ROOF

33. Adhesive Retrofit
Strong hurricanes can exert uplift and suction pressures of over 100 pounds per square foot on your roof—which may only be designed to resist half that amount!  This exhibit shows how a variety of adhesives (AFG-01 rated) can be applied with a caulking gun to triple the capacity of a roof to resist uplift forces.  A ¼-inch bead of adhesive is applied to each side of the roof rafters at the junction with the plywood roof decking.  With a relatively small financial investment and a greater commitment of time and energy this can be done on a “do-it-yourself” basis by a homeowner.  Ask the Center staff about - or order online  - theClemson University video  “Holding on to Your Roof: Part 1” for details. 

Here at the house, a similar retrofit was employed using an experimental product called “Foamseal”.  Foamseal and other similar products are applied professionally by commercial vendors.  The product, applied with a sprayer, comes out as a liquid and quickly “sets-up” as a foam. 
 
 

34. Screw Retrofit
Although adhesives work well and may be the best choice in certain circumstances, an even better long-term retrofit for an existing roof or for houses under construction is the use of screws to attach plywood roof decking to roof rafters or trusses.  This retrofit is best done at the time of re-roofing or during the new construction process.  It involves placing two inch, #8 size screws in the spaces between the existing nails on the roof decking.  The addition of screws to nails applied according to code standards may increase the capacity of a roof to withstand uplift forces from winds by five times over nails alone.  This process is illustrated in a Clemson University videotape entitled ““Holding on to Your Roof: Part 2”.  This exhibit shows how easy it is to use screws, with an automatic feed screw gun, to make your roof more wind-resistant.
 

35. Asphalt Shingle Roofs
While this house has a metal roof, most houses have asphalt shingle roofs.  In a strong windstorm or hurricane, one of the first things to happen to a house is the loss of shingles.   Asphalt roof shingles are simply not designed to resist strong wind forces.  They are especially vulnerable along the eaves and roof ridges.  Wind gets under the shingles causing them to peel back and tear off or wind pressure actually sucks them off.  This often results in roof leaks that allow rainwater into the house causing extensive damage to the interior and its contents. 

The performance of asphalt shingle roofs can be improved with a few simple steps. First, seal the joints in the plywood roof decking with a self-sealing bitumen-based tape generally used in flashing around chimneys.  If all else fails, this tape will prevent water from leaking through the roof into the house.  Second, apply extra tin or plastic tabs to help hold “felt” or “tar” paper onto the roof decking.  Third, use thicker 30 lb. felt paper or increase the overlap of standard 15 lb paper to cover the decking.  Fourth, be sure to use six nails per three-tab shingle as specified by the manufacturer.  Fifth, apply a dab of roofing cement under the flap of shingles, especially those along eaves and roof ridges. 

This exhibit illustrates how these elements work together to create a more wind and water resistant asphalt shingle roof system. 

36. Hurricane Clips
Hurricane clips and straps are a specialized form of metal connector to hold the roof to the walls of the house and a critical element in creating a continuous load path that holds the house together as a unit.  There is a wide-variety of hurricane clips and straps available from a number of manufacturers.  Some of these can be seen on the east wall where the roof rafters join to the house frame.  More can be seen on the “wind wall” display.
 
 
 

37. Weather
Weather instrumentation mounted on the roof is measuring humidity, barometric pressure, air temperature, wind speed, wind direction, and rainfall.  That data is fed to this computer and displayed here. This allows center staff and visitors to monitor weather conditions on site.  The system is linked, via the Internet, with 2,700 other weather monitoring sites around the nation.  Most of these sites are located in schools that teach their students about weather and weather effects.  This system provides the Center the ability to interact with school children about weather and weather hazards, and is an important facet of its educational mission. 
 
 

On the optional video you can see our 'unfinished' third floor, and take note of some of the things we've done to strengthen the roof.

1. Enter (LOOK SIDEWAYS AT FIRST!) (328 KB)
2. West Side (261 KB)
3. Roof (568 KB)
4. Good-bye (296 KB)

Thanks for stopping by!  Be sure to read About 113 Calhoun Street and take a look at our Publications.