Cobble, Cobble, Cobblestones

In memory of Roger Billings, a staunch defender of our cobblestone streets.

Queen Anne is blessed (bicyclists disagree about that) with many cobblestone streets. Every fan of Queen Anne history knows that the stones provided traction for horses struggling up the hill. Most history buffs can’t explain their conservation, although their prevalence on steep streets suggests they helped both horses and horseless carriages navigate the slopes for a long time. Even though the street surfaces are not official city landmarks, they are charming anachronisms someone at the Seattle Engineering Department, now SDOT, decided to protect.

Looking west down Blaine at 7th.
Looking west down Blaine at 7th.

The most notable Queen Anne cobblestone streets on the west side of the hill can be found at Blaine where it drops down off Queen Anne Boulevard at 7th Ave., and on Howe as it plunges from the steps below 7th to 10th. On the east side, there is a stretch of cobbles on Warren N. running south from Lee that the Fire Department favors. Queen Anne has the greatest share of Seattle’s 93 cobblestone streets with the east side of Capitol Hill a close second.

Looking south to Elliott Bay from the top of the hill on Warren.
Looking south to Elliott Bay from the top of the hill on Warren.

In March 1993, the city surveyed its cobblestone streets assessing the quality of the stones and ranking them per five standards of conservation from excellent to poor. In January 1996, the Seattle Engineering Department and the Department of Neighborhoods signed an agreement that provides a procedure for maintaining the two top categories. It included storing the best blocks from the most deteriorated streets for eventual repairs to the best ones. The city has generally respected the terms of agreement, but tight budgets and relatively low traffic volumes on the protected streets have made it a low priority. The promise to reevaluate the condition of the streets every five years does not seem to have been kept.

Looking east up Howe from 10th W.
Looking east up Howe from 10th W.

The opening paragraph of the agreement reads:

Department of Neighborhoods (DON) and the Seattle Engineering Department (SED) want to preserve as many of Seattle’s stone block streets as possible. However, both departments recognize that some of these streets have deteriorated to the point that preservation may not be practical.  Stone block streets wear unevenly and are susceptible to localized settlements when the sand or mortar setting bed fails. Utility cuts and trenches are particularly damaging to stone block streets.

As one might expect, the cobblestone (and brick) surfaces in the Pike Place Market Historic District are the best protected in the city, but they are not covered by the 1996 cobblestone agreement.

Repairing stone block streets today is just as arduous as when they were laid down in the first place. Blocks are laid by hand and tapped into place in a bed of tamped sand, usually over gravel. Even though the 1996 agreement suggests Seattle’s streets may have had mortar setting beds, concrete or mortar beds are not required. The paving blocks fit tightly together in their beds of tamped sand which acts as a cushion and level to compensate for minor irregularities in the gravel or soil. If the soil is naturally well-drained and stable, the sand bed is placed directly on the excavated subgrade. If not, a gravel drainage base is utilized. The last step involves sweeping fine mason’s sand into the thin joints between the stones. As witnessed last summer in Estonia where a World Heritage Site was being restored, blocks are still set in place manually and separated by plastic spacers that create even gaps to be filed with the fine sand.

As usual, when we have questions about Seattle geology, we turn to David Williams. He wrote in a March 11, 2009 website blog (http://geologywriter.com/blog/stories-in-stone-blog/good-old-cobblestones/ ):

Between the 1890s and 1910s, sandstone cobbles were a popular road-paving material in Seattle. The most commonly used varieties came from quarries in Wilkeson, a small town about 45 miles south of Seattle. Workers could easily cut the brick-sized blocks, which provided good traction for horses, although horse shoes did wear down the stone. And the stone cobbles lasted longer and created less of a mess than the mud or wood of the past.

Williams describes the streets as made of (very soft) sandstone cobbles while the city calls them stone blocks. The two very different terms make us wonder what a cobble really is.

Turns out Seattle’s blocks are not cobbles at all, but rather setts. Even more troubling, Wikipedia (https://en.wikipedia.org/wiki/Sett) reports that setts are cut from granite where ours, Williams points out, are cut from sandstone. Again according to Wikipedia, “A sett, usually referred to in the plural and known in some places as a Belgian block, is a broadly rectangular quarried stone used for paving roads.” It continues, “A sett is distinct from a cobblestone in that it is quarried or worked to a regular shape, whereas the latter is generally a small, naturally-rounded rock. Setts are usually made of granite.” In the United States, naturally formed stones are classed by the Wentworth scale size as grains pebbles, cobbles or boulders. The terms are units of measure. The house on the northeast corner of 10th W. and W. Wheeler (on Queen Anne Boulevard) displays true cobbles as decorative elements on the porch and chimney.

Real cobblestones at 10th and Wheeler.
Real cobblestones at 10th and Wheeler.

The Queen Anne Historical Society is now faced with a dilemma. For decades, it has published a newsletter called The Cobblestone honoring our historic paving stones. With this new understanding of ‘cobble,’ the society may be compelled to change the newsletter’s name to The Setts, a choice that doesn’t resonate quite like cobblestone!

Marga Rose Hancock and SDOT’s Benjamin Hansen inspired this article.