The masonry restoration work at the Emil Bach House has progressed well. Over the years, various efforts at tuckpointing were done on an “as needed” basis. Unfortunately, they were, by and large, maintenance work done with little regard to the original masonry work. This is particularly evident in the mortar joints where previous repairs basically installed all the mortar joints flush with the bricks or sometimes striking them with a slightly concave joint. Originally, in the Bach House, Wright had all the horizontal joint at about 1/2″ wide, then struck and raked back about 3/8 of an inch. All the vertical joints were laid in tight at less than 1/4” and the mortar was stuck flush with the brick. This was a detail that was used in other Wright projects and it complimented the horizontal lines of the building. We able to find several areas of the house that still had this detail due to those areas never having been tuckpointed after the original construction.
Typical section of “repaired” masonry
Grinding the “repaired” mortar joints back.
Helen checking the depth of the horizontal mortar joint.
Close up of joint depth.
Close ups of finished tuck pointing
We had an interesting discovery last week when a wall in the master bedroom was opened up for measurement where the original built-in dresser is to be installed – original plaster wall! Several things are significant with this discovery:
1. It is the first visual evidence that the original built-ins were actually installed and not left out of the final project for budgetary or other reasons. Actual dimensions can be verified by the “ghost outlines” of the drawers visible on the plaster.
2. Up to this point, the only original plaster finish that had been found was on the ceiling of the first floor living room, now we have an actual piece of wall plaster AND the finish is significantly smoother than the ceiling plaster finish.
As a result there will be a rougher textured plaster ceiling finish than on the walls, although the wall finish is not anywhere near what anyone would call a “smooth” finish. The following photographs show original ceiling plaster finish and wall plaster finish.
Original ceiling plaster finish discovered under drywall.
Close up of original ceiling plaster
Original wall plaster finish above built in dresser
In order to replicate the plaster textures required, the correct sand aggregate must be selected, then applied in a trial and error manner until the original finishes are duplicated.
Trying to match plaster aggregate for the various plaster finish textures
A Surprise Repair from an Earlier Renovation
After discussing the pros and cons of replacing the plaster ceiling versus spot repair in the main living areas, i.e. the living room and dining area, or just making repairs, it was decided that merely repairing the ceiling would be an inadequate solution for a variety of reasons; in some areas there were already three layers of ceiling, the original plaster on wood lath, a later plaster finish attached to the original with metal lath and finally another layer of plaster board with a veneer plaster finish.
The multiple campaigns had left the ceiling with some slight bumps and waves in the finish, but what really drove the decision was that in some areas the plaster “keys” between the wood lath had broken and portions of the ceiling were slightly loose. When the ceiling was taken down, it was actually in worse condition than we anticipated (in retrospect it’s hardly a surprise – it is sort of the name of the game in old buildings) with portions of the original plaster completely detached from the wood lath. Besides the failing plaster lath system, several second floor joists were found to be severely compromised with notches that had been cut in to accommodate the plumbing when the original maid’s room was converted to a second bath. The new plaster ceiling afforded the opportunity to repair all these issues.
Another interesting discovery was made during the removal of ceiling. The area over the dining area had no plaster, just drywall. Sometime earlier, possibly in the 1960′s, the steel beams shown in the photographs were installed in what appears to be a successful attempt to straighten or reinforce the second floor cantilever on the north elevation of the building.
Dry Tamp Concrete in the Emil Bach House
In an earlier renovation of the Emil Bach House, a basement storage room was added underneath the rear porch. This required “underpinning” the existing foundation excavating approximately 7 feet under the porch and installing new concrete beneath the original. When the Bach House was built in 1915, concrete was often cast using a “dry tamp” method. This method involved taking the dry mix of cement, sand and aggregate and just dampening it with enough water until it had a sort of clay like consistency, but was barely wet to the touch. It was then placed in the forms in layers of approximately 12 to 18 inches and tamped down until the moisture rose to the surface, then the next layer was added and so on.
In Emil Bach House case, it looks like a trench for the porch foundation was excavated to “frost line” and then the dry tamp concrete was placed directly into the trench in some places and framed or formed in others. Considering that it is almost all sand in the area, I would imagine most of the work, excavation and concrete placement had to be done in one day just to keep the sides of the trench from collapsing.