Facilities (Campus Spaces)
Five Key Waterproofing Focus Areas
HGA’s Kevin Donaghey offer tips in considering the following specific areas
where water can present challenges.
1. Above-grade Walls
It’s important to acknowledge that most exterior
materials will take on rainwater at some point over the life of the building,
and that an exit route for this water should always be accounted for
in exterior wall assemblies. Rainwater should be viewed not as a passive
element, but a force actively trying to penetrate the exterior barrier’s
lines of defense. Analyzing exterior assemblies through this mindset
can help to identify and provide adequate drainage pathways out of a
rain-screen system for water that has found its way in.
2. Below-grade Systems
Ground water from surface rainfall or the water
table, and its ability to infiltrate large areas of earth and into foundation
systems, can be easily underestimated. Diversion of storm water run-off,
extensive below-grade drain tile systems, and comprehensive membrane waterproofing
at below-grade foundation walls can all serve to keep water out.
Selecting a roofing system that meets the owner’s criteria for
performance and budget can be a challenge, with reduced membrane
thickness or warranty coverage being a tempting cost-reduction measure.
We encourage the owner to err on the side of caution with roofing
selection, even if it means adjusting project scope elsewhere.
4. Windows and/or Skylights
Skylights are typically more horizontally
orientated than exterior wall window systems, and thus
run a higher risk of water infiltration. Even with adequate slope, it
is important that skylight assemblies be equipped with drainage
channels, gutters and drop edges to usher rainfall onto the roof, and
away from the skylight frame/roofing transition, which typically
serves as the most susceptible part of the assembly. This can serve
dual purposes (Example: the Language Arts and Humanities Building
at East Los Angeles College features sloped skylights at a third-floor
courtyard situated over occupied space, which funnel the rainwater
into adjacent concrete planter boxes).
Doors located on exterior walls with exposure to the elements
will pose increased risk of water infiltration. Drip edges, especially
at the horizontal portion frame head, will divert water that would
otherwise work its way inward.
This article originally appeared in the December 2016 issue of College Planning & Management.