|(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
(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.
(ii) Exterior walls. Exterior walls shall be designed to withstand
the pressures specified in clause (i) of this subparagraph, acting either
inward or outward.
(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
(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
(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.
(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
(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.
(I) Wood roof decks to which prepared shingles are applied
shall be solidly sheathed. Sheathing shall be well seasoned and dry. Sheathing
boards shall be at least one inch nominal dimension boards not over six inches
wide. Plywood sheathing shall be at least 5/8 of an inch thick.
(II) Attic spaces shall be vented with vent openings so placed
as to circulate air in all parts of the attic.
(III) Nails shall be of sufficient length to extend through
the roof deck (sheathing).
(IV) Thick-butt asphalt shingles shall be nailed in the thick
portion of the shingle.
(V) All butts or tabs of asphalt shingles shall be securely
spotted or tabbed with a plastic, fibrous, asphalt cement or anchored by clips
or locks, and all edges at eaves and gable shall be set in such cement three
inches back from the edge.
(VI) Metal drip edges shall be nailed to the roof deck with
nails not less than ten inches on centers.
(iii) Built-up roof coverings.
(I) For built-up roof coverings cant strips shall be provided
at the angle of roof and vertical surfaces.
(II) Built-up roof coverings shall be carried at least six
inches above the cant strip to a reglet in the parapet and covered with metal
flashing caulked into the reglet. Reglet may be omitted at parapet walls
provided two layers of felt or the equivalent are carried across the top of
the parapet under coping and down the parapet to the lower edge of the cant
strip. The said layers are to run vertically, properly lapped and cemented
to the parapet.
(III) All resinous places in the wood roof deck shall be covered
with sheathing paper or unsaturated felt.
(IV) The first layer or anchor sheet shall be not less than
30-pound felt nailed six inches on center along with a two-inch lap and nailed
12 inches on center both ways in the area between laps with tin caps and one-inch
nails; or shall be not less than two layers of 15-pound felt lapped 18 inches
and nailed through both sheets on six-inch centers along the lap and on 12-inch
centers in the area between laps with tin caps and one-inch nails; or where
the underside of the roof sheathing is to be exposed and its appearance considered,
the first layer shall be not less than a 30-pound felt or two layers of 15-pound
felt nailed six inches on centers along the rafters with tin caps and 1-1/4
inch nails, and nailed 12 inches on centers both ways, between rafters, with
tin caps and 3/4 inch nails.
(V) Each additional sheet above the anchor sheet shall be thoroughly
mopped between layers with a bituminous compound so that no layers touch an
unmopped layer. Bituminous compound for mopping plys together shall be air
refined asphalt or coal tar pitch but shall not be any type of emulsion, cold
or cut back liquid cement, oil, or grease.
(VI) Gravel stop and drip strips, and eave and gable drips
shall be not less than Number 26 gauge galvanized metal, 16 ounce copper or
0.024 inch aluminum, with not less than three-inch flange on roof and nailed
with not less than 3/4 inch nails spaced not more than six inches apart.
(iv) Roll roofing.
(I) Roll roofing shall be applied only over a smooth surface.
Roll roofing shall not be applied over shingle roofs.
(II) Roll roofing applied in a shingle layer shall be spot
mopped and applied by concealed nail method with a minimum three inch head
lap and a minimum six inch end lap properly cemented. Nail spacing shall be
not less than four inches on centers.
(III) Nails that secure roll roofing to the roof deck shall
be driven at least 3/4 of an inch from the edge of the sheet.
(v) Tile roofing.
(I) Tile roofing shall be laid over not less than one layer
of 30-pound asphalt felt securely fastened by nailing with tin caps.
(II) All tile shall be thoroughly watered with a hose before
(III) Every tile shall be laid full length in portland cement
mortar and in addition the first three horizontal courses shall be nailed.
Under certain conditions additional nailing may be required to prevent the
tile from slipping. Mortar shall be not less than one part cement and three
parts sand and not more than 25% lime by volume.
(IV) All nails for flashing and tiles shall be copper.
(vi) Corrugated metal roofing, protected metal roofing, corrugated
and flat sheet asbestos cement roofing.