Foundation Waterproofing – Proper Installation and What NOT to do!

As mentioned in Foundation Waterproofing 101, water damage to a foundation can be very costly and difficult to repair. By paying close attention to how and where water might enter the foundation during the early stages of construction, typical failures can be avoided by following these simple guidelines…

For the Designer: Keys to proper installation

Design and Quality Assurance

  • Don’t wait to design the foundation waterproofing system after you’re already in the ground!
  • Specify and detail the appropriate system for each project. Meet with manufacturer reps early!
  • Require shop drawings and kickoff meetings to ensure the entire team understands the importance of the design! Review examples of common failures.
  • Get your consultants on board early: Geotechnical engineer, Structural engineer, Waterproofing/enclosure consultant.
  • Review warranties, require third party inspections, installer certification, and contractor training.

For the Installer: Keys to proper installation

Substrate preparation

  • Provide smooth continuous surfaces to install waterproofing – minimize jogs, protrusions, and sharp edges.
  • At slabs: compacted fill/rigid insulation board/rat slabs
  • At walls: fill bugholes, remove/grind concrete fins, mortar snots, fill form tie holes, verify form release agents and compatibility.

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Foundation Waterproofing 101

Foundation Waterproofing Cutaway

Credit: Basement Waterproofing Baltimore (2018, February 20). http://aquaguardwaterproofing.com

Designing buildings with water protection in mind is critical to protecting buildings from future damage, difficult/costly repairs, and potential litigation. Foundations are by necessity in the ground. So is water. Foundation waterproofing is intended to keep them separate, by providing a layer of protection between a below-grade structure and the moisture present in the surrounding soil and fill. Waterproofing is especially important when the foundation lies below the water table or in a flood zone. Read on to learn about different approaches and materials used to waterproof foundation walls and slabs and specific detailing needed to provide a watertight enclosure. And, check out Part 2 of this series for specific guidance and examples to achieve a watertight enclosure.

Why is foundation waterproofing necessary?

Did you know? Water intrusion makes up more than 70% of construction litigation.Water

Foundations are basically holes in the ground that want to fill with water. Poor site drainage, through-wall penetrations, concrete cracking/mortar joints and movement, door/window/vent openings, flooding, high water tables, hydrostatic pressure – all contribute to the propensity for water to fill the subterranean void we have established. Foundation leaks are difficult and costly to rectify, not to mention designer/contractor financial liability. Water in a basement is water in a building. Excess moisture within a building is a recipe for higher RH and increases the potential for condensation, and mold and other allergens.

Luckily, foundation water intrusion is usually preventable. The goal is to identify all the potential water transport mechanisms, and address them, through good design practices, proper detailing, and quality execution. Read more

Tech Notes: Accessible Design Solutions for Protruding Objects

Limits of Protruding Objects
[US Access Board]

When most people think about accessible design, the first thing that comes to mind is designing for people in wheelchairs. However, there’s a lot more to it than that. Requirements in federal, state, and local accessibility laws and codes account for a wide range of disabilities, including vision impairments. One of the most important design considerations for people with vision impairments is eliminating projections into the circulation path. Objects projecting from walls or other fixed elements can pose a hazard if they do not meet certain requirements. Any object that extends more than 4 inches into the circulation path between 27 and 80 inches above the finished floor is considered a protruding object and must be protected by a fixed cane detectable barrier installed below the object.

There are many ways to provide adequate protection at protruding objects and our accessibility consultants are always keeping an eye out for accessible design solutions that look like they were an intentional part of the design, rather than an afterthought. Here are just a few of the more successful and aesthetically pleasing examples of cane detectable barriers that we have come across…

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Multifamily Passive House Ventilation Design Part 2: HRV or ERV?

In climates with significant heating and/or cooling seasons, Passive House projects must have a balanced heat or energy recovery ventilation system. These systems use a heat exchanger to transfer heat and moisture between the outgoing return and incoming outdoor airstreams. The operation of recovery ventilators reduces the energy required to heat and cool decreasing the building’s carbon footprint. Project teams can select either:

  • Heat Recovery Ventilators (HRV) that transfer heat from the return air stream to the outside air stream; or,
  • Energy Recovery Ventilators (ERV) that transfer heat and moisture from the return air stream to the outside air stream.

Deciding between an HRV and an ERV gets more complex when the Passive House concept is scaled from a single-family home to a multifamily program. What the industry has learned from the development of airtight buildings and programs such as Passive House and R2000, is that indoor relative humidity must be controlled through continuous ventilation. The extremely air tight building envelope required of a Passive House, combined with high internal moisture gains from an occupant dense multifamily program (coming from occupants, kitchens and bathrooms), forces additional moisture management considerations during mechanical ventilation design. Maintaining acceptable interior relative humidity in both the heating and cooling season is paramount for building durability and occupant comfort. It’s appropriate that Passive House professionals claim this simple motto: “Build tight, ventilate right!”

In New York City where the multifamily Passive House market is rapidly growing, there is a significant heating season and a demanding cooling season with high humidity (Climate Zone 4A). With this seasonal variation, there are four primary operating scenarios for an HRV or ERV that need to be considered during design:

Summer Condition – HRV

An HRV operating in the summer (hot-humid exterior air and cool-dry interior air) introduces additional moisture to the building through ventilation. Heat is transferred from the incoming outside airstream to the return airstream leaving the building which cools supply air, but exterior moisture is not removed from the incoming air. The building’s dehumidification load increases as a consequence of additional moisture from the outdoor air.*CON*

HRV Summer operation Read more

Multifamily Passive House Ventilation Design Part 1: Unitized or Centralized HRV/ERV?

 

Project teams pursuing Passive House frequently ask, “Where do we locate the HRV/ERV?” The answer is complex when the Passive House concept is scaled to a multifamily program.  While there are two primary arrangements for HRV/ERV systems, the trade-off is dynamic and needs to be carefully considered as multifamily Passive House projects begin to scale. A low volume HRV/ERV unit ventilating an individual apartment is a unitized HRV/ERV. High volume HRV/ERV units ventilating multiple apartments and often servicing several floors, is referred to as centralized HRV/ERV.

As Passive House consultants we can attempt to address the system arrangement question with building science; however, in New York City rentable floor space is very valuable, so considering the floor area trade-off is of particular interest to project teams. When a unitized HRV/ERV system cannot be located in a drop-ceiling due to low floor-to-floor height, it is placed in a dedicated mechanical closet. This closet is typically no smaller than 10 ft2 and includes the necessary ductwork connections to the HRV/ERV unit. The alternative solution is to increase the floor-to-floor height to accommodate the HRV/ERV unit and horizontal duct runs in the ceiling. Centralized HRV/ERV systems, however, allow short horizontal duct runs but require floor space to accommodate vertical shafts. With supply and exhaust ducts coupled together the required floor area is about 8-12 ft2. As a result, centralized HRV/ERV systems may actually require more floor area than a unitized system.

Example: In the case of Cornell Tech, vertical supply and exhaust duct work for the centralized HRV/ERV system required 222.5 ft2 per floor, or 13 ft2 per apartment (see image 1 below). Unitized HRV/ERV mechanical closets would have required an estimated 170 ft2 per floor, or 10 ft2 per unit (image 2 on right).

Comparison images HRV/ERV

Image 1 & 2:  These images compare the amount of floor area required for centralized and unitized HRV/ERV systems. Image 1 on the left, shows the 12ft2 floor area required for vertical shafts servicing the centralized ERV at Cornell Tech. Image 2 on the right is hypothetical, showing the typical location and 10ft2 floor area required for a unitized HRV/ERV mechanical closet.

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