Architectural Linear Drains for Indoor and Outdoor Use

Different product offerings suit many situations beyond bathrooms
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Sponsored by Infinity Drain
By Peter J. Arsenault, FAIA, NCARB, LEED AP

Learning Objectives:

  1. Identify and recognize the need and options for proper water drainage to provide safety and accessibility in buildings and sites.
  2. Investigate the design opportunities to create attractive, safe, and well-drained outdoor paths of travel.
  3. Assess the means to provide different types of outdoor spaces with effective and safe drainage systems.
  4. Specify architectural linear drainage systems in buildings in spaces beyond just showers.


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This course can be self-reported to the AANB, as per their CE Guidelines
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This course can be self-reported to the AANB, as per their CE Guidelines
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This course can be self-reported to the NLAA
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Many commercial and residential building design projects incorporate very desirable connections between indoor and outdoor spaces. A key aspect to this design approach is keeping rainwater or snow melt from seeping or migrating to places where it is not wanted. Commonly, some utilitarian drains have been installed to collect and divert such water away from the building. However, many architects are paying closer attention to the quality of the drainage products and moving from commodity to architectural solutions. This is particularly true where higher amenities are concerned such as outdoor spaces, wellness spaces, wet rooms, balconies, etc., where good appearance is required but so is compliance with performance requirements such as accessibility. In this course, architectural or decorative drainage solutions are reviewed as a very viable solution for creating wet spaces that are safer, more accessible, more hygienic, easier to clean, and cost effective. While such architectural drains have been commonly used in the bathroom shower, they also offer great design and functional benefits in many other building and site areas, too. They can help to mitigate water damage, provide a safe and accessible pathway for guests, extend the life of floors or balconies, and may help architects avoid costly, ongoing water issues.

Photo courtesy of Infinity Drain

Architectural drains help make a visual design statement while also providing the water drainage, safety, and hygiene needed in different building locations.

Overview Of Drainage Systems

In the design and construction of buildings and sites, if there is water present (and there almost always is) then that water needs to be managed and controlled. It is common to think about how the water is being supplied (i.e., piped in through plumbing or irrigation systems) or where it may be coming from naturally (e.g., groundwater, precipitation, etc.). However, it is just as important to determine how it is being drained and carried away from the areas where it is present. Failure to properly drain means too much water is present and this can lead to a little, or a lot, of standing water. That water can cause structural or cosmetic damage to buildings, landscapes, or other areas. It is also a human safety issue in that wet surfaces are more slippery and can cause people walking on them to slip, fall, and become injured. Therefore, the design intent of a proper drainage system is to provide the long-term, ongoing remediation of excess water and the hazards that it may entail.

Of course, drains are usually covered with a grille or grate that is visible on floors or outdoor surfaces. In some settings, a purely functional and utilitarian drain cover may be appropriate. However, in many building locations, there is a desire to have the drains and their covers blend with a higher level of design. That means the shape of the drain, the depth of the drain catchment, the material for the cover, and other factors all come into play. In order to be sure that the look of the space being drained is not compromised, the selection of appropriate architectural drains and their integration into an overall scheme is critical. That means that these items aren’t just for mechanical and plumbing engineers to consider. Rather, they require the review, input, and collaborative decision-making process of architects, landscape architects, and interior designers, too. Only in this way is the total design able to meet the aesthetic and performance needs of the project.

In the following sections, we consider some of the different aspects of designing architectural drainage systems.

Drainage Types

Not all drainage solutions are the same. Some require very standard components and others are better served by specialty items. Generically, there are three types of drains discussed, as follows.

  • Center Drains These are probably what most people think of when considering the use of a floor drain. In this case, a floor area, whether for a room, a shower, or an outdoor surface, is gently sloped from each side to a low point in the center. The drain catchment, commonly square or round, is connected to a suitably sized drainpipe that carries the collected water away from the area to its appropriate next destination (i.e., sewer, storm drain, retention pond, etc.). The catchment mechanism is typically covered with a grate or grille of some type that allows water to enter but keeps out other things such as debris. The cover also provides the needed safety protection for people, such that their foot lands on a smooth, flat surface instead of dropping into the open area of the catchment. The shape of a center drain is commonly square or round and available in standard sizes to suit different common conditions.
  • Photo courtesy of Infinity Drain

    Center drains are based on sloping the surrounding floor or other surface to a central point that receives water into a catchment with a protective cover.

  • Architectural Linear Drains A different, and often more elegant, approach for designing a floor drain, is to simply slope the surface all to one side. Then, along the length of the low end of the surface, a linear floor drain is installed in a recessed manner to drain away the water. In this case, the drain catchment area (also called a channel assembly) is long and rectangular, with either a vertical or horizontal drain outlet. That drain outlet can be connected in an appropriate manner to suitable drain piping that is located within the floor assembly or outdoor surface system. The drain channel assembly is covered with a long, rectangular grille or grate that functions the same way the center drain cover does – allowing water to enter while keeping out debris and providing a safe surface for people to walk on.
  • Photo courtesy of Infinity Drain

    Architectural linear drains provide an elegant drainage solution based on sloping the floor surface to one side and removing water along the low end.

  • Custom Drain Solutions In some cases, neither center drains nor purely linear drains are the right architectural solution for a project condition. For those situations, it is good to be aware that custom drains are indeed possible. They can take the form of curved or circular drains around a similarly shaped surface where water needs to be captured and redirected. Or they can be rectilinear by marrying several linear drains together to suit the geometry of a space. There are many different options and configurations possible, but as with any custom solution, it is best to check with a manufacturer during project design to determine fabrication parameters and tolerances that are possible and factors that influence cost management.

Photo courtesy of Infinity Drain

Custom drain solutions can take many forms and shapes subject to review with a manufacturer.

For example, a custom drain can address unique performance requirements, such as the percent of open or free area of the top grate or a larger outlet diameter that may be required in geographic areas that receive higher levels of precipitation. Custom drain grates can also be designed to address certain load requirements that may be in place for outdoor drains, such as heavy cleaning or maintenance equipment around a pool.

Performance Considerations

Performance is measured in several different ways when it comes to floor and surface drains. Some of the common performance items are as follows.

  • Drainage The reason floor and surface drains are provided in the first place is because there is a performance need to drain away water. All drains will have a capacity of how much water can be drained away over a given amount of time (i.e., gallons per minute). The drain piping is usually sized by a consulting engineer to match the needs of the area being drained based on a calculated volume and rate of water being managed. In the same way, any drainage system, particularly the catchment area, must be assessed for the capacity of the water that it can receive and drain away over time. If the catchment area is too large compared to the piping, then there is a risk of water pooling at the drain, since water is captured faster than it can be drained away. If the catchment area is too small, water may again pool outside of the drain because it cannot adequately capture all the water present. For linear drains, the size of the drain is not just the length, but also the depth of the catchment trough, which can vary. Therefore, for the best drainage performance, water flow calculations need to be considered for anything that is not a small or typical drainage condition, such as a bathroom shower. Outdoor drainage designs in particular should be addressed in this way since an abundance of rainwater can overwhelm any drainage solution at times.
  • Safety Anywhere a floor or outdoor surface is being drained, there are certainly people who are occupying those spaces. Hence, there is a need to be sure that the drainage system does not provide a safety hazard or compromise the ability for anyone to walk or travel over it. The proper drainage of the area is the first safety priority such that there is not the danger of excess water causing a condition which leads to a slip and fall accident. After that, it is important that the installation be designed and carried out such that the drain is flush with the adjacent finish materials. This requires proper detailing to allow for the correct depth of the recess for the channel and the drainage cover so as to avoid any tripping hazard. The surface of the cover also needs to be considered to be sure it does not have holes or openings that are too large, such that they could cause a heel or toe to get stuck. Most of the covers are standardized by manufacturers and have likely already been tested for safety, but if there is any concern, a review of any safety testing should be done. There are many choices of cover types and styles, so it is likely that an appropriate one is available for most situations.
  • Hygiene The presence of water is always a concern for cleanliness and the health of people since it can be a breeding ground for bacteria, mold, and other less than desirable conditions. Hence, it is important that any drainage system can be readily and easily cleaned as needed. This is the best way to be sure that any growth is eliminated but also to be sure that any foreign objects or debris that may enter can also be removed. Fortunately, most drain covers are designed to be removable so they can be cleaned and sanitized as needed. That removal also allows for access to the catchment area or trough to remove any unwanted items but also to clean and sanitize that area as well.
  • Barrier-Free Accessibility Whether dictated by code or desired for anticipated lifestyle, barrier-free accessibility is a very typical performance requirement for anything that is part of a walking surface. The ability to make architectural drains flush with the surrounding surface and support the loads of people walking or riding in wheelchairs means that they have a head start on providing an accessible surface. In fact, they may facilitate accessibility. For example, it is common to see accessible shower stalls that use linear drains to capture the drainage water while allowing a wheelchair to enter smoothly into the shower area – the floor is simply sloped slightly (commonly ¼-inch rise per 12 inches) to direct the water to the drain and still allow for wheelchair access.

Photo courtesy of Infinity Drain

Barrier-free accessibility can be maintained or created through the use of recessed linear drains.


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Originally published in Architectural Record
Originally published in June 2022