Bandelier Historic Structure Report: CCC Buildings

BUILDING COMPONENTS (continued)

Vigas, Canales, Columns, and Lintels

At the outset of Package 224, the most critical deterioration concern on the buildings was deteriorating wood — primarily vigas, canales, and columns. It was this "Rehab Decaying Structural Members" that was identified in the project's initial 10-238. Earlier applied oil preservatives had been lost over the years, and exposure to rain and snow had promoted an environment of decay and fungal attack. Natural checking within log members had only aggravated this condition. Most of the viga deterioration was limited to the exposed areas, but a number of vigas had deteriorated through the wall and therefore deprived the member of its structure-bearing integrity (figures 161-163). Many of the original viga ends had been periodically replaced over the years. The prevalent method had been to remove the exposed deteriorated end or stub and mortar a new stub in place. Many of these stubs had since become loose and fallen (figure 164). Another technique was to use opposing lag screws welded to a base plate as a method to attach the new stub to the original viga (figure 165). On B-1, B-6, B-7, and B-26, some or all of the exposed ends had been removed and the resultant void filled in with a mud mortar similar to the original plaster (figure 166). Similar deterioration was occurring on the majority of canales. Many of the portal columns were decayed at their bases, primarily because they were embedded in adjacent masonry surfaces that trapped both moisture and soil (figure 167). From the crushing of this rotten wood, several of the overhead parapets were deformed, particularly the B-29 portal. Many of the edge latias and window and door lintels had similarly deteriorated (figure 168). Much of the lintel decay was caused by moisture running down the masonry wall and wicking into the wood.

Figure 161. Viga deterioration through the wall of B-13 poses the potential for structural failure, 1984. (Photo: Copeland for NPS)

Figure 162. Severe deterioration of wood viga ends, B-7, 1984. (Photo: Copeland for NPS)

Figure 163. Severe deterioration on viga end, B-2. (Photo: Copeland for NPS)

Figure 164. Area of viga stub replacement, B-29. Note fallen and displaced stubs. (Photo: Copeland for NPS)

Figure 165. One method of attaching former replacement stubs using steel plate and lag screws. (Photo: Copeland for NPS)

Figure 166. Two techniques of addressing deteriorated viga ends, B-6: (1) cutting off exposed end and (2) cutting back exposed end and filling in with mud mortar. (Photo: Copeland for NPS)

Figure 167. Column base deterioration, B-17, portal. (Photo: Copeland for NPS)	Figure 168. Deteriorated lintel, B-25. (Photo: Copeland for NPS)

Following the approval of various work proposals developed as components of this historic structures report, repair work was initiated in 1986. [1] All existing canales were replaced with an EPDM membrane that extended the copper canale flashing onto the roof and parapet (figure 169). This work was done on 115 canales, 87 by contract and the balance through regional day labor forces. The EPDM membrane was applied both as additional flashing and as a potential base for future roof replacement.

Figure 169. Installation of secondary EPDM flashing over canale copper flashing under way on B-13/14 portal. (Photo: Hose for NPS)

Canale scuppers at intermediate roof parapets were replaced with 6-inch PVC scuppers on B-18 and B-32; on B-19, two scuppers were completely removed and flashed with spray urethane. Masonry over some of the canale openings had been previously removed on B-13, B-17, and the B-15/16 portal, presumably to lessen ice buildup. During this canale work, the masonry was restored on B-13 only; to do so on the remaining areas would have involved impact on the existing roofing and extensive flashing repairs.

Except for B-25, all vigas, columns, edge latias and lintels were inspected, and where they had deteriorated they were replaced in kind or repaired. This work was also done by regional day labor forces; Viga repairs consisted of

full replacement in kind where deterioration had significantly penetrated the building interior (B-13, B-21, and B-8's woodshed)

structural epoxy repairs where deterioration had penetrated the building interior but the log perimeter shell was sound (B-21)

replacement of all deteriorated ends

patching with flexible epoxy at areas of minor surface deterioriation

replacement of missing or fallen vigas

B-26's vigas had previously been removed to lessen potential impact from passing vehicles. Because of the significant role this building plays as the initial visual component of the park, these members were reinstalled but with a shorter extension than originally to avoid hitting increasingly larger recreational vehicles. The predominant system of attaching these new ends was the "viga splice" method using fiberglass rods and epoxy, a system reviewed and approved under the preservation plan prepared for this work [2] (figures 170 and 171). Through several years of working with this technique, an additional technique of casting threaded fiberglass rods into the stubs was developed and used on B-28 and B-29. Records were maintained on the technique used for all repairs, records that will be included with the project as-built drawings and the historic structures preservation guide for the buildings. Deteriorated columns were replaced in-kind but with a modified base detail using a raised concrete pad with an embedded drift pin connector.

Figure 170. Structural epoxy repair, B-21, 1985. (Photo: Hose for NPS)

Figure 171. Structural epoxy repair and viga splice repair, B-13, 1985. (Photo: Hose for NPS)

On new wood, members were sized to match the original. Exposed surfaces were drawknifed to simulate the original finish, exposed viga ends were given the original axed finish, and, except for B-28 and B-29, the wood was pressure treated with chromated copper arsenic. Originally, exterior wood was apparently left unstained, but by the 1940s, preservative treatment was initiated. Currently, the majority of all exterior structural wood has a dark stain attained from a variety of opaque stains and oils; portal ceilings and interior woodwork are primarily unstained but have achieved an aged, natural patina. For new replacement wood, with the exception of B-28 and B-29 (where limited staining exists), staining was deemed appropriate to blend the new with the existing exterior woodwork. In addition, staining alleviated the green color resulting from the chromatic copper arsenic treatment. Before staining, the treated wood was scrubbed with a 50 percent bleach solution, rinsed, and allowed to dry as long as possible. In areas of total viga replacement, interior exposed surfaces were left natural to blend with adjacent vigas, and the exposed end was spliced like other viga splice work.

Two additional areas warrant mention. Two viga ends have been removed from B-2 to allow hanging of the visitor center sign; a metal pipe "flying canale" has been added to one of the canales of B-18 to extend drainage farther from the building wall. In both cases, a more sensitive response to the issue at hand could and should have been pursued.