Seismic expansion joint at entrance to Regence Blue Cross SJS System EMSEAL

Seismic Expansion Joint Upgrade: Regence Blue Shield, Tacoma


Date: 2016

Seismic expansion joints are typically wider than the average structural expansion joint. This means a wider footprint–visually and literally. For any application where traffic, and especially pedestrian traffic and the possibility of high heels is expected, a cover plate or expansion joint cover usually makes sense over seismic expansion joint openings. What doesn’t make sense is screwing the cover plate to the concrete and especially not to pavers. Non-invasive anchoring of expansion joint systems is one of EMSEAL’s R&D golden rules.  The SJS System anchors non-invasively to the joint substrates and the cover plate cleverly anchors to the SJS System. This means no screws, pins, anchors or embeds into the concrete or substrates.

Regence Blue Shield is a great case study in a retrofit of a non-working seismic expansion joint treated with a compression seal. The end result is an installation that is watertight, trafficable and looks better than it used to. Here’s what the applicator had to say about the owner’s reaction:

“Wanted to share the end result of the Regence Blue Shield Entry in Tacoma, Washington, in comparison to what was there before. The customer loves it, and wants us to put together some comparative information versus other expansion joint materials, so she can look for other locations to install.

Here’s how it went down:

Removing Old Compression Seal

Non-functioning compression seal

The old, non-functioning, joint system was what is commonly known as a “compression seal”. This technology dates back to the 1940’s yet, surprisingly, is still synonymous with “expansion joint” for many. Compression seals are generally not watertight. They additionally suffer significant ‘compression set’.  This leaves them unable to exert a backpressure and subject to failure due to adhesion in tension. Compression seals in larger seismic expansion joints additionally leave a surface that is not ideal for pedestrian traffic, especially high-heel traffic.

Fortunately,  compression seals are easily removed. In this case, waterproofed metal angles are the substrate. With the compression seal removed and the angles ground clean, the joint was ready to receive the retrofit.

Seismic Expansion Joint Replacement

Seismic expansion joint replacement SJS System EMSEAL

The SJS System seen fully installed. The custom end bevel on the cover plates makes for a tidy edge detail. The cover plate is anchored to the central spline of the SJS System. It simply slides on the surface of the adjacent pavers as then joint opens and closes.

Finished Seismic Expansion Joint Retrofit

Seismic Expansion Joint Complete SJS System EMSEAL

Seen from the entrance looking toward the street, the SJS System is ready for service.