Key Modeling Tools to Craft Brick Rotation and Joint Spacing at St Mary Mercy Hospital Chapel
Mostly brick veneer over an air barrier on studs, this contemporary chapel addition to a half-century-old hospital facility is nearly all raked and radial with a conical feature, brick lintels and a cast stone cap that resembles a roller coaster. Meeting with PLY+ in Ann Arbor design studio, elements such as control and expansion joints, integrating masonry with glass fiber reinforced concrete (GFRC) and executing specialty brick patterns detailed within were on the agenda. Tools for discussion included a 3D model and an actual wooden model of the NW brick feature.
Infant Step into BIM
Material selected includes 2000 CMU, 35,000 brick and 135 pieces of cast stone coping. While not a sizeable project, what it lacks in mass is made up for in technical difficulty. It also turned out to be an infant step into the realm of BIM, demonstrating potential to coordinate all the exterior systems into a single 3D, editable document to be updated for producing as-builts as well as integrating digitally into systems for building management. One example could be managing and tracking activity in the fire alarm systems, sprinklers, egress and even real-time tracking for firefighters within the building on a live 3D model. This model created in the design phases of construction, executed properly, would include all of the updates for an accurate digital as-built. Exciting stuff!
Soil condition on the site was the worst I’ve seen in many years, a product of deep underground installations at the building’s perimeter. Greasy clay and cold wet conditions were rectified by a couple truckloads of mats for building temporary roads supplied by construction manager Granger Construction. Working through upfront formalities and a few unexpected obstacles finally allowed us to begin construction with loadbearing CMU backup replacing the existing stairwell, making it compliant with new construction. Normal weight CMU, heavily reinforced, supports its own roof.
Exterior systems were coordinated into a single 3D editable document to be updated for producing as-builts as well as integrating digitally into systems for building management
Modeling Simplified Complexities
THE MASONRY LINTEL
Moving to the east side of the project, we began working at the garden wall with 12" CMU very heavily reinforced vertically and horizontally, including structural masonry lintels with brick veneer and cast stone cap. This screen wall encompasses a courtyard with a series of windows 8" wide x 4' in height, allowing light to spill onto a section of existing brickwork throughout morning hours. At the top of each window is a brick lintel assembled with stainless steel threaded rods and epoxy. Each lintel laid out dry on plywood patterned for the correct size, marked and slotted for rods, was assembled wit h mortar and allowed to set. Lastly, rods were embedded into epoxy filled slots. Lintels were then installed as one-piece units, slid in above brick jambs and under CMU bond beam, already in place.
Courtyard side of the wall is lined with green glazed thin brick. Two walls are straight in plane; a sloped top is covered by cast stone with soft joints typical. At the top of the second rake, the long radial slope to the north begins with a compound miter in three dimensions and a radius of 36'4". As stone shop drawings were produced in a 2D environment, the corners for cast stone coping had to be modeled on site and with limited digital resources. Polystyrene insulation was used to make a full-scale mockup of each corner. Pictures of each were utilized to markup for creation of new shop tickets in 3D.
MODELING BRICK ROTATION
Wall assembly is brick veneer over extruded polystyrene, over air barrier, on a metal stud backup system. After completing one large radius at the courtyard, another pair at 3' each was next, incorporating a brick pattern that rotates each brick on an axis centered on the brick itself, then flattening out again. The degree of rotation is increased from nothing at the point of tangency to the maximum of about 22° at the apex, in each case. Brick are rotated and reversed on alternating courses creating a texture seldom seen on any unit masonry projects of the day. Keeping the bond pattern lined up, true and plumb, mason line was used as a guide. Each string jack line was laid out with a laser before being anchored above. A mockup for each of the specialty patterns was built in place, looking for feedback on rotation and tooling.
Water penetration is always a potential concern with raked joints. The concern at the specialty brick patterns was with its reduced bed depth. The first attempt at this mockup didn’t pass inspection with a cut flush tooled edge. A new mockup was built with raked joints around every piece. Approved.
Next, is a section of wall in a straight line (sigh) for little more than 30'. At the end of this stretch, another radius brick wall with individual brick rotations, differing from the first two round corners only by the radius point increasing to 9'2". It’s much easier to layout and stay on bond with the larger radius. Brick rotate gradually, increasingly needing more of the wall per brick in length. This little detail wasn’t part of the equation until after the first three courses were installed in running bond fashion to facilitate flashing installation. Trying to squeeze this pattern in place on 8" centers simply was not possible. Some creativity was required here to catch the running bond pattern around the corner without stacking the first course over the flashing on the north elevation.
Brick are rotated and reversed on alternating courses creating a texture seldom seen
THUMB PRINT HARD
After the layout was established, first and second course, vertical jack lines were located by laser and anchored to the hard ceiling, keeping the lines true. Tooling raked joints takes the thumbprint hard method and cranks it up a notch: set long enough that the mortar falls away clean when tooled. Using a skate for this type of joint finishing seems like the ideal choice however, not on these rotated patterns. A tuck pointer or similar-type square-edged trowel better reaches into the niche that is created at each head joint. The top course is smooth to simplify the transition to the hard surface at the soffit. Directly above the 9'2" radius, structural steel cantilevers beyond, out to the east elevation, carrying brick to the corner then switching to GFRC.
Viewed from a northern perspective, a colorful reflection from the dichroic glass on the west elevation is displayed over brick and more vividly onto the GFRC. The theme of radial, sloped walls continues with more complex angle corners and another bump or two in the plan. With juggling bond patterns becoming second nature for a bricklayer, adjusting window locations to accommodate structural steel has only added to the challenge.
Modeling was Mandatory
This final area to dissect begins with a square corner that transforms into a round corner, where the radius gets larger with every new course. Essentially, there is a cone embedded into the corner. Add in the specialty brick pattern with rotation, resulting in the bond being pushed ever further around the corner as the wall gets taller. This, in turn, means fewer brick per course, sequentially.
A view from above during construction illustrates its complexity and how it resembles a weave. To lay this out, use of the model was mandatory. Transferring the coordinates to their real 1:1 scale location with some primitive tools such as a laser for height and vertical alignment, in comparison to the most modern devices that use GPS, was a bit tricky. Pinpointing locations for control lines would have been much more difficult without the use of software as well as the input from PLY+.
It is obvious that this project is personal. Architect PLY+was on site every day to make sure we were on track and everything was looking smooth. This sort of collaboration works well at the time of execution as well as pre-construction, for follow up and to work through design issues that could not be seen in the design process. One thing that had to be resolved was the fact that the vertical plane of this wall was not vertical. At least not plumb. It is believed, if it’s not plumb, exposing itself to the sky, then it is a roof. The stud framing behind the veneer leans back as well, making this an excellent place to collect water. Water penetrating this area would be especially troublesome as it is adjacent to the altar.
The vertical plane of this wall was not vertical. At least not plumb. It is believed, if it’s not plumb, exposing itself to the sky, then it is a roof.
Special care was taken to ensure water would not enter the building with the use of 100% solid brick with all head joints 100% full. The joints are minimally raked as well as not penetrating the air barrier at its most vulnerable locations. The air barrier did the rest.
Can you even imagine constructing this project without being able to model it first to be sure it would work? We embraced the opportunity and appreciate the attention the architect provided.
Mike Piazza is an on-site supervisor for Davenport Masonry, Holt MI. He has been with DMI for 23 years, managing work from the field and the office as well. Structural masonry, historic recreation, stone veneer and otherwise challenging brick projects are among his specialties. The railroad roundhouse at The Henry Ford, the Milliken State Park Lighthouse, and St Mary Mercy Hospital Chapel are among his most interesting and challenging projects. Piazza is an active member of the Masonry Institute of Michigan’s Generic Wall Design Committee. 517.699.4279 |email@example.com
Upon reading the article you will be able to:
1 Demonstrate benefits to sharing digital models of exterior systems with all teams
2 Evaluate details of installation that help ensure performance expectations, including water-tightness
3 Explore ways to use low-tech on-site tools with high-tech digital tools for best outcomes