What siding will you be installing on your mountain home construction project? Logs, clapboard, board & batten, shingles of various materials, cement planks…there are options and varying costs. Rand Soellner home architects have been involved with mountain home construction a long time: 36 years. These articles are created to assist the homeowner and should not be undertaken without the assistance of a licensed professional.
EXTERIOR SIDING FOR MOUNTAIN HOME CONSTRUCTION.
By Rand Soellner Architect
Special Design Consultant to Keller Williams – Village Realty
(C)Copyright 2004-2010 Rand Soellner, AIA / NCARB Licensed Architect, Cashiers, North Carolina, 828-269-9046
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. This is one of the most important considerations for mountain home construction. It is what keeps the weather outside your walls.
SIDING OPTIONS in mountain home construction: a complete list would be too long. Let’s consider those that are most often used in mountain home construction :
BOARD & BATTEN in mountain home construction: This is a time-honored tradition for mountain home construction that one finds in upscale communities of multi-million dollar houses 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 1×12’s is installed next to each other, then 1×2’s or 1×3’s or 1×4’s are nailed over the base layer of siding, centered on the joints. Rand Soellner home architects 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 in mountain home construction: 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 in mountain home construction.
SHINGLES in mountain home construction: there are several. Cedar shingles seem to be preferred by some people from tailored suburban areas like Buckhead, while others seeking a more Appalachian mountain home construction look enjoy novel shingles like poplar bark. Not everyone is familiar with poplar bark shingles. One 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 in mountain home construction. Although rarely used, there are also copper shingles, which can result in a unique fish scale like finish.
LOG SIDING in mountain home construction: Real logs compose a traditional log cabin or log house. Historic log residences 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 in mountain home construction. 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 house “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 wicking of water into the harvested log ends rots them over time. In the particular log house 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 mountain home construction. 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 cabin 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 in mountain home construction. 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 for mountain home construction. 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 mountain home construction. 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.
MOUNTAIN HOME CONSTRUCTION & STONE AND OTHER ASPECTS.
ROCKWORK in mountain home construction: everyone loves a rock wall, particularly in mountain home construction. Rockwork typically costs
between $25 to $34/sf of wall area in the Blue Ridge Mountain area of Western North Carolina. This means if you have 1,000 sf of stone wall area, you have spent $25,000 to $34,000. This is 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 in mountain home construction: 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 out. Ask any carpenter involved in mountain home construction 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 in mountain home construction: 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 for mountain home construction? 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 in mountain home construction 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.