Tag Archives: water

Masonry Sealers and Historic Exteriors

masonry-test-pmapdxAre masonry sealers necessary on historic multi-wythe exterior walls? In general, likely not. Traditional exterior mass unit masonry walls, 3 to 4 wythes thick, leak. But rarely does the amount of water intrusion cause damage to the masonry, the masonry ties, or the interior finishes. Why wouldn’t a sealer be effective for these older walls?

Traditional means and methods of construction multi-wythe walls consist of course work bonded and tied together with header courses, row-lock courses, hidden headers, and set in full beds and back beds of mortar. There is no direct pathway for water intrusion following the mortar beds. And most sealers do not bridge bond line cracks between the masonry unit and mortar bed.

brick-test-pmapdxThe porosity and absorption rates of older masonry are often exaggerated because of the brick appearance. Many older masonry units show the results of imperfect firing techniques. It is not unusual to see older masonry with vertical and horizontal cracks due to low firing temperatures or impurities in the original clay mix. The surface cracks may lead to higher rates of absorption around the crack but rarely increase the overall absorption or alter the overall characteristics of the masonry. Masonry sealers will not bridge these firing cracks.masonry-water-test-pmapdx

If older walls exhibit a level of moisture intrusion, the drying dynamics have traditionally been from warm interior side and evaporation towards the exterior. Interior insulation techniques will result in a colder exterior wall that will stay wetter longer. Masonry sealers can impede the natural drying process and movement of water towards the exterior. Vapor permeable “breathable” sealers limit the outward movement of water by natural capillary action impeding the drying dynamics. The major concern with applying sealers to masonry is related to drying.

The Brick Industry Association, Technical Note No. 6A states: “Application of a water repellent coating is not necessary to achieve water resistance in brickwork subjected to normal exposures where proper material selection, detailing, construction and maintenance have been executed.” BIA goes further: “Application is not recommended on newly constructed brick veneer or cavity walls…” There is little to no research showing the effectiveness of sealers on reducing water intrusion in masonry walls. Sealers primarily reduce the initial rate of absorption at the brick surface. Sealers also cannot change water intrusion due to poor construction techniques. Wind driven rain is rarely impeded by sealer applications. “the use of water-repellent coatings to eliminate water penetration in a wall with existing defects can be futile.”

WSU-DD-hall-building-envelope-pmapdxTo control water intrusion and to increase performance of a masonry wall, it is much more effective to maintain mortar joints through re-pointing process, assure that mortar joints have no voids, replace brick with spalled faces, replace brick that are cracked the full depth, and repair bond line failures. The use of masonry sealers should be based on known research and field tested success and not chosen as a means to remedy poor construction methods.

Written by Peter Meijer AIA, NCARB Principal

Washington Park Reservoirs

With the Portland City Council’s final decision not to further delay projects to build new reservoirs to replace the five historic open reservoirs, on the west side of the city in Washington Park a new below grade water storage tank is being planned in the general footprint of one reservoir. The second of the two reservoirs at Washington Park will be decommissioned and used for new purposes. The implementation of underground storage tanks may still elicit a spirited discussion. And at the heart of the discussion is how to implement thoughtful change to a historic, well loved cultural resource to the rigors of rapidly evolving public safety and seismic protection mandates.
WA Park Reservoirs
Reservoirs 3 and 4
Reservoirs 3 and 4 were constructed as part of the Bull Run water system, a gravity-fed mountain watershed system built between 1894 and 1911 to provide the City of Portland with high quality drinking water. Reservoirs 3 and 4 continue to function as the city’s primary water distribution source for the west side of Portland. The reservoirs have been in continuous operation for more than 100 years. They serve as a featured amenity enriching the landscape of Washington Park, one of Portland’s largest and oldest parks, with vistas of open water, and period historic structures. Also due to their location on hills on the west side of the city, scenic views are afforded across the reservoir water.

As summarized in the National Register of Historic Places nomination, “one of the most defining landscape principle of Reservoirs 3 and 4 is the open expanse of water, their irregular shape, rusticated concrete structures, and ornate wrought iron detailing of fences and lampposts. The reservoirs are a striking and elegant addition to the serene forest that makes up this end of Washington Park. The surrounding forest is composed primarily of Douglas fir, western red cedar, and big leaf maple all predominating native tree species of the Pacific Northwest.”
Historic 1894 photo of WA Park Reservoir 3
The Design Challenge
The challenge is to design a 100 year plus engineering solution while simultaneously designing a thoughtful change to the context, natural park setting, and historic district. Arising from the Olmsted Brothers vision for Portland and the City Beautiful movement, the changes to the Reservoirs offer an opportunity to evaluate the evolution of development outside Washington Park within the Park, changes to the Reservoirs themselves, public access, and protection of cultural amenities. If access to the “water” is transformed to a public amenity, how does the design enhance the serene qualities of the site? How should the change reconnect the reservoir area with the surrounding neighborhood and Park features?

WA Park ZOO circa 1900The reservoirs embody the challenge associated with retaining a historic place as both a visual element and a dynamic landscape. The safety, security and seismic solutions may alter the purpose of the visual feature and the interaction with the “water,” but that does not translate into a diminishing of a historic place. There are no easy answers. In the end, this final decision should be assuring that the Washington Park Reservoirs will continue to provide safe, reliable water storage, and to elicit wonder well beyond the next 100 years.

Written by Kristen Minor, Preservation Planner