Wood: Softwood vs Hardwood

Wood is one of the most natural and popular materials used in house building. From a health perspective, materials used in conventional wood construction are tolerated well by most people. 

 

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Yet for some, exposure to certain kinds of wood can trigger mild or even serious health problems. Softwoods naturally release volatile organic compounds which can cause health issues for those with chemical sensitivities or respiratory-related illnesses. 

In many cases the wood itself isn’t the problem. Chemical treatments used to preserve and protect wood from termites and other creatures can cause negative reactions and illness. The glues used in plywood and other manufactured wood outgas chemicals which can negatively impact health.

Understanding the characteristics of wood will make for better choices when deciding on products to be used for home construction and remodeling projects. 

Softwood vs Hardwood

Wood is typically classified as being either a softwood or a hardwood.

Softwood trees are evergreen or needle-bearing (e.g. pine, fir, spruce, redwood, cedar, cypress, and hemlock). The technical name for softwood is conifer because many softwood trees bear cones. In the U.S. most softwood lumber is grown in the South or the Pacific Northwest.

Virtually all the wood framing in today’s houses is derived from softwood trees because it can be produced more cheaply than hardwood.

Hardwood trees are deciduous, meaning broad-leafed. As the name implies, hardwoods are usually harder than softwoods—but not always. Balsa trees produce a very soft wood but are classified as hardwood because they don’t have needles or cones and are not evergreen. Common U.S. hardwoods include oak, maple, beech, birch, walnut, ash, and poplar. Most U.S-grown hardwood comes from the Midwest.

Hardwood trees are slower growing than softwood trees, which is why hardwood lumber tends to cost more. Appreciated for their attractive coloring and grain, hardwoods are widely used in the furniture industry. Flooring, doors, trim, and cabinetry are typical uses for hardwoods in houses.

Softwood Characteristics

The natural resins in softwood lumber outgas terpenes and other volatile organic compounds (VOCs). Terpene vapors may be unhealthy to breath. For those with chemical sensitivity, terpenes are often intolerable. 

The aroma from a cedar closet can often elicit symptoms in those with sensitivity to softwood. Of the various softwoods widely available, fir, spruce, or hemlock are a little less odorous than pine or cedar. Redwood has less natural odor, and is often better tolerated.

Some of the softwood framing in a house can be separated from the living space by the use of an air-tight, aluminum-foil barrier, thus protecting a sensitive occupant from bothersome odors. It’s also possible to use less bothersome (but considerably more expensive) hardwood lumber for framing, or to eliminate wood completely and use something other than wood. In many cases, a combination of softwood, hardwood, steel, concrete and masonry can be a viable solution.

If a sensitive person plans to use interior trim, cabinetry, or doors made of softwood lumber, the wood can be coated with a tolerable paint or clear finish on all sides to seal in the odor. This can sometimes reduce the odor enough to make the wood tolerable—but not always. After testing a sample of sealed softwood for personal tolerance, many sensitive people opt for hardwood cabinets, interior trim, and doors

Buying Softwood

Softwood lumber is usually marked with a stamp specifying which species of tree it was cut from. The most common stamp is “S‑P‑F”, meaning Spruce-Pine-Fir. Lumber with this marking can come from any of those three types of trees. “Hem-Fir” is another stamp that means the lumber is either from a hemlock or a fir tree.

Sometimes a single-species stamp is seen, such as “Spruce.” Fir and Douglas Fir are sometimes used for longer, larger sizes of framing (e.g. a 24'-long 2 x 12). Redwood and cedar lumber might be available because of their decay resistance, but they are not often used for general construction because of increased cost.

Buying single species lumber, such as fir, can be difficult. Placing a special order could mean ordering a railroad-car full—not a very cost effective solution when you are considering a small room addition. A few lumberyards do stock specific species of lumber; checking with local lumber suppliers can be worth the effort to find the wood you want.

Redwood is often used for porches, decks, and in damp areas, because of its natural resistance to mold, decay, and insects. Redwood is usually readily available. While not always stocked, redwood can be special ordered through most lumberyards. Delivery is typically less than a week in most parts of the U.S.

Redwood has fewer volatile resins and oils than other softwoods, so it is often a reasonably safe choice for someone sensitive to the odors of pine—especially when used outdoors where there is enough fresh air to counteract its very slight odor. But redwood isn’t perfect—some workers report skin irritation from redwood sawdust, probably due to the natural chemicals in redwood that make it resistant to insect attack.

Hardwood Characteristics

Hardwoods are usually not as odorous as softwoods, but each species does have a characteristic smell. Some sensitive individuals may react to one species but not another.

Maple, tulip poplar, beech, and birch are usually less odorous than oak and walnut. Oak is one of the more popular hardwoods currently in use, but it is also fairly odorous. Some sensitive people can’t tolerate it--even after it has been coated with a paint or clear finish—unless it has aired out for a couple of months.

Buying Hardwood

Prices vary considerably for different hardwood species, with walnut being relatively expensive and poplar being lower in cost. Because of the higher cost, hardwoods are almost never used for house framing. Instead, hardwood is reserved for the finish cabinetry and woodwork.

Hardwood lumber can be difficult to locate for construction purposes. In some parts of the country, there are small sawmills that can supply lumber cut from locally grown trees.

 

Buying wood this way presents problems because it will still be green. This refers to wood that is not dry enough to use. Its moisture content is well above 19% and it’s subject to fungus attack. It’s difficult to use green lumber successfully for construction because there will be a considerable amount of shrinkage as it dries.

Wood will dry to less than 19% on its own over time—if stored properly. This is called air drying and it can take a year or more. The process can be speeded up by kiln drying—if there happens to be a lumber kiln in the area of a local sawmill. Most furniture-grade hardwood lumber is kiln-dried.

Another difficulty with sawmill lumber is its roughness. It will not have a smooth surface and its dimensions can vary by as much as 1/4". A 2x4 directly from the sawmill will measure 2" x 4"—plus or minus. A softwood 2x4 from the lumberyard will measure 1 1/2" x 3 1/2" because it has a smooth, planed surface.

Green hardwood lumber purchased directly from a sawmill can seem reasonably priced, but by the time it’s been kiln dried and planed smooth, it can end up being quite expensive.

Lumberyards can generally order hardwood trim or doors; local woodworkers can sometimes supply hardwood materials. Individual woodworkers will usually be able to supply a sensitive person with small samples of various woods for testing purposes.

To find woodworkers in your area, look in the telephone book under Woodworking or ask the high-school Industrial Arts teacher for a recommendation.

Excerpted from:
The Healthy House, 4th Edition
John Bower, Author
Copyright © The Healthy House Institute

 

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