Log Home Basics
Log homes may be site-built or pre-cut in a factory for delivery
to the site. Some log home manufacturers can also customize
their designs. Before designing or purchasing a manufactured log
home, you need to consider the following for energy efficiency:
The R-Value of Wood
In a log home, the wood helps provide some insulation. Wood's
thermal resistance or resistance to heat flow is measured by its
R-value. The higher the R-value, the more thermal resistance.
The R-value for wood ranges between 1.41 per inch (2.54 cm) for
most softwoods and 0.71 for most hardwoods. Ignoring the
benefits of the thermal mass, a 6-inch (15.24 cm) thick log wall
would have a clear-wall (a wall without windows or doors)
R-value of just over 8.
Compared to a conventional wood stud wall [31 D2 inches (8.89
cm) insulation, sheathing, wallboard, a total of about R-14] the
log wall is apparently a far inferior insulation system. Based
only on this, log walls do not satisfy most building code energy
standards. However, to what extent a log building interacts with
its surroundings depends greatly on the climate. Because of the
log's heat storage capability, its large mass may cause the
walls to behave considerably better in some climates than in
others. Logs act like "thermal batteries" and can, under the
right circumstances, store heat during the day and gradually
release it at night. This generally increases the apparent
R-value of a log by 0.1 per inch of thickness in mild, sunny
climates that have a substantial temperature swing from day to
night. Such climates generally exist in the Earth's temperate
zones between the 15th and 40th parallels.
Minimizing Air Leakage in Log Homes
Log homes are susceptible to developing air leaks. Air-dried
logs are still about 15–20% water when the house is assembled or
constructed. As the logs dry over the next few years, the logs
shrink. The contraction and expansion of the logs open gaps
between the logs, creating air leaks, which cause drafts and
high heating requirements. To minimize air leakage, logs should
be seasoned (dried in a protected space) for at least six months
before construction begins. These are the best woods to use to
avoid this problem, in order of effectiveness:
Since most manufacturers and experienced builders know of these
shrinkage and resulting air leakage problems, many will kiln dry
the logs prior to finish shaping and installation. Some also
recommend using plastic gaskets and caulking compounds to seal
gaps. These seals require regular inspection and resealing when
Controlling Moisture in Log Homes
Since trees absorb large amounts of water as they grow, the tree
cells are also able to absorb water very readily after the wood
has dried. For this reason, a log home is very hydroscopic—it
can absorb water quickly. This promotes wood rot and insect
infestation. It is strongly recommended that you protect the
logs from any contact with any water or moisture. One moisture
control method is to use only waterproofed and
insecticide-treated logs. Reapply these treatments every few
years for the life of the house. Generous roof overhangs,
properly sized gutters and downspouts, and drainage plains
around the house are also critical for moisture control.
Building Energy Code Compliance for Log Homes
Because log homes don't have conventional wood-stud walls and
insulation, they often don't satisfy most building code energy
standards—usually those involving required insulation R-values.
However, several states—including Pennsylvania, Maine, and South
Carolina—have exempted log-walled homes from normal energy
compliance regulations. Others, such as Washington, have
approved "prescriptive packages" for various sizes of logs, but
these may or may not make sense in terms of energy efficiency.
The American Society of Heating, Refrigerating, and Air
Conditioning Engineers (ASHRAE) 90.2 standard contains a thermal
mass provision that may make it easier to get approval in those
states that base their codes on this standard. To find out the
log building code standards for your state, contact your city or
county building code officials. Your state energy office may be
able to provide information on energy codes recommended or
enforced in your state.
Building & Restoration of Log Cabins
The foundation of a log cabin is made of stone pillars. The
stones provide a sturdy base to support the cabin and act as a
barrier between the cabin and the earth. The stones may settle
over time and the foundation is carefully examined for damage or
wear and subsequently repaired during restoration.
The walls are made of logs, placed either vertically or
horizontally, depending on the style and size of the cabin. The
logs are notched at the corners to allow them to fit together.
Corner notching is a notable characteristic of log cabin
construction because it provides stability by locking the log
ends in place, enabling the logs to fit together in a secure
manner. Many different methods of corner notching exist, ranging
from simple "saddle" notching to the common "V" notching or
"steeple" notching, which get their name from the shape of the
notch cut into the wood. These notching methods are marked by a
cut into the wood that allows another cut piece of wood to fit
together like a puzzle piece. Another commonly used technique,
"square" notching, differs in that the logs are secured with the
addition of pegs or spikes.
The number of logs used per wall varies with the size of the
cabin. The spaces between logs are usually filled with a
combination of materials in a process known as "chinking" and
"daubing." This process seals the exterior walls, protecting
them from weather and animal damage.
Log cabin roofs are often gabled and are comprised of
hand-split, wood shingles. The roofs often develop damage and
leaks over the years and are commonly included in restoration.
Many log cabins have both a front and rear door. Due to the many
times the doors are opened and closed over the years, the doors
are often not in good working order and require repair during
restoration. Both doors on the cabin can be comprised of boards
that are hand-dressed, open inward and are fastened to the log
structure with pegs.
The cabin features two windows, located on either side of the
chimney. The windows hold glass panes, which most likely need to
be replaced during the restoration of the cabin.
The cabin has a chimney that sank and deteriorated into many
different pieces over the years. The chimney was rebuilt during
Handcrafted log home
A home that is constructed of logs that are individually fit
Milled log home
Constructed of machine-lathed logs, and is also used to
describe a log home built from a kit.
Insulated log home
Constructed with half-logs attached to a standard 2x6 frame
The mixture used to fill the gaps between logs - can be natural
materials or synthetic.
The normal loss of diameter in logs as they lose moisture.
The downward movement of log courses as the logs shrink.
The natural cracking of logs as they shrink.
Occur when two logs are placed end-to-end.
One layer of logs placed atop the entire foundation of the home.
Log wall exterior
The inspector shall inspect exterior surfaces of log walls, when
such surfaces are visible, looking for:
presence of mold, mildew or fungus
cracks located at tops of logs and facing up
discoloration, graying, bleaching or staining of logs
loose or missing caulking
separation of joints
condition of chinking, to include cracking, tears, holes, or
separation of log courses
condition of log ends
Log wall interior
The inspector shall inspect interior surfaces of log walls, when
such surfaces are visible, looking for:
separation between logs, including light or air penetration
separation between exterior log wall and interior partition
separation between log walls and interior ceilings
Other exterior concerns
In addition to the items specified in NACHI and
ASHI Standards of Practice, the inspector shall inspect:
grading and water flow away from log walls
vertical support posts under and on all porches
Other interior concerns
In addition to the items specified in NACHI and ASHI Standards
of Practice, the inspector shall inspect:
Slip joints, adjustable sleeves, looped water supply lines,
flexible hose sections, and flexible ductwork that are
visible as part of the standard heating and plumbing
The inspector is not required to:
inspect or predict the condition of the interiors of logs
predict the life expectancy of logs
climb onto log walls. However, the inspector may inspect log
walls by use of a ladder, if this procedure may be done
safely and without damaging the walls.
inspect components of the porch support system, or of the
plumbing or heating systems, that are not readily visible