Continuous Load Path Provided with Connections from the Roof through the Wall to the Foundation

    Scope Images
    Image
    Right - A continuous load path connects the roof and wall framing to the foundation.
    Scope

    Provide a strong and continuous load path from the roof to the foundation to avoid structural damage and to keep the building intact during hurricanes and other extreme storms.

    Best practice steps for new construction:

    • Determine the wind design velocity and if the house is in a hurricane-prone region. 
    • For hurricane-prone regions, a licensed structural engineer must determine the continuous load path connections.
    • For areas where design wind speed is less than that of hurricane-prone regions, a prescriptive design approach may be used:
      • Ensure that roof framing, floor framing, wall framing, and foundations are constructed in accordance with all applicable building codes.
      • Specify and install a continuous load path, such that the building has positive connections from the roof to the foundation to resist and transmit wind uplift and lateral shear loads to the ground (see Description tab for above-code connectors):
        • Install roof sheathing-to-framing connections
        • Install roof-to-wall connections
        • Install wall above-to-below connections
        • Install wall-to-foundation connections
        • Install any chimney-to-roof member connections.

    See the Compliance Tab for related codes and standards requirements, and criteria to meet national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR Certified Homes, and EPA Indoor airPLUS.

    Description

    Load path failures can lead to the loss of parts or all of the building assembly (Figure 1). This guide presents an overview of the continuous load path, with a focus on connections between building component assemblies (roof, wall, foundation) for houses in hurricane-prone regions, high-wind areas, and earthquake-prone regions. Establishing a continuous load path is a requirement in the IBHS FORTIFIED Home Hurricane Standard and IBHS FORTIFIED Home High Wind Standard for the FORTIFIED Gold designation.

    Failure of the load path enabled hurricane winds to pull apart this gable end wall.
    Figure 1. Failure of the load path enabled hurricane winds to pull apart this gable end wall. (Source: FEMA P-762 2009.)

     

    Buildings must be constructed with a strong and continuous load path from the roof to the foundation to avoid structural damage and to keep the home intact during hurricanes, high winds, and earthquakes (FEMA 232 2006).

    The term continuous load path describes the structural condition required to resist all loads acting on a building. Vertical loads include downward gravity forces (weight of the building) and uplift forces from wind. Horizontal (lateral) loads include wind loads perpendicular to a wall (out of plane) and parallel to a wall (in plane or shear). Flood and seismic events can present both vertical and horizontal loads. A continuous load path must transfer all vertical and horizontal loads to the ground. Figures 2, 3, and 4 below illustrate the concept of a continuous load path.

    The connections between major building component assemblies (i.e., roof, walls, floors, and foundations) tend to be the weakest link within a load path. If a connection fails, an alternative load path will form. If the members and connections in the new load path are not strong enough, progressive failure can occur (Figure 1). Loads must be routed around openings such as windows and doors (Figure 4). Accumulated loads on headers are transferred to the studs on the sides of the opening. See the Training tab for several examples of connector details to transfer loads from one building component to another.

    The International Residential Code (IRC) states that constructing buildings as prescribed by the code will result in a system that provides a complete load path for the transfer of loads from their point of origin through the load-resisting elements to the foundation (IRC R301.1). The IRC requires structural assemblies and their attachments to be capable of resisting design wind pressures. For some high-wind regions, the IRC requires design in accordance with other methods, including the International Building Code.

    Homes located in coastal high-wind areas including hurricane-prone regions generally require enhanced attachment that can withstand greater wind speeds than the rest of the country. The IRC defines “hurricane-prone regions” as areas along the Atlantic and Gulf Coasts where wind velocity is greater than 115 mph, and Hawaii, Puerto Rico, Guam, the Virgin Islands, and American Samoa. (See the IRC wind map in the Climate tab). Confirm with the local building department if the house is in a hurricane-prone region and if local requirements exceed those of the IRC.

    A continuous load path uses structural connections to transfer horizontal and vertical loads from the roof to the foundation to help keep the building intact in high-wind and seismic events.
    Figure 2. A continuous load path uses structural connections to transfer horizontal and vertical loads from the roof to the foundation to help keep the building intact in high-wind and seismic events. (Source: FEMA P-499 2010.)

     

    Hurricane straps, hold-down connectors, and bolts help to transfer loads from the building’s walls to its foundation, increasing resistance to vertical and horizontal pressures acting on the building from wind, waves, or ground movement.
    Figure 3. Hurricane straps, hold-down connectors, and bolts help to transfer loads from the building’s walls to its foundation, increasing resistance to vertical and horizontal pressures acting on the building from wind, waves, or ground movement. (Source: FEMA P-499 2010.)

     

    A continuous load path uses structural connections to transfer horizontal and vertical loads from the roof to the foundation to help keep the building intact in high-wind and seismic events.
    Figure 4. A continuous load path uses structural connections to transfer horizontal and vertical loads from the roof to the foundation to help keep the building intact in high-wind and seismic events. (Source: FEMA P-499 2010.)

     

    Table R602.3(3) of the 2018 IRC specifies minimum fastening (nailing) requirements for various components of wood-framed construction, including roof rafter or roof truss to wall top plate; wall bottom plate to floor framing; floor framing to sill or top plate below; and wood structural panels for subfloors, walls, and roofs. Section R602.10 of the IRC provides prescriptive construction details and requirements for braced wall lines and braced wall panels for buildings exposed to different wind speeds.

    Section 2304.10.6 of the International Building Code specifies requirements to a ensure continuous load path. It requires the members to be secured where the wall framing members are not continuous from the foundation sill to the roof.

    The Insurance Institute for Business and Home Safety® (IBHS) offers guidance, best practices, and voluntary construction standards and programs for building in disaster-prone areas including hurricane and high-wind zones. The IBHS FORTIFIED HOME™ standard is designed to make homes more resilient and durable; guidance is available for new construction and existing homes in hurricane zones and high-wind zones. There are three levels of FORTIFIED Home: FORTIFIED Roof™ focuses on the roof; FORTIFIED Silver focuses on roof overhangs, opening protection, gable ends, and attached structures; FORTIFIED Gold focuses on tying all components of the structure together.  The continuous load path is addressed in FORTIFIED Gold.

    The IBHS FORTIFIED Home Hurricane Standard requires that a design professional registered in the state where the home is located must incorporate the continuous load path in the home’s design plan for new construction.

    The IBHS FORTIFIED Home High Wind Standard provides prescriptive measures for a continuous load path for one-story or two-story buildings where the distance between shear walls is less than or equal to 2.5 times the building width. The measures are in addition to the normal fastening schedules specified in the IRC for new homes. For existing homes, the standard requires analysis by a licensed structural engineer for program certification, although the standard does provide some prescriptive retrofit measures.

    Note that IBHS defines high wind areas as areas where the design wind velocity is less than or equal to 115 mph. The term high wind is not defined by the IRC. The IBHS definition of a hurricane-prone region is consistent with the IRC, that is, coastal locations where the design wind velocity is greater than 115 mph. So, in essence, the IBHS definition of high wind areas includes all areas of the continental United States that are outside of hurricane-prone regions. 

    The primary groups of prescriptive measures for the FORTIFIED Home High Wind Standard are shown here; see the Compliance tab for full details:

    1. Specify minimum, or better, roof sheathing thickness, roof sheathing attachment, and roof framing structure for trusses and rafter system.
    2. Anchor the roof structure to the exterior wall below using metal straps.
    3. Specify requirements for interior shear walls.
    4. Specify construction of exterior walls and interior shear walls.
    5. Install wall-to-wall connections for multi-story wood frame buildings.
    6. Specify strapping requirements for openings in wood frame exterior walls.
    7. Anchor floor system and exterior walls to foundation.
    8. Install hold-downs connecting exterior walls and interior shear walls to the foundation.
    9. Install blocking within floor assemblies as required.
    10. Specify gable end bracing requirements.

    How to Provide a Continuous Load Path for New Construction

    • Determine the wind design velocity and if the house is in a hurricane-prone region (See Climate Tab).
    • For hurricane-prone regions, a licensed structural engineer must determine the continuous load path connections.
    • For areas where design wind speed is less than that of hurricane-prone regions, a prescriptive design approach may be used:
      • Ensure that roof framing, floor framing, and wall framing are constructed in accordance with all applicable building codes.
      • Specify and install a continuous load path, such that the building has positive connections from the roof to the foundation to resist and transmit wind uplift and lateral shear loads to the ground (see Description tab for above-code connectors):
        • Install roof sheathing-to-framing connections
        • Install roof-to-wall connections
        • Install wall above-to-below connections
        • Install wall-to-foundation connections
        • Install chimney-to-roof member connections

    Example Details for New Construction from the Fortified Home High Wind Standard

    • Requires metal straps to connect the roof to the wall to meet the load requirements shown below (Table 1):

    Table 1. Roof-to-Wall Connector Minimum Capacities Based on Roof Span and 24-in. Spacing between Rafters and Trusses (Source: FORTIFIED Home High Wind Standard).

    Roof Span (ft)

    12

    16

    20

    24

    28

    32

    36

    Strap Capacity (lb)

    275

    335

    395

    455

    510

    570

    630

    • Connect walls above-to-below to resist cumulative uplift and applicable shear forces using one of the following methods:
    • Install metal straps for connecting wall studs from the wall above to the wall studs in the wall below or from the wall studs above to the rim board and from the rim board to the wall studs below. Straps can be installed on each stud or at some other convenient spacing not to exceed 8 ft.
    • Use a minimum of 4 ft. continuous sheathing that spans across the floor depth to connect the upper wall to the lower wall with the specified number of nails (see Table 2) in the wall studs above the floor and wall studs below the floor. Nail spacing along the studs should not be less than 3 in.

    Table 2. Number of 8d common, 10d box, or 8d ring-shank nails in each stud required to transfer
    loads from studs in wall above to studs in wall below based on roof span indicated
    and a stud spacing of 16 in. (Source: FORTIFIED Home High Wind Standard).

    Roof Span (ft)

    12

    16

    20

    24

    28

    32

    36

    Number of nails in each top and bottom stud for load transfer through continuous sheathing

    2

    3

    4

    4

    5

    6

    6

    • Connect ground wall-to-foundation to resist cumulative uplift and applicable shear force.
    • Bolt the shear wall hold-down connector through the stud. See Figure 5.
    • Specify chimney framing and its connection to roof support members.
    Brackets and straps anchor a shear wall to the bottom plate and band joist.
    Figure 5. Brackets and straps anchor a shear wall to the bottom plate and band joist. (Source: FEMA P-762 2009.)

     

    Ensuring Success

    For a durable continuous load path, it is recommended to hire a licensed structural engineer to specify all building connections, ensure compliance with local building codes, and comply with the requirements defined by the IBHS Fortified Home program

    Climate

    Continuous load path connections are important for all locations but are critical in regions prone to hurricanes, high winds, earthquakes, tornadoes, and floods to reduce the risk of structural damage and failure.

    Wind Regions of the United States.
    Figure 1. Wind Regions of the United States. (Source: IRC 2018, Figure R301.2(5)A)

     

    Seismic map of the 2018 International Residential Code adapted by FEMA to show Seismic Design Categories in color.
    Figure 2. Seismic map of the 2018 International Residential Code adapted by FEMA to show Seismic Design Categories in color. (Source: FEMA 2020).

     

    Right and Wrong Images
    Image
    Right – Examples of framing connectors and brackets.
    Right – Examples of framing connectors and brackets.
    Image
    Right – Examples of roof-top plate framing connectors and brackets.
    Right – Examples of roof-top plate framing connectors and brackets.
    Image
    Right – Examples of wall stud to top plate and stud to rim joist framing connectors and brackets.
    Right – Examples of wall stud to top plate and stud to rim joist framing connectors and brackets.
    Image
    Right – Examples of wall stud to sill plate and foundation and wall rod connectors and brackets.
    Right – Examples of wall stud to sill plate and foundation and wall rod connectors and brackets.
    Image
    Right – Examples of sheathing fastener patterns.
    Right – Examples of sheathing fastener patterns.
    Image
    Right - A continuous load path connects the roof and wall framing to the foundation.
    Right - A continuous load path connects the roof and wall framing to the foundation.
    Image
    Right - Metal connectors provide uplift resistance at the rim joist between floors in new construction for a continuous load path.
    Right - Metal connectors provide uplift resistance at the rim joist between floors in new construction for a continuous load path.
    Image
    Right - Metal connectors provide uplift resistance at the stud-to-bottom plate connection in new construction for a continuous load path.
    Right - Metal connectors provide uplift resistance at the stud-to-bottom plate connection in new construction for a continuous load path.
    Image
    Connection of floor framing to support beam for a coastal home built on piles (band joist nailing to the floor joist is adequate to resist uplift forces).
    Connection of floor framing to support beam for a coastal home built on piles (band joist nailing to the floor joist is adequate to resist uplift forces).
    Image
    Connection of floor support beam to foundation for pile foundation.
    Connection of floor support beam to foundation for pile foundation.
    Image
    Connection of wall to floor framing for a coastal home built on piles.
    Connection of wall to floor framing for a coastal home built on piles.
    Image
    Connection of window header to exterior wall.
    Connection of window header to exterior wall.
    Image
    Continuous load path failure due to improper connections between the roof decking and roof framing resulting from hurricane force winds.
    Continuous load path failure due to improper connections between the roof decking and roof framing resulting from hurricane force winds.
    Image
    Continuous load path failure due to improper connections between a home and its foundation allowed this building to be overturned in hurricane force winds.
    Continuous load path failure due to improper connections between a home and its foundation allowed this building to be overturned in hurricane force winds.
    Image
    Correct roof sheathing to framing connection technique; nails into framing.
    Correct roof sheathing to framing connection technique; nails into framing.
    Image
    Critical connections for providing a continuous load path in buildings and storm shelters
    Critical connections for providing a continuous load path in buildings and storm shelters
    Image
    Framing anchors, anchor bolts, joist hangers, and bridging pieces all help to tie the components of the floor system together and to the foundation to increase resistance against seismic forces.
    Framing anchors, anchor bolts, joist hangers, and bridging pieces all help to tie the components of the floor system together and to the foundation to increase resistance against seismic forces.
    Image
    Shear Strength Comparison Between a Foundation Stud Anchor (on left) and a Shear Transfer Angle (on right)
    Shear Strength Comparison Between a Foundation Stud Anchor (on left) and a Shear Transfer Angle (on right)
    Image
    Uplift forces acting on the roof are met with roof-wall connections that distribute the forces down the walls and into the foundation along the continuous load path.
    Uplift forces acting on the roof are met with roof-wall connections that distribute the forces down the walls and into the foundation along the continuous load path.
    Image
    Right – Hurricane strapping attaches every roof truss to a wall stud.
    Right – Hurricane strapping attaches every roof truss to a wall stud.
    Videos
    Publication Date
    Description
    Video demonstrating the rebuilding in Alabama following April 2011's tornadoes to strengthen new homes by building safer structures with recommendations based on FEMA guidelines.
    Publication Date
    Description
    Video presentation describing the importance of a continuous load path and how good design and construction practices can improve storm resistance per APA guidelines.
    Publication Date
    Description
    Video presentation covering seismic and wind design for wood-framed structures on the topics of load path continuity, building codes, and shear wall design alternatives.
    Publication Date
    Author(s)
    FLASH Strong Home
    Organization(s)
    FLASH
    Description
    Video showing how to create a continuous load path using hurricane straps and anchor bolts to comply with FLASH Strong Home practices.

    Compliance

    The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

     

    The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher.

     

    2018 and 2021 International Residential Code (IRC)

    Table R602.3(3) specifies minimum fastening (nailing) requirements for various components of wood frame construction, including: roof rafter or roof truss to wall top plate; wall bottom plate to floor framing; floor framing to sill or top plate below; wood structural panels for subfloors, walls, and roofs.

    R602.3 Design and construction.

    R602.3.5 Braced wall panel uplift load path.

    R602.10.1.3 Spacing of braced wall lines.

    R602.10.2.1 Braced wall panel uplift load paths.

    Retrofit:  2009, 2012, 2015, 2018,  and 2021 IRC

    Section R102.7.1 Additions, alterations, or repairs. Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with the requirements of this code, unless otherwise stated. (See code for additional requirements and exceptions.)

    Appendix J regulates the repair, renovation, alteration, and reconstruction of existing buildings and is intended to encourage their continued safe use.

     

    2018 International Building Code 

    Section 2304.10 Connectors and fasteners requirements

    Section 2304.10.6 Load paths

     

    IBHS FORTIFIED Home Hurricane Standard

    FORTIFIED Gold Designation Requirements Section

    Appendix D has provisions for corrosion protection retrofit requirements.

     

    IBHS FORTIFIED Home High Wind Standard

    FORTIFIED Gold Designation Requirements Section

    The prescriptive measures required by the FORTIFIED Home High Wind standard for new homes in high wind areas are shown below. These measures are in addition to the normal fastening schedules of the IRC:

    IBHS Fortified Home New Home High Wind Standard: Prescriptive Requirements

    Prescriptive Measures for one-story or two-story buildings where the distance between shear walls is less than or equal to 2.5 times the building width.

    In addition to the normal fastening schedules specified in Table R602.3(1) of the 2006 or later edition of the International Residential Code (IRC)—except for roof and wall sheathing nailing patterns which are replaced by the following minimum requirements when they are more stringent than local code requirements—the following minimum fastening and reinforcing requirements are provided as a prescriptive method for providing a qualified FORTIFIED Home High Wind Continuous Load Path (CLP).

    1. Roof framing system with roof sheathing and sheathing attachment constructed to meet or exceed the following minimum requirements:
      1. Minimum 7 ⁄16-in.-thick wood structural panels
      2. Sheathing attached in accordance with one of the following fastening schedules:
        1. 8d common nails or 10d box nails at 4 in. o.c. on all roof framing members
        2. 8d ring-shank nails at 6 in. o.c. on all roof framing members
      3. Roof structure
        1. If trusses–Engineered trusses designed for minimum Vasd= 110 mph 3- second gust (ASD) design wind loads for terrain Exposure B.
        2. If rafter system: 
          1. Collar ties on all rafter pairs
          2. Rafters sized for span and Vasd= 110 mph 3-second gust (ASD) design wind loads for terrain Exposure B
          3. Install strap, with the minimum capacity listed in Table 9, over top of ridge board connecting tops of rafter pairs.
    2. Anchor roof structure to exterior wall below using metal straps following the requirements listed below:
      1. Metal straps connecting roof structure to exterior wall system at all wall-to-roof framing connections (trusses and rafters) sized to meet the load requirements of Table 8.
      2. If wall sheathing is used to transfer loads from top plate in wood frame walls to studs, metal straps connecting the trusses/rafters to the top plate of the wall must be on the same side as the sheathing or additional metal connectors are required to transfer loads from the wall top plate to the wall studs and they must be located on the same side of the top plate as the metal straps connecting the trusses or rafters to the top plate.
      3. Metal straps from trusses/rafters with the minimum capacity listed in Table 8 can be used to connect directly to wall studs in wood frame walls below if they align vertically within 1½ in.
      4. Wood frame roof structures on masonry walls must be connected to reinforced bond beam at the top of the wall using embedded metal straps that meet the load requirements of Table 8.
    3. Interior shear walls (wood frame walls sheathed with wood structural panels on either side, reinforced masonry walls, or other shear walls, depending on the type of construction) are required when the building length is more than 2.5 times its width. Shear walls must be located at intermediate locations between the end walls so that the distance between shear walls (end or interior shear walls) is never greater than 2.5 times the building’s width.
    4. Exterior wall and interior shear wall (if needed) construction:
      1. Wood frame exterior walls must be fully sheathed including areas above or below wall openings with minimum 7 ⁄16-in. wood structural panels. Interior shear walls must be fully sheathed including areas above or below wall openings with minimum 7 ⁄16-in. wood structural panels on both wall faces. Wall sheathing shall be attached to the wall framing using the following:
        1. For one-story building or top story of two-story building, wood structural panels shall be fastened to the wall studs with 8d common nails, 10d box nails or 8d ring-shank nails at a minimum of 6 in. o.c. along all edges and 12 in. o.c. to framing members in the field of the panels.
        2. For bottom story of two-story building, wood structural panels shall be fastened to the wall studs with 8d common nails, 10d box nails or 8d ringshank nails at a minimum of 3 in. o.c. along all edges and 12 in. o.c. to framing members in the field of the panels.
      2. Masonry exterior walls and interior shear walls must have bond beams with two (2) #5 bars continuous or lapped at least 25 in. Bond beams must be tied together at corners and at the intersection of interior shear walls with the exterior walls with a minimum 25-in. lap on either side of the corner. The bond beam on interior shear walls shall be continuous across the width of the building. Vertical wall reinforcing shall be tied into the bond beam with a minimum 7½-in. hook. All vertical reinforcing shall be continuous or be lapped at least 25 in. to provide adequate development length. Vertical reinforcing (minimum #5 bars) in masonry walls shall be at all corners, on both sides of openings more than 6 ft wide and not more than 8 ft apart along wall segments without openings. Alternatively, reinforcing may be designed using masonry design standards for Vasd= 110 mph 3-second gust ASD design wind loads for terrain Exposure B.
      3. Other wall systems must be built following minimum design requirements for Vasd= 110 mph 3-second gust (ASD) design wind loads for terrain Exposure B and the roof structural system must be adequately anchored to the wall system using connectors with the minimum capacities provided in Table 9.
    5. For multi-story wood frame buildings, load bearing exterior wall systems above and below each floor system shall be connected so that loads pass from the wall system above the floor to the wall system below the floor using one of the following methods to achieve the uplift capacities outlined in Table 9.
      1. Install metal straps that connect wall studs from the wall above to wall studs in the wall below or from wall studs above to the rim board and from the rim board to the wall studs below. Straps can be installed on each stud or at some other convenient spacing not to exceed 8 ft. For example, a 24-ft roof span with straps installed at 4-ft spacing, the required capacity of the strap would be 680 lb (170 lb multiplied by 4-ft spacing).
      2. Use continuous sheathing (minimum 4 ft) that spans across the floor depth to connect the upper wall to the lower wall with the specified number of nails listed in Table 10 in the wall studs above the floor and wall studs below the floor. Nail spacing along the studs shall not be less than 3 in.
    6. Strapping is required at ends of openings in wood frame exterior walls when openings are greater than 3 ft wide:
      1. Strap double top plate to king stud using strapping with 840 lb capacity at each end of opening.
      2. Strap double top plate to header at 16 in. o.c. using strapping with 420 lb capacity at each connection.
      3. Strap end of header to jack stud using strapping with 840 lb capacity at each end of header.
      4. Connect king/jack stud to foundation using strapping with capacity of 1,700 lb at each end of opening.
    7. Anchor floor system and exterior walls to foundation using 5 ⁄8-in.-diameter anchor bolts with 3-in. x 3-in. x ¼-in.-thick plate washers using the appropriate spacing described below:
      1. For slab-on-grade, 24-in. spacing of anchor bolts and within 12 in. of the end of plate. For raised floor foundation including stem-wall foundations:
        1. 72-in. spacing for a one-story structure along exterior walls in long direction of building
        2. 56-in. spacing for a two-story structure along exterior walls in long direction of building
        3. 36-in. spacing for a one-story structure along exterior walls (and interior shear walls if present) in short direction (across width) of building
      2. 24-in. spacing for a two-story structure along exterior walls (and interior shear walls if present) in short direction (across width) of building.
      3. Note: Alternative connections can be developed using guidance provided in Section 2.2 of the American Forest and Paper Association, American Wood Council “Guide to Wood Construction in High Wind Areas for One- and Two-Family Dwellings 110 MPH Exposure B Guide.” If using an alternate method, a description of the connection size and spacing including appropriate references to the American Forest and Paper Association, American Wood Council “Guide to Wood Construction in High Wind Areas for One- and Two-Family Dwellings 110 MPH Exposure B Guide” must be provided to the FORTIFIED Home Evaluator.
    8. Hold-downs connecting exterior walls and interior shear walls to foundation shall be installed as indicated below:
      1. For one-story wood frame construction, hold-downs with a minimum allowable capacity of 3,490 lb (for an 8 ft wall height; 4,360 lb for a 10 ft wall height) must be installed at the exterior corners of the building and at the ends of any interior shear walls where they connect to the exterior walls.
      2. For the top story of two-story wood frame construction, straps or hold-downs with a minimum capacity of 3,490 lb for an 8 ft wall height (4,360 lb for a 10 ft wall height) are required at each exterior corner and each intersection of an interior shear wall with the exterior wall that connect the corner stud system of the wall above to the corner stud system of the wall below.
      3. For the bottom floor of a two-story wood frame building, hold-downs with a minimum allowable capacity of the sum of the required capacity for each story must be installed at the exterior corners of the building and at the ends of any interior shear walls where they connect to the exterior walls. For a second-story wall height of 8 ft and a first-story wall height of 10 ft, the required hold-down capacity for the bottom floor would be 3,490 lb plus 4,360 lb = 7,850 lb.
    9. Blocking shall be installed at floor deck edges in the first 2 joist or truss bays from exterior walls for edges where walls are parallel to floor joists or floor trusses. Blocking shall be spaced a maximum of 4 ft o.c. and connected using three (3) 16d nails at each end and two (2) 16d nails through the floor sheathing above. For a second-floor-level floor system, a strap with a minimum capacity of 200 lb shall be installed so that it wraps the outside edge of the double top plate of the wall below and is connected to the bottom of the blocking in the first bay.
    10. Gable end bracing is required for systems not using balloon framing or walls with continuous reinforcing to the roof deck level. For wood frame roof structure, install continuous 2x4-in. lateral brace at ceiling from gable end truss to opposite end of attic at 6 ft o.c. Each lateral brace to have a minimum 20 gauge metal strap connected to the lateral brace that also wraps over bottom chord of gable end wall plate/truss, over the top plate of wall below and is connected to stud in wall below or to bond beam if wall is masonry construction. Strap to be fastened with ten (10) 8d nails at each end of strap for wood frame wall below or by masonry screws to bond beam for masonry wall below. Blocking (2- x 4-in.) must be added in bay between gable wall framing and first ceiling joist or truss and attached to bottom of lateral brace with four (4) 10d nails.

    Table 7. Required Minimum Capacities for Ridge Straps Connecting Pairs of Rafters Based on Roof Span and 24-in. Spacing between Rafters (Source: IBHS High Wind Standard).

    Roof Span (ft)

    12

    16

    20

    24

    28

    32

    36

    Strap Capacity (lb)

    290

    385

    485

    580

    675

    775

    870

    Table 8. Roof-to-Wall Connector Minimum Capacities Based on Roof Span and 24-in. Spacing between Rafters or Trusses. (Source: IBHS High Wind Standard).

    Roof Span (ft)

    12

    16

    20

    24

    28

    32

    36

    Strap Capacity (lb)

    275

    335

    395

    455

    510

    570

    630

    Table 9. Floor-to-Floor Connection Loads per Ft of Wall Length Based on Roof Span. (Source: IBHS High Wind Standard).

    Roof Span (ft)

    12

    16

    20

    24

    28

    32

    36

    Strap Capacity (lb/ft of wall length)

    80

    110

    140

    170

    195

    225

    255

    Table 10. Number of 8d Common, 10d Box or 8d Ring-Shank Nails in Each Stud Required to Transfer Loads from Studs in Wall Above to Studs in Wall below Based on Roof Span Indicated and a Stud Spacing of 16 in. (Source: IBHS High Wind Standard). 

    Roof Span (ft)

    12

    16

    20

    24

    28

    32

    36

    Number of Nails in Each Top and Bottom Stud for Load Transfer Through Continuous Sheathing

    2

    3

    4

    4

    5

    6

    6

     

    Existing Homes

    IBHS Requirements for Compliance for Existing Homes / Retrofit

    Determining if an existing home has a continuous load path is difficult since the connections that are required to meet the continuous load paths are concealed by finished materials including drywall, trim boards, exterior claddings, etc. FORTIFIED Home High Wind Standards require a licensed structural engineer to perform an analysis for an existing home to provide opinions about whether an adequate continuous load path exists.

    Basic requirements for the retrofit of existing homes to meet the FORTIFIED Gold requirement include:

    • Roof Construction and Framing
    • Ensure truss framing does not exceed 24 in. o.c. The existing truss members should appear to be in sound condition. Wood members of any truss should not be damaged or deteriorated and all truss connector plates must be in good condition.
    • Ensure the roof rafter and ceiling joist framing member size, spacing, span, and framing complies with the minimum requirements of the IRC.
    • The roof rafter framing should either be braced rafter construction or collar ties or ridge strap construction.
    • Wall Construction and Framing
    • Fasten the bottom wall to the foundation and the top of the wall to the floor framing systems with sufficient horizontal diaphragm capacity.
    • Protect the portions of the walls in contact with soil by water-resistant materials.
    • Properly support the floor framing system and sufficiently connect to safely transmit all applicable gravity, uplift, and lateral forces to the structural support system below.

    More Info.

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    References and Resources*
    Author(s)
    APA - The Engineered Wood Association
    Organization(s)
    APA
    Publication Date
    Description
    A publication highlighting recommendations that contribute to improved overall performance in the structural shell and focus on good connection details to tie together exterior walls, roofs and floors.
    Author(s)
    Insurance Institute for Business & Home Safety
    Organization(s)
    IBHS
    Publication Date
    Description
    Report summarizing the requirements for strenghtening and protecting the roof, openings in the house, and creating a continuous load path to strengthen walls and foundation per the IBHS Fortified Homes Hurricane Standard for New Homes.
    Author(s)
    Coulbourne,
    Jones,
    Durham,
    Kapur,
    Koumoudis,
    Line,
    Low,
    Overcash,
    Passman,
    Reeder,
    Seitz,
    Smith,
    Tezak
    Organization(s)
    FEMA
    Publication Date
    Description
    Volume II of a two-volume report providing a comprehensive approach to desing, construction, and renovation of homes located in coastal environments.
    Author(s)
    Federal Emergency Management Agency
    Organization(s)
    FEMA
    Publication Date
    Description
    A guide aiming to assist local officials and community decision makers in coastal areas in adopting and implementing sound mitigation measures to lower building natural disaster vulnerability.
    Author(s)
    International Code Council
    Organization(s)
    International Code Council
    Publication Date
    Description
    2018 edition of code for commercial buildings that brings together all structural, plumbing, mechanical, fuel gas, energy and electrical provisions for all buildings except detached one- and two-family residences and townhouses up to three stories.
    Author(s)
    Insurance Institute for Business & Home Safety
    Organization(s)
    IBHS
    Publication Date
    Description
    Guide describing the requirements by FORTIFIED Home™ for improving the home's resistance in severe thunderstorms, straight-line wind events, and high winds at the outer edges of tornadoes.
    Author(s)
    Federal Emergency Management Agency
    Organization(s)
    FEMA
    Description
    Short article from FEMA explaining what a continuous load path is and the key connection points that make it up.
    Author(s)
    Federal Emergency Management Agency
    Organization(s)
    FEMA
    Publication Date
    Description
    Factsheet describing the concept of load paths and the important connections in a wind uplift load path; also published in FEMA P-499 “Home Builder’s Guide to Coastal Construction: Technical Fact Sheet Series.”
    *For non-dated media, such as websites, the date listed is the date accessed.
    Contributors to this Guide

    The following authors and organizations contributed to the content in this Guide.

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