Tag: Municipal Historic Resource

Editor’s note: Our first article recognizing #HistoricPlacesDays takes us to southern Alberta. The banner image above, featuring low-lying rear lots with gardens in Lethbridge’s Chinatown in 1956, looking west, is courtesy of the Galt Museum and Archives.

Written by: Fraser Shaw, Heritage Conservation Advisor

Since its construction in 1924, the Chinese Free Masons Building has been an anchor in the physical and social fabric of downtown Lethbridge and on of Alberta’s most intact historic “Chinatowns”. A large crack zigzags across the west wall of the Provincial Historic Resource and propagates east down the block, telegraphing through the walls of its historic neighbours and terminating at the old No. 1 Fire Hall. The crack recently presented repair challenges and is the legacy of a historic landscape and a transformed physical and cultural geography.

Some 12,000 years ago, as the Laurentide ice sheet retreated toward Hudson Bay, torrents of meltwater carved deep channels across southern Alberta, including today’s Oldman River valley. Long tributary coulees reached like fingers from the valley’s east side, a pattern evident today along the escarpment behind the Galt Museum. One of these coulees extended east between what is now 2^nd and 3^rd Avenue South and appears in early plans and photographs of Lethbridge. Uneven and difficult to build on, the block attracted Chinese immigrants and entrepreneurs who established new businesses on lots that were strategically close to the fledgling town centre but slightly apart from it, a development pattern reinforced by discriminatory policies of the day that relegated Chinese-owned businesses to marginal land away from the commercial core.

Development has infilled the coulee such that the historic landscape today survives only in the sunken rear lots of the Bow On Tong Company Building and Wing Wah Chong Company Building, both of which are Municipal and Provincial Historic Resources. These low-lying back yards were historically put to good use, providing direct access to basement apartments for newly arrived immigrants from China and serving as vegetable gardens (see banner image at top of page). Though hidden, the buried coulee survives as relatively weakly consolidated infill soil under the back portions of the block’s historic buildings. These areas move and crack as soil compacts, takes up water from the poorly drained rear lots, or moves seasonally where shallow rear foundations are susceptible to frost heave. The rear lot at the Chinese Free Masons Building has been infilled but unstable soil conditions persist and cause structural movement and recurrence of the west wall crack despite repeated patching.

Foundation underpinning on deep piles into undisturbed soil would stop the structural movement and cracking but is very costly. A local architect assessed no immediate threat to the building and recommended a practical and cost-effective crack repair alternative. This consisted of saw cutting a new flexible control joint into the outer wythe or layer of brick beside the old crack, to accommodate ongoing structural movement while maintaining integrity as a weather seal. The existing crack was too irregular for proper installation of a reliable sealed joint. As a precaution, the established crack was also repaired with flexible sealant, into which masonry sand was pressed to resemble a traditional mortar joint and disguise the repair as much as possible.

Conservation work normally favours traditional materials but a deep mortar repair risked “locking” the wall in place and causing cracks to appear elsewhere. Correctly formulated lime mortars can absorb some movement and even “self heal” as free lime recrystallizes within emerging hairline cracks — but structural movement at the Free Masons Building demanded a more elastic joint.

The second floor offers a large open space that has served as a Masonic hall for almost a century. The interior walls are original plaster applied to the interior face of the brick masonry exterior walls. Coated with many layers of paint, the walls deteriorated rapidly after the interior was repainted to hide smoke damage after a fire in 2009. Driving rain through the west wall crack was initially suspected as a moisture source but the extensive paint failure was actually in another location. Further assessment determined that the problem was excess moisture within the wall combined with the wall’s inability to dry through impermeable layers of paint.

The west wall is thus a highly porous brick that readily absorbs moisture. Like many old brick buildings, the Chinese Free Masons Building uses a high-quality, durable brick on the front facade with less expensive bricks on the side walls that were often intended to be protected by adjacent buildings. Mortar joints also play a role: lime mortar both binds the masonry and actively wicks moisture in the wall to the surface, where it then evaporates. However, as mortar weathers, leaching of the lime binder reduces this wicking action and eroded joints provide more surface area for water absorption, effectively turning a wall into a sponge. On the wall’s inner face, permeability declines with each layer of paint and as old alkyd paint ages. The most recent repainting was the last straw: acrylic latex paint is vapour-permeable but drying of the wall fabric relies on liquid (if microscopic) capillary moisture transfer. The result is that moisture absorbed through the exterior brick trapped within the wall literally pushes the paint off the plaster.

To correct the problem, peeling interior paint was stripped by hand and moisture-damaged plaster was patched with a compatible gypsum plaster free of latex or polymer additives that might otherwise impede prevent drying. A special, highly permeable clay-based paint was applied to the wall and colour-matched to the historic interior. Combined with renewing or “repointing” the exterior masonry with a compatible lime mortar, these measures avoid sealing the wall and instead restore the historic fabric’s intrinsic ability to absorb, buffer and release moisture by drying to the interior and exterior. The repaired west wall with its new control joint and evidence of the old crack are a testament to ancient landforms, local history and Lethbridge’s evolving urban landscape.

Sources:

C.B. Beaty and G.S. Young, The Landscapes of Southern Alberta: A Regional Geomorphology (Lethbridge: University of Lethbridge, 1975), 66-77.

For a discussion of the early development of Lethbridge’s Chinatown, see David Chuenyan Lai, Chinatowns: Towns Within Cities in Canada (Vancouver: University of British Columbia Press, 1988), 90-91.