 |
 |
|
|
EXTERIOR SIDING FOR CONSTRUCTION OF
MOUNTAIN HOMES AND LUXURY RUSTIC HOME DESIGNS
By Rand Soellner
Architect
Special
Design Consultant to Keller Williams-Village Realty
Rand
Soellner, AIA / NCARB Licensed Architect, Cashiers, North Carolina,
828-743-6010
 |
What
siding will you be installing on your mountain home? Logs,
clapboard, board & batten, shingles of various materials,
cement planks…there are options and varying costs. I've
been designing homes and buildings for 36 years. These articles
are created to assist the homeowner and should not be undertaken
without the assistance of a licensed professional. |
WHAT
IS SIDING? The material that is used to clad the exterior of a
home's walls is generally referred to as its siding, because it
the material on the "sides" of the home.
SIDING
OPTIONS: a complete list would be too long. Let's consider those
that are most often used in the mountains:
BOARD &
BATTEN: This is a time-honored tradition that one finds in
upscale communities of multi-million dollar homes to compact
cottages in outlying areas. It is probably one of the least
expensive real-wood siding systems to use that fits in with
almost any community's standards and is aesthetically appealing
for nearly all tastes. Often, an initial layer of vertical
1x12's is installed next to each other, then 1x2's or 1x3's or
1x4's are nailed over the base layer of siding, centered on the
joints. I recently created a random board & batten pattern
for a project in Wade Hampton that opens a whole new dimension
to this historic system. Wood species often used in the
Carolinas: white pine, although #2 SYP (Southern Yellow Pine)
p.t. (pressure-treated) should last for decades, if regularly
stained. Rectangular cementitious planks could also be used, but
some material purists find this objectionable, and the stamped
wood grain texture can be obvious if studied too closely. The
advantage to this material is that it will probably be here
until well after you and I are gone.
CLAPBOARD: also
called horizontal lapped siding. It typically consists of
horizontal boards that are beveled, thinner at the top and
thicker near the bottom. Boards overlap each other and are
nailed through the overlap to form a tight, weather-resistant
joint. Cedar is the preferred natural wood, although
cementitious planks (like Hardi-plank) have some favor with
consumers due to their longevity. Although vinyl horizontal
siding may have its place on tract housing down the mountain,
appraisers will tell you that this will devalue an otherwise
nice mountain home. This has nothing to do with performance, but
rather aesthetics and perceived cheapness as opposed to a
quality genuine wood.
SHINGLES: there are several.
Cedar shingles seem to be preferred by some people from tailored
suburban areas like Buckhead, while others seeking a more
Appalachian look enjoy novel shingles like poplar bark
(available from Furniss Enterprises in Lake Toxaway). Not
everyone is familiar with poplar bark shingles. Jim Furniss,
owner of a company that manufacturers them, harvests the bark
right off the trees in early to mid January. Bark harvested then
tends to stay on the substrate wood rather than peeling. These
shingles are about 18" to 24" square. Any kind of wall
shingle should be overlapped about 50% of its height when used
outside, to avoid water from seeping into cracks between the
shingles. Although rarely used, there are also copper shingles,
which can result in a unique fish scale like finish.
LOG
SIDING: Real logs compose a traditional log cabin or log home.
Historic log homes possess a captivating primitive feel that
looks cozy and warm, and use logs that can be anywhere between 8"
to 24" in diameter. More modern "kit" log homes
typically use machined "logs" that are approximately 6"
wide x 8" tall. Log homes do require special precautionary
treatments and maintenance. We recently renovated and created
additions to a kit log home that was 18 years old. We had not
designed the original structure. Typical log home "kits"
are often made from white pine (cypress and locust logs are more
rot-resistant). The log corner overlaps and exposed end-grain
outriggers, if untreated and unprotected, draw water into the
logs into the xylem and phloem, the minute capillaries that draw
water from the ground in which the trees grow while alive. This
drawing of water into the harvested log ends rots them over
time. In the particular log home we recently renovated, the rot
had traveled back into the walls; the bad ends had to be cut,
the decayed wood ground out, the holes patched with fiberglass
and new wood extensions screwed on. Also, the logs being placed
on top of each other horizontally creates wide seams. In the old
days, cement mortar chinking was used to patch these joints and
this mortar eventually cracked and fell out as the logs dried
and shrank. This created gaps in the wall which allowed air
infiltration, which also offered access to insects. Today's log
home kits have hidden splines inside the top and bottom of the
logs which are used to help reduce infiltration and foam strips
are also part of the joints, which compress when the logs are
laid on top of them, providing assistance in securing a tighter
joint. Sealant also helps, however, the system is not perfect.
Any log used outside will benefit from a boric acid spray from a
company like Terminix, which renders the wood more resistant to
insect attack. Also, an oil-based stain will help protect the
wood from the weather. Lack of insulation in an all-log wall is
another concern. Although there is some insulation value in a
solid log wall, it is not as effective as traditional fiberglass
batt insulation in the cavities of a thinner stud wall.
Electricians and plumbers are challenged as to where to route
wiring and piping in solid log walls, although crawl spaces and
vertical chases offer assistance. Another issue is the greater
square footage consumed by the thick logs; this is space you
cannot use, but for which you pay. Of possible interest may be a
log siding material that we invented. It is made of p.t. wood,
so it will be highly rot-resistant if periodically stained and
is under overhangs. It is 1-1/2" thick and is distressed
before installation by craftsmen to give the boards the
appearance of historic rectangular logs about 1' tall. We
created special horizontal chink-boards with a flexible coating
resembling mortar to give the chinking effect. After
installation, sealants help close gaps and a second coat of the
two colors is spread to hide nail heads. Ends of the boards are
never exposed. This log siding is applied over the water barrier
over the wall sheathing, so conventional economical frame
construction with high R-value batts can be used, resulting in
tight, durable construction. We typically use real log posts in
a number of locations, detailing them carefully to prolong their
life. This accentuates the effect of a true log structure and
imparts the warmth and strength desired in a log home. Whether
we are designing historic large-log homes or hybrids, we cap the
ends of exposed logs with copper discs, hammered back for 3"
over the end of the shaft, set in a troweled-on bed of
polyurethane sealant for water protection of the ends of the
logs. There are also other manufacturers of "log"
siding that has a gentle rounding to it to give the effect of
thin logs, but I remain unconvinced by the look of this
material.
ROCKWORK: everyone loves a rock wall.
Rockwork typically costs between $25 to $34/sf of wall area.
This means if you have 1,000 sf of stone wall area, you have
spent $25,000 to $34,000. This is extremely expensive; nearly
five to ten times the cost of white pine or cedar siding. All of
my clients start their projects saying: "I want big stone
walls in front, perhaps all around the house." These
sentiments usually change when they come to understand the
economic impact of these choices. The typical solution is to use
stone judiciously, in areas where people will readily see the
rockwork on the entry approach side, with more economical siding
like board & batten around the majority of the structure.
SIDING FASTENERS, SHEATHING: my recommendation is to
use either stainless steel siding nails or galvanized ringshank
nails. If you have the time to order your fasteners, the very
best would be stainless steel ringshank nails. The length and
diameter of the nail depends on the thickness of your siding and
your structural substrate. If your siding is the typical ¾"
thick and you are using wood studs at 16" o.c. (on center)
and have 25/32" OSB sheathing or ½" CDX sheathing
(two of the most common sheathing materials), you may wish to
consider 8d nails, which will penetrate your siding and embed
into the studs over an inch to provide a solid attachment. If
your siding is thicker, your nails should be longer and of
larger diameter, because the nails tend to bend (and are weaker)
if their slenderness ratio becomes too pronounced. One of the
reasons I like ringshank nails: they stay put. They cannot back
out, like smooth shank common nails. What causes nails to back
out? Wood shrinkage, thermal movement of the building, seismic
activity, heavy vibrations adjacent to the building, impacts,
moisture variations, wind pressure. Ringshank nails have a
spiral deformity gouged into the nail's shaft which makes it
impossible to pop. Ask any carpenter if he has ever tried to
remove a ringshank nail once it has been hammered into place.
The head of the nail will rip off before the shaft will budge a
millimeter.
SIDING WATER BARRIERS: This is sure to
stimulate some controversy. I only specify good old 15# or 30#
asphaltic felt as the water barrier to be placed directly over
the wall sheathing. Many builders will say: "What's wrong
with housewrap? I use that all the time." Well, I once saw
an Ivy League study in which the large housewrap material was
compared to asphaltic felt. It seems that the housewrap product
was originally conceived as an infiltration barrier, not
necessarily a water barrier. It had a perm rating (the
permeability to the passage of water) of somewhere around 70 as
I recall. The higher the number the more moisture penetrates.
30# asphaltic felt was rated somewhere around 3 or so. 15#
asphaltic felt was a little higher than that. So, according to
the study, old-fashioned asphalt-impregnated felt appears to
resist moisture penetration much better than any of the
large-sheet housewrap products. I specify the felt to be
installed horizontally, overlapping at least ½ of the
height of the roll, which is typically a 30" sheet, with 15"
exposed. Wall siding is typically nailed directly over the water
barrier. That being said, siding can rot due to the moisture
that may collect on the water barrier behind it, which is why
some contractors and engineers recommend that the rear of wood
siding be back-primed with paint or wood preservative. I do not
know any contractors who practice what I am about to describe,
as it would be costly: ideally, it would be best to have the
siding held off the wall water barrier with p.t. furring, with
the top surface of the furring slightly sloped down and out. In
this manner, the siding can dry on both sides.
Rand
Soellner Architect, Cashiers, NC 828-743-6010
randsoellner@earthlink.net Website: randarch.com
|
|
This article will be of interest to people
looking for information on:
Please contact Rand Soellner,
Architect at:
randsoellner@earthlink.net
for more information and assistance,
or at 828-743-6010 |
| NAVIGATION:
click on the thumbnails below to go to those
subjects: |
|
http://randarch.com
© Copyright 2004-2008 Rand Soellner,
All Rights Reserved Worldwide.
Photo background
of historic timbers courtesy of: Antique Cabins &
Barns (antiquecabinsandbarns.com)
00537
Visitors
|
|
|
|
|
|
|
|
|
|
