Wind Damage >> Protecting Against Hurricanes

Attachment of Brick Veneer in High-Wind Regions Table 1. Brick Veneer Tie Spacing Wind Speed (mph)(3-Second Peak Gust) Maximum Vertical Spacing for Ties 16" stud spacing 24" stud Protecting Against Hurricanes spacing 90 18.0a 16.0a 100 18.0a 16.0a 110 18.0a 14.8 120 18.0a NAb 130 15.9 NAb 140 13.7 NAb 150 10.2 Nab 

Wind Pressure (psf) Maximum Vertical Spacing for Ties 16" stud spacing Protecting Against Hurricanes 24" stud spacing 17.8 18.0a 16.0 a 22.0 18.0a 16.0 a 26.6 18.0a 14.8 31.6 18.0a NA b 37.1 15.9 NA b 43.0 13.7 NA b 49.4 10.2 Na b Notes: 1. 

The tie spacing is based on wind loads derived from Method 1 of ASCE 7-02, for the corner area of buildings up to 30' high, located in Exposure B with an importance factor (I) of 1.0 and no topographic influence. For other heights, exposure, or Protecting Against Hurricanes importance factor, an engineered design is recommended. 2. 

Fastener strength is for wall framing with a Specific Gravity G=0.55 with moisture contents less than 19% and the following adjustment factors, Protecting Against Hurricanes Ct=0.8; and CD, CM, Ceg, and Ctn=1.0. 3. 

Nail embedment depth of 2" for 2.5" long 8d common (0.131" diameter) ring- shank fasteners a Maximum spacing allowed by ACI 530-05 b 24" stud spacing exceeds the maximum horizontal tie spacing of ACI 530-05 prescribed for wind speeds over 100 mph [End table] Attachment of Protecting Against Hurricanes Rooftop Equipment in High-Wind Regions

Hurricane Katrina Recovery AdvisoryMay 2006, Revised July 2006FEMA Purpose: To recommend practices for designing and Protecting Against Hurricanes installing rooftop equipment that will enhance wind resistance in high-wind regions. [Begin text box]

Note: For attachment of lightning protection systems, see Hurricane Katrina Recovery Advisory on Protecting Against Hurricanes Rooftop Attachment of Lightning Protection Systems in High-Wind Regions. [End text box] Key Issues Rooftop equipment frequently becomes detached from rooftops during hurricanes. 

Water can enter the building at displaced equipment (see Figure 1); displaced equipment can puncture and Protecting Against Hurricanes tear roof coverings (thus allowing water to leak into the building). Equipment blown from a roof can damage buildings and injure people. Damaged equipment may no longer provide service to the building. Figure 1 caption. 

This gooseneck was attached with only two small screws. A substantial amount of water was able to enter the building during the hurricane. [end of caption] Construction Guidance Mechanical Penthouse: Protecting Against Hurricanes By placing equipment in mechanical penthouses rather than being exposed on the roof, equipment within penthouses is shielded from high-wind loads and windborne debris. 

Therefore, use of mechanical penthouses designed and constructed in accordance with a current building code are recommended, Protecting Against Hurricanes particularly for critical and essential facilities.Design Loads and Safety Factors: Loads on rooftop equipment should be determined in accordance with the 2005 edition of ASCE 7. Figure 2 caption. 

This 30’ x 10’ x 8’ 18,000-pound HVAC unit was attached to its curb with 16 straps (one screw per strap). Although the wind speeds were Protecting Against Hurricanes estimated to be only 85 to 95 miles per hour (3-second peak gust), it blew off the building. [end of caption] 

Note: For guidance on load calculations, see "Calculating Wind Loads and Anchorage Requirements for Rooftop Equipment,” ASHRAE Journal, volume 48, number 3, March 2006. A minimum safety factor of 3 is recommended for critical and essential facilities, and Protecting Against Hurricanes a minimum safety factor of 2 is recommended for other buildings. 

Loads and resistance should also be calculated for heavy pieces of equipment (see Figure 2). Simplified Attachment Table: To anchor fans, small HVAC units, and relief air hoods, Protecting Against Hurricanes the following minimum attachment schedule is recommended (see Table 1) (note: the attachment of the curb to the roof deck also needs to be designed to resist the design loads):   

Number of #12 Screws for Base Case Attachment of Rooftop Equipment Case No.: 1 Curb Size and Equipment Type: 12”x 12” Curb with Protecting Against Hurricanes Gooseneck Relief Air Hood Equipment Attachment: Hood Screwed to Curb Fastener Factor for Each Side of Curb or Flange: 1.6 Case No.: 2Curb Size and Equipment Type: 12”x 12” 

Gooseneck Relief Air Hood with Flange Equipment Attachment: Flange Screwed to 22 Gauge Steel Roof Deck Fastener Factor for Each Side of Curb or Protecting Against Hurricanes Flange: 2.8 Case No.: 3Curb Size and Equipment Type: 12”x 12” Gooseneck Relief Air Hood with FlangeEquipment Attachment: Flange Screwed to 15/32” OSB Roof Deck 

Fastener Factor for Each Side of Curb or Flange: 2.9 Case No.: 4Curb Size and Equipment Type: 24”x 24” Curb with Gooseneck Relief Air HoodEquipment Attachment: Hood Screwed to Protecting Against Hurricanes Curb Fastener Factor for Each Side of Curb or Flange: 4.6 Case No.: 5Curb Size and Equipment Type: 24”x 24” Gooseneck Relief Air Hood with Flange

Equipment Attachment: Flange Screwed to 22 Gauge Steel Roof Deck Fastener Factor for Each Side of Curb or Protecting Against Hurricanes Flange: 8.1 Case No.: 6Curb Size and Equipment Type: 24”x 24” Gooseneck Relief Air Hood with Flange Equipment Attachment: Flange Screwed to 15/32” OSB Roof Deck Fastener Factor for Each Side of Curb or Flange: 8.2 Case No.: 7

Curb Size and Equipment Type: 24”x 24” Curb with Exhaust Fan Equipment Attachment: Fan Screwed to CurbFastener Factor for Each Side of Curb or Protecting Against Hurricanes Flange: 2.5 Case No.: 8Curb Size and Equipment Type: 36”x 36” Curb with Exhaust FanEquipment Attachment: Fan Screwed to Curb

Fastener Factor for Each Side of Curb or Flange: 3.3 Case No.: 9Curb Size and Equipment Type: 5’-9”x 3’- 8” Curb with 2’- 8” high HVAC UnitEquipment Attachment: HVAC Unit Screwed to CurbFastener Factor for Each Side of Curb or Protecting Against Hurricanes Flange:  

Case No.: 10Curb Size and Equipment Type: 5’-9”x 3’- 8” Curb with 2’- 8” high Relief Air HoodEquipment Attachment: Hood Screwed to CurbFastener Factor for Each Side Protecting Against Hurricanes of Curb or Flange: 35.6* Notes to Table: 1. The loads are based on the 2005 edition of ASCE 7. The resistance includes equipment weight. 

The Base Case of the tabulated numbers of #12 screws (or ¼ pan-head screws for flange-attachment) is a 90-mph basic wind speed, 1.15 importance factor, 30’ building height, Protecting Against Hurricanes Exposure C, using a safety factor of 3.

Hurricane Protection Techniques

 For other basic wind speeds, or for an importance factor of 1, multiply the tabulated number of #12 screws by to determine the required number of #12 screws or (¼ pan-head screws) required for the desired basic wind speed, VD (mph) and Wind Damage Hurricane Protection Techniques importance factor, I.4. 

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