Causal agent
Abiotic
Juvenile wood related breakdown of treated wood in decks
Mon, 07/20/2009 - 21:45 — jwinandySometimes treated and even untreated decking boards are used that contain varying degrees of juvenile wood. Because juvenile wood shrinks longitudinally from 2-20x more than mature wood, decking boards with high-degrees of juvenile wood that are restrained by metal fasteners and that are regularly exposed to direct rainfall (wetting) followed by intense sunlight (drying) sometimes experience visual degradation of the top surface and later may eventually experience mechanical failure of the wood.
Avoidance Strategy:
Avoid juvenile wood for the top decking when at all possible in building treated wood decks. Another more practical solution is to regularly treat the decking boards with water-repelant treatments.
Remediation Strategy:
When the problem first is noticed, begin a regime of regularly treating the decking boards with brush-applied water-repelant treatments. If the problem becomes extensive, replacement is the most practical solution.
Chemical Defibration of Softwood Rounds
Wed, 06/17/2009 - 15:17 — rotbotuserSoftwood rounds used as a parking lot bumper near Jackson Hole, Wyoming showed signs of defibration on the upper surface. Salt defibration has been reported from Antarctica (Blanchette et al. Polar Rec 38:313–) as an unusual decay phenomenon, but here it is near 45 degrees latitude in the intermountain West of the Rocky Mountains. This defibration results in accumulation of wood fibers on the surface and exposes fresh wood to UV damage and more defibration. In this case, if there was any preservative treatment in the wood, this slow progressive decay could expose less resistant wood and hasten decay problems. The defibration may also be as a result of diffusible treatment chemicals. Although in historic objects and buildings this would be a worry, this process in low-value situations like this is mostly curious and perhaps useful to scientists interested in delignification processes. When I first looked at this 'fuzzy' surface and saw two furry mountain dogs playing around in the owner's cabin porch, I thought I was looking at dog fur, but you can see in the close-up photos that wood fibers are sloughing off. I would never have looked closer if I hadn't read about defibration in polar huts. This area in Wyoming receives 300+ inches (750+ centimeters) of snow annually, and this means the snow plow and the salt are nearly in constant action during the winter. This was on a gravel road portion, however, so it is unclear if salt would be used. Additionally, visitors using the parking lot probably stand on these horizontal rounds often (see the image of me performing my version of a three-point bending test). Salt or preservative chemicals (etc.) may help delignify the wood near the surface, a phenomenon that has been seen in Antarctica on explorer's huts exposed to salty air and wind, as well as in other sea-side areas I'm told . Here, this problem may be exacerbated in the high desert weather that can bake the surface. As in any situation, the size of the problem depends on the cost of the material replacement and the risk. Both are low here, so this is not a major financial loss or safety hazard. Instead, it is just a nice example of how learning about a problem common to one situation (windy polar buildings) can be useful for deducing similar problems occurring in new contexts (visitor-rich, landlocked Wyoming).
Avoidance Strategy:
Well, to avoid this aboitic problem, the best solution is to avoid exposure. If you must expose to salt, limit the abrasion. If you must expose to abrasion, limit salt. If diffusible preservative ingredients are the issue (we don't know this without knowing the preservative used) change the system or limit exposure. Because the progressive sloughing is occurring at such as slow rate, and because the wood rounds can probably be effective at doing their job as parking lot bumpers long after you would care to use them structurally, this is probably no big deal.
Remediation Strategy:
To remediate, if you worried that the wood underneath might get exposed to other problems like decay fungi, you may want to lightly sand off the loose fibers and treat with Cu-Napthenate or perhaps a deck sealer, depending on how often you want to reapply and your tolerance of the smell of diesel solvents in the Cu-Napthenate.
