| (a) General Requirements: For units built on or after
September 1, 1997, the installer must verify that the unit is designed
for the Wind Zone in which it is to be installed and must follow all
applicable installation instructions for that Wind Zone as set forth
herein. Note: A Wind Zone I unit, built on or after September 1, 1997,
may not be installed in a Wind Zone II area. However, a Wind Zone
II unit may be installed in a Wind Zone I area. The counties are defined
in the FMHCSS.
(b) Material Specifications:
(1) Strapping shall be Type 1, Finish B, Grade 1 steel
strapping, 1.25 inches wide and 0.035 inches in thickness, certified
by a licensed professional engineer or architect as conforming with
the American Society for Testing and Materials (ASTM) Standard Specification
D3953 91, Standard Specification for Strapping, Flat Steel, and Seals.
Strapping shall be marked at least every five feet with the marking
described by the certifying engineer or architect.
(2) Tie materials shall be capable of resisting an
allowable working load of 3,150 pounds with no more than 2% elongation
and shall withstand a 50% overload (4,725 pounds total). Ties shall
have a resistance to weather deterioration at least equivalent to
that provided by coating of zinc on steel of not less than 0.30 ounces
per square foot on each side of the surface coated (0.0005 inches
thick), as determined by ASTM Standards Methods of Test for Weight
of Coating on Zinc-coated (galvanized) Iron or Steel Articles (ASTM
A 90-81). Slit or cut edges of zinc-coated steel strapping are not
required to be zinc coated. Ties shall be designed and installed to
prevent self disconnection when the ties are slack.
(3) Anchor spacing ONLY applies to units with roof
pitch of 20 degrees or less. For anything over 20 degrees, it must
be designed by a professional engineer or architect.
(c) Anchors shall be installed:
(1) in direction of load.
Attached Graphic
(2) against direction of load (vertical and/or angled),
and a stabilizer plate must be installed. See the following Placement
of Stabilizing Devices.
Attached Graphic
(d) WIND ZONE I Installation:
(1) Typical anchor layout, single and multi-section
units (WIND ZONE I ONLY).
Attached Graphic
(2) Maximum spacing for Diagonal Ties for Wind Zone
I.
Attached Graphic
(3) Minimum Number of Diagonal Ties for Wind Zone I.
Table based on 2 feet inset of anchors at each end.
Attached Graphic
(4) When auger anchors cannot be inserted into a difficult
soil after moistening, such as mixed soil and rock or caliche (heavily
weathered limestone) that is not solid rock, cross drive rock anchors
may be used in accordance with the values and notes for the table
modified as follows:
(A) Since the ultimate anchor pull out in the difficult
soil will be reduced, the maximum spacing for diagonal ties per side
is one half the spacing allowed by the table in paragraph (2) of this
subsection which will require adding one additional cross drive rock
anchor for each anchor specified for the sides and ends;
(B) The rods of the cross drive rock anchors must be
fully inserted, have at least 24 inches of the rod lengths embedded
in the difficult soil, and be restrained from horizontal movement
by a stabilizer device between the rods and the home; and
(C) Each cross drive rock anchor is connected to one
diagonal tie and is not connected to a vertical tie.
(5) Where vertical tie locations are not easily discernable,
the vertical ties may be connected to the main I-Beam rails and the
anchor installed directly below that connection point. The diagonal
tie must be connected to the opposite main I-Beam. In no case shall
the distance between those ties exceed 5'-4" on-center.
(e) WIND ZONE II Installation:
(1) In place of the requirements as shown in subsection
(d) of this section, units designed for Wind Zone I and built prior
to September 1, 1997, and units designed for Wind Zone II and built
prior to July 13, 1994, require diagonal ties as set forth in this
paragraph when these units are installed in Wind Zone II. See also
§1201.256 of the Standards Act. Items not specifically addressed
in this section are the same as for Wind Zone I installations.
Attached Graphic
(2) Units built to Wind Zone II on or after July 13,
1994.
(A) Units built to Wind Zone II on or after July 13,
1994, should have either built-in, or provisions for connecting, vertical
ties along the sidewall(s) of each unit(s). A diagonal tie must be
installed at each vertical tie location (except for designated shearwall
tie). Built-in vertical ties shall be connected to anchors. If there
are brackets or other provisions for connecting vertical ties, vertical
ties shall be added at the brackets or provisions and connected to
anchors.
(B) Only factory installed vertical ties may be closer
than 4 feet from each other.
(C) Where tie locations are clearly marked as a shear
wall strap, a perimeter pier must be installed at that location. Diagonal
tie is not required.
(D) Where the vertical tie spacing exceeds 8'-0" on-center
(see also note 6 in the table in this paragraph for exception), the
anchoring system must be approved by the home manufacturer's installation
manual, or designed by a professional engineer or architect licensed
in the state of Texas.
(E) Where pier heights exceed 36 inches in height,
the diagonal strap shall be connected to the opposite I-Beam.
(3) Multi-section centerline anchoring requirements
(Wind Zone II only):
(A) Centerline anchor ties are required for ALL Wind
Zone II installations, regardless of the date the unit was manufactured,
when installation occurs on or after the effective date of these rules.
(B) Factory installed centerline vertical ties, brackets,
buckles or any other connecting devices must be connected to a ground
anchor. No additional anchors as described in subparagraph (D) of
this paragraph are required.
(C) To avoid obstructions and/or piers and footers,
the anchor may be offset up to 12 inches perpendicular to the centerline.
(D) Where factory preparations do not exist, install
anchors and angle iron brackets at each side of mating line openings
wider than 48 inches.
(i) Where equal spans exist opposite each other (i.e.,
each section), a double bracket assembly may be used. The maximum
opening is per the table in subsection (f)(4) of this section. Total
uplift load may not exceed the anchor and/or strap capacity (i.e.,
3150 pounds).
(ii) The angle iron bracket is minimum 1 1/2" x 1 1/2"
x 11 gauge. The holes for the lag screws are a maximum of 4 inches
apart and 3/4" from the edge of the bracket.
(iii) Lag screws/bolts are minimum 3/8" diameter x
3 inches, full thread. Note: Pre drill pilot holes.
(4) For openings separated by a wall or post 16 inches
or less in width, the opening span is the total of the spans on each
side of the wall/post.
(f) Bracket Installation.
(1) See the table in paragraph (4) of this subsection
concerning the maximum centerline wall opening for column uplift brackets.
(2) Use a single bracket for openings which exist on
one section only. Use double bracket where openings are opposite each
other on two sections of the home.
(3) When only one bracket assembly is required, it
may be installed on either side of the column/opening stud(s), but
no more than 12 inches from the column or opening stud(s).
(4) When two bracket assemblies are required, they
must be installed on each side of the column/opening stud(s), but
no more than 12 inches from the column/opening stud(s), and they must
be angled away from each other a minimum of 12 inches.
Attached Graphic
(5) Example: A double section unit with each section
being 14 feet wide;
(A) Span "A" is 18'-0", matching span both sections;
(B) Span "B" is 14'-8", matching span both sections;
(C) Span "C" is 6'-8", matching span both sections;
and
(D) Span "D" is 13'-4", one side only.
Attached Graphic
(6) Longitudinal ties:
(A) Longitudinal ties are required for ALL wind zone
installations, regardless of the date of manufacture, when installation
occurs after the effective date of these rules.
(B) Longitudinal ties are designed to prevent lateral
movement along the length of the home.
Cont'd... |
