Page 201 - Construction Waterproofing Handbook

3.90 CHAPTER THREE
difficult areas include inaccessible places beneath mechanical equipment, and electrical con-
duit protrusions too close to adjacent equipment to properly flash roof transition materials.
By limiting the number of roof penetrations, providing areas large enough to install tran-
sition detailing, and ensuring minimum heights above roof for termination, detailing will
limit common 90 percent leakage problems. All equipment should be placed on concrete
curbs a minimum of 8 in above roofing materials. Wood used for curbs can rot and even-
tually damage the roof. This minimal height provides sufficient areas to transition, and
terminates roofing materials properly into equipment that becomes part of the building
envelope.
Curbs should be placed to complement roof drainage and not block it. Roofing membranes
should extend both under the curb and over it, completely enveloping it to prevent leakage.
Any conduits or drains running to and from equipment should be raised off the roof so
as not to prevent drainage and damage to roof membranes. Any rooftop-mounted equip-
ment such as balustrades, signs, and window-washing equipment should be placed on
curbs. Equipment fasteners used at curb detailing, as well as the equipment itself, should
be waterproofed to prevent transition and termination water infiltration.
Roof penetrations and all protrusions, such as electrical conduits, should be kept in as
absolute a minimum of groupings as possible. Roofs should not be used as penthouse areas
for electrical and mechanical equipment nor storage areas for excess equipment. Too often
equipment is placed on a roof in groupings that make maintenance and drainage impossi-
ble. Further, any equipment added after roofing completion should be reviewed by the
material manufacturer and roofing contractor to ensure that warranties are not affected by
the installation.
Roofs should be tested for adequate drainage before membrane installation. Once
rooftop equipment has been installed, drainage should be checked and adjustments made
where necessary. After roofing is installed, it is too late to repair areas of ponded water.
Roof drains must be placed at the lowest elevations of the roof and not be obstructed.
All related roof envelope equipment should be tested for watertightness after installa-
tion. Roofing envelope portions are often damaged by equipment that allows water or con-
densation to bypass roof membranes and to enter directly into interior areas.
Sealants should not be used excessively as termination or transition detailing anywhere
within the roofing envelope. Sealants typically have a much shorter life cycle than roof-
ing membranes. Sealants then become a maintenance problem, since when not properly
attended they create leakage.

ROOFING SUMMARY

As with a complete envelope, typically it is not roofing materials or systems that directly
cause water infiltration; it is the 1 percent of a roofing envelope portion. This 1 percent
includes termination and transition details including flashings, protrusions, and mechanical
supports that typically occur within a roofing application.
Roofing envelope installation often involves more subcontractors and trades than any
other building envelope portion; these people range from sheet metal mechanics to window-
washing-equipment installers. This extreme multiple-discipline involvement call for the