What's The Best Material For Your Home's Exterior?

When the David Dobbs family bought a 100-year-old house in Vermont, new siding was the first entry on their list of things to do. The clapboards were shedding paint. Many had cracked, split or cupped. He thought replacing it would be easy. I envisioned the house encased in the sort of siding I had seen not long before on a neighbor's house. I was returning a dog that had followed me home, and as I waited for my neighbor to answer the door, I rubbed my hand along the siding's smoothly milled surface and thought, "This is the stuff I want: clear, straight-grained western red cedar." It was coated only with a lightly tinted penetrating stain, which enhanced the wood's honeyed tones.

I envisioned the house encased in the sort of siding I had seen not long before on a neighbor's house. I was returning a dog that had followed me home, and as I waited for my neighbor to answer the door, I rubbed my hand along the siding's smoothly milled surface and thought, "This is the stuff I want: clear, straight-grained western red cedar." It was coated only with a lightly tinted penetrating stain, which enhanced the wood's honeyed tones.

However, when I phoned my local siding suppliers, they hit me with some rude news. At over $200 per applied square (enough to cover a hundred square feet) that siding would cost me - owner of more than 15,840 square feet of ugly siding - roughly $5,500. I had $2,000 . . .

I had known the good stuff would cost, but I hadn't expected it to be that much. To find out why it was so expensive, I made some calls. The most succinct answer came from Brian Buchanan, a wood technologist at the Texas Forest Products Laboratory in Lufkin, Texas. "It always gets back to this," he said. "You've got to use what's out there. And there aren't that many thousand-year-old trees out there anymore."

The lumber sawn from younger, faster-growing trees isn't as good as that made from the large-diameter trees they have replaced. Siding from young trees is more apt to warp, cup or split, and it doesn't hold paint or stain as well. This explained the ratty siding on my house, which was made from young pine. It also explains the high cost of the really good stuff.

So those of us who need new siding and who like the look of wood are faced with a dilemma. Do we have to lay waste to the ancient forests and our savings accounts in order to get siding that's attractive and durable? Fortunately, no . . .

One option is to go ahead and use cedar or redwood, but choose one of the "knotty" or "rustic" grades, which can be milled from second-growth lumber. These grades are a step below the expensive architectural grades so prized for their finish, but a step above the construction grades, which can't stand the rigors of exposure that siding must endure.

Knotty grades cost about half as much as premium grades and are only slightly more expensive than manufactured alternatives like hardboard.

As the name suggests, knotty-grade lumber has more knots and a rougher look than the top grades. Probably the biggest limitation is in finish: knots don't take paint well, and young lumber tends to move more than lumber from old trees.

For these reasons, knotty grades hold paint poorly and should generally be stained instead. However, despite its defects (which may include not only knots, but streaks, splotches and checks), knotty siding performs well if properly selected, installed and finished.

Dave Utterback, district manager for the Western Wood Products Association, has two key pieces of advice: buy at or near the top of the knotty-siding grades and install the siding properly. A less obvious tip is to choose a siding pattern that will tolerate a certain amount of movement in knotty lumber after it has been installed.

Narrow patterns work best (particularly with a knotty grade of lumber) because there is less movement and the joints tend to stay together. Utterback recommends 8-inch widths or narrower. "Wide patterns go up faster," he says, "but you get more movement and more potential for cupping and splitting, not to mention paint problems."

Many siding problems are caused by patterns with joints that are not forgiving enough to accommodate shrinking or swelling. The tight joints of tongue-and-groove siding, for instance, can cause buckling if the wood expands. Board-and-batten siding, on the other hand, allows some room for movement behind the battens.

Shiplap patterns work well for the same reason; they look less formal than classic beveled clapboards, but are much more forgiving. If you want a classic beveled-siding look, the rabbeted bevel pattern known as Dolly Varden is less prone to cupping than ordinary clapboards, because Dolly Varden siding lies flat on the sheathing.

Another option is to choose real wood siding that is not made from redwood or western red cedar, but from some other local species - ponderosa pine, western white pine, Douglas fir, hemlock and other species in the West.

It's important to select siding from these species in the medium to high grades and to install it correctly. In addition, these woods aren't as naturally resistant to moisture as redwood or western red cedar, so you must keep the siding well finished. Paints provide better protection than stains.

Alternatives to wood

-- The oldest surviving wood imitator is hardboard, around since before World War II. To make it, manufacturers compress short, threadlike wood fibers under heat and pressure, which causes chemical bonding. In some products, a phenolic resin is added for bonding, and various other additives increase strength and moisture resistance. Hardboard comes in even more patterns than lumber siding, ranging from 4 to 16 inches in width and up to 16 feet in length. It's also available in large panels.

Moisture is hardboard's nemesis. "Hardboard, as it comes out of the factory, is pretty dry," says Dobbin McNatt, who has studied the material extensively at the U.S. Forest Products Laboratory in Madison, Wis. "If it's not acclimated to the site before it's put up, it will pick up moisture and expand. Since it's homogenized wood, you get more expansion in length than you would with a piece of solid-wood siding. And if it's nailed down when it expands, hardboard will buckle."

Moisture usually enters hardboard through overdriven nail holes or through the unpainted backside or butt ends. Some companies eliminate these weak spots with blind-nailed, prepainted products with longer warranties. Blind-nailing - putting the nails at the top of each lap so they are covered by the next one - not only hides the most common conduit for moisture, but also results in a cleaner appearance.

Hardboard has some aesthetic limitations. Its butt joints must be at least 1/16 inch wide and sealed with caulk or 1/8 inch wide with a special joint cover. If you don't vary the board lengths, these joints, appearing regularly every 8 or 16 feet, can give the house a monotonous, prefab look. And hardboard must be painted, so it holds no appeal to those who like the look of stain. Still, if you're on a budget and planning to paint anyway, hardboard deserves serious consideration.

-- Plywood, another time-tested alternative to solid wood, is available either as lap siding or in panels with finish veneers that mimic lap patterns or even shingles. Generally speaking, the lap-siding products look a lot better than the panels. But either way, you have a choice of several different face woods, including western red cedar and redwood. These products can be either stained or painted.

Plywood lap siding is cut to the same dimensions as the comparable solid-wood siding. In the better plywood products, such as those made by Plylap Industries, cross-lamination of veneers results in siding that is stronger than hardboard and more stable than solid wood.

Plylap clapboards are available unfinished, preprimed, prestained or completely prefinished. Notches along the bottom edge of each piece align it with the piece below. This speeds installation and makes the siding sturdier by tying the courses together. Installation of this kind of siding does require extra care, however. You have to caulk the seams and nail the clapboards at both the top and bottom.

-- I've already mentioned plywood panels with a finish veneer that looks like shingles, but you can also get real cedar shingles bonded to plywood. They're as thick and durable as the shingles you apply one at a time, but they go up faster, produce less waste and are fairly easy to install.

Eight-foot lengths of plywood are covered with one or two courses of cedar shingles; you nail up the sections much as you would lap siding, snugging each course down on top of the previous one. The result is a house that looks like it was shingled by an expert.

The most prominent maker of this type of siding is Shakertown in Winlock, Wash. Its panel products are available with two grades of shingles cut from western red cedar: premium clear heartwood or "rustic" mixed-grin. (Of course, premium-grade shingles have the same drawbacks as premium-grade lumber. They generally come from older trees, and they're expensive.) The panels are well-made and nicely designed; even up close, you can't spot the seams between plywood sections.

The pros and cons of vinyl

Dare I mention vinyl siding? I'd better, since it accounts for about 24 percent of all siding sold and has some real advantages. Chief among them is affordability; at $45 to $60 per 100 square feet, vinyl costs about one-half to two-thirds as much as hardboard (the next cheapest popular competitor) and about one-fourth as much as premium wood siding. It is also easy to maintain, since it never requires paint, although you can repaint for a change of color.

The best vinyl siding is more attractive now than it was even 10 years ago. The fake wood grain is a bit more convincing, the color selection more appealing. And the trim options are expanding, with some manufacturers offering molded window or door trim to alleviate the plainness of standard vinyl trim. These improvements have enabled vinyl to pretty much bury the more expensive aluminum siding, which once occupied the same market niche.

But vinyl siding also has definite drawbacks. For one thing, it sounds funny - a hard rain produces a soft rattly sound that can be irritating. And in an older house that is poorly insulated, vinyl's lack of permeability can cause moisture problems in exterior walls.

Generally, these problems can be prevented by adding kitchen and bathroom vents, which every house should have anyway, and by installing the siding over a backing material that lets the house breathe.

More stubborn are the visual problems. The lap patterns in vinyl siding are in multiple courses that end together in a conspicuous vertical line. And the 4-inch trim that is most commonly used looks undersized and insubstantial on many houses.

Does that matter? To some people, vinyl siding epitomizes everything that is cheap, flimsy and artificial in contemporary Western culture. To others - the ones reading in hammocks while the rest of us paint - vinyl shines for its economy and low maintenance.

New alternatives

One of the few heartening consequences of the old-growth-lumber shortage is that it has inspired the development of more resource-efficient alternatives. At least two new products stand out as up-and-coming competition for both solid-wood siding and its traditional substitutes. They are Louisiana-Pacific's Inner-Seal and Fibre Cem's Handiboard lap siding.

-- Inner-Seal has been on the market for about seven years. To make it, a substrate of oriented-strand board (made from finger-sized strands of wood shredded from small trees) is overlaid with heavy kraft paper and sealed with a synthetic resin. Inner-Seal siding comes smooth and preprimed for painting, or textured and prestained to resemble cedar. It blind-nails for a clean appearance. Louisiana-Pacific guarantees the product for 25 years, and builders and distributors say it holds up well.

-- HandiBoard lap siding is a wood-grained cement product leavened with fly ash from coal plants and reinforced with recycled newspaper. It is blind-nailed and has no measurable shrinkage or expansion. The original off-white color runs all the way through. The siding can be left as is or painted.

As you might expect, it's heavier than wood and more brittle, but once it's up, it's incredibly durable. FibreCem backs the product with a 50-year transferable warranty. The one major drawback of the material is the cost, which is comparable to B-grade cedar or redwood.

What kind of siding did I choose for my own home? I went for some knotty western red cedar, which I stained with a cedar-tinted "natural-look" penetrating stain. The siding has been up almost a year now, and a walk around the house doesn't reveal any warping, cupping, splitting or other misbehavior.

It looks pretty good. It doesn't have that beautiful grain and silky feel that I admired in my neighbor's siding, but I figure I got 95 percent of the value he got - my siding works as well and should last as long - and I paid half as much for it.

And I'm glad no one had to take another tree out of an old-growth forest just so I could nail it to the side of my house.

David Dobbs is a freelance writer on environmental and building subjects and senior contributing editor of Harrowsmith Country Life magazine where this article first appeared. ------------------------------------------------------------------- SIDING TERMINOLOGY

-- Board-and-batten: A batten is a narrow board used, in this reference, to cover the seams between siding boards (often used for vertical siding applications).

-- Clapboard: A long board used as siding, thicker on one side than the other and installed so the thick side overlaps the thin side.

-- Lap: Refers to the overlap of one board over the next (as commonly seen on houses with horizontal cedar siding).

-- Rabbet: A type of joint made by cutting the edge of a board so that another piece fits into it. Shiplap siding, for example, is rabbeted so the boards are flush where they join.

-- Tongue and groove: Boards (or other material) cut with a ridge of wood along one side and a groove along the other so one board can lock into the next, making a flush joint.