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.

3. Roofs
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).

5. Doors
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.

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