While the buttresses on the church are fake and hollow (plaster with wood and tarpaper behind them) the aisle columns in the sanctuary are concrete (hopefully reinforced). The piers under the sanctuary floor are 3 ft. square and the columns somewhat smaller. The tower is constructed of reinforced concrete (you can see the rebar as you climb up to the tower top) as is the sanctuary (per newspaper story). Throop Hall has steel I-beams.
Throop hall has huge I-beams in its walls and ceiling. Inspect via trapdoor in ceiling of Janitor's closet. The horizontal I-beams (above each visible wood beam) are 2 ft. high (height of the center web of I). Two other smaller vertical I-beams are visible inside the sliding partition storage cavity next to the Fireside Room. How the I-beams are attached to the foundation walls is not clear, but all I-beams have a foundation wall under them. The center of the N. Room ceiling is supported by thick metal straps hung from the roof ridge (top of roof).
The exterior thick walls of the sanctuary are filled with hollow tile made of red clay (terra cotta) of dimension 1'x1'x6". It's often called "hollow clay tile". The walls of this tile (used as construction block) are about 5/8" thick. Each has 3 hollow rectangles. One may see these 1. as one climbs to the Sanctuary attic (see access); 2. under the floor (in the crawl space) in the exterior sanctuary walls; 3. just under the tower top deck where they are used as blocking. In the sanctuary walls they are enclosed by a reinforced concrete framework which keeps them in place during earthquakes.
In the crawl space some posts have termite shields (metal plates) on top of them. In the area between the sanctuary and the dance floor auditorium mud sills on interior foundation walls are not bolted down.
The thickness of the plaster-lath in Throop hall is almost 1 inch. Lath seems to be mostly metal lath. The thickness of the exterior stucco (Gunite) varies but is about an inch thick in some places. Metal lath was used for some interior and exterior walls.
The purlins are used in the N-S roof (steep). Some of them are visible in the storage closets of North room and the Morrison room. Each is a "triple" consisting of 3@ 2" x 15" rough wood boards which touch each other over their entire length. There are 3 such purlins on a roof slope (all at different elevations of course) resulting in 6 purlins on a section of roof (18 @ 2" x 15" boards total). There are at lest two sections of roof that have purlins, one to the N and the other to the S. To see the upper pair (at the same elevation) you must go into the attic. They seem to bear a vertical load but are tilted about 50 deg from vertical (tilted the same as the roof). It might have been more efficient if they were not tilted but then there would be the problem of notching them for the rafters to rest on. Perhaps the 3 boards could have been staggered so as to minimize the amount of wood needed to be removed for notching.
The ends of the purlins are supported by studs or by special A-frames with each side of the A-frame consisting of a 3@ 2" by 15" boards nailed together. These A-frames rest on the I beams of Throop Hall or on the reinforced concrete of the E wall of the tower.
The the N. part of the ceiling of the N room (and part of the ceiling of the S. room) are supported by wood hangar boards which hang down from the upper purlins and hold up strongbacks attached to the ceiling joists. The attachment of the wood hangars to the strongbacks is poor since the wood hangars are not exactly vertical but are nailed to the vertical sides of the strongbacks. Some of the nails seem to be pulling out. As a fix, one could replace them with metal straps, or make wood wedges to fill the air gaps and pound in more nails.
N wall studs: 2 x 8 (finished) (visible in N. room closets).
There are a set of trusses that support much of the ceiling on the second floor (over Throop hall). These trusses are made of wood with a 10 ft. metal hangar bar supporting each ceiling joist at its center. These hangar bars are suspended from the ridge for these trusses, which are located several feet below the N-S roof ridge. The only part of the roof directly supported by these trusses is the gentle sloped roof facing the patio. Thus if one looks upward in the attic at them, one sees the roof ridge and then another ridge several feet below that which has no roof connected to it (looks strange). The steep roof is supported by short rafters connected near the top of the truss. This is the part of the steep roof that rises several feet to its peak above the flat roof well by the tower.
These trusses are only in the middle section of the main N-S roof. This middle section is located between the twin gables seen from the patio and includes the gables.
A 7/8" nut was found near the Del Mar crawl space entrance (S of the sanctuary chancel). It's American Standard Special 12-pitch series (12 threads/inch). Hardware stores generally only carry the course and fine series of Am. Std. but don't stock the 12-pitch series. Where this nut was used is unknown.