Roof sheathing is installed with a 1/8" to 1/4" space at
the seams. Therefore, this leaves gaps of 12 to 24
square inches per4x8 sheet of sheathing. A 4,000 square
foot building can have approximately 200 sheets of
sheathing; thus, a fully exposed roof deck could have up
to 33 square feet of open space for water to enter the
building. This is the equivalent of 1 full sheet of
plywood not installed.
Testing at ITW Foamseal's
Technical Center shows that the application of Foamseal
Hurricane Adhesive to the sheathing seams reduces water
intrusion. Roof coverings (shingles and tile) are
usually the first things to fail in high winds like
those experienced during hurricanes. Once the roof
covering fails, water intrusion is likely and
significant damage to the building and contents occurs
even if the roof sheathing stays in place.
Testing at Clemson University's Civil Engineering
Department shows that roof structures can be
strengthened to increase uplift resistance from 2 to 4
times the strength of nails alone.
Building Code required
nailing patterns should develop sufficient uplift
resistance for winds developed in lower category
Hurricanes (Category I, II and III). However, if the
building envelope is breached, internal pressures can
double, thus exceeding sheathing uplift resistance. That
causes roof failures. Category IV and V hurricanes may
develop sufficient uplift to remove roof sheathing
without window or door failure. Increasing the uplift
resistance of a roof structure can easily be
accomplished in many instances through the application
of Foamseal Hurricane Adhesive.
Roof movement due to expansion and contraction of the
roof structure is necessary and common in all types of
buildings. The application of Foamseal Hurricane
Adhesive does not significantly limit expansion and
contraction of the roof assembly. Independent testing
laboratory reports show that the average movement
measurements differ by 0.003" for assemblies with and
without Foamseal applied.
An independent study by
Applied Research Associates, Inc. examined the potential
reduction in average losses in selected residential
structures. The analysis indicates that the application
of Foamseal Hurricane Adhesive to the underside of a
roof deck is a cost effective means of reducing
hurricane induced losses.
The level of loss
reduction depends upon several factors. The above chart
reflects typical estimated reductions in average losses
using impact resistant protection devices on all
openings and using Foamseal Hurricane Adhesive.