Cobble, cobble, cobblestones

In memory of Roger Billings, a staunch defender of Queen Anne’s cobblestone streets.

Queen Anne is blessed (though bicyclists may disagree) 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.

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 Seventh Avenue, 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.

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 the maintenance of the two top categories. It included storing the best blocks from the most deteriorated streets for eventual repairs to the best ones. Is not clear that the city has respected the terms of agreement. For sure, the promise to reevaluate the condition of the streets every five years does not seem to have been kept.

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 most protected, although not the best-preserved, cobblestone streets are not covered by the 1996 cobblestone agreement. Those surfaces are in the Pike Place Market Historic District.

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 2009 blog post:

“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 use of 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 notes 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 … 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 Avenue West and West Wheeler Street (on Queen Anne Boulevard) displays true cobbles as decorative elements on the porch and chimney.

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 call its newsletter The Setts, a choice that doesn’t resonate like cobblestone!

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