Hear the cry: Bring back the viga
When I began building homes in Santa Fe more than 30 years ago, locally sourced logs were used for roofs as they had been for a thousand years. Then the 2006 International Residential Code decreed that structural timbers, meaning beams and vigas, needed to be graded and certified by structural engineers. That effectively killed vigas as roofing material.
Sure, we still see vigas and beams on new ceilings, but now they have expensive and unnecessary truss systems above them. The vigas are purely decorative. That is ridiculous.
The first home I owned in Santa Fe was a wrecked 100-year-old adobe on Agua Fría Street. It had vigas, the fattest no more than 6 inches in diameter. They did have a pronounced bow from the tons of dirt above the wide planks, but they were in no danger of breaking.
Rachel Wood, an appropriately named Santa Fe forester, is attempting to overturn the restrictive rules and bring back New Mexican logs for roofs. She recently made a pitch for funding under the Collaborative Forest Restoration Program. The federal program, established in 2000, is administered by the U.S. Department of Agriculture and was the brainchild of former U.S. Sen. Jeff Bingaman.
Wood’s proposal seeks to recognize, through a branding program called Good Wood, that forests in New Mexico are as sustainably managed as any forests certified by the Forest Stewardship Council, the supposed gold standard for sustainably harvested timber. Currently, no New Mexico forests are FSC certified, mainly because getting a stand of timber certified is onerous and expensive.
The Good Wood program would establish chain-ofcustody protocols from chain saw to lumber yard to assure consumers that small-diameter wood products from our forests have followed rigorous forest sustainability princi
ples that in many cases exceed stewardship council standards.
New Mexico forests are overseen by a variety of entities, including federal, state, tribal and private. All practice sustainability principles blessed by the National Environmental Protection Act and the Endangered Species Act, and all support local economies, healthy forest restoration and watershed protection.
Small-diameter logs are considered anything 16 inches or skinnier. A 16-inch viga can support a lot of weight. Back in the day, permitting officials all recognized a New Mexico viga span chart. It was a matrix that said if a certain diameter viga was used and they were spaced a certain distance apart, they could span a certain distance. Everybody used it and everybody trusted it until it went away after the 2006 code was approved.
Wood’s program seeks to bring back the span chart. It should be relatively simple, and she would get help from engineers in Los Alamos. The idea is to take the weakest viga species, which is spruce, assume an average grade, and then determine its span capability based on butt-diameter and on-center spacing. The specifications for spruce would then make ponderosa and fir, also common in New Mexico forests and substantially stronger,
automatically approvable.
Many green-building programs only recognize the stewardship council’s legitimacy, but locally sourced wood from sustainably harvested forests is greener than that from any out-of-state FSC forest. The New Mexico Construction Industries Division, the arbiter of our state codes, would support viable span charts. Build Green New Mexico, our widely used green certification program, would as well.
The West Coast fires have sharpened our focus on forest restoration. Though the science is clear that climate change and a 20-year megadrought in the West have created the conditions, it’s also true that neglected forest management has made conditions worse.
Nobody is suggesting we all go up and rake the forest floors, but harvesting small-diameter logs through sustainable thinning and putting that wood in our homes will undoubtedly help.
No New Mexico forests are FSC certified, mainly because getting a stand of timber certified is onerous and expensive.
Kim Shanahan is a longtime Santa Fe builder and former executive o∞cer of the Santa Fe Area Home Builders Association. Contact him at shanafe@aol.com.