A.Will Beemer, co-executive
director of the Timber Framers Guild in Becket,
Mass., responds: You are proposing an infill
system, as opposed to the usual enclosure system,
which wraps the entire structure with insulating
panels. Traditional infill systems used materials
such as adobe or wattle-and-daub. You are probably
planning to build stud walls covered with stucco
between the posts of the timber frame.
Unfortunately, the finishing details where this
infill meets the timbers would prove daunting.
Your proposal could work, but the success of the
system would depend on a number of conditions: You
must be located in an arid climate; you must use
dry timbers; and you must be meticulous about
caulking. In a mild, dry climate, such as that of
the arid Southwest, you would not have the moisture
migration and condensation problems we do in the
Northeast. In a cool, damp climate, your timber
frame is at risk of rotting from rain on the
exterior or from the condensation of interior
moisture on cold surfaces near air leaks.
Most timber frames are built with green timbers
that shrink as they dry. Because shrinking timbers
will magnify the difficulty of caulking any gaps
between the infill system and the timbers, you
should begin with dry timbers. One option is to use
dry reclaimed timber, although such timbers are
more expensive than green timbers.
Choose a species that is rot resistant and that
swells and shrinks little with moisture changes.
Cedar would be a good choice, although cedar is
expensive and not very strong. I would probably use
Eastern white pine, which shrinks very little, and
get around the rot-resistance problem by keeping
the frame well off the ground and protecting it
from the weather with wide roof overhangs. Water
does the most damage, not exposure to sunlight or
Any gaps that open up between the infill system
and the drying timber would have to be caulked,
both inside and out. This caulk could be the infill
material itself (adobe, etc.) or one of the new
synthetic caulks that bonds to wood and masonry.
Since wood can swell and shrink with humidity
changes, these caulk joints will require vigilant
maintenance. If all of these requirements are
discouraging, and you want an easier way to keep
your timber frame lasting a few centuries, you
should wrap it in an insulating skin.