Green Decking

Here is a great rundown of alternatives to normal decking. It is by a fellow emailer Tim Keating, director of
Rainforest Relief.

Re: wood-plastic composite lumbers (WPCLs) a la Trex, Weatherbest, etc.), imho, these are fine for a home but have problems that ‘true’ recycled plastic lumbers don’t have. First, many of these lumbers are manufactured using plastic that is not post-consumer recycled and, indeed, some use virgin plastic – even PVC. Additionally, the wood component allows the material to take up moisture, thus allowing them to rot, delaminate, warp, etc. Many also tend to chip on the edges.

These materials are not ‘structural’. That is, the mechanical properties aren’t close to woods conventionally used for decking.

True RPLs are still using post-consumer plastic furnish, simply don’t rot and don’t absorb moisture. Some manufacturers either make only structural RPL or also make it – so structural RPLs (SRPLs) are readily available.

Imho, using SRPL for the understructure of a deck (the posts (or pilings), runners and stringers) is the way to go, since the larger pressure-treated beams are the more-expensive components in the first place and are generally toxic – plus, these are the most expensive components to replace. So, even if one wants the beauty of wood for the deck, using SPRL for the hidden understructure still makes sense.

Re: the deck: an excellent alternative to rainforest woods is black locust (Robinia pseudoacacia). This domestic hardwood will outlast almost all tropical hardwoods (including, very likely, ipê). It is the US “teak”. US Forest Products Lab rates black locust (hereafter, BL) as “extremely durable”, a designation reserved for teak and other tropicals. BL is considered a ‘weed’ tree in most of its naturalized range, so cutting is virtually always sustainable (email me for more details about the original native range). BL was brought to Europe in the mid-1600s and is planted in plantations extensively there, as well as in South Korea, which sports the most extensive plantations. Somehow, the Europeans and Koreans have realized the value of this extremely durable wood, yet here in the US, we’re bonkers for ipê, massaranduba, tigerwood, cumaru, Shorea, apitong, garapa, etc. for our decks.

Re: reclaimed wood vs. RPL (not WPCL): tough to answer. I think both are excellent choices but, if one is okay with the aesthetics of RPL (some are quite nice, now – email for contact info), it’s probably the better choice, leaving reclaimed woods for other uses (better for indoors, where they will can last as long as the building is standing). Also, reclaimed for outdoors (redwood, Western red cedar, etc.) are very expensive (and I’d be very careful with so-called “salvage” when it comes to road-clearing, etc. – one must either rely on a chain-of-custody oversight or know exactly where this is coming from, to assure it’s really sustainable). Using true RPL will last outdoors as long as the building is there, thus negating the need to replace the deck (including the energy that went into processing the reclaimed wood and shipping it).

Using RPL helps to expand an industry that creates 6 jobs for every one in sales of the secondary material (reclaimed wood probably comes close), sequesters carbon, offsets landfilling, etc.

The benefits of these two materials can be extremely comparably and may come down to how far away the manufacturing is from the job site, where the furnish (or original wood) is originating, etc. But I think the kicker may be the durability. Is the building (that is, the deck) going to be there for the next 200 years? If so, I think the RPL makes the most sense.

And the plastic can be re-recycled back to the manufacturer (if it’s all HDPE, any RPL company will be able to take it; if it’s a particular blend, possibly only the particular manufacturer will accept it), if one is willing to get it there. Or, perhaps, when they deliver the new decking (100 years from now), they can throw the old stuff on the empty truck! : )

I’m happy to connect anyone to companies making SPRL and also mills supplying black locust. As far as the latter, I’ve found that Armster Reclaimed Lumber is very knowledgeable and reliable when it comes to BL. They can be found at or emailed at A word of caution: BL shouldn’t be used in exactly the same way as a tropical wood. First, tropicals are typically 250 – 1000 year old trees, logged from old growth rainforests. That means that the wood is extremely stable (true of 1800 year old redwoods, Western red cedars and Alaskan (yellow) cedars, and 600 year old cypresses, too!). But BL trees are typically 35 – 60 years old. BL tends to have a lot of tension in it and thus needs to be dried just right. A thicker profile (4/4 actual or even 5/4, for instance) might be called for, depending on the application. Or extra care in fastening (pre-drilling is required – just like ipê). But I’ve seen properly dried and well-milled BL on porches and small decks that looks just as good as any other wood.

Hope this helps. I’m happy to provide more info to anyone on BL or RPLs.

tim keating, director
Rainforest Relief

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