ABSTRACT FROM TRIP REPORT ON EXAMINATION OF BEAM SOCKETS AT QUARAI
To: Associate Regional Director, Planning and Cultural Resources, SWR
Through: Chief, Southwest Cultural Resources Center,
From: Historian, Division of History, SWR
Subject:Trip Report, Salinas National Monument, June 5, 6, 7, 1986.
Purpose of Trip: . . . 2) to examine beam sockets of Quarai in search of evidence of the actual roof structure of the church . . .
. . . I examined a number of beam sockets on the walls of Quarai. Some of the examinations used the scaffolding erected by the stabilization crew, but most were made from the top of an extensible ladder.
The examinations resulted in several specific observations. I will discuss these observations in three groups: nave, transepts, and sanctuary. I am including a detailed summary for Tom Carroll, the superintendent of SALI, and as an official record of the observations that I may cite in the Salinas Historic Structures Report.
The Nave. I examined nine sockets on the west side of the nave and five sockets on the east side. The southernmost four sockets on the west and two sockets on the east were not examined. In this area the roof beam structure consisted of a viga resting on two corbels. The sockets left by each set of viga and corbels average 11 inches wide and 36 inches high. Weathering has made the sockets somewhat larger at the surface of the nave wall. Each socket is separated from the next by an average of 16 inches. The viga and corbels were carefully squared with an adze so that they were about 10 1/2 inches side to side and about 12 inches vertically. The imprint of the faces on the remaining clay mortar in the sockets were flat and smooth, except for the faceting left by the adze. The edges of the beams were straight, sharp and square. The ends were flat and square.
No decorative carving left its imprint on the clay mortar. Unfortunately, the areas most likely to retain such imprints were the first several inches of each socket closest to the nave wall surface--these areas had been covered with repointing mortar by stabilization crews in all the sockets examined.
Every socket examined in the nave showed clear evidence that fire destroyed the church of Quarai. The clay mortar was baked hard, and was a rich orange in color. Most of the clay surfaces of the sockets themselves were clean, the result of an oxidation environment in the fire. Heavy sooting and ash deposits were visible in cracks running away above the sockets, indicating a reduction environment with lower oxygen levels and a slightly cooler temperature. Apparently a chimney effect was created through the cracks above the beam end as the beams burned, allowing the beam bases to burn completely to the rear of the sockets. This tells us two things: a) the fire was quite hot, and b) every socket examined probably had a beam in it at the time of the fire. Without a beam, no chimney effect would have occurred in a given socket, and the temperature deep within the socket probably could not have risen high enough to bake the clay mortar in it.
The sockets varied considerably in depth. Most of the surviving sockets are in the faces of the tower buttresses of the church walls. In these areas the builders of the church had allowed the vigas to remain several feet longer than they were in the central areas of the nave. On the west side of the nave, the two measured depths of the viga inset were 7 feet 6 inches and 5 feet 8 inches for the first and third sockets south from the transept, respectively. On the east side, the first viga was inset 8 feet, while the second inset was 7 feet 4 inches. The third viga inset was only 4 feet 7 inches. The first viga, spanning a nave of 27 1/2 feet with an inset of 7 1/2 feet on the west and 8 feet on the east, was almost exactly 42 feet long, and just over 10 inches square for that entire length. The third viga was 37 3/4 feet long. These are surprising lengths for squared vigas. They indicate that large trees were available in the area of Quarai in ca. 1630, or that the carpenters responsible for collecting wood for the roofbeams were willing to go whatever distance was necessary to secure such beams. They also indicate that the Franciscans of the seventeenth century were not willing to accept the shortcut of using round beams (easier to find in a given length), but preferred to go to the extra trouble needed to locate and square up the larger trees necessary to give a uniform 10 inches thickness for a length of up to 42 feet.
Corbel insets in the buttress areas are more consistent than are the viga insets. They average 4 1/2 feet for the top corbel and 4 feet 1 inch for the bottom corbel.
The vigas from the central area of the nave had insets considerably less than the maximum of 8 feet seen at the north end. The wall thickness here is about 5 feet on the west side and 4 1/2 feet on the east. In this area the surviving sockets averaged 3 1/2 feet deep, with no appreciable difference between the inset of the viga and that of the corbels. This indicates viga lengths of about 35 1/2 feet for most of the nave.
The ceiling of the church (at the top of the viga) was at an average height of 28 1/2 feet above the present floor. The average height from the bottom of the lowest corbel to the floor was about 25 1/2 feet. Field measurements and measurements on Perry Borchers's HABS drawings of Quarai made in 1978 show that the roof had a slope of about 1 foot downward east to west and about 3 inches downward north to south. This indicates that the major drainage from the nave roof was in the southwest corner of the church, probably against the north side of the west facade tower.
In many places the masonry between the beam sockets had cracks and gaps. These blocks of masonry, averaging 16 inches wide, were apparently built up between the corbels and vigas after they were set in place. Most sockets have several flat stones 8 to 10 inches square that were placed vertically, directly against the beam surfaces. They were then mortared over, with standard horizontally-laid stones against their outside faces. On the top surfaces of the beams a layer of mortar perhaps one inch thick covered the wood.
One large chunk of baked clay was removed from the third socket south on the west side, in order for it to be analyzed for its components and to photograph the imprint of the viga on its surface. It had been applied as mortar to the top of the viga, 42 inches in from the face of the nave wall. It is baked hard and bears the clear imprint of the beam cast onto its lower surface. Adze marks and the woodgrain itself can be seen in the surface of the cast. The construction crew apparently used a tool similar to a trowel to apply the mortar, leaving toolmarks visible on the top surface of the clay, away from the wood imprints. Flat stones were laid into this coating of mortar, and then the stonework of the parapet continued upward.
The Transept. The viga and corbel arrangement in the transept was somewhat different from that in the nave. A viga and two corbels were used as in the nave, but were somewhat smaller. They were 9 inches side to side and 11 inches vertically. The sockets averaged 10 inches wide and 33 inches high, with an average of 11 inches between sockets. The amount of inset of the vigas and corbels varied from wall to wall of the transept. On the north face of the east transept, for example, the lower corbel was set in about 3 feet, the upper corbel about 2 1/2 feet, and the viga about 4 feet. On the south face of the same transept, the two corbels were set in about 3 feet, while the viga was inset 3 1/2 feet. In the south face of the west transept, the bottom corbel was inset 4 1/2 feet, the top corbel 3 1/2 feet, and the viga 3 feet. Vigas in the transept averaged 32 1/2 feet in overall length, with a clear span of 25 feet.
The height of the ceiling in the transept was 36 1/2 feet. The transept roof apparently sloped downward to the south about one foot, and downward to the east about three inches, indicating that the transept roof drainage ran off the southeast corner of the transept onto the roof of the convento.
The Sanctuary. The sockets in this area were 29 inches high, on the average, and 8 1/2 inches wide. They contained a viga and two corbels, each about 8 inches wide side to side, and 9 1/2 inches wide top to bottom. The beams and corbels of the sanctuary had a shallow inset of 20 inches, with no difference in depth between corbels and vigas. The beams are set into a wall varying between 4 and 10 feet in thickness. They could have been made at least two feet longer, adding strength to the structure. Apparently the builders felt that there was no need for added strength. This implies that the roof of the sanctuary did not have to support much weight, unlike the nave and transept.
The northernmost set of two corbels and a viga left a poorly defined imprint on the north wall of the sanctuary that gives some idea of the length of the corbels outside their sockets. The corbelling apparently almost touched at the center of the northernmost viga, with a span of 11 feet. Each pair of sanctuary corbels must therefore have extended from the wall about half this width, or 5 1/2 feet. The lower corbel was 2 3/4 feet long with decorative scrollwork the entire length of the underside. The upper corbel had no decorative scrollwork along the first 2 3/4 feet, where it rested on the lower corbel, but the remaining 2 3/4 feet extending beyond the lower corbel would have had identical decoration. The larger corbels of the nave and transept would have had longer lengths, about 3 1/2 feet for the lower corbel and 7 feet for the upper.
Recommendations. This brief examination of the beam sockets of Quarai was surprisingly rewarding. When time permits, the remaining sockets should be examined. It is always possible that casts of decorative carving were preserved in some sockets. In most cases the first six inches of the cast surface has been covered by new mud plaster during stabilization work, but perhaps some areas of casts of decorative carving extended further back than this into the socket. A similar examination of Abó and Gran Quivira will be conducted next year. Sam Chavez, leader of the Quarai stabilization crew this year, tells me that when he worked at Abó several years ago he found baked clay and charred wood still in place in the deeper holes. Photographs of the sockets and wood are on file at park headquarters and will be examined.
I strongly recommend that during future stabilization work at the Salinas missions the beam sockets be treated carefully. The crews should not cover any more of the interior of the sockets with mortar. If possible, none of the socket interiors should be repointed. Covering the already-pointed surfaces of the sockets with any additional mortar should be avoided. . .
PCR Reading File
1 Manuscript on file in Southwest Regional Office, National Park Service, Santa Fe.
Last Updated: 28-Aug-2006