Alternatives to TimberSIL
We are designing a commercial project in Gulfport, Mississippi where we were planning to use TimberSIL. We were looking for something that was durable, low-maintenance, and highly resilient in addition to being environmentally friendly. We chose TimberSIL since it was one of BuildingGreen’s Top Ten Green products several years ago, was the first non-toxic preservative product approved by the EPA, had been around for over a decade, and seemed to have one of the best warranties available among pressure-treated woods.
In light of the recent news of this product’s performance in the Make It Right homes in New Orleans, however, we are now seeking alternatives. The Make It Right projects seem to be replacing the TimberSIL with Trex, which won’t work for us since we were using it in structural applications. Please let me know if you have done any research on this and have any suggestions for us.
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You didn't explain what the lumber will be used for. Is this for exterior decking, or for some other purpose?
You may be interested in this article: Special report: Summit House project’s woes linked to wood choice.
Sorry about that! We had planned on using TimberSIL for all exterior applications (save for decking which is a plastic composite) including structural trusses and columns and EcoShield for interior framing. None of the lumber will be in contact with the ground as all columns will attach to helical piers. We would like to find pressure treated lumber that will not wreak havoc on the watershed. Thanks!
Will these structural trusses be exposed to the weather? It's hard to visualize an example where they would be, unless you are building a bridge.
Yes, they will be exposed to weather. The project includes a lot of outdoor programming (education pavilions, access to water, etc.).
Unfortunately, I don't think there is any perfect material for your application. For a discussion of the relevant issues, see this article from Environmental Building News: Treated Wood in Transition: Less Toxic Options in Preserved and Protected Wood.
Here is a portion of the executive summary:
"Following the ban of chromated copper arsenate (CCA) treated wood by the U.S. Environmental Protection Agency in 2004, manufacturers have worked to find substitutes. This article examines and compares the current market leaders and cutting-edge alternatives.
"The most common treated wood products use copper-based fungi and insect inhibitors, which are relatively safe to humans but toxic to aquatic life, prone to leaching, and corrosive to metal fasteners. Borates protect wood from insects and fungi and are relatively non-toxic to mammals, but in most products borates are water-soluble and recommended only for interior use. Organic (carbon-based) preservatives using agricultural biocides are becoming available in the U.S. in both solvent-based treatments and waterborne treatments.
"Pressure treating wood with sodium silicate surrounds individual wood fibers in glass, making them impervious to pests and moisture. The single sodium silicate treated product currently being marketed, TimberSIL, has faced regulatory and production issues and is available in the southeastern U.S., but not elsewhere. Naturally rot-resistant lumber is attractive and avoids toxic chemicals, although it is typically expensive, not universally available, and often not harvested sustainably. Plastic and wood-plastic composite lumber can contain recycled content, won’t rot, absorb water, crack or corrode fasteners. However, it is relatively expensive and does not look or feel like wood. Other less common treatment alternatives include chemical modification of wood through acetylation or furfurylation, and thermal modification of wood with high heat."
Whatever you do, do NOT use TimberSIL.
My dock decking out of TimberSIL is rotting after only 4 years, and it has a 40 year warranty.
Forget about contacting TimberSIL about their rotting wood, they will ignore you. Even a celebrity like Brad Pitt looking for compensation for having used TimberSIL to rebuild those affected by hurricane Katrina is having a hard time getting TimberSIL to step up to their warranty.
Do NOT use TimberSIL.
Edit: Just noticed that this is a 2-year-old question. Oops. Here was my comment, which is surely no longer relevant.
Is using steel an option? It's tricky to use for residential structures because it can introduced thermal bridging across the insulated envelope, but it sounds like you are building things where that's not an issue? For example, Trex makes steel frames and posts for decks.