Patent Application
20250084992
The present invention relates to a lightweight chimney crown.
A chimney crown is a common feature used to prevent moisture seepage into and around a chimney in residential, commercial, and industrial applications. The chimney crown is typically constructed of concrete poured on top of a chimney or of a precast concrete or composite placed on the top of a chimney; the crown may also be made of a metal or stone. Each of these versions of the chimney crown are heavy and place a high structural burden on the existing chimney and the roof to which it attaches. The crown constructed of such materials also may prone to eventual cracking or other deterioration which reduces the lifespan of the chimney crown and if the owner of the building and/or the maintenance crew do not detect the deterioration of the chimney crown may also reduce the lifespan of the chimney itself.
It is important to prevent moisture from entering a chimney as any moisture that enters into the chimney can work its way between the outer masonry of the chimney and the chimney liner. As the moisture freezes and thaws it will eventually cause the chimney to crack. The moisture may also cause discoloration of the chimney which is not a serious threat to the structural integrity of the chimney but does adversely affect the aesthetics of the chimney.
The chimney crown prevents moisture from entering the chimney by having a sloped upper surface which is sloped away from the chimney flue and by extending beyond the outer perimeter of the chimney. This extension, known as a kerf, directs moisture such as rain, snow, and the like away from the chimney.
A concrete or composite chimney crown is typically constructed utilizing wooden forms that are built in place at the top of the chimney. It can be time consuming and cumbersome to either build the form atop and around the chimney structure or to build it on the ground and then attempt to properly position it atop the chimney. A chimney crown that is constructed prior to placing it upon a chimney can be difficult to properly install in place due to the weight of the crown and the cumbersome weight and dimensions that the chimney crown possesses. An improperly placed chimney crown can result in improper drainage of moisture off the chimney crown which could still result in moisture seepage into and around the chimney. The improperly placed chimney crown can also cause poor weight distribution of the chimney crown putting excessive weight over a portion of the chimney. That the chimney crown is often installed atop a sloped roof adds to the safety hazards involved in installation.
West et al. (U.S. Pat. No. 6,959,903) describe a cast in place chimney form which in itself is lightweight relative to the typical wooden forms that are used to pour a concrete chimney crown; but it still uses a poured concrete to form the bulk of the chimney crown and as such will still be quite heavy on the chimney. There remains a need for a light weight chimney crown.
There is a need for a light weight chimney crown which can readily be placed upon an existing chimney and yet still prevents moisture seepage around and into the chimney. The present invention provides such a chimney crown.
The present invention is directed towards a lightweight chimney crown. The chimney crown is preferably made with a main body comprised of a light weight structurally sound material such as a molded polystyrene insulating foam and is preferably covered by a cementitious coating such as the Sto reinforced structural coatings provided by Sto Corp. of Atlanta GA. The main body of the chimney crown is preferably comprised of a single piece of polystyrene foam as this will provide substantial structural strength benefits relative to a body comprised of multiple sections each fastened together via readily available means such as bonding with an adhesive or doweling and gluing or the like.
Compared to a poured concrete chimney crown, the lightweight chimney crown of the present invention will weigh approximately about 10-25 percent of the poured concrete chimney crown.
Embodiments of the present invention will be described by reference to the following drawings, in which like numerals refer to like elements, and in which:
The present invention provides an exemplary chimney crown which is manufactured to be lightweight, strong, weather resistant, and with a long service life while providing protection from moisture seepage around and into the structure of a chimney. Referring to
The chimney crown 100 has a central opening to allow a chimney flue 2000 to penetrate the chimney crown 100. To simply the description of the present invention, the chimney 1000 which the chimney crown 100 is protecting will be presumed to have a single chimney flue 2000. As those skilled in the art will be aware, the chimney crown 100 of the first embodiment of the present invention could be modified without undue experimentation to protect a chimney with multiple flues and a chimney crown designed to protect one such representative example of a chimney with multiple flues will be described later. The chimney crown 100 also has exterior side walls 120, interior side walls 100 adjacent to the central opening, an upper surface 140, and a lower surface 150. The chimney crown 100 is constructed with a body 160 and a structural coating 170. The body 160 provides for the primary structure of the chimney crown and also has exterior side walls, interior side walls, an upper surface, and a lower surface and is preferably comprised of a structural foam such as an expanded polystyrene (EPS) foam, an extruded polystyrene (XPS) foam, or the like. The structural coating 170 covers the upper surface, the exterior side walls, and the interior side walls of the body 160. The lower surface of the body is also preferably coated with the structural coating 170. In the preferred embodiment, the lower surface of the body remains covered by the structural coating but as those skilled in the art are aware if the lower surface of the body is uncovered by the structural coating the teachings of the present invention are not avoided.
As stated above, the body 160 is preferably comprised of a structural foam and more preferably of a rigid, cellular polystyrene geofoam. The structural foam may be comprised of a two pound molded polystyrene insulation geofoam such as the Tru-R 100 rigid, cellular polystyrene geofoam provided by Thermal Foams, Inc. of Albany, New York. The structural foam may also be comprised of a three pound molded polystyrene insulation geofoam, a low density rigid polystyrene insulation geofoam, or other structural polymer foams such as Tru-R Geofoam 15 or the like.
The body 160 is preferably comprised of a single piece of structure foam. The interior side walls are cut out of the structural foam to accommodate the chimney flue(s) 2000 penetrating the chimney crown 100. While the interior cutout or cutouts of the body 160 could be provided for by comprising the body of multiple sections of structural foam each attached to an adjacent body section via glue, dowel and glue, dovetail grooves cut into the adjacent sections of structural foam and the like, it is preferable for the body 160 to be comprised of a single piece of structural foam as a unibody construction will increase the strength and useful life of the chimney crown 100 relative to a chimney crown with a multisection body.
The chimney crown body 160 will be dimensioned to accommodate the chimney 1000. As most chimneys are designed with a rectangular cross-sectional geometry, the chimney crown body 160 exterior and interior walls will typically have a rectangular geometry as well. As those skilled in the art are aware, chimneys may also come in oval, circular, or other custom shapes and the chimney crown of the present invention may be dimensioned and shaped appropriately to work with such chimneys. The upper surface of the chimney crown body will have a slope away from the chimney flue(s) 1000 which will allow for moisture to drain away from the chimney and flue. The downward slope of the upper surface will preferably be at least 10 degrees and will preferably run from the edge of the interior wall to the edge of the exterior wall.
The lower surface of the chimney crown body 160 will preferably have a notch 130 cut out which functions as and will be referred to as a drip slot. The drip slot 130 will preferably be a rectangular notch and will form a complete loop which completely encircles the chimney 1000. In one preferred embodiment the drip slot 130 may preferably be about ¼ inch wide and at least about ¼ inch deep. The drip slot 130 will also preferably be located at least about 1½ inches away from the chimney outer wall. By locating the drip slot 130 at least about 1½ inches from the chimney outer wall the chimney crown 100 will be able to meet the local building code in all or nearly all jurisdictions. When the chimney crown 100 is to be used in a jurisdiction with a building code which recommends locating the drip notch further from the chimney wall, the drip slot 130 will be so arranged to meet the more stringent building code.
To adhere to standard local building codes, the chimney crown body is preferably constructed to allow for the body to extend horizontally at least two inches beyond the outer perimeter of the chimney at all points on the chimney perimeter. This extension horizontally beyond the chimney outer perimeter may herein be referred to as the bottom overhang of the chimney crown. As will be readily apparent to those skilled in the art, the extent to which the chimney crown body overhangs the chimney perimeter may be effected to meet the building code of the local municipality wherein the chimney crown is to be installed.
The chimney crown exterior side walls 120 are preferably flat and aligned perpendicular to the chimney crown bottom surface 150 and parallel to the vertically rising chimney 1000. The exterior side walls 120 preferably have no flaring outwardly away from the chimney 1000 nor inwardly toward the chimney 1000.
The vertical thickness of the chimney crown body 160 is preferably sized to meet local building codes. In one preferred embodiment, the thickness is at least about 2 inches at the chimney crown's outer edge 120. In another preferred embodiment, the vertical thickness of the chimney crown body 160 is between about two inches and about four inches. In yet another preferred embodiment, the vertical thickness of the chimney crown body 160 at the outer edge 120 is between about 3 ½ inches and about four inches. To accommodate unusually tall flues, the vertical thickness may be greater as it is preferable to meet local building codes which typically allow for a maximum flue projection of four inches above the chimney crown 100.
The chimney crown body 160 is preferably covered with a structural coating 170. The structural coating 170 is preferably comprised of a cementitious coating such as the Sto Corporation's Sto Therm CI which is a reinforced mortar comprised of Sto BTS Plus, Sto Reinforcing Meshes; Sto Prime Sand; with outer coating of Stolit Lotusan. As those skilled in the art will realize other cementitous coatings such as the Sto Corporation's Sto Powerwall or Comproco and the like may be used in the alternative.
When the structural coating is comprised of a cementitious coating it is preferably applied to the outer surface of the body in a layered approach with a “scratch coat” placed directly onto the body. As those skilled in the art are aware a scratch coat is a first coat of the material applied with lines scratched into the surface to improve the bond with the next coat to be applied The scratch coat is covered with a mesh and the mesh is covered with an outer coating. It is preferable for the entire structural coating to be about ¼ inch or less thick. It is more preferrable for the entire structural coating to be between about ⅛ inch and about 3/16 inch thick. As those skilled in the art are aware, the mesh may be comprised of a wire mesh, a macrofiber mesh, or a microfiber mesh. It is preferable to comprise the mesh of a microfiber such as a coated glass fiber fabric such as the Sto Corporation's Sto Reinforcing Meshes.
The chimney crown 100 is preferably attached to chimney 1000 with masonry adhesive such as a polyurethane based adhesive or a silicone based adhesive or the like; such as the Rutland 500° F. RTV High Heat Silicone Sealant or the 600° F. RTV High Heat Silicone Sealant manufactured by Rutland of Jacksonville IL. Other readily available means well known in the art such as epoxy and pins may also be used to attach the chimney crown 100 to the chimney 1000. It is preferrable for the chimney crown bottom overhang to extend below the top of the chimney, as this will provide for better sealing of the chimney crown on the chimney as lateral (horizontal) wind forces cannot move the chimney crown from off the chimney; only updrafts need to be accounted for when determining how strong the adhesive bonding the crown to the chimney will be when the crown bottom overhang extends below the top of the chimney. To promote the chimney crown base lower surface extending below the top of the chimney, the lower surface may have a channel carved which is sized to accommodate the top of the chimney.
It is also preferrable for the gap between the chimney crown 100 and the chimney flue 2000 to be filled with a thermally resistant material such as fiberglass insulation. To prevent moisture from entering the fiberglass insulation, it is preferable for the upper surface of the fiberglass insulation to be sealed with a material such as a high temperature caulk designed for masony applications. It is preferrable for the caulk to be a high temperature caulk suitable for masonry applications. The caulk will preferably cover the entire gap between the chimney flue and the inner wall of the chimney crown.
Following generally accepted chimney construction practice, expansion joint material (for versions that the foam isn't comprised of a single piece), caulk (preferably silicone based), metallic or polymer flashing, reinforcing material (for the coating), and any other commonly used materials may be utilized to complete the installation of the chimney crown 100 upon the chimney 1000.
In another preferred embodiment of the chimney crown 200 of the present invention depicted in
As those skilled in the art are aware, the chimney crown of the first embodiment of the present invention could be modified without undue experimentation to protect a chimney with multiple flues.
Although several embodiments of the present invention, methods to use said, and its advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. The various embodiments used to describe the principles of the present invention are by way of illustration only and should not be construed in any way to limit the scope of the invention. Those skilled in the art will understand that the principles of the present invention may be implemented in any suitably arranged device.
Priority for this patent application is based upon provisional patent application 63/532,126 (filed on Aug. 11, 2023). The disclosure of this United States patent application is hereby incorporated by reference into this specification.
| Number | Date | Country | |
|---|---|---|---|
| 63532126 | Aug 2023 | US |
