Imported Lumber, Your New Construction Home and the Inspection

Derived from an article written by Ted Cushman – Contributing editor Ted Cushman reports on the construction industry from Hartland, Vt.

The recent pandemic has had many ripple effects on the US economy. Along with other factors, it has affected the supply of framing lumber in American lumberyards. Restricted supply of US and Canadian lumber has led suppliers to look to Europe for wood to satisfy the high domestic demand. That means lumber produced in Europe has been showing up in US lumberyards and home centers. It may have different qualities than lumber from North America.

Background. Most lumber in the world market is visually graded. A lumber grader at the sawmill look at each piece and sorts the wood based on visual qualities—in particular, the size and number of knots in the wood. This characteristic is of aesthetic importance, but it also makes a difference in the structural performance of framing lumber in service.

The structural strength of lumber also varies widely by species and where the wood was grown and harvested. That’s why a grade stamp on a piece of framing lumber will specify the wood species and region of origin, not just the visual grade. Sometimes, species are grouped based on their similarity in structural performance. So, you may see a piece of wood marked SYP for southern yellow pine; this designation could refer to several different species of pine that grow in the southern US. “Hem fir,” by the same token, might be hemlock or fir; the two species have comparable performance.

The common species and species groupings in the US market are routinely tested for structural characteristics under a lumber grading program developed by the American Lumber Standard Committee (ALSC), a voluntary standards group based in Washington, DC. The ALSC publishes design values for the various species and grades of lumber, and engineers use those values to design wood structures.

Multi-species wrinkle. Mills in the US usually process wood of a single species or species group from a single region. But imported European lumber appearing in the market these days comes from mills that process multiple species grown in multiple regions. So, for example, wood may bear a grade stamp indicating that the lumber could be 

  • Scots pine from Germany
  • Norway spruce from Germany or Northeastern France
  • Switzerland Douglas fir
  • European larch from Austria, the Czech Republic, or Bavaria

The mill happens to process all those different kinds of logs.

The wrinkle is this: The various kinds of wood coming out of European mills may have very different structural characteristics, even if their visual grading is very similar. While a piece of wood might bear a “Number 2” grade stamp based on its visual characteristics, engineering properties will differ. Properties such as fiber stress in bending, modulus of elasticity, or density (specific gravity) could vary widely within lumber supplies that bear the same stamp. This stamp complicates things for engineers and code officials trying to design or inspect structures built with this Euro lumber.

The wood species identified on this grade stamp are woods processed at a German mill that are not among the four North American categories that the ICC building codes recognize.

Today, the ICC codes in the US don’t formally recognize all those European species and countries of origin. Tables in the IRC refer to four North American categories: southern yellow pine (SYP), Douglas fir, hem-fir, and spruce-pine-fir (SPF). Requirements in the code are based on those species and the properties that go with those species. SPF is the weakest species grouping among the eight design values that engineers use in wood building design.

(Note: Multi-species grading is not limited to European mills only. European import lumber is the most common with multi-species grade stamps in the US market now.)

The West Coast Lumber Inspection Bureau, or WCLB (as identified on this grade stamp), merged operations with the Pacific Lumber Inspection Bureau (or PLIB).

Design values have been published for the European species now appearing in the US. But the design process is complicated by the mixing of species and countries of origin within one grade. To figure out the value for a given design problem, an engineer would have to look at each design value for each imported wood species and select the lowest value for any given property.

Significance to design engineers. In many cases, the design values are lower for the Euro wood than for SPF, the weakest North American category listed in the IRC. In the case of shear wall and connector performance, specific gravity is a controlling factor.  The specific gravity influences fastener performance; the weaker Euro woods could significantly reduce the capacity of a shear wall. Similarly, specific gravity affects the gripping strength of truss gang nail plates. More fragile Euro wood could substantially compromise the resilience of critical truss connections if the design software is not adjusted to take the wood variations into account. And in high-wind regions, the bending strength of lumber is significant for the resistance of walls to the lateral pressure of the wind.

Unless an engineer can determine that import lumber is adequate for a given design, there is a risk that the structure as built may not comply with the code. A recently released addendum to the 2018 Edition of the Design Values for Wood Construction allows engineers to evaluate a design built with European wood varieties. In many cases, the design values for the European lumber currently circulating in the US are lower than for spruce-pine-fir, the weakest code-listed US category.

Significance to builders. Up until now, this lumber strength issue may not have had a recognizable importance to builders. But the problem has been circulating in the code enforcement community and is being noticed by code officials. In the future, inspectors in the field could be flagging critical structures, such as shear walls, constructed with lumber that bears an unfamiliar stamp.

Chinese Drywall

Amidst a wave of Chinese import scares, ranging from toxic toys to tainted pet food, reports of contaminated drywall from that country have been popping up across the American Southeast. Chinese companies use unrefined “fly ash,” a coal residue found in smokestacks in coal-fired power plants in their manufacturing process. Fly ash contains strontium sulfide, a toxic substance commonly found in fireworks. This substance can off-gas into hydrogen sulfide, carbon disulfide, and carbonyl sulfide in hot and wet environments, thus contaminating a home’s air supply. 

The bulk of these incidents have been reported in Florida and other southern states, likely due to the high heat and humidity levels in that region. Most of the affected homes were built during the housing boom between 2004 and 2007, especially in the wake of Hurricane Katrina when domestic building materials were in short supply. An estimated 250,000 tons of drywall were imported from China during that period because it was cheap and plentiful. Builders used the drywall to construct approximately 100,000 homes in the United States. Many believe this has led to severe health and property damage.

Although not believed to be life-threatening, exposure to high levels of airborne hydrogen sulfide and other sulfur compounds from contaminated drywall can result in the following physical ailments:

  • Sore throat
  • Sinus irritation
  • Coughing
  • Wheezing
  • Headache
  • Dry or burning eyes
  • Respiratory infections

Due to this problem’s recent nature, there are currently no government or industry standards for inspecting contaminated drywall in homes. Professionals who have handled contaminated drywall in the past may know how to check for sulfur compounds, but no agencies offer certification in this form of inspection. Homeowners should beware of con artists attempting to make quick money from this widespread scare by claiming to be licensed or certified drywall inspectors. InterNACHI has assembled the following tips that inspectors can use to identify if a home’s drywall is contaminated:

  • The house has a strong sulfur smell reminiscent of rotten eggs.
  • Exposed copper wiring appears dark and corroded. Silver jewelry and silverware can become similarly corroded and discolored after several months of exposure.
  • The inspector can check a label on the back of the drywall to link it with manufacturers known to have used contaminated materials. One way to look for this is to enter the attic and remove some of the insulation. 
  • Drywall samples can be sent to a lab to be tested for dangerous levels of sulfur. Testing is the best method but also the most expensive.

Contaminated Chinese drywall cannot be repaired. Affected homeowners have two options: 

1. Suffer from lousy health and failing appliances due to corrosion, or 

2. Replace the drywall entirely, a procedure that can cost tens of thousands of dollars. 

This contamination further reduces home values in a real estate environment already plagued by crisis. Some insurance companies refuse to pay for drywall replacement, and many of their clients face financial ruin. Class-action lawsuits have been filed against homebuilders, suppliers, and importers of contaminated Chinese drywall. Some large manufacturers named in these lawsuits are Knauf Plasterboard Tianjin, Knauf Gips, and Taishan Gypsum.

The Florida Department of Health recently tested drywall from three Chinese manufacturers and a domestic sample and published their findings. They found “a distinct difference in drywall that was manufactured in the United States and those that were manufactured in China.” The Chinese samples contained traces of strontium sulfide. When exposed to moisture and intense heat, they emitted a sulfur odor, while the American sample did not. The U.S. Consumer Safety Commission is currently performing similar tests. Other tests performed by Lennar, a builder that used Chinese drywall in 80 Florida homes, and Knauf Plasterboard, a drywall manufacturer, came to different conclusions than the Florida Department of Health. Both found safe levels of sulfur compounds in the samples that they tested. There is currently no scientific proof that Chinese drywall is responsible for the allegations against it.


Regardless of its source, contamination of some sort is damaging property and health in the southern U.S. The media, who have publicized the issue, almost unanimously report that the blame lies with imported Chinese drywall. They contain corrosive sulfur compounds originating from ash produced by Chinese coal-fired power plants. Homes affected by this contamination can suffer severe damage to the metal parts of appliances and piping and lead, potentially leading to significant health issues. While no governing body has issued regulations regarding contaminated drywall, more home inspectors are becoming aware of the danger it poses.

Radon and New Construction

Why should I buy a radon-resistant home?

Radon-resistant techniques work. When installed properly and completely, these simple and inexpensive passive techniques can help to reduce radon levels. In addition, installing them during construction makes it easier to reduce radon levels further if the passive techniques don’t reduce radon levels below 4 pCi/L. Radon-resistant techniques may also help to lower moisture levels and those of other soil gases. Radon-resistant techniques:

  • Easy upgrades:  Even if built to be radon-resistant, every new home should be tested for radon after occupancy. If you have a test result of 4 pCi/L or more, a vent fan can easily be added to the passive system to make it an active system and further reduce radon levels.
  • Cost-effective:  Building radon-resistant features into the house during construction is easier and cheaper than fixing a radon problem from scratch later. Let your builder know that radon-resistant features are easy to install using common building materials.
  • Money savings:  When installed properly and completely, radon-resistant techniques can also make your home more energy-efficient and help you save on your energy costs.

In a new home, the cost to install passive radon-resistant features during construction is usually between $350 to $500. In some areas, the cost may be as low as $100. A qualified mitigator will charge about $300 to add a vent fan to a passive system, making it an active system and reducing radon levels. It usually costs between $800 to $2,500 to install a radon mitigation system in an existing home.

What are radon-resistant features?

Radon-resistant features may vary for different foundations and site requirements. If you’re having a house built, you can learn about the EPA’s Model Standards (and architectural drawings) and explain the techniques to your builder. If your new house was built (or will be built) to be radon-resistant, it will include these basic elements:

  1. Gas-permeable layer:  This layer is placed beneath the slab or flooring system to allow the soil gas to move freely underneath the house. In many cases, the material used is a 4-inch layer of clean gravel. This gas-permeable layer is used only in homes with basement and slab-on-grade foundations; it is not used in homes with crawlspace foundations. 
  2. Plastic sheeting:  Plastic sheeting is placed on top of the gas-permeable layer and under the slab to help prevent the soil gas from entering the home. In crawlspaces, the sheeting (with seams sealed) is placed directly over the crawlspace floor. 
  3. Sealing and caulking:  All below-grade openings in the foundation and walls are sealed to reduce soil-gas entry into the home. 
  4. Vent pipe:  A 3- or 4-inch PVC pipe (or other gas-tight pipes) runs from the gas-permeable layer through the house to the roof to safely vent radon and other soil gases to the outside. 
  5. Junction boxes:  An electrical junction box is included in the attic to make the wiring and installation of a vent fan easier if, for example, you decide to activate the passive system if your test results show an elevated radon level (4 pCi/L or more). A separate junction box is placed in the living space to power the vent fan alarm. An alarm is installed along with the vent fan to indicate when the vent fan is not operating correctly.

Pre-Drywall Inspections

One way to ensure that a house is built according to its specifications is by performing a pre-drywall inspection. “Pre-drywall” refers to a phase during the homebuilding process just after the installation of certain elements – such as the doors, windows, foundation, flooring, wall and roof components, plumbing, and electrical rough-in – and right before the drywall is hung. This in-progress or construction-phase inspection is useful because drywall can obscure some aspects of the interior and make identifying or fixing any problems both difficult and expensive, once the new home is completely finished.
A pre-drywall inspection can be performed after the insulation is installed, which is convenient because it allows the home inspector to determine whether it was done properly. However, the insulation may conceal some components in much of the same way that drywall does.
What is inspected during a pre-drywall inspection?

During a pre-drywall walk-through, the areas of the house that the inspector can check include:

  • the foundation;
  • floor system;
  • roof system;
  • wall system;
  • plumbing system;
  • electrical system;
  • HVAC;
  • exterior wall covering;
  • roof covering; and
  • the interior.
When performing a pre-drywall walk-through, the home inspector may inspect:
  • electrical wiring and junction box placement;
  • framing;
  • foundation slabs, walls and drains;
  • footings;
  • notching of floor joists;
  • firestop material;
  • pier pads;
  • crawlspace;
  • retaining walls;
  • plumbing pipe placement;
  • waterproofing;
  • flashing for windows and doors;
  • wall studs;
  • any missing metal clips; and
  • the placement of HVAC air ducts and registers.
There are many common concerns that a pre-drywall inspection can address.  These questions include:
  • Is there an appropriate number of electrical outlets in every room?
  • Is there a drain pan installed for the washing machine so that water is caught in the event of a leak?
  • Are there wood blocks in places where extra support may be necessary?
An important element to a pre-drywall inspection is the inspection report. Most home inspectors typically include photos and/or video. These are especially beneficial to the client because of the level of detail that they can provide. When it comes to documentation, more is more!  So, as long as you have permission to do so, record everything that you can.
Finally, remember that safety is key. InterNACHI’s Standards of Practice states that no home inspector is required to inspect any component that may compromise his or her safety.
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