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Usonian window wall mullions
Posted: Thu Feb 02, 2006 12:31 pm
We decided to design and self-build a small Usonian type retirement home for ourselves here on Battle Lake. This is similar to, but not a copy of, those that FLLW would shake out of his sleeve in 1950's, stone, wood, and glass. Its construction is a hobby, and although extremely labor intensive, always a joy.
We have foundations, bedrooms, and tall stone kitchen/fireplace built, as well as part of the living/dining room. As soon as the weather warms, we will tackle the big glass window wall that opens onto the terrace.
The technical question is this. Searching FLLW details and looking at many of his houses from this period, it appears that the window mullions were set right onto the concrete floor. Sometimes they were steel, clad in wood, but usually only wood, that is holding up the roof. It has been suggested that we make a steel bracket to support the mullion and transfer the load to the foundation, and hide it inside the concrete floor. Good idea and we will do it. But I would like to know from those who may be familiar with maintenance of the Usonians, how do they prevent rotting of the wood at this junction of wood and concrete?
Doug Kottum, Battle Lake, MN
Posted: Thu Feb 02, 2006 1:40 pm
Can you post photos of the house so far?
Posted: Thu Feb 02, 2006 3:21 pm
My FLW house was built in the 50's. It has many Usonion features such as the one you are describing. I have noticed that there has only been one repair made, presumably due to rotting, at the base of the mullion at the concrete. For this house, it does not appear to have been a significant maintenance factor in the life of the house to date. I would imagine that keeping the wood well sealed and the concrete sealed as well will be the most help. Also, a small bead of high quality caulk at the juncture will also prohibit penetration. Good night and good luck!
Posted: Thu Feb 02, 2006 5:43 pm
At the Kraus House the mullions are set in a metal (bronze?) shoe
about 2 inches tall. Also the french doors appear to have a taller
theshold than Wright typically used. I believe these changes were
made as part of the restoration to prevent water from wicking up
and damaging the wood. Particularly important in snow country.
Posted: Thu Feb 02, 2006 8:45 pm
I am very famiar with a FLW House that was built in the early 50's. It is not a Usonian, however it has details similar to your condition. The vertical mullion extends dow to the concrete slab without visible flashing other than a thin bead of sealant. It appears to have aged well for 50 years. At locationss where a scupper drains water onto the pavement which splashes the wood window frame, a high maintence condition is created. This requires wood refinishing at a higher cycle than the rest of the house. The Usonaians that I have observed recently typically had a vertical 2x6, approximately, for the bottom horizontal mullion against the pavement. This worked well for maintenace purposes and it was beautiful because it matched the hieght of the bottom rail of the door.
Posted: Fri Feb 03, 2006 1:36 am
The typical detail indeed was the sill, almost always a "bulkhead" type sill, sealant or gasket closing the gap betwwen the wood and the concrete pad. These window walls , which of course included operable panels, lead out to a hardscape terrace, sometimes elevated above grade, and usually protected by a generous overhang, but not always. Even near grade, the slab extended at least 6", but usually more, and sloped away from the building, to keep landscaping, soil, moisture at a distance.
On the Hanna House, Wright used a metal spline in the concrete. Interesting to me is Wrights' method for dealing with the desired long spans of window walls. If the wall was long and straight, vertical posts were used. The obtuse angles of the hex, eliminated the need for additional vertical support because, as I understand it, Wright thought the window and door frames, configured at 120 angle bays, acted as collectors to resist lateral load.
Looking forward to pics of your project, sounds like great fun!