Wood Flooring: Nice or Knotty?

Jim Vallette - March 14, 2012

Wood stirs a yearning for simplicity.  From Walden Pond to the Muir Woods, trees inspire.  The same feelings can surround us also indoors, from framing to floor, where wood provides a comforting, renewable counterpoint to synthetic materials.

We began the process of evaluating wood flooring with the preconceived notion that unfinished wood floors could achieve some of the highest ratings in the Pharos system.  Despite its apparent simplicity, we discovered that unfinished wood flooring has several health and environmental challenges. 

Pharos users can now explore these challenges in the Wood Flooring category, which we opened today in the Pharos Building Materials Library. [1]

Solid wood flooring (CSI 09 64 29 Wood Strip and Plank Flooring) is a simple plank of solid wood. It may be sold unfinished or finished. Finished has the advantage that the finishing curing process is taken care of in the factory so occupants and installers have a reduced potential exposure to the smelly and potentially toxic VOCs released during curing.  Unfinished wood, however, puts the owner/occupant in control of the decision of what, if any, toxics to use for finishes.

While developing this product category, we confirmed that some unfinished wood floors achieve nearly perfect evaluations for renewable materials, toxic content, and manufacturing toxicity.  But we also discovered some real differences in how wood floors are sourced, and how they may be treated:


  • FSC-certified wood, especially FSC Pure.

The most important environmental distinctions between these products are whether they were harvested sustainably. Forest certification is the most important indicator that flooring products made from an imported hardwood, such as teak, are not removed from vulnerable rainforests in damaging ways.  Seek reclaimed or certified sustainably-harvested options when purchasing imported hardwoods. The Forest Stewardship Council (FSC) was the first major forest certification program to set rigorous guidelines for sustainable harvest of lumber that preserves habitat and minimizes impact on ecosystems and indigenous rights and still far exceeds the criteria of other lumber certification programs.  [2]

  • Reclaimed wood.

The most sustainable source for flooring is reclaimed wood: boards and beams recovered from the demolition of old barns and buildings, then prepared for reuse by de-nailing and planing. [3]


  • Low value renewable material.

The forest industry has established competing programs to the FSC, most notably the Sustainable Forestry Initiative (SFI). Due to their more relaxed standards, these programs score very low in Pharos.  Some wood floor is not certified at all.

  • Anti-sapstain treatments. 

Unfinished wood flooring also has a significant chemical toxic hazard issue, as many mills treat freshly-sawn wood with biocidal solutions called anti-sapstains. These chemicals combat the cosmetic blemish known as “blue stain.”   Some wood flooring manufacturers acknowledge the use of these treatments in the production process, but not all do.  Residues from these treatments remain in the wood flooring during its use.  Past formulations of anti-sapstains were extremely toxic. Today’s concoctions are no longer persistent, bioaccumulative toxicants (PBTs), but common treatments still include developmental and reproductive toxicants and carcinogens that are red listed in Pharos. [4]

Pharos’ evaluations may dispel the sylvan aura of simplicity about wood floors, but we hope, also point toward some real solid choices.  Unlike the traveler in Robert Frost’s yellow woods, when Pharos users are deciding between two roads, they will know which way to go.



[1] Wood flooring comes in a wide variety of types, including solid wood, engineered, laminate and bamboo. Pharos opened this category with unfinished solid wood flooring initially, and will assess prefinished and engineered floors over time.  We will also be assessing wood finishes used with these floors.

[2] Within the FSC certification program, there are several levels.  The FSC Pure label gets the highest rating with FSC Mixed slightly lower.  You can read more about the different rating systems and how they are scored behind the “Evaluation Framework” tab on the Pharos homepage.

[3] Be cautious about wood referred to as “salvaged. ” Salvage may refer to this kind of reclamation from old buildings, but it may also refer to harvesting trees from lake bottoms, or even forest thinning operations. In both underwater recovery and forest thinning, there can be significant impacts on habitat, and this kind of salvaged wood product should only be purchased if it is certified sustainable under a rigorous sustainable harvest program such as FSC. 

[4] These chemicals are most likely to be used on wood harvested in warm or moist climates, most frequently in softwoods and white hardwoods and can be avoided by putting the lumber straight into a dry kiln. For more information see the Pharos team notes under the Common ingredients: anti-sapstain treatments http://www.pharosproject.net/product/show/id/1003144

Jim Vallette is the Research Director for the Healthy Building Network.