Keeping the Water Out

Frank Lloyd Wright Guggenheim New York 54

       There are numerous stories about famed American Architect Frank Lloyd Wright. One of my favorites occured about the time that his masterpiece house, Falling Water, in rural Pennsylvania was just completed. The story is that not long after the house’s completion there was a heavy rainstorm that settled over the house. The owner of the house noticing several small leaks in the home, called Wright. He expressed his concerns that there were leaks coming through this new wonderful new house and asks “What should be do?!” Wright simply replied, “Put a bucket under them” and hung up.

      In another famous Frank Lloyd wright story, the architect was asked “What is the most difficult challenge when you design an award-winning building?” Wright stated simply “Keeping the water out”. His statement still holds true today. Even though we, as professional Architects, have many more tools to use in the battle against water and moisture, it is still a challenge to indeed “Keep the water out” of our buildings. Let’s take a brief look at the challenge of keeping liquid water and water vapor out of the interior of our buildings. 

       Every building has what we call an envelope. This envelope is comprised of numerous elements. The first one is the foundation or floor system. The sides of the building are called exterior walls. The last component is the roof element. Everyone of these components play a critical part to keep water and moisture out of the interior of the building. This function is a primary reason that we design and construct buildings in the first place. That is to create a comfortable controlled environment to carry out functions of our daily lives. 

        The first component of the envelope is the foundation. There are many types of foundations, but the most common is the concrete foundation. Every type of concrete foundation will have a moisture barrier element. This will protect the building interior from having liquid water or water vapor penetrate through the concrete foundation or basement walls. Concrete is not a moisture barrier in any capacity. It is porous and absorbs water like a sponge. So there must be a water barrier of some type. This is located on the underside of a concrete slab foundation or the outside facing wall surface of a basement wall. Most ground or soil has moisture in it. This moisture will always try to move from an area of more to less moisture. The water barrier must stop it from moving into the concrete.

FLW Jacobs House Foundation
Frank Lloyd Wright ( Pictured wearing the leftmost person with a hat on ) testing the floor heating system in Jacobs House I

        The second component of the envelope is the exterior walls of the building. There are even more types of exterior wall systems available to us as Architects today than what wright had at his disposal. Walls are constructed out of wood, steel, gypsum sheathing, brick, stone, aluminum, and even foam blocks. No matter what the wall is composed with, it must have an air & moisture barrier element built into its composition. Most people are familiar with a wood stud wall that has sheathing and brick veneer. Once again, the brick exterior is not water resistant. Water can make its way through the brick and into the interior of the wall cavity and eventually the building interior, in the last century a common water barrier was asphalt impregnated felt paper. This was attached to the sheathing before the brick veneer was installed. In today’s terminology we call that a water shed plane. Today there are several products that are better than the asphalt felt paper. These are building wrap membranes and spray-on water proofing. The water vapor or moisture hits the surface of the water plane and then gravity pulls it down to the foundation. The collected water is then let back out of the wall cavity by a weep hole system at the bottom of the brick veneer. 

      In addition to an air/water barrier inside the exterior walls, every wall usually has doors and windows as part of the envelope composition. The doors and windows must be constructed to stop moisture penetration into the interior of the building. Most door and window systems manufactured today do this extremely well. However, an even larger importance must be given to the flashings and sealants around the doors and windows. The flashings are like a barrier placed on the gap at the top, side and bottom of the window. The water trapped by the wall’s water shed plane must deflect and channel the water around the window or door. Sealants around the doors and windows are also of critical importance to keep water from getting inside the wall cavity. 

Masonry Wall Details
Masonry Wall Details | Jeremy Wright Illustrations

      The final element of the envelope is the roof system. Once again there are numerous types of roofing systems. There are fiber glass shingles, metal roofing, single ply membranes, built up roofing systems. and several others. However, they all have the same purpose to keep wain and water vapor from penetrating the top of the building and entering the interior. It is of utmost importance in the battle against water that a high-quality roofing system be installed on every building. It does not matter if it is a simple vacation cabin, small town home, high-school or a famous billion-dollar museum sitting on a hill. If the roof is not selected carefully and installed properly there will be water penetration problems for the structure. Like the flashings over the windows, the intersections, joints, and corners of the roof system are critical to the water tightness of the roof. They must be detailed with great care and attention. They must all be constructed with the same care and attention to the small details. 

      So, the nature of a building envelope must be designed and constructed properly in order to win the battle of keeping the water out. If there is no care and attention to details the new building will be subject to water penetration into the walls and interiors. This is a huge problem for the quality of the interior environment and the long-term maintenance and sustainment of the building. As Architects it is imperative that a design be detailed and specified to keep the building from having water penetrate the building envelope. We do not want a phone call or email from an owner telling us that they have water dripping from the ceiling. Unlike Frank Lloyd Wright, we cannot tell them to place a bucket under it.


FLW Falling Water Roof
Water ponding on one of the roofs in Fallingwater
FLW Falling Water Terrace
Volunteer repairing one of Fallingwater's terraces as cracking mortar joints in the stonework and failures in the underlying waterproofing membranes let water seep inside.

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