15C-1.0103. Foundations and Piers

These guidelines shall be used when the installation of foundations and piers is not specified in the manufacturer’s instructions or when the manufacturer’s installation instructions are not available.

(1) Piers:

(a) Piers shall be centered under the I-beam and installed in accordance with Table A. The maximum spacing of piers shall be eight feet (8'). First pier shall be within two feet (2') of either end of the home. The pier foundation shall be a minimum of 4'' x 16'' x 16'' solid concrete pad precast or poured eight inch (8'') minimum in place or other material approved and listed by the department.

(b) Piers may be constructed of regular 8'' x 8'' x 16'' concrete blocks, open cells (with open cells vertical), centered on the footing or foundation. A 2'' x 8'' x 16'' pressure treated or other material approved and listed by the department, pursuant to Rules 15C-1.0105 and 15C-1.0106, F.A.C., shall completely cover the top of the pier with pressure treated shims (1/4'' minimum and 1 1/2'' maximum thickness x 3 1/2'' minimum width × 6'' minimum length) centered and driven tight from both sides of the I-beam between the wood plate or cap and the main frame. Single tiered block piers shall be installed perpendicular to the main I-beam. Exception: When a pier has been capped with at least a four inch (4'') solid concrete block or other material approved and listed by the department, pursuant to Rules 15C-1.0105 and 15C-1.0106, F.A.C., one-fourth inch (1/4'') of wood stock or wood shims or other material approved and listed by the department, pursuant to Rules 15C-1.0105 and 15C-1.0106, F.A.C., shall be installed between the pier and steel I-beam. (See Figures A, B and D)

(c) Center Line and Perimeter Piers: Center line piers shall be located at each end of center line and eight feet (8') on center, except where openings of four feet (4') or greater occur, piers shall be located on each end of the opening within six inches (6'') of jamb studs or ridge beam posts. (See Figures A, B, C and D) Any openings fifteen feet (15') or larger in the exterior sidewall and/or marriage wall shall require blocking at each end of the opening with three (3) 4'' x 16'' x 16'' pads (See Figure D). Piers shall also be installed on each side of any perimeter door or fireplace. Bay windows or any opening forty-eight inches (48'') or more shall require blocking at each end. Fourteen feet (14') or wider units with I-beam spread of less than eighty-two inches (82'') and twelve feet (12') wide units with an I-beam spread of less than seventy-five and one-half inches (75 1/2'') shall have perimeter blocking installed at a minimum of eight foot (8') on center. Piers shall not be required under the clear (open) spans between ridge beam posts.

(d) All piers over thirty-six inches (36'') and corner piers over twenty-four (24'') in height shall be double tiered with blocks interlocked and capped with two (2) 4'' x 8'' x 16'' solid concrete blocks side by side and perpendicular to the I-beam or other material approved and listed by the department pursuant to Rules 15C-1.0105 and 15C-1.0106, F.A.C., and cushioned with wood shims or pressure treated plate. Pier height is measured from top of footer or foundation to top of cement block stack, including 4'' cap block(s). (See Figures B and D)

(e) All piers over fifty-two inches (52'') shall comply with local requirements.

(f) Metal and/or precast support piers shall be installed on a base or footer of a minimum size of 4'' x 16'' x 16'' solid concrete or other material approved and listed by the department. (See Figure C)

(g) Metal and/or precast support piers shall be restricted to a maximum four inch (4'') locking mechanical height adjustment and shall be restricted to a maximum height of not more than twenty-four inches (24'') measured from the ground base or footer. This twenty-four inch (24'') maximum shall not include the four inch (4'') mechanical extension or adjustment. Exception: Center line or perimeter supports are permitted to exceed the twenty-four inch (24'') maximum. (See Figure C)

(h) The minimum distance between the finished grade under all new and used mobile/manufactured homes and the bottom of the I-beam shall be eighteen inches (18''). Where the grade is sloped, twenty-five (25%) of the lowest member of the main frame may be set below eighteen inches (18''); however, under no circumstances may the bottom of the I-beam be set below twelve inches (12'') from the finished grade.

(2) Foundations:

(a) Concrete pads or foundations shall be a minimum of two thousand five hundred (2,500) pounds per square inch (psi).

(b) Plastic pads or foundations shall be tested in the lower fifty percent (50%) of each soil class.

Rulemaking Authority 320.011, 320.8325(2) FS. Law Implemented 320.77(10), 320.822(12), 320.8285, 320.8325, 320.835(2) FS. History–New 1-10-94, Amended 10-2-95, 3-31-99.