Anchoring system for manufactured housing

An anchoring system for a manufactured home and a method of anchoring a manufactured home utilizing longitudinal central and exterior slabs, strap anchors embedded in the slabs, and straps connecting the home to the slabs, where the straps extend from the central slab to an exterior I-beam underneath the home and from the exterior slab to an interior I-beam on each end of home, and where frame straps extend from the home to anchors in the exterior slabs and longitudinally spaced interior straps extend from the exterior slabs to the interior I-beams.

BACKGROUND OF THE INVENTION
 This invention relates generally to the field of systems, methods, or
 devices used to secure, stabilize or anchor manufactured homes to the
 ground after the homes have been transported to the building site and
 mounted onto support piers. More particularly, the invention relates to
 such systems, methods or devices which utilize metal tie down straps
 connected to ground anchors.
 Manufactured homes are produced at factories and then transported to sales
 centers and final building sites for assembly and use. The overall size of
 the transportable units are limited by transportation considerations, in
 that they cannot exceed certain maximum dimensions for travel over
 roadways. It is thus very common to provide for manufactured homes which
 are built in separate components or units which can be individually
 transported to the sites and then assembled. Such homes are often referred
 to as double wide home, since it is very common to provide two
 longitudinally extensive units which are joined lengthwise to form the
 larger finished home. The units are constructed on two parallel chassis
 I-beams, the I-beams providing longitudinal support and allowing for the
 attachment of wheels to the units for transport. The I-beams remain
 exposed beneath the floor of the home. At the assembly or use site, the
 I-beams are usually supported by a large number of spaced support piers or
 columns, constructed of concrete blocks with wedge-shaped wooden inserts
 to provide for the proper support height beneath the I-beam at each
 location.
 Because the manufactured homes are to be transported, excessive weight
 cannot be tolerated, and so manufacturing considerations stress strong but
 light materials for construction. This fact, along with the fact that they
 are positioned several feet above ground level, means that the homes are
 very susceptible to adverse effects of high winds, especially if the area
 below the structure is not covered. Therefore, federal and local codes and
 standards related to manufactured homes require that the homes be provided
 with an anchoring system to stabilize the home against wind load effects.
 The most commonly utilized system involves a large number of metal straps
 which are secured to the frames, trusses or I-beams of the manufactured
 homes and then to ground anchors embedded into the ground around and
 beneath the home. A major problem with these systems is that the fixation
 and retention of the ground anchors, which usually comprise a shaft with
 helical plates which is rotated into the ground, is highly dependent on
 the type and density of the soil as well as the particular angle of
 insertion relative to the tensile load. Under high wind loads, movement of
 the anchors or actual bending of the upper portion of the anchor is not
 uncommon, resulting in loss of stabilization of the manufactured home. The
 home may shift horizontally or vertically relative to the support piers,
 which can cause damage or complete destruction of the home.
 An example of an improved stabilization system for manufactured housing is
 shown in U.S. Pat. No. 5,697,191 to MacKarvich. Straps are connected in a
 crossing manner from the I-beams to ground anchors, and stabilizing plates
 extend between adjacent support piers and from the support piers to the
 ground anchors, thus maintaining the ground anchors in a spaced relation
 to prevent movement of the anchors in a direction which would loosen the
 straps. This system continues to utilize helical anchors placed into the
 ground, and does not provide any means to directly counter movement in the
 longitudinal direction.
 It is an object of this invention to provide a system and method for
 securing, stabilizing and anchoring a manufactured home which effectively
 precludes movement in all directions, horizontal and vertical, when placed
 under wind load forces. It is an object to provide such a system and
 method which utilize standard metal straps and embedded anchors which
 receive the straps, such that the system can be assembled easily and
 quickly without recourse to special equipment. It is an object to provide
 the system and method where the straps are connected directly to the
 I-beams supporting the manufactured housing units. It is an object to
 provide such a system and method where lateral and longitudinal movement
 is less than one half inch at 150% of the design load.
 SUMMARY OF THE INVENTION
 The invention comprises in general an anchoring or stabilization system and
 method for securing and immobilizing manufactured homes which are
 prefabricated on parallel chassis I-beams and transported to a remote site
 for installation, where two units are joined lengthwise to create a larger
 home often referred to as a double wide home. Support piers are positioned
 at spaced intervals under the I-beams to support the entire home a short
 distance above the ground, and tie down metal straps connect the I-beams
 or the frame of the home to ground anchors to prevent excessive movement
 during high winds.
 The system of the invention comprises longitudinally extending foundation
 slabs of poured concrete which extend beneath the I-beams of the home,
 preferably a relatively wide central slab which resides beneath both
 interior I-beams and a pair of less wide exterior slabs, one positioned
 beneath each exterior I-beam. The support piers are positioned atop the
 foundation slabs, and typically comprise concrete blocks and wedges for
 leveling adjustments. Anchors which receive the straps are embedded in the
 foundation slabs at particular locations, with certain straps running
 longitudinally while the majority of the straps extend laterally. At each
 end of the home, lateral end straps are crossed to form an "X" between the
 exterior slab and the central slab for each of the two home component
 units, with one lateral strap extending from an anchor embedded in the
 central slab to the exterior I-beam of the unit and the other lateral
 strap extending from an anchor embedded in the exterior slab to the
 interior I-beam of the same unit. The lateral straps are preferably
 connected to the I-beams by a clip or hook attached to the end of the
 strap, with the strap wrapped around the I-beam to secure the clip in
 place. For each unit, a longitudinal strap extends from an anchor embedded
 in the central slab to the interior I-beam at each end, with the strap
 preferably connected to the vertical component of the I-beam by a
 mechanical fastener. Frame straps extend downward at spaced longitudinal
 intervals along the sides of the units from the outside frames or trusses
 of each unit and are connected to the ground anchors securing the interior
 lateral straps which extend upward to the interior I-beams. For longer
 units, a second pair of anchors may be centrally positioned on the central
 slabs, with the lateral straps extending upward from the central slab to
 the exterior I-beams.
 This combination of longitudinal foundation slabs, embedded anchors,
 crossed lateral end straps, interval-spaced interior lateral straps and
 frame straps provides an anchoring system which rigidly connects the
 manufactured home to the ground, such that very little movement occurs
 under relatively severe wind load.

DETAILED DESCRIPTION OF THE INVENTION
 With reference to the drawings, the invention will now be described in
 detail with regard for the best mode and the preferred embodiment. The
 invention is a system and method for stabilizing, securing and anchoring a
 manufactured home, and in particular a manufactured home comprised of two
 prefabricated component units joined lengthwise to form a unitary home, to
 severely limit movement of the home when exposed to high wind loads. In
 general, the system comprises a longitudinally extending central
 foundation slab 11, a pair of longitudinally exterior foundation slabs 12,
 anchors 21 embedded into the slabs 11 and 12, sets of lateral crossing end
 straps 31 and 32 connected to the anchors 21 and to the I-beams 91 of the
 manufactured home 90, longitudinal straps 33 connected to anchors 21
 embedded in the central slab 11 and to the I-beams 91, interior lateral
 straps 34 connected to anchors 21 embedded in the exterior slabs 12 and to
 the I-beams, and exterior frame straps 35 connected to anchors 21 embedded
 in the exterior slabs and to the frames or trusses of the manufactured
 home 90.
 The system may be utilized with homes 90 of differing dimensions, and the
 preferred dimensions and locations of various components are often
 determined by the particular location of predetermined features on the
 manufactured home 90. In particular, the length, width and separation of
 the foundations slabs 11 and 12, and the location of most of the anchors
 21 are a function of the dimensions of the home 90, the location of the
 I-beams 91 and the location of the frame straps 35, for example.
 Therefore, the dimensions set forth herein are for illustration purposes
 only and are not to be taken as limiting regarding the scope of the
 invention.
 Referring to FIG. 1, the relative positions of the foundation slabs or
 footers 11 and 12 are indicated, along with the positioning of the anchors
 21 and support piers 13. The elongated rectangular foundation slabs 11 and
 12 are formed of poured concrete preferably containing reinforcing fibers,
 mesh or the like, each approximately about 12 inches in depth. The lengths
 of the slabs 11 and 12 are approximately equal to the length of
 manufactured home 90. The central foundation slab 11 is of sufficient
 width so as to reside beneath both interior I-beams 91 on the home 90.
 Preferably, central slab 11 is composed as a unitary member, but it could
 be composed of two individual narrow slabs. The exterior foundation slabs
 12 are parallel to the central slab 11 and are positioned directly beneath
 the exterior I-beams 91, with a width sufficient to fully underlie the
 support piers 13. The foundation slabs 11 and 12 are produced with a
 relatively planar surface, and the support piers 13 are constructed
 directly atop the slabs 11 and 12. The support piers 13 may be of any
 suitable known construction, such as multiple concrete blocks or metal
 jacks, and typically are topped with wedge-shaped wooden inserts for
 precise height control are each pier 13. The support piers 13 are spaced
 at intervals longitudinally, and preferably are aligned laterally as well,
 as shown in the drawing.
 Prior to hardening of the poured concrete in the slabs 11 and 12, strap
 anchors 21 are embedded at various locations. Anchors 21 may be of any
 known type used in conjunction with metal tie down straps 30 and which are
 suitable for concrete embedment, and typically comprise a depending curved
 or jointed rod or rods connected to a generally U-shaped bracket retaining
 one or two slotted bolts to receive the straps 30. The bracket remains
 above the surface of the concrete with the rods embedded therein to secure
 the anchor 21. On the exterior slabs 12, the anchors 21 are embedded at
 generally evenly spaced, longitudinal intervals, preferably toward the
 outer edge of the slabs 12, and are oriented to receive straps 30
 extending in the lateral direction. The anchors 21 are typically spaced at
 about five foot intervals, and an anchor 21 should be positioned within
 five feet of each end of the exterior slabs 12. On the central slab 11, a
 pair of anchors 21 for receiving laterally oriented straps 30 are
 positioned within about five feet of each end, with the anchors 21
 preferably located toward the outer edge of the central slab 11. One or
 two anchors 21 are positioned on each end of the central slab 11, each
 preferably aligned beneath one side of the interior I-beams 91, and these
 anchors 21 are oriented to receive straps 30 extending in the longitudinal
 direction. For longer homes 90, an additional pair of laterally oriented
 anchors 21 may be located in the middle region of the central slab 11. In
 many homes 90, marriage wall straps 36 are provided near each end, and a
 corresponding anchor 21 is embedded along the midline of the central slab
 11 for attachment of these straps 36.
 With reference to FIGS. 2, 3 and 4, the arrangement of the strap members 30
 can be seen. Such straps 30 are well known and standard in the industry,
 and typically comprise thin steel strips about 1.25 inches wide and about
 0.037 inches thick, usually galvanized and capable of withstanding loads
 in excess of 5500 pounds without failure. Lengths may be joined by
 crimping connectors to form longer straps 30 where necessary. The strap
 members 30 comprise interior lateral crossing end straps 31, exterior
 lateral crossing end straps 32, longitudinal straps 33, interior lateral
 straps 34 and exterior frame straps 35. Frame straps 35 are secured to the
 structure during the manufacturing process, and extend from the internal
 frame or trusses of the manufactured home 90 outward beneath and behind
 the side walls at spaced intervals, typically about five feet apart. The
 remaining straps 30 are usually connected on site in the assembly process.
 Focusing now on FIGS. 2 and 3, the home 90 comprises two separate units 93
 and 94 joined lengthwise along a marriage wall 92. The arrangement of the
 anchors 21 and straps 30 are preferably symmetrical with respect to each
 unit. At each end of each unit 93 and 94, an interior lateral crossing end
 strap 31 extends from an anchor 21 embedded in the central slab 11 up to
 the exterior I-beam 91, and an exterior lateral crossing end strap 32
 extends from an anchor 21 embedded in one of the exterior slabs 12 upward
 to the interior I-beam 91, such that the straps 31 and 32 form an X-shape
 when viewed down the longitudinal direction. The straps 31 and 32 are
 secured to the anchors 21 and tightened in standard fashion. The straps 31
 and 32 are preferably connected to the I-beams 91 as shown in FIG. 6. A
 clip or hook member 37 is connected to the end of each strap 31 or 32, and
 the clip 37 is mounted onto the far edge of the top member of the I-beam
 91. The strap 31 or 32 is then wrapped around the I-beam 91 to completely
 encircle it so as to further retain the clip 37 in place when the strap 31
 or 31 is tightened and secured to the anchor 21.
 The endmost frame straps 35 are connected to anchors 21 mounted in the
 exterior slabs 12, preferably the same anchors 21 retaining the exterior
 lateral crossing end straps 32. The anchors 21 are mounted so as to be
 positioned inward from the exit point of the frame straps 35, so that the
 straps 35 angle inwardly toward the exterior slabs 12. The home 90 is also
 anchored at spaced longitudinal intervals as shown in FIG. 4. The interior
 frame straps 35 are connected to longitudinally spaced anchors 21
 positioned in the exterior slabs 12. Interior lateral straps 34 are
 disposed from longitudinally spaced anchors 21 positioned in the exterior
 slabs 12 and extend to the interior I-beams 91, with the straps 34
 encircling the I-beam 91 and clipped in place as shown in FIG. 6.
 Preferably, some or all of the anchors 21 mounted in the exterior slabs 12
 retain both an interior lateral strap 34 and a frame strap 35.
 A pair of longitudinal straps 33 connect the interior I-beams 91 to the
 central slab 11 on each end. The straps 33 are connected in known manner
 to longitudinally oriented anchors 21 preferably mounted beneath the
 exterior edges of one or both of the interior I-beams 91 near each end of
 central slab 11. The longitudinal straps 33 are connected to the vertical
 member of the I-beam 91 by suitable mechanical fastening means 38, such as
 a bolt and nut combination extending through an aperture cut into the
 I-beam 91, as shown in FIG. 5. The longitudinal straps 33 are joined to
 the I-beams 91 inward from the anchors 21, so that the strap 33 is
 positioned at an angle to better resist longitudinal movement. Similar
 longitudinal straps 33 could also be mounted and connected to the exterior
 I-beams if desired.
 The anchoring system described above is much superior to the standard
 anchoring systems currently in use. Load testing under established
 protocols were performed on a 28' by 44' double wide manufactured home
 anchored with the system of the invention. Load ratings based on the
 Federal Manufactured Homes Construction and Safety Standards were
 employed, to wit, 47 pounds per square foot horizontal wind load and 32
 pounds per square foot uplift wind load. Three lifting beams were placed
 under the I-beams, perpendicular to the main frame. Air operated jacks
 were placed on rollers under the lifting beams, two for each beam. Lateral
 and longitudinal loads were applied, with steel beams used to distribute
 the transverse and longitudinal loads to the home. For lateral testing,
 the loads were applied to the outer ends of the 2" by 6" floor joists by
 means of the steel beams. For longitudinal testing, the loads were applied
 to the ends of the I-beams. Load cells were utilized to measure the
 applied loads. Rulers and plumb bobs were used to indicate horizontal
 movement. Loads were applied in increments equal to 25% of the design load
 up to an upper limit of 150%.
 Because of the shortcomings of the known anchoring systems, regulations
 typically allow for horizontal travel of up to 9 inches in any one
 direction under design load. Thus in a wind reversal situation, such as
 would be encountered with a tornado or hurricane, where the wind would
 first strike the home from one direction followed by wind striking the
 home from the opposite direction, a home which is secured under acceptable
 standards can travel a total of 18 inches, which would at a minimum result
 in extensive damage to the structure and most likely would result in the
 home being knocked from its supports. The test results for the system at
 hand show an incredible improvement in stabilization of the home. For the
 lateral load test at 27,500 pounds, horizontal movement ranged only from
 0.30 to 0.16 inches, with an average of approximately 1/16" at design load
 and less than 1/4" at 150%. For the longitudinal load test at 19,360
 pounds, the horizontal movement ranged only from 0.61 to 0.32 inches, with
 an average of approximately 3/16" at design load and less than 3/8" at
 150%. Thus in a wind reversal situation, the home would only move a
 maximum of 1/2 inch. Vertical movement in these tests was negligible.
 It is contemplated that equivalents and substitutions for elements set
 forth above may be obvious to those skilled in the art, and therefore the
 true scope and definition of the invention is to be as set forth in the
 following claims.