Quantcast Design Recommendations

Share on Google+Share on FacebookShare on LinkedInShare on TwitterShare on DiggShare on Stumble Upon
Custom Search
 
  
 


MIL-HDBK-1001/5A
h)
Exterior damage is localized by its closed cell
structure;
i)  Recoating will "renew" the system; some coatings
are guaranteed for 10 years.
7.2.2
Disadvantages.  Compared with conventional built-up
roof systems, sprayed polyurethane foam has some offsetting
disadvantages:
a)  Added cost of recoating the fluid-applied membrane
periodically;
b)  Greater difficulty in obtaining a level surface and
uniform insulation thickness;
c)
Extremely high dependence on applicator's skill;
d)
High dependence on good substrate preparation;
e)
Reduced traffic and impact resistance;
f)
High vulnerability to degradation in hot, humid
climates;
g)  Vulnerability to bird-pecking.  Birds will peck
through the outer covering, dig out the foam, and sometimes build
nests in the cavity.
7.3
Design Recommendations.  Consider both design and
field-application requirements.  First, consider the following
design items:
a)  Slope of substrate.  Do not rely on applicator
varying foam thickness to provide slope-to-drain (minimum 1/2
inch per foot (4 percent) for new construction and 1/4 inch per
foot (2 percent) for reroofing);
b)  Wind uplift resistance conforming to FM
requirements;
c)  Substrate requirements.  Most systems prohibit foam
application directly to a conventional ribbed steel deck.  They
require a minimum 3/8 inch (10 millimeters) thick exterior-grade
plywood (untreated) fastened to the deck.  Fastenings should
conform with FM requirements for anchoring insulation boards
27





 


Privacy Statement - Copyright Information. - Contact Us

Integrated Publishing, Inc.