Groovy laser colors document historic Independence house’s shifting walls

Dude, dig that nationally registered but structurally challenged historic Independence home.

It’s never looked like that before.

To explain: Brian and Sharon Snyder, owners of the antebellum Owens-McCoy House in Independence, long have been worried about its stability.

Some of the mortar binding the home’s bricks has grown porous and crumbling, and its brick walls have been shifting and settling.

That could be ominous news for the structural integrity of the two-story Greek Revival residence listed on the National Register of Historic Places.

Brian Snyder, however, is a structural engineer with Burns & McDonnell, the Kansas City engineering firm. And in recent years it has used a relatively new 3-D laser scanner technology to document large industrial facilities such as power sub-stations, piping facilities and cargo ship fueling stations.

Snyder wondered whether that technology could be applied to historic properties like his, and whether its use would yield precise detail as to how much the home’s exterior walls have shifted.

This summer Burns & McDonnell staff members set up a tripod-based 3-D laser scanner at 12 points around the home. Over six hours they collected about 400 million data points.

They fed that data into an engineering software program that quantified and illustrated the extent of the walls’ shifting. It did so through the use of psychedelic neon colors that rendered the historic structure less Greek Revival and more Grateful Dead. (See attached video.)

“It’s mind-blowing,” said Snyder.

“With one glance, we can see where the problems are.”

In their more than 20 years of owning the structure, the Snyders have collected archival photos, plat drawings, aeriel photographs and archaeological artifacts such as plaster wall remnants, all to better document their home and place it within the community’s overland trails and frontier history.

In 2009 the Snyders signed an agreement with the National Park Service pledging to maintain the home as part of the historic trail network through the city. They one day imagine their home a nonprofit community museum.

One of the bigger problems they face is the heavy truck traffic that runs by the house, which is northwest of the Independence Square at 410 W. Farmer Ave.

Whether the trippy scanner-generated images and animations will hasten their ongoing dialogue with city officials regarding heavy truck traffic near their home is unclear.

“We want to ensure the home’s legacy,” said Sharon Snyder.

The Snyders acquired the residence in 1992.

Samuel Combs Owens, a Santa Fe Trail merchant and early Jackson County clerk, built its oldest-surviving section in 1840. William McCoy, the first mayor of Independence who later bought the property, added a section in 1852.

Still others followed, using various construction techniques and materials, each with its own idiosyncracies.

Much of the home’s bricks are bound by a clay-and-lime mortar material that likely pre-dated the local introduction of Portland cement. Today some of that mortar crumbles to the touch. And, at some point during the 1980s, the west wall was reinforced with a hard mortar that apparently proved stressful to the bricks, as many have developed interior fractures since.

The walls were distressed, and the Snyders wanted to know just how much.

Enter the Burns & McDonnell 3-D laser scanner.

Although many engineering firms use similar technology, often using outside firms, Burns & McDonnell maintains its own staff members trained on the hardware.

The scanner compiled data from each of the 12 completed scans into individual “point clouds” that then were stitched together by the software.

The results documented the walls’ lateral deviations relative to the corners of the building.

The Snyders most were concerned with the home’s south and west walls.

“We had the engineering software compare a point cloud to a perfect plane and told it to colorize each point that was a quarter-inch of deviation,” said Jack Riley, Burns & McDonnell senior applications specialist.

The bulges coming out of the home’s south wall that were at least a quarter-inch registered on the software as bright green. Meanwhile, the building’s corners appeared as blue. So did those areas near two star-shaped cast-iron wall anchors installed in 1852 to stabilize the walls.

The software suggests the anchors have worked as intended.

“The blue colors around the anchors means those wall areas are very similar in location to the corners of the building,” Daniel Nyberg, a Burns & McDonnell staff civil designer who is also civil engineering senior at the University of Missouri-Kansas City.

The final results?

The scanner measured the maxium deviation on the home’s south wall to be almost three-quarter inches outward. The results on the west wall were more dramatic: a maximum deviation of almost three inches.

The scanner technology is more often used to document new or existing industrial facilities with accuracy and efficiency.

“To physically draw such a building would be a huge feat with almost countless man-hours,” Riley said.

The technology’s application with historic structures is growing more common, Riley added. Those investigating the integrity of Washington’s National Cathedral following a 2011 earthquake used such scanners to document approximately $26 million in damage.

The Snyders intend to take the information gathered from the 3-D scan and consider several options. If, for instance, they want to preserve the west wall, the scanning technology revealed those areas that would most benefit from lateral bracing.

“We may be looking at partial demoliton and re-construction in some cases,” Brian Snyder said. “With this much movement, we can’t just push these walls back into place.”

Two years ago the Snyders asked the Independence city officials to discourage truck traffic from North Ridgway Street, which runs near their home’s western wall. They were concerned that the cumulative effects of heavy truck traffic associated with a scheduled $14 million upgrade of a nearby apartment tower would further imperil their home’s walls.

That renovation has yet to begin, as developers seek state development funds, said Tom Scannell, the Independence community development director. A sign prohibiting truck traffic has been installed just outside their home.

But the Snyders may opt to demolish part of the west wall and build a historically accurate reproduction of a long-demolished wing that stood on the home’s west side in the 1830s.

As the structure is listed as a local Independence landmark, the Snyders will have to run any demolition or alteration plans past members of the city’s heritage commission.

Laser technology has not been used by state historic preservation officers, according to Steph Deidrick of the Missouri Department of Natural Resources.

Wendy Shay, Independence historic preservation officer, has no problem with the Snyders using the scanner software to evaluate the structure.

“Some people think that, because we deal with historic preservation, we only use traditional tools, but we love technology,” she said.

“Anything that can show us how to better retain our historic resources is a great thing.”

At minimum, Snyder is confident that — with his laser scanner images and animation — he’s got a killer visual presentation that could excite fellow preservationists.

“This is a tremendous tool and I see it as a way of bringing an entire new generation of young professionals into building restoration,” he said.

This story was originally published October 7, 2015 at 1:30 AM with the headline "Groovy laser colors document historic Independence house’s shifting walls."