Structural Drying >> Structural Drying Wet Carpet

To avoid wind and windborne debris damage to rooftop ductwork, it is recommended that ductwork not be installed on the roof (see Figure 5). If ductwork is installed on the roof, it is recommended that the gauge of the ducts and their attachment be sufficient to resist the design wind loads. Figure 5 caption. Two large openings remained (circled area and inset to the right) after the ductwork on Structural Drying Wet Carpet this roof blew away. 

Condensers: In lieu of placing rooftop-mounted condensers on wood sleepers resting on the roof (see Figure 6), Structural Drying Wet Carpet it is recommended that condensers be anchored to equipment stands. (Note: the attachment of the stand to the roof deck also needs to be designed to resist the design loads.) 

In addition to anchoring the base of the condenser to the stand, Structural Drying Wet Carpet two metal straps with two side-by-side #14 screws or bolts at each strap end are recommended (see Figure 7).Figure 6 caption. Sleeper-mounted condensers displaced by high winds. [end of caption] Figure 7 caption. This condenser had supplemental securement straps (see arrows). 

Two side-by-side screws with the proper edge and end distances are recommended at the end of the strap. Vibration Isolators: When equipment is mounted on vibration isolators, an isolator that has sufficient resistance to meet the design uplift loads should be specified and installed, Structural Drying Wet Carpet or an alternative means to accommodate uplift resistance should be provided (see Figure 8).

The equipment on this stand was resting on vibration isolators that provided lateral resistance Structural Drying Wet Carpet but no uplift resistance (above). A damaged vibration isolator is shown in the inset (left). [end of caption]Access Panel Attachment: Access panels frequently blow off. To minimize blow-off of access panels, job-site modification will typically be necessary (for example, the attachment of hasps and locking devices such as a carabiner). 

The modification details will need to be tailored for the equipment, Structural Drying Wet Carpet which may necessitate detail design after the equipment has been delivered to the job site. Modification details should be approved by the equipment manufacturer.Equipment Screens: Equipment screens around rooftop equipment are frequently blown away (see Figure 9). 

Equipment screens should be designed to resist the wind loads derived from ASCE 7.Note: The extent that screens may reduce or increase wind loads on equipment is unknown. Therefore, Structural Drying Wet Carpet the equipment behind screens should be designed to resist the loads previously noted.Figure 9 caption. Several of the equipment screen panels were blown away. 

Loose panels can break glazing and puncture roof membranes. Other resources: Three publications pertaining to seismic restraint of equipment provide general information on fasteners and edge distances: Structural Drying Wet Carpet Installing Seismic Restraints for Mechanical Equipment (FEMA 412)  

Installing Seismic Restraints for Electrical Equipment (FEMA 413) Installing Seismic Restraints for Duct and Pipe (FEMA 414)[end text box] Rooftop Attachment of Lightning Protection Systems in High-Wind Regions Hurricane Katrina Recovery Advisory FEMA May 2006, Revised July 2006 Purpose: To recommend practices for Structural Drying Wet Carpet installing lightning protection systems (LPS) that will enhance wind resistance in high-wind regions.Key Issues 

Lightning protection systems frequently become disconnected from rooftops during hurricanes. Displaced LPS components can puncture and tear roof coverings, Structural Drying Wet Carpet thus allowing water to leak into buildings (see Figures 1 and 2). Also, when displaced, the LPS is no longer capable of providing lightning protection in the vicinity of the displaced conductors ("cables") and air terminals ("lightning rods"). Figure 1 caption: 

This displaced air terminal punctured the membrane in several locations. [end of Figure 1 caption] Figure 2 caption: View of an abraded end of a Structural Drying Wet Carpet conductor that became disconnected. [end of Figure 2 caption] Lightning protection standards such as NFPA 780 and UL 96A currently provide inadequate guidance for attachment of LPS to rooftops in high-wind regions. 

Some LPS manufacturers provide guidance for attachment, while other manufacturers refer to the roofing material manufacturer for attachment guidance. Some roofing material manufacturers provide guidance for attachment, Structural Drying Wet Carpet while other manufacturers refer to the LPS manufacturer for attachment guidance. 

In most cases, the attachment guidance provided by LPS and roofing material manufacturers is inadequate for hurricane-prone regions. LPS conductors are typically attached to the roof at 3 foot intervals. Because the conductors are flexible, Structural Drying Wet Carpet when they are exposed to high winds, the conductors exert dynamic loads on the conductor connectors ("clips"). Guidance for calculating the dynamic loads does not exist. 

The attachment guidance that follows is therefore based on professional judgment. LPS conductor connectors typically have prongs to anchor the conductor. When the connector is well-attached to the roof surface, Structural Drying Wet Carpet during high winds the conductor frequently bends back the malleable connector prongs (see Figure 3). 

Conductor connectors have also debonded from roof surfaces during high winds. Based on observations after Hurricane Katrina and other hurricanes, Structural Drying Wet Carpet it is apparent that pronged conductor connectors do not provide reliable attachment.Figure 3 caption: During high winds, the conductor deformed the prongs and pulled away from this conductor connector. 
 

Construction Guidance Parapet attachment: When the parapet is 12-inch high or greater, it is recommended that the air terminal base plates Structural Drying Wet Carpet and conductor connectors be mechanically attached with #12 screws that have 1.25 inch minimum embedment into the inside face of the parapet nailer and properly sealed for watertight protection. 

In lieu of conductor connectors that have prongs, it is recommended that mechanically attached looped connectors be installed (see Figure 4). Figure 4 caption: This conductor was attached to the coping with a looped connector (above). However, Structural Drying Wet Carpet a gasket was not installed between the connector and the coping. 

Also, because the connector screws were too short to engage the wood nailer, the screws pulled out and the conductor was displaced in some areas. Attachment to built-up, modified bitumen and single-ply membranes: For built-up and modified bitumen membranes, Structural Drying Wet Carpet attach air terminal base plates with asphalt roof cement. 

For single-ply membranes, attach air terminal base plates with pourable sealer (type recommended by the membrane manufacturer). In lieu of attaching conductors with conductor connectors, Structural Drying Wet Carpet it is recommended that conductors be attached with strips of membrane installed by the roofing contractor. 

For built-up and modified bitumen membranes, use strips of modified bitumen cap sheet, approximately 9-inch wide minimum. For single-ply membranes, use self-adhering flashing strips, approximately 9" wide minimum. If strips are torch-applied, Structural Drying Wet Carpet avoid overheating the conductors. Start the strips approximately 3 inches from either side of the air terminal base plates. Place strips that are approximately 3' long, followed by a gap of approximately 3 inches.

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