The present invention relates to reinforcement of wooden roof structures of houses and low-rise buildings, and more particularly to a retrofitting apparatus and method for reinforcement of roof frame structures.
Many millions of houses and small buildings located in hurricane or tornado areas in, for example, the United States, are at high risk of damage from the strong winds of hurricanes or tornadoes. Recent studies of hurricane damage indicate that the most extensive damage to a house occurs when the roof is torn off, allowing the rain which often accompanies strong winds, to ruin the contents of the house and often allowing walls to collapse.
There is a great need for affordable retrofitting methods for reinforcement of wooden roof frames. While prior art connectors of steel strip tie-down types excel as affordable connectors of roof structures to underlying walls in new construction of houses and small buildings, they are not as applicable when retrofitting existing roof frame structures. These fittings pose difficulties in retrofitting applications because an upper portion of the steel-strip tie must extend over the top of a rafter/truss and down the other side in order to ensure adequate tie-down strength, by applying the restraining force mainly at the top of the roof frame, as compression across the grain, which wood withstands quite well. If the tie-down connectors are simply nailed into the side of the rafter/truss, as commonly done in the prior art, localized tensions are induced across the grain of the wood such that the rafter/truss member tends to split under high uplift conditions, which can release the connector's nails.
The over-the-top method is now widely recommended or required in the “Hurricane Belt” of the United States, even for retrofits of existing buildings. During retrofitting however, accessing the top portion of the rafter/truss requires removal and later restoration of an area of roofing and sheathing, which are laborious and costly operations, and thus tend to discourage such retrofit upgrading of the existing housing and building stock.
Prior art efforts to devise retrofits for reinforcement of roof structures have also been made. A number of United States patents as examples of such efforts are briefly discussed below.
In U.S. Pat. No. 5,257,483 (Netek) discloses some of the complications of retrofitting by installing anchor points in fascia and the wall below, allowing temporary placement of ties in the face of an impending storm. Winger, in U.S. Pat. No. 5,319,816, and several other inventors, disclose various temporary arrangements of multiple cables or nets over the roof which are anchored to the ground. Such temporary devices demand that the householder be at home through the hurricane season, ready to react to storm warnings quickly and competently.
In U.S. Pat. No. 5,311,708, Frye shows a retrofit roof tie-down method in which lag screws are installed upwardly through a steel angle into the lower edges of the rafter/trusses, a lower leg of the steel angle being lag-screwed into the underlying wall. Frye's lag screws into the narrow edge of the rafter/truss would however invite splitting and cause tension failure. Furthermore, only the screws near the junction of rafter/trusses with the top of the wall would contribute effectively, and the usual absence of a stud directly under a rafter/truss would leave Frye's wall lag screws rather ineffective.
Thompson, in U.S. Pat. No. 6,763,634, tries to resolve the retrofit problem by inserting ties down through the roofing and sheathing from above, with one strip on each side of the rafter/truss to form a saddle across it, which is able to effectively hold down the roofing and sheathing together with the rafter/truss. Thompson's ties extend down to connect to the underlying wall below. All this entails laborious and uncertain sealing of the roof penetrations, and interferes with any subsequent re-roofing job.
Therefore, there is a need for an improved retrofitting apparatus and method for reinforcement of roof frames structures.
One object of the present invention is to provide a retrofitting apparatus and method for reinforcement of roof frame structures.
In accordance with one aspect of the present invention there is a retrofitting apparatus provided for reinforcement of an existing roof frame structure which comprises a first plate adapted to be mounted to a surface of a roof frame support member; a second plate connected with the first plate, adapted to be mounted to a first side of a roof frame supported by said roof frame support member, the second plate being substantially normal to the first plate; and a substantially flat load bearing member with a free end, projecting from a top end of the second plate for securing the roof frame at the first side of the roof frame.
In accordance with another aspect of the present invention, there is a method for reinforcement of an existing roof frame structure which comprises (a) providing a retrofitting apparatus having at least a first mounting plate and a second mounting plate substantially normal to the first mounting plate, the second mounting plate having a load bearing member with a free end extending away from a top end of the second plate; (b) positioning the retrofitting apparatus to allow the first and second mounting plates to be placed against a surface of a wall and a side of a roof frame supported on the wall, respectively, thereby causing the load bearing member to engage the roof frame at a location adjacent to an under side of a roof panel mounted on a top of the roof frame; and (c) securing the first and second mounting plates to the surface of the wall and the side of the roof frame, respectively by means of fasteners in order to prevent the roof from moving upwardly under uplift forces.
Other features and advantages of the present invention will be better understood with reference to the preferred embodiments described hereinafter.
Reference will now be made to the accompanying drawings showing by way of illustration the preferred embodiment of the present invention, in which:
A retrofitting apparatus generally indicated by numeral 24, according to one preferred embodiment of the present invention, includes a first mounting plate 26 to be mounted to a surface of a roof frame support member, for example the underlying wall 20, and a second mounting plate 28 which is substantially normal to the first mounting plate 26. The second mounting plate 28 is adapted to be mounted to the first side 16 of the roof frame 10, and is connected to the first mounting plate 26, preferably but not necessarily in an integral form. In this embodiment the first and second mounting plates 26, 28 are made from a single metal strip which is twisted at a middle portion such that a lower section thereof (which forms the first mounting plate 26) and an upper portion (which forms the second mounting plate 28) are twisted about 90 degrees with respect to each other. The second mounting plate 28 includes a free end projecting from a top end of the second plate 28 to form a substantially flat load bearing member 30 which may be substantially normal to the second mounting plate 28. The load bearing member 30 functions to secure the roof frame at the first side 16 thereof, near the top 12, to the underlying wall 20. In this embodiment, the load bearing member 30 can be conveniently made by bending a top section of the second mounting plate 28 into a right angled position with respect to the remaining section of the second mounting plate 28.
When the respective mounting plates 26, 28 are mounted to the surface of the underlying wall 20 and the first side 16 of the frame 10 as illustrated in
There are usually little or no gaps between an under side of the roof sheathing panel 22 and the top 12 of the roof frame 10, and therefore even when the load bearing member 30 is inserted along the interface between the under side of the roof sheathing panel 22 and the top 12 of the frame 10, as shown in
The engagement position of the load bearing member 30 with roof frame 10 is preferably but not necessarily adjacent to the under side of the roof sheathing panel 22, or close to the top 12 of the roof frame 10 in order to allow a maximum cross-section of roof frame 10 to bear a load under uplift forces caused by wind passing over the attached roof sheathing panels 22 while the roof frame 10 is restrained by the load bearing member 30 of the retrofitting apparatus 24, from moving upwardly relative to the underlying wall 20.
The load bearing member 30 may be in an angular position less than 90 degrees with respect to the first mounting plate to substantially match the roof angle in order to achieve an engagement position as shown in
The respective first and second mounting plates 26, 28 may have one or more mounting holes 32, 34 for receiving fasteners extending therethrough. Optionally, mounting hole 34 in the second mounting plate 28 may be located near the top end of the second mounting plate 28 and may have a relatively larger diameter. When the retrofitting apparatus 24 is placed in position as shown in
In
The retrofitting apparatus 36 further includes a third mounting plate 44 which may be similar to the second mounting plate 40, adapted to be mounted to side 18 of the roof frame 10 opposite to the side 16. The third mounting plate 44 is substantially parallel to the second mounting plate 40 and is spaced apart from same at a distance slightly greater than the thickness of the roof frame 10 such that the roof frame 10 is fitted into the space between the second and third mounting plates 40, 44 when the retrofitting apparatus 36 is in position, as shown in
The first, second and third mounting plates 38, 40 and 44 are connected together, for example, by a further plate 48 substantially normal to each of the respective mounting plates 38, 40 and 44. The fourth plate 48 is connected with an upper end of the first mounting plate 38 and with lower ends of the second and third mounting plates 40, 44.
In this embodiment, the retrofitting apparatus 36 is made from a single piece of sheet metal blank indicated as 36a in
It should be noted that lines 68 and 70 might not be parallel to lines 64, 66, but may define an angle A with respect to line 62 (also the longitudinal edges of the strip portion 52). When the corner sections of the opposite ends of the strip portion 52 are bent along lines 68, 70, the resulting substantially flat load bearing members 42, 46 have an angular position resulting from the angle A, as shown in
When the retrofitting apparatus 36 is placed in position as shown in
Referring now to
In this embodiment, the first mounting plate 74 of the retrofitting apparatus 72, projects from a side edge (not indicated) of the second mounting plate 76 and extends away from one side of the second plate 76 while one substantially flat load bearing member 78a with a free end (may have a tip to form a tooth configuration) projects and extends away from an opposite side of the second mounting plate 76. In addition, the substantially flat load bearing member 78b with a free end, similar to the load bearing member 78a, projects from a bottom end of the second mounting plate 76, and is substantially normal to the second mounting plate 76. The load bearing member 78b also defines an angular position less than 90 degrees with the first mounting plate 74 but is not parallel to the angularly positioned load bearing member 78a. It is preferable but not necessary that the angularly positioned load bearing members 78a and 78b are symmetric about a central axis 80 of the second mounting plate 76, as shown in
Mounting holes (not indicated) are provided in the respective first and second mounting plates 74, 76. The specific shapes of the respective first and second mounting plates 74, 76 as illustrated in this embodiment, are a choice of design, and any other appropriate shapes such as simple strips may be selected.
The retrofitting apparatus 72 may be made from a single sheet metal blank 72a in a similar process, as described with reference to
The present invention advantageously facilitates retrofitting an existing roof frame such that it is securely anchored to the main body of the structure without having to remove the roof shingles or roof deck which is generally referred to as roof sheathing panels or roof panels throughout this specification and the appended claims. The present invention provides a simple means for reinforcing the hold-down strength of a roof frame and thus resists upward loads on the roof typically caused by winds. The present invention will also reduce the risk of wood splitting problems inherent in other retrofitting devices caused by insertion of screws or nails.
Changes and modifications to the embodiments of the present invention described above may be made without departure from the spirit and scope of the invention. For example, other configurations may be developed as a result of the implementation of the general and common concept incorporated into the above-described embodiments. Such modifications fall within the scope of the present invention and will be apparent to those skilled in the art in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.