water ponding, consider replacement in kind. Otherwise where
adding slope is impractical, replace the membrane with a minimum
of four plies in coal-tar pitch and aggregate surfacing. Also,
consider providing additional drains where necessary. Asphalt,
single-ply, or foam systems are not permitted on any roofs which
Where practical, a new roof design should incorporate
positive slope that will eliminate all standing water conditions
within a 24 hour period after rain. Review the number, type,
sizing and location of drains, use of scuppers for overflow, and
use of crickets for slope to prevent ponding between the drains.
Never use wet fills to achieve slope.
The Insulation System.
Consider the following:
Required R-value of the system;
Formation of roof slope including preformed
Method of attachment to the substrate and new
components to existing components and ability of existing
construction to accept new attachments;
Compatibility with adjacent roof composite
Fire and wind requirements;
Load carrying ability of the structure;
Dimensional stability relative to temperature
change and exposure to moisture;
Product availability and maintainability;
Costs, life cycle economics, etc.
10.4.2.1 Tapered Insulation.
Tapered insulation has the
Difficult design coordination for flashing heights
and other roof details affected by varying insulation thickness;
Require fairly complex field operations for some
materials involving special drawings and coded insulation pieces;