This is a complete guide to non-toxic decking – types, materials, additives, and brands.
For most people, the main choice is between composite decking and solid wood decking. For the chemically sensitive you will have to get samples yourself of the decking materials as well as the stains needed for real wood – as this choice is very individual.
The long-term benefits of not having to do any maintenance on composite decking can outweigh the initial concerns.
There are also some more unusual options to choose from like aluminum decking.
Material Make Up
Composite decking material is generally made from a mix of wood fibers and plastic. The plastic is polypropylene (PP) or polyethylene (PE), mixed together with wood dust, pigments, UV inhibitors, and usually borate. This plastic is usually recycled, like from plastic grocery bags.
If you do well with polyethylene or polypropylene that should be OK for you, but ask to see a sample of the ones available near you and see if you can get a sample of one that is as newly manufactured as the one you would buy. These plastics do have a little bit of odor.
Most of them now are capped in an outer layer of plastic. The type of plastic is not always specified, but you should ask, especially if you are avoiding PVC vinyl.
Additional Chemicals During Install
Glue is not used to install composite decks, but you are meant to seal the rough edges of some brands with a lumber wax – be sure to tests out the product that the company recommends if you are super sensitive.
Trex does not recommend using a lumber wax, sealant, or any other glue or sealant in the installation.
The only maintenance needed for most brands is soap and water.
Many have reported their composite decking becoming prone to growing mold. Some experts have recommended only going with brands that are capped with plastic on all sides to help prevent this issue. Brands with bamboo fibers might also be less prone to mold since the fibers do not clump as much.
Capped composites like Trex Transcend or TimberTech Earthwood Evolutions use a traditional composite decking core with an added plastic polymer cap.
Trex is the most well-known brand of composite decking made with recycled bags (PE), and it is capped with an unspecified type of plastic, which they said is not PVC.
Dura-Life brand is a blend of polypropylene (about 20 percent), recycled wood and plastic (about 25 percent), and hardwood flour (about 55 percent). Dura-Life planks have a polypropylene cap outer shell covering the extruded composite core.
I have heard from really chemically sensitive folks who did well with Dura-Life. I sampled this one and I would describe the odor as a fairly mild glue odor when sniffed directly.
A non-wood composite, Lumberock Premium Decking, offers a line of decking materials made from a combination of plastics and mineral materials instead of wood fibers. You might want to check that one out if you are sensitive to the natural odorants of wood.
Wood-based composites do still retain some wood odor. For example, a cedar composite that I tested definitely smelled like cedar. The ones I tested (Trex, Dura-Life) also have an odor that I would describe as a light glue odor.
A Trex deck typically runs from $9 to $16 per square foot.
Non-toxic cleaning products that won’t damage composite decks are here.
Material Make Up
Some PVC decking is 100% plastic and some is a composite decking made of PVC and wood fibers.
Many chemically sensitive folks like to avoid PVC since it tends to be higher in offgassing, odors, and added chemicals, however, the odor here of the wood-PVC composites is fairly mild and in my experience was milder than the composites above.
These are some brands that make PVC decking which generally look the same from the atop view as the non-PVC composites.
Additional Chemicals During Install
With solid PVC boards you would not need to seal the edges.
Mold growth would only be superficial on solid PVC boards since it cannot grow in the material. With composite products, if they have real wood in them they likely are prone to mold to some degree, especially if not capped on all sides.
AZEK and TimberTech AZEK products are made from a solid PVC which they claim is highly resistant to stains, scratches, splits, mold, and mildew.
Despite being PVC, I found that the TimberTech AZEK only had a slight odor when new (when sniffing it up close) – less than the odor of TREX and Dura-LIfe composites, in my opinion.
TimberTech Pro and TimberTech Edge are composites – a mix of wood fibers and plastic PVC, capped with PVC. (Not capped in PE as some websites say).
Envision Composite Lumber with no natural wood fibers and PVC. Some lines are capped (in PVC) and some are not.
EverNew by CertainTeed line includes decking materials that are either solid vinyl or a blend of PVC vinyl and wood flour.
Fortress Apex PVC Decking’s “foam core” is cellular PVC reinforced with bamboo. The boards are encapsulated in an acrylic polymer.
Fiberon company makes surface decking, railing components, and fencing products that are made from a solid PVC “Permatek” outer shell bonded to a wood composite core.
Azek is 2-3 times the cost of Trex composite.
Non-toxic products that won’t damage vinyl decks are outlined in this post on deck cleaners.
Real Wood Decks
Pressure Treated Decks
Pressure-treated wood for decking is usually pine, treated with copper and quaternary ammonia. The ammonia will offgas from the pine, but for those who are extremely sensitive, they can have challenges with this when it is fresh.
One other challenge with pressure-treated wood is that it can not be sealed or stained for about 6 months when it is new unless it’s already been dried out.
Cedar is the most common natural wood option and it’s good for those avoiding toxins since it doesn’t need pressure-treating (with copper-quats) like pine does.
Cedar does have a rather strong natural odor which bothers some people with extreme chemical sensitivity. My post on the odorants of wood looks more at this issue.
Although it doesn’t require pressure treating you should stain it every few years, so you will have to find a sealer you can tolerate. My post on deck sealers goes through the options.
Usually the base structure of decks is made from pressure-treated wood.
Redwood is another naturally rot-resistant wood used for decking in North America. Like Cedar, it is not pressure treated and does require a sealant.
Cedar and Redwood are pricier than pressure-treated pine.
Ipe is a wood species for decks that could be ideal for those avoiding toxins.
Though it’s quite pricey, pricier than Cedar and Redwood, it does not require sealing (or pressure-treating). Though adding a sealer can help preserve it. You can choose between natural oil options and a very low VOC oil/water hybrid detailed here.
Other Rot-Resistant Woods Used in Decking
Massaranduba, Cumaru, Tigerwood, Garapa, Mahogany, and Teak are a few other naturally rot-resistant tropical woods that can hold up as outdoor decking.
Out of the woods used for decking, Cedar is the highest odor wood and Garapa is the lowest. If you find yourself sensitive to the natural odorants of wood, get a few samples of different species and see how you do.
Non-Toxic Modified Woods
Thermally Modified Wood
Thermally modified wood for decking is treated with heat. This makes it more durable and gives it protection against rot and termites. No chemicals are used in the treatment. It has the smell of smoked wood.
Thermory is a heat-treated wood brand, they say it lasts as long as a tropical hardwood like Ipe.
There is a wax to seal the edges of Thermory. Other than those edges it comes finished and you don’t have to refinish this again if you don’t want to.
Accoya wood is Radiata Pine and Alder species treated with acetic anhydride. The treatment leaves the wood harder, more dimensionally stable, and immune to insects. Some acetic acid is left in the wood and that does leave it smelling a little bit like vinegar.
You can add a finish or leave it unfinished.
Aluminum decking by Nexum, pictured above, is made from powdered coated aluminum. A chemically inert product and certainly the safest one on this list for the extremely chemically sensitive.
The above type is gapless which can help to provide usable area under the deck.
Non-Toxic Deck Stains & Sealers
Corinne Segura is a Building Biologist Practitioner with 8 years of experience helping others create healthy homes.
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