In contemporary bathroom architecture, the drain has evolved from a purely functional component into a design element that guides layout, accessibility, and long-term performance. When drainage, slope geometry, and waterproofing are designed as one system, the tiled surface achieves both visual refinement and reliable function—qualities that are critical for hotels, spas, and residences. Schluter® establishes the essential drain-to-waterproofing connection in a controlled factory setting, rather than relying on field assembly.
Balcony House / Ryo Matsui Architects. Image Courtesy of Ryo Matsui Architects Inc
We walk on "flat" ground every day and rarely think twice—but how flat is it, really? In the city, curbs are chamfered, sidewalks pitch toward grates, and roadways are crowned to shed water into shallow gutters. In suburbs and on unpaved paths, irregular terrain is the norm. Inside buildings, by contrast, we pursue near-perfect horizontality—structural frames, slabs, and finishes are all disciplined to create level walking surfaces in the name of safety and accessibility. Yet flatness is inherently at odds with water. A closer look reveals a quiet repertoire of accommodations: slight falls at entries, thresholds raised a few millimeters, wet areas with barely perceptible pitches. The floor is read as flat, but it is in fact carefully tuned—micro-topographies masquerading as plane—to manage water without calling attention to themselves.
What are the common ways architects "keep things flat" while actually managing water—the perennial enemy of buildings? A useful way to look at it is by zooming into three recurring conditions: exterior or roof decking, bathrooms and other wet rooms, and exterior ground planes. Each relies on a slightly different toolkit—pedestal systems over sloped waterproofing, micro-gradients to floor traps, hidden perimeter drains, split slopes—to maintain the illusion of a seamless, level surface. Studying these situations side by side reveals just how much design effort goes into reconciling perceptual flatness with the messy reality.
Office in Sanno / Studio Velocity. Image Courtesy of Studio Velocity
Historically, architecture and the built environment have insisted on creating flat, hard surfaces. In earlier eras, walking without paved ground meant mud-caked shoes, uneven footing, tripping hazards, standing water after rain, and high maintenance. Hence, as we shaped cities, we prioritized a smooth, continuous, solid horizontal datum. The benefits are real: easier walking, simpler cleaning, and straightforward programming—furniture, equipment, and partitions all prefer a level base. This universal preference for building on flat ground remains the norm and, for many practical reasons, will likely continue to be.
What's less recognized is that making a truly flat surface is surprisingly difficult—and many well-executed "flat" floors aren't perfectly flat at all. They are often gently sloped, calibrated to precise gradients for drainage. While interior spaces do not always require this, many ground floors and wet areas do incorporate subtle inclines as a safeguard—whether for minor flooding or to manage water that overflows from the street or plumbing when one of the discharge systems is malfunctioning.
The Busan Slope Housing project by OMA addresses urban redevelopment on the steep hillsides of Busan, South Korea, drawing on the city's topographical complexity and historical settlement patterns. Developed in collaboration with the BusanArchitecture Festival and the Department of Housing and Architecture, the project explores strategies to rethink hillside neighborhoods while responding to both contemporaryhousing needs and the social and spatial legacies of these areas. Rather than replacing these areas with conventional high-rise estates, OMA envisions a flexible, context-responsive framework that integrates contemporaryhousing typologies with the site's inherited structure.
When we think about cities, we often assume the orthogonal grid is the norm: neat, predictable, and rational. However, many urban areas around the world, notably those shaped by hills and uneven terrain, defy this convention. In cities like Lisbon, in Portugal orthogonal grids appear only in flatter zones such as Baixa, while surrounding areas like Alfama adapt organically to topography. These areas create more layered, irregular, and visually dynamic urban forms. Yerevan in Armenia, offers another urban example of this adaptation: the Cascade Complex transforms a steep hill into a terraced public space that connects different city levels while framing panoramic views. For other countries, this response to topography becomes even more critical. Cities like Tegucigalpa in Honduras or Valparaiso in Chile are defined by steep, irregular terrain that requires architects to engage deeply with the land. Designing in these contexts, especially for residential projects, demands technical adaptation and a contextual understanding that allows the slope to become a generative element in the design process.
