Patent Application
20100037547
The present invention relates generally to building structures and in particular, to an insulated rim board and building structure employing the same.
In flooring systems, rim boards run around the perimeter of the building structure and serve as framing members to enclose the floor joists. Typically the rim boards sit on sill plates that rest on the building structure foundation. Floor sheathing that spans the floor joists overlies the rim boards to provide a generally planar support surface for the load bearing exterior walls of the building structure.
Elongate lengths of oriented strandboard (OSB) are commonly used as rim boards. Although OSB rim board has been widely accepted, the thermal rating of OSB rim board is less than desired. To address this problem, insulated rim boards have been considered such as those supplied by Emercor Ltd. of Calgary, Alberta. The Emercor insulated rim board comprises a polyurethane foam core sandwiched between a pair of OSB skins. Lengths of 2″ by 2″ lumber run along the top and bottom surfaces of the foam core between the OSB skins. Although this rim board has better thermal characteristics than conventional OSB rim board, problems exist in that the design of the insulated rim board does not permit the width (i.e. vertical dimension) of the rim board to be altered at the building site due to the fact that altering the width of the insulated rim board changes its load bearing characteristics. As a result, to employ effectively the Emercor insulated rim board at a construction site, a stockpile of different size rim boards must be maintained.
As will be appreciated, rim boards that have good thermal characteristics and permit on-site width adjustment are desired. It is therefore an object of the present invention at least to provide a novel insulated rim board and building structure employing the same.
Accordingly, in one aspect there is provided a three-piece insulated rim board comprising:
first and second elongate structural layers; and
an intermediate elongate insulating layer sandwiched between and bonded to said first and second structural layers.
In one form, the intermediate layer is formed of foam material such as for example expanded polystyrene foam, urethane foam, polyurethane foam and isocyanurate foam. The intermediate layer has thickness in the range of from about 2½″ to about 7⅜″. The rim board is symmetrical about vertical and horizontal planes coincident with the central longitudinal axis of the rim board. Each of the first and second structural layers has a thickness in the range from about ⅛″ to about 1⅛″. The first and second structural layers are formed of material selected from plywood, oriented strandboard (OSB), metal sheet or other suitable material.
According to another aspect there is provided a floor structure for a building structure comprising:
insulated rim boards running around the perimeter of said building structure and sitting on sill plates; and
joists framed by said rim boards, wherein said insulated rim boards are alterable in vertical dimension without changing the symmetry of the rim boards above the sill plates when looking at the rim boards in side elevation.
Embodiments will now be described more fully with reference to the accompanying drawings in which:
a and 3b show tie and angle plates used in the floor structure of
Turning now to
The I-joists 32 are toe-nailed to the sill plates 24 using suitable fasteners 40, such as for example nails or screws. Angle plates 42 are also secured to the upper surface of the sill plates 24 and the interior surface of the rim boards 22 using suitable fasteners 44, such as for example nails or screws, at spaced locations about the building structure.
Each insulated rim board 22 is of a three-piece structure and comprises an intermediate insulating layer or core 60 sandwiched between and bonded to interior and exterior structural layers or panels 62 and 64 respectively by suitable adhesive such as for example urethane adhesive. In this embodiment, the intermediate insulating layer 60 is formed of expanded polystyrene (EPS) foam and has a thickness equal generally in the range of from about 2½″ to about 7⅜″. The thickness of the intermediate insulating layer 60 is selected to give the rim board 22 the desired thermal rating. The interior and exterior structural layers 62 and 64 are formed of a suitable structural material such as for example oriented strandboard (OSB) or plywood and have a thickness generally in the range of from about ⅛″ to about 1⅛″. The thickness of the interior and exterior structural layers 62 and 64 is typically selected to give the rim board 22 the desired fire rating. In this embodiment, the rim board 22 when viewed in side elevation is symmetrical about a horizontal plane coincident with the central longitudinal axis of the rim board 22. The rim board 22 is also symmetrical about a vertical plane coincident with the central longitudinal axis of the rim board.
Typically, the rim boards 22 are manufactured in standard widths W (e.g. 9½″, 11⅞″, 14″ and 16″) to match conventional I-joist sizes. Notwithstanding, due to the symmetrical design of the rim boards 22, the widths of the rim boards 22 can be altered (i.e. reduced) on-site when needed to accommodate for example steps, windows etc. without compromising the load bearing characteristics or thermal characteristics of the rim boards 22. As a result, rim boards 22 of any standard width can be tailored on-site to satisfy construction needs.
Although dimensions for the rim boards are provided above, those of skill in the art will appreciate that the dimensional information is exemplary. Depending on the environment in which the rim boards are being deployed, the overall dimensions of the rim boards may vary from those discussed above.
In the embodiments described above, the interior and exterior structural layers are described as being formed of OSB or plywood. Those of skill in the art will appreciate that the interior and exterior structural layers may be formed of other suitable structural material such as for example metal sheet, fire resistant board etc. Also, the intermediate foam layers need not be formed of EPS. Other foam material such as for example urethane foam, polyurethane foam, isocyanurate foam etc. or other suitable non-foam material such as for example honeycomb board may be used.
Although embodiments have been described above with reference to the drawings, those of skill in the art will appreciate that variations and modifications may be made without departing from the spirit and scope thereof as defined by the appended claims.
