Putting it back the way it was

BOULDER –Michael Schuller can peer inside walls, but he might be best known for developing historically accurate mortar mixes as he plans the repair, restoration and maintenance of stone and brick buildings worldwide.

?He’s really like a forensics guy,? said Ann Sullivan, executive director of the Rocky Mountain Masonry Institute. ?He understands the history of a building, why it is the way it is, how stable it is and what’s in its future, and he helps develop plans so the building can be restored sensitively, so you don’t destroy what came before.

?He knows how to evaluate exactly what’s happening with an historic building without hurting it,? Sullivan said.

The trade group has named Schuller its 2001 Masonry Hero, for his leadership of Atkinson-Noland & Associates, a Boulder structural engineering firm.

Schuller is an engineer and president of the 27-year-old firm, which specializes in non-destructive assessment, evaluation and repair of masonry buildings. Atkinson-Noland has a global reputation and has been called to work on high-profile historic restoration projects as far away as Slovenia, Italy and Easter Island and as close to home as Cripple Creek and downtown Denver. In addition to preservation projects, the firm also works on maintenance and repair programs for large manufacturers, such as Nabisco and is at work on earthquake retrofit projects in San Francisco and Sonoma, Calif.The big secretBuildings that have been standing around for a century or even two are reluctant to give up their secrets ? whether for repair or posterity. It used to be that the only way to understand how a wall was constructed was to take a brick or two out and look around inside.

But engineers today are more likely to do their work using infrared, radar, ultrasonic and tomographic tools than a pick or a drill, especially when they’re assessing buildings considered local and national treasures.

?A lot of times, you can’t even drill a little hole to look inside the wall because you’re destroying the historic fabric,? Schuller said. ?You can patch the hole, but it never gets patched perfectly, and it’s never invisible.?

Schuller’s firm is now involved in a wall assessment and repair project at the Basilica of the National Shrine of the Assumption of the Blessed Virgin Mary in Baltimore. The project is part of a larger historic preservation effort that began in 1999. Designed by Benjamin Henry Latrobe — architect of the U.S. Capitol building ? the church is considered the Mother Church of Roman Catholicism in the United States.

For more than a year, Atkinson-Noland has had monitoring equipment in place, collecting data about cracks in the building. The data will be used to determine whether the cracks are worsening and how they behave in freeze and thaw and damp and dry cycles. ?You have to let the building tell you what it’s doing, before you try and do something to it,? Schuller said. ?With some repairs, you can do more damage if you choose the wrong repair approach.?

Schuller and his colleagues also use technology to spy on their forefathers.

?Sometimes, we’re getting information for diagnostics, other times, we’re gathering it for historical accuracy and completeness,? he said. ?In the case of the basilica, Latrobe was a well-respected architect, and there has been debate about how he built the dome structure. We spent a lot of time trying to find an iron tension ring, and it’s not in there.?

Atkinson-Noland engineers occasionally find themselves solving problems on modern job sites, Schuller said. ?These are projects where they get through and realize they have a lot of steel left over and are sure they ordered the correct amount. We figure out how to get it in there without starting over.?

Getting the steel in is key in the firm’s earthquake retrofit practice. The engineers recently completed plans for stabilizing an historic two-story building on the town square in Sonoma, Calif. The owners had to choose between moving out residential and commercial tenants, gutting the stone structure and building a new steel frame inside, and drilling vertically through the stone faces and using threaded steel bars to tie the building to the foundation. The owners opted for the latter, cheaper, solution, Schuller said.

In Denver, Atkinson-Noland developed a repair plan for the brick carriage house at the Molly Brown House Museum. Grading and moisture problems had damaged the bricks near the ground level. In theory, the building could have been fixed by slapping up a couple of courses of modern brick and mortar, but in practice that probably would have done serious damage to the historic structure.

The engineers instead developed strength and absorption specifications for the bricks that would be used to replace the damaged pieces and developed an appropriate mortar mix based on the historic mortar in the rest of the building.

?You have to develop the right composition so the mortar looks the same and acts the same,? Sullivan said. Make the mortar too strong and it will crack the bricks. ?Mortar is always intended to be the sacrificial material and you have to be very careful with the mix.

?Those are the kinds of weird little things that Mike pays attention to, and God bless him for it,? she said.

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