framing of the add-on building structure are already assembled and existing. Additionally, the structural mechanics of these prior art devices are not adequately addressed or realized, including whether each contact point is designed as: “Roller”, whereby translation is resisted in one direction but rotation is not significantly resisted; “Pinned”, whereby translation is resisted in all directions but rotation is not significantly resisted (which is characteristic of most conventional screwed or bolted connection); or “Fixed”, whereby translation is resisted in all directions and rotation or moment is resisted. As a result, some prior art devices include complex features that are not necessary for structural purposes.

U.S. Pat. No. 7,254,926 to Eldeen discloses a connector composed of a rod with a sleeve at the end of a rod. The nature of the sleeve design and its use in an application with only two contact points suggests that a fixed connection at the sleeve was intended and realized. However, in an application where the rod has three contact points, fixity at the sleeve connection is redundant and unnecessary. Eldeen describes an option where the rod has a third contact point, but apparently fails to realize that fixity at this third contact point is unnecessary. Resisting moment at this connection point requires the sleeve to be of thick material, highly specialized, difficult to install, and expensive.

Additionally, Eldeen locates the third contact point on the side of the supporting structure opposite the ledger board. This is undesirable for several reasons. The space within the floor system of the original building structure is typically difficult to access. Additionally, when gravity loads are applied on the add-on building, an uplift load is imposed on the third contact point. This load must be transferred to the floor joists of the original building structure. Resisting an uplift load requires there to be an adequate amount of dead load to resist it, and the add-on building contractor is most often not aware of the design of the original building's floor system.

U.S. Pat. No. 4,953,339 to Jewell and U.S. Patent Publication 2014/0215956 A1 to Smith disclose larger devices with two contact points. The large custom size of these devices is necessary to facilitate a fixed connection at the rim board. This moment transfer appears to cause rotation of the rim board when vertical loads are applied on the deck. Preventing rotation of the rim board is dependent on the connection at the top and bottom of the rim board, which may be existing and impossible to reasonably verify. Additionally, the large size of these devices appears to require significant removal of exterior cladding to install.

Eldeen, Jewell, and Smith disclose a vertical plate behind the ledger board as a component of the connector device. These plates serve to transfer lateral load from the ledger board through the connector, via compression, to the rim board. Without these plates, it appears that the ledger board could move freely into the gap when subjected to a lateral load towards the supporting structure. In a retrofit application, it would be difficult to install these components without rebuilding the deck.

Thus, it is an object of this invention to provide an improved connector to support a ledger board of an add-on building structure on a rim board of an adjacent original building structure that can span through an unsupported gap between the buildings. Other objects of this invention include providing a cantilevered connector rod with a stabilizer extension that can transfer load about all space axes between joined buildings, can avoid or reduce significant removal of exterior cladding, can be installed in both retrofit and new construction applications, uses readily available materials of readily available shapes, does not require unconventional support of the joists attached to the ledger board, and does not require access to the floor system of original I building structure.

SUMMARY OF THE INVENTION

A connector and method of attaching an add-on building structure with joists perpendicular to a ledger board to a supporting structure are disclosed. The connector is described as a cantilevered rod with a stabilizer extension located within the add-on building structure that is constructed to span through an unsupported gap between building structures and transfer loads about all three space axes from the ledger board to the supporting structure. The unsupported gap may consist of air or material not designed to support a load. Typically, the material not intended to support a load would consist of exterior cladding, including, but not limited to, siding, stucco, exterior insulating finishing system (EIFS), or masonry veneer.

The cantilevered rod is used for mounting through openings in a rim board of an original building structure and openings in a ledger board of an adjacent add-on building structure, so that the facing portion of the add-on building structure is supported by the original building structure. The stabilizer extension maintains the bracket in its desired attitude, usually in a horizontal attitude.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example of a single shear failure mode II from National Design Specification for Wood Construction. (Prior art.)

FIG. 2 is a side cross sectional view of the adjacent portions of an original building structure and an add-on building structure, such as a deck, joined by the cantilevered connector rod with the stabilizer extension and a plate-insert assembly at the end of the road at the rim board

FIG. 3 is an expanded view of the plate-insert socket assembly of FIG. 2

FIG. 4 is an expanded view of the both ends of the connector rod of FIG. 2

FIG. 5 is an expanded view of the spacer assembly of FIG. 2

FIG. 6 is a side cross sectional view of the adjacent portions of an original building structure and an add-on building structure, such as a deck, joined by the cantilevered connector rod with a bolt at the end of the rod at the rim board (not a plate-insert assembly)

FIG. 7 is a side cross sectional view of the adjacent portions of an original building structure and an add-on building structure, such as a deck, joined by the cantilevered connector rod with a screw at the end of the rod at the rim board (not a plate-insert assembly)

FIG. 8 is an expanded view of the connector rod of FIG. 2 with the spacer assembly

DETAILED DESCRIPTION

FIG. 2 illustrates an original building structure 28 and an add-on building structure 29 that is to be connected to the original building structure. A cantilevered connector rod 9 connects the original building structure to the add-on building structure.

A conventional original building structure may include parallel floor joists 14, rim board 13, and flooring 21 mounted on a foundation wall 18. A sheathing 19, such as plywood or OSB, may be applied to the stud wall 28 of the building structure, and an exterior cladding 8 such as a brick veneer may be applied to the original building structure, usually with an internal air space 7 formed between the exterior cladding and the stud walls and the other exterior wall covering. Rim board 13 surrounds most of the original building structure and is supported by the foundation wall 18. The rim board 13 supports parts of the building structure above the lower foundation wall in the conventional structure.

The add-on building structure 29, that may be in the form of a conventional outdoor deck, is positioned adjacent the outdoor cladding of the original building structure, such as the brick veneer 8. The add-on building structure includes a ledger board 11 that is placed parallel to the rim board 13 of the original building structure, and parallel joists 3 are mounted to the ledger board with conventional joist hangers 10. Flooring 20 is supported by the joists 3, in the usual manner.

The connector rod 9 is used to support the add-on building structure 29 and attach it to the rim board 13. The connector rod 9 includes a cantilevered portion 30 and a back span or stabilizer extension 31. Multiple connector rods may be used to attach the add-on building structure. The connector rods are located between floor joists 3 of the add on. The spacing between the connector rods is primarily based on the span of the joists 3 and the associated loads at the ledger 11, the length of the cantilever and the length of the stabilizer extension 31.

As shown in FIG. 4, the connector rods 9 may be comprised of a hollow pipe made of steel or aluminum. Preferably the rod is comprised of 1¼″ Schedule 40 steel pipe, which has an outer diameter of 1.66″ and a wall thickness of 0.14″. This diameter and wall thickness is selected based on a rod spacing of approximately 2′-0″, assuming a 15′-0″ floor joist span and the associated structural demand to cantilever approximately 6″ through a gap composed of brick veneer while having 14″ stabilizer extension.

FIG. 4 illustrates an expanded view of one end of the connector rod 9. A bolt 25 with external spiral threads 77 has its head 73 inserted into the end of the rod 9. Preferably the bolt has a diameter of ¾″ making the inside face 71 of the pipe in close contact with a standard hexagonal head 12 of the ¾″ diameter bolt. The bolt head 12 is welded at 72 and 73 to the inside face 71 of the rod. The weld 73 may be a continuous butt weld made around the circumference of the rod 9. This single plane weld may not alone provide significant resistance to bolt rotation within the pipe 70. Therefore, six equally spaced holes are drilled around the circumference of the pipe 70 aligning with the external points of the hexagonal head 12 of the bolt 25. A plug weld 72 is made in each of these holes creating an additional plane of welds.

The connector rod 9 includes a cantilevered portion and a stabilizer extension portion 31. Preferably the stabilizer extension portion is at least 12 inches long. However, the stabilizer extension may be shortened if desired, thereby increasing rod shear forces, increasing rod bearing forces, and decreasing rod deflection, or lengthened if desired, thereby decreasing rod shear forces, decreasing rod bearing forces, and increasing rod deflection.

The stabilizer extension portion 31 of the connector rod extends through a supportive or “blocking” structure 5 that is displaced from the rim board and ledger board, out between adjacent joists of the add-on building structure 29. The supportive structure 5 can be wood blocking, such as 2×8 lumber, mounted at its ends to adjacent joists 3 with conventional framing clips 4. The blocking 5 includes an opening with the bolt 1 extending through the opening and attached thereto with a suitable nut.

The supportive structure 5 at the stabilizer end of the connector rod maintains the connector rod 9 at a fixed height. This tends to avoid any pivoting movement of the connector rod 9. It is of importance to calculate the load imposed on the joists 3 by the blocking 5. This load can be determined by first solving for the load at the rim board 13 (considering a free body diagram of the add-on building) and then by solving for the loads at the ledger 11 and blocking 5 (considering a free body diagram of the connector rod 9). Given that the stabilizer extension 31 is located on the side of the add-on building structure 29, this load is a downward force when a gravity loads are applied on the deck. This downward force must be considered in the design of the floor joists 3 and floor joist hangers 10.

FIG. 3 illustrates an expanded view of the plate-insert assembly 26. A hollow cylindrical steel insert 50 includes internal spiral threads 51 that match and engage the spiral threads of the bolt 25. The length of the insert is preferable 2 inches, or a length sufficient to create a moment resistant connection between the bolt 25 and the insert 50. This insert 50 is welded to a round steel plate 52, preferably 5 inches diameter with a thickness of ¼ inch. At least four holes 53 are spaced about the perimeter of the plate are made for passage of four wood ¼″ diameter screws 27 that are to be driven into the rim board 13. Compared to a scenario in which the end of the bolt 25 has a conventional washer/nut as shown in FIG. 6, this plate-insert assembly can resist moment or rotation.

Resisting rotation is beneficial at this connection point for two reasons. It decreases deflection of the rod (a failure mode determined to be a controlling factor based on testing and analysis), and it creates a stable condition without the stabilizer extension 31 attached to blocking 5. In a new constriction application, wherein the add-on building has not yet been built and floor joists are not installed prior to the ledger being installed, a moment resistant connection at this location here eliminates the need for temporary shoring. It should be noted that this applied moment on the rim board is less during construction (under a typical 20 pounds per square foot construction live load compared to service conditions (under a typical 40 PSF live load).

The plate-insert assembly 26 of FIG. 3 could also be installed in a mirrored position about the rim board 13, wherein the screws 27 are driven from within the original building floor system. This would be beneficial in a retrofit application where the exterior cladding 8 is already installed.

As shown in FIG. 2, in order to avoid load being transferred from the rod 9 to the exterior cladding 8 (when loads are applied to the add-on building structure 29 and the rod 9 deflects) the hole in the exterior cladding 8 would ideally be made of larger breadth than the breadth of the connector rod 9. However, if the add-on building and original building already exist, it would be difficult to only over-drill the hole in the exterior cladding 8, without also over-drilling the holes in the ledger board 11.

As shown in FIG. 5, the spacer assembly 17 provides a means to over-drill the hole through the ledger board and exterior cladding, while facilitating contact between the connector rod 9 and ledger 11.

In most deck applications the connector rod 9 would be hot dipped galvanized steel. This zinc coating can be damaged and removed, thereby exposing the bare steel and increasing risk of corrosion. For this reason the spacer assembly 17 would is made of a polymer sufficiently soft to avoid damaging the zinc coating on the rod 9, ideally this polymer would be polyvinyl chloride (PVC).

As shown in FIG. 5, the spacer 17 is in the form of a cylinder 200 and a flange 130 that together form a slot 133 that extends along the cylinder to enable the spacer to open and surround the connector rod 9 and form an increase in outside diameter along the portion 130 of the threaded end of the of the connector rod 9. When the spacer is installed around the connector rod 9, the installer could push the spacer too far into the hole drilled in the ledger 11. This increase in outer diameter of the plate 52 prevents an installer from rotating the spacer 17 too far into the ledger 11. The entire spacer assembly could be injection molded or the main shaft 200 could be made of ½ inch Schedule 40 PCV and the lip 130 could be made from 2 inch Schedule 40 PVC adhered to shaft 200. ½ inch Schedule 40 PCV has wall thickness of 0.145″. When snuggly fitting surrounding a 1.66″ OD 1¼″ Schedule 40 connector rod, total outside diameter of the PVC spacer is 1.95 inch, making a standard 2 inch diameter hole saw bit acceptable for creating the hole in the ledger 11.

The gap between the connector rod 9 and the ledger board 11 eventually gets filled with spacer assembly 17. But before the spacer assembly is pushed into place, an impermeable material, such as caulk or silicon, is injected between the rod 9 and exterior cladding 8 to prevent leakage of air or water into the interior of the original building structure.

FIG. 6 illustrates an optional installation where the end of the connector rod does not include the plate-insert assembly. Instead, a conventional nut and washer is installed on the end of the bolt 93. FIG. 6 would be used in a retrofit application, where the entire add-on building structure is already installed, and also in municipalities where building officials do not allow screws to attach ledger boards to rim boards.

FIG. 7 illustrates an optional installation where the end of the connector rod does not include the plate-insert assembly. Instead, a wood lag screw 112 with external spiral threads 113 and a hexagonal head 110 is inserted and welded into the end of the connector rod 9, similar to the application of FIG. 4. FIG. 6 would be used in a retrofit application, where the entire add-on building structure is already installed, and also in municipalities where building officials do allow screws to attach ledger boards to rim boards.

FIG. 8 illustrates the connector rod 9 composed of 1% inch Schedule 40 pipe. The PVC spacer assembly 200 includes a sleeve and a rim 130. The sleeve 200 is free to slide along the rod 9. The slot 133 allows the spacer assembly to expand and fit snuggly around the connector rod 9. After the rod is installed in a building structure, the PVC spacer assembly 200 is moved with the installer's hands or with a hammer a small hammer if required) in the hole drilled in the ledger 11 until the flange 130 prevents it from moving any further.

As shown in FIG. 4, the diameter of the bolt 12 of the connector rod 9 is less than the connector rod 9. The connector rod 9 should have a large diameter to cantilever through the brick 8. The maximum moment occurs at the ledger 11 and decreases linearly closer to the ends of the rod. Therefore, the structural demand of the rod 9 at its ends is less than at its center. The smaller bolt 12 require only smaller nuts/washers and are therefore less expensive (compared to a scenario in which the outer surface of the connector rod is threaded). Additionally, the surface at the end of the rod 9 with the weld 73 bears against the rim board 13 at one end and blocking 5 at the opposite end. This enables the user to tighten a nut 92 on the opposite side of the rim board as shown in FIG. 6 and a nut 2 on the opposite side of the blocking. The rod is prevented from passing through the rim board and blocking because of the difference in outer diameter of the rod 9 and the bolts 25 and 1.

While the expressions “rim board” and “ledger board” have been used to describe the structural features of the connection points of the add-on building structures and original building structures, these expressions are to include other supporting structures that are suitable for connection together by the inventions disclosed herein.

Although preferred embodiments of the invention have been disclosed in detail herein, it will be obvious to those skilled in the art that variations and modifications of the disclosed embodiments can be made without departing from the spirit and scope of the invention as set forth in the following claims.

Claims

1. A retrofit connector bracket for supporting an add on building structure with a ledger board to a rim board of original building structure, including

an elongate intermediate connector rod with opposed ends,

a threaded bolt extending from each end of the connector rod of a length for extending through the rim board and through a supportive member spanning between joists of the add on building structure

a first internally threaded socket for surrounding the threaded bolt in a position for bearing against the rim board of the original building structure, and

a second internally threaded socket for surrounding the threaded bolt in a position for bearing against the supportive member spanning between floor joists of the add on building structure

a third socket for surrounding the connector rod in a position for bearing against the ledger board.

2. The retro fit connector of claim 1, wherein the first internally threaded socket includes a cylinder defining a cylindrical opening, and a disk mounted to the cylinder, the disk defining an opening in alignment with the cylindrical opening.

3. The retrofit connector of claim 2 wherein the third socket is flexible and includes a slot allowing the socket to expand and enlarge its diameter.

4. The retro fit connector of claim 1 wherein the bolts are formed of a breadth smaller than the elongate hollow intermediate connector rod.

5. The retro fit connector of claim 1, wherein a cylindrical spacer is mounted on the elongate hollow immediate connector rod for fitting an enlarged opening in the ledger board.

6. A connector for connecting the joists of an add on building structure to a rim board of an original building structure,

the connector comprising a connector rod including an elongated hollow intermediate portion and a first externally threaded extension extending from an end of the hollow intermediate portion,

a first externally threaded extension being of a length to extend through a hole in the rim board that aligns with a hole in the ledger,

a second externally threaded extension being of a length to extend through a supportive member attached to the joists of the add on building

a first internally threaded socket threaded onto the externally threaded extension at a position for bearing against the rim board, and

a second internally threaded socket threaded onto the externally threaded extension at a position for bearing against the supportive member for holding the add on building at a desired distance from the rim board.

7. The connector of claim 6, wherein a third socket is moved laterally on the connector rod to a position to facilitate contact between the connector rod and ledger board.

8. The connector of claim 7, wherein the first and second internally threaded sockets are of a smaller diameter than the elongated hollow rod.