This article continues our series on the Lowenstein Mansion project here in Memphis,` outlining the process from imagination to implementation to convert a bearing wall brick building, what we engineers call "unreinforced masonry," into a modern open-concept bright and airy co-working space...and doing it affordably by avoiding use of steel framing.
Architect Andy Kitsinger's vision for this building was for the two-story 50' x 40' interior floors of the 1930 Annex to be clear spanning open space. This meant the removal of all interior lath-&-plaster sheathed studwalls on both floors. On the second floor, it also included removing most of the stick-framed ceiling in order to vault into what used to be the attic space. Opening up floorplans can greatly weaken these historic structures, yet it only makes sense for the new uses we imagine for them today, so it needs to be an option for historic preservation.
Therefore this desire for open-concept space did not come without its set of challenges. One obstacle early on was that by removing all of the interior lath-&-plaster-sheathed stud walls, we would bring ALL the building loads to the perimeter historic brick walls. This would severely overload the already degrading, nearly one-hundred-year-old materials. Additionally, it would be a severe seismic hazard. So what could we do? A common approach is to use grouted CMU walls due to their economy and strength to resist both gravity and lateral loads, and that's what we did, installing a series of short, full height CMU piers around the inside perimeter of the brick.
Next was how to tackle the vaulting of the ceiling. The roof relied on the existing ceiling joists to tie it together so it would not spread. To compensate for removing the existing joists, we created an inner vault under the outer roof, coupled to the rafters to reinforce each other. This vaulted ceiling would now serve as a hybrid roof diaphragm, in conjunction with the roof being the main diaphragm, to redistribute seismic loads to the new shearwalls and tie it all together. This ceiling framing design would have to be strong enough structurally to reach down along the old perimeter brick walls to anchor them where they are still strong. Aging unreinforced brick buildings in the mid-south are delicate structures, and the top of the brick walls of this building are crumbling, which is a common problem.
Custom steel trusses were a strong option for the vaulted ceiling support but likely a budget killer for this project, and no doubt many others.
So, we decided it would be great to stick frame this structural inner vault out of ordinary lumber and fasteners. This would allow for affordable materials, AND a framing crew could do it without bringing the added cost of specialty subcontractors. So, that is exactly what we designed. A stick frame vaulted truss framing out the ceiling feature, using 2x lumber, 1-3/4 LVL, and off the shelf metal hardware from Simpson strong tie. The integrated vault provides good anchorage for the old brick walls, distributes loads to the new CMU piers, and functions as a diaphragm to strengthen and stabilize the entire annex.
This vault has become a central element in our design and is a wonderful example of structure integrating with architecture to create inspiring open spaces efficiently and safely.
By going this route and not relying on a conventional steel solution, we were able to achieve substantial cost savings, provide a high level of seismic strengthening, and keep the historic fabric of the roof and eaves as well as the historic brick in place. This project is ongoing and we will link updates here.