|
Home inspections are important to have done on every home being bought or
sold.
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:
- Cedar
- Spruce
- Pine
- Fir
- Larch
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
necessary.
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
Foundation
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.
Wall
Construction
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.
Roof
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.
Doors
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.
Windows
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.
Chimney
The cabin has a chimney that sank and deteriorated
into many different pieces over the years.
The chimney was rebuilt during cabin restoration.
Definitions:
Handcrafted log home
A home that is constructed of logs that are individually fit together.
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 structure.
Chinking
The mixture used to fill the gaps between logs - can be natural materials or
synthetic.
Shrinking
The normal loss of diameter in logs as they lose moisture.
Settlement
The downward movement of log courses as the logs shrink.
Checking
The natural cracking of logs as they shrink.
Butt joints
Occur when two logs are placed end-to-end.
Log course
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 from outdoors
- separation between exterior log wall and interior partition walls
- separation between log walls and interior ceilings
Other exterior concerns
In addition to the items specified in NACHI Standards of Practice 2.1 and 2.2,
the inspector shall inspect:
-
downspout extensions
- 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 Standards of Practice 2.4 and 2.6,
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 inspections.
Exclusions
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 and accessible.
|