(a) Areas Seaward of the Intracoastal Canal.
  (1) Applicability. This code contains requirements for the construction of buildings to minimize damage to such buildings by severe windstorms which occur along the Gulf Coast. Where specific requirements for particular devices or methods of construction are specified, alternate methods or practices which are considered equal may be used. Such consideration is to based on sound engineering practice and experience. The degree of protection against damage from windstorm provided by these requirements cannot be assured for tornadoes, but such compliance should be helpful to some degree in reducing tornado damage. The requirements herein are applicable only to properties located seaward of the Intracoastal Canal on the Texas coastline (or seaward of the boundary authorized to be established by the Commissioner by the Insurance Code, Article 21.49, as amended). The requirements herein shall apply, on or after October 10, 1988, to May 31, 1998, to new construction of, and additions or repairs to, structures located seaward of the Intracoastal Canal in areas previously exempt from the requirements of this subsection. The property previously exempt was that property protected by a sea wall constructed by the Corps of Engineers.
  (2) Building code standards.
    (A) Wind pressure.
      (i) When considered. All buildings and structures shall be designed to resist a horizontal wind pressure on all surfaces exposed to the wind, allowing for wind in any direction, in accordance with the following table. No allowance shall be made for the shielding effect of other buildings or structures. The height is to be measured above the average level of the ground adjacent to the building or structure.
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      (ii) Exterior walls. Exterior walls shall be designed to withstand the pressures specified in clause (i) of this subparagraph, acting either inward or outward.
      (iii) Roofs.
        (I) The roofs of buildings and structures shall be designed and constructed to withstand pressures, acting outward normal to the roof surface, equal to 1 1/4 times the pressures specified in clause (i) of this subparagraph. The height is to be taken as the vertical distance from the average elevation of the ground adjoining the building to the average elevation of the roof.
        (II) Roofs or sections of roofs with slopes greater than 30 degrees shall be designed and constructed to withstand pressures, acting inward normal to the surface, equal to those specified in clause (i) of this subparagraph and applied to the windward slope only.
        (III) Overhanging eaves and cornices shall be designed and constructed to withstand outward pressures equal to twice those specified in clause (i) of this subparagraph.
      (iv) Chimneys, tanks and towers. Chimneys, tanks, solid towers, and similar structures shall be designed and constructed to withstand the pressures specified in clause (i) of this subparagraph multiplied by the following factors:
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      (v) Other structures. The design wind pressures for structures not covered in this paragraph shall be in accordance with generally accepted engineering practice and shall be subject to the approval of the building official.
      (vi) Stability. The overturning moment due to wind pressure shall not exceed 50% of the moment of stability due to the dead load only, unless the building or structure is securely anchored to the foundation to resist this force.
      (vii) Roofing materials. Roofing materials must pass the U.L. Standard 997 or a comparable test certified by the Commissioner and be installed as required by the Department, to promote wind resistance of the materials.
    (B) Anchorage.
      (i) Heavy timber construction (as defined in the Texas Commercial Property Rating Manual in effect prior to September 1, 1994). Every roof girder and every roof beam shall be anchored to an exterior or interior wall or to a properly designed interior column. Wall beams and plates shall be anchored to the wall with approved type anchors not more than four feet apart. Roof planking where supported by a wall shall be anchored to such wall at intervals not exceeding four feet. Roof trusses shall be securely anchored to masonry walls at point of bearing. Monitor and saw tooth construction shall be anchored to the main roof construction. Anchors shall consist of steel or iron bolts or straps of sufficient strength and ample anchorage to resist vertical uplift of the roof as required in subparagraph (A)(iii) of this paragraph.
      (ii) Ordinary construction (masonry).
        (I) All trimmers and at least one beam or joist in every four feet resting on masonry walls shall be secured to such walls by approved metal anchors attached at or near the bottom in a manner to be self-releasing. Each end of a trimmer, beam, or joist that is supported by a girder shall be secured or tied in an approved manner to such girder or to a trimmer, beam, or joist correspondingly supported from the opposite side of such girder. Anchors and ties shall be so arranged as to form continuous ties between opposite masonry walls.
        (II) Where floor or roof joists or beams run parallel to masonry walls, such walls shall be secured to four or more joists of the floor or roof construction by approved metal anchors at maximum intervals of eight feet for dwellings, and six feet in other buildings.
        (III) Wall plates and roof construction shall be anchored to the walls at least every six feet, except that wall plates and roof construction shall be anchored at intervals of four feet to hollow concrete masonry walls which do not have cast-in-place reinforced concrete tie beams.
        (IV) Wooden girders shall be anchored to the walls and fastened to each other with suitable steel straps placed near the bottom of the girder.
        (V) At least every third rafter shall be anchored to the ceiling joists or partitions directly beneath by not less than the equivalent of one-by-six-inch boards securely nailed. Such braces shall be attached to the rafters at their midpoints or at the third points if two are used per rafter. In peaked roofs opposite rafters shall be laterally braced to each other at the ridge in a manner satisfactory to the building official.
        (VI) Roof trusses shall be securely anchored to masonry walls at points of bearing.
        (VII) Anchors shall consist of steel or iron bolts or straps of sufficient strength and ample anchorage to resist vertical uplift of the roof as required in subparagraph (A)(iii) of this paragraph.
      (iii) Wood frame construction.
        (I) Sills shall be anchored to the foundation walls to develop a strength equivalent to 1/2-inch bolts with proper washers embedded six inches in concrete foundation walls and spaced six feet apart.
        (II) Rafters shall be anchored to the wall plate by approved metal anchors attached to at least every other rafter or shall be otherwise anchored in an approved manner.
        (III) In all buildings 20 feet or more in width where joists run at right angles to the rafters, the rafters shall be tied to the ceiling joists with wood or metal ties nailed to the foot of alternate rafters and extending across four joists well nailed to each joist.
        (IV) Girders resting on masonry foundation walls or piers shall be anchored thereto with not less than 1/2-inch bolts embedded at least six inches in masonry.
        (V) Wooden columns and posts shall be securely anchored to their foundations and to the members which they support.
        (VI) At least every third rafter shall be anchored to the ceiling joists or partitions directly beneath by not less than the equivalent of one-by-six-inch board securely nailed. Such braces shall be attached to the rafters at their midpoints or at the third points if two are used per rafter.
        (VII) Each rafter shall be laterally braced to the opposite rafter at a point underneath the ridge, in order to form a brace known as the "A" type of "collar beam," except that roof construction of the "exposed cathedral type" or "exposed shed type" may have such bracing omitted when the rafters are securely anchored and braced in an approved manner. Roof framing and trussing of all other types of roof construction shall be anchored by an approved method.
    (C) Roof covering installation.
      (i) General requirements for all roof coverings. Roof coverings shall be securely attached to the roof in accordance with the manufacturer's installation instructions and specifications and with the methods approved by the building official. Nails, clips, and similar attaching devices shall be galvanized or otherwise suitably corrosion resistant.
      (ii) Prepared shingle roof coverings.
Cont'd...