This post is not for everyone, but it shows where my head has been this week. Even if you don’t have a hoophouse, or are not even thinking about getting one,you might be interested in recycled plastic decking boards, or buying repurposed material from an “industrial thrift store”!
We made cedar baseboards when we put up our hoophouse 20+ years ago, and they have rotted. We have done partial replacements, including a major one maybe five years ago, but are now considering either plastic decking “lumber” (recycled plastic, with or without any wood filler), or steel.
I did some research:
https://hightunnels.org/design-construction-of-high-tunnels-west-virginia/ Lewis Jett (WV Extension)
“Baseboards and hip boards add strength to the base of the frame (Figure 8). For most high tunnel frames, 2 inches x 6 inches x 10 feet wood (or recycled plastic) boards are suitable. Pressure-treated wood can be used for both hipboards and baseboards. Each section of baseboard is bolted onto the ground post or secured with a pipe strap. The baseboard and hipboard must be level across the length of the high tunnel. Each joint between sections can be spliced with a small segment of board.” Our hoophouse is 96ft long, so we’d need 192ft plus some way of joining them (metal brackets?)
So, same dimensions, whether wood or plastic. 2” x 6” x 10’. We don’t need “structural grade” lumber (wood or plastic) as the ground-posts provide the strength and are not going to move sideways.
Next, I asked local growers: Do any of you have advice based on experience?
Replies ranged across the spectrum
- Sounds like cedar serves well for that. 20 years is a good run for wood. Maybe locust or old chestnut barn boards would serve well, too.
- We replaced the rotting wood baseboard with plastic deck “wood” about 5 years ago and haven’t had any problems with it. Didn’t even think about using steel. Ignorance is bliss.
- When we redo base boards I would like to go with hat channel. I think sidewalls would air seal better and I’m finding that more important than insulation value. We’ve been putting straw on the tunnel edges for weed control and insulation for the winter.
I replied: We’re not content with living with the state of decline of the wood. Currently we have about 12 ft of the south wall where the plastic and wigglewire channel are not attached to the earth. We have to fix that before the chills of winter get in!
See the ATTRA publication Pressure-Treated Wood: Organic and natural Alternatives 2011. Be aware that many of the alternative lumber treatments described in the ATTRA article are NOT currently allowed for use on organic farms. Certified farms should consult their Organic certifier.
“Lumber treated with prohibited materials is not allowed under the National Organic Program (NOP) Regulations. The NOP prohibits most but not all synthetics. Lumber is pressure treated to resist insects and fungi, but the materials used are toxic to humans. For posts and lumber that are in contact with soil, crops, or livestock, the options include untreated lumber, alternatively treated lumber, alternative plywood products, and untreated fence posts.
Borates (boric acids and borax) have long been used for alternative wood protection and can be used with all types of lumber, logs, and ply-wood. Borax, a naturally occurring mined material, is allowed for organic production. Borates and boric acid are synthetic substances allowed for use as an insecticide in organic production as what is described in the National List 205.601 as a “structural pest control, [not in] direct contact with organic food or crops.” Borate-treated lumber and borate wood treatments are available commercially.
Borate wood treatments will penetrate to the center of the wood when the wood is dipped, especially when the wood is freshly cut or when seasoned wood is rewetted. Because borates are water soluble; however, they will leach from the wood when in contact with water in the soil, leaving the wood unprotected. This is the reason that borate-treated lumber should be used only in locations that are at least six inches above the ground and protected from excessive rain. Borate-treated wood is not considered suitable for unprotected outdoor use, such as for fence posts or poles, but it is suitable for most building-construction purposes.”
Recycled Plastic Lumber and Plastic/Wood Composite Lumber
(from ATTRA 2011)
“Lumber” made of recycled plastic or composites of plastic and wood can provide durable weather-resistant alternatives to wood for some applications. In organic operations, formed plastic is approved only for use in nonstructural applications because it doesn’t have strength comparable to wood. However, plastic lumber can easily substitute for treated wood in nonstructural applications such as fences, sill plates, and raised beds. The plastics are rot- and corrosion-proof and don’t crack, splinter, or chip. Even in exposed and sub-grade conditions, plastic lumber has a long life expectancy. It will not leach chemicals into the ground, surface water or soil as treated wood can. A challenging aspect of working with plastic lumber is its relatively high likelihood of expanding, which varies for each product and manufacturer and has to be considered during installation. Thermal expansion is the change in dimensions of a material due to temperature changes.
The number of plastic-lumber manufacturers and their variety of products has notably increased recently. Some companies use only High Density Polyethylene (HDPE) plastic, while others use commingled plastic wastes. A few manufacturers even mix plastic with recycled tire rubber. Some plastic lumber will contain wood fiber, which helps strengthen the plastic and reduces expansion.
Plastic lumber is available in many configurations and sizes, including solid- and hollow-core dimensional products and tongue-and-groove designs. The quality and product performance will vary by manufacturer; many manufacturers have independent testing results available.”
The Composite Lumber Manufacturers Association offers publications and links to member companies that manufacture and distribute plastic lumber. See All About Composite Decking. It requires no maintenance, comes in lengths up to 20ft, can be fastened with self-drilling screws, and can be drilled and sawn with power or hand tools used for wood.
The California Integrated Waste Management Board Recycled Plastic Lumber website provides a good introduction to the types and uses of recycled-plastic-lumber products.
Suppliers of plastic lumber
Growers Supply has 2” x 6” x 8’or 12’ recycled plastic boards in black (Expands in heat, don’t buy dark color?). We’d need 16 boards at 12ft long ($1887.20 plus shipping), or 24 at 8ft long ($1894.80 plus shipping). Can get 10% discount. “A 12foot board will shrink .029/inches over a 5 degree drop in temperature. Note your starting point is what temperature the board started at when assembled. Typically use 60 degrees as a baseline. In this case a temperature drop to 0 degrees will net 11/32″ over the 60degree swing. A direct sunlight board will shrink less in a temperature drop and expand more in a temperature increase.”
On decks, the boards are tightly fastened every 16” and can’t go anywhere much sideways.
Home Depot and Lowes only have short pieces.
Plastic Lumber Yard, PA. Can get 5% discount.
Premium Grade is the nicest looking, and best for decking. Structural grade is reinforced with fiberglass, making it stiffer, the best under high traffic. Molded grade is recycled high-density polyethylene (HDPE), suitable for landscaping, buildings and near food.
Molded grade 2” x 6” x 12’ $126.23 each. $2,019.68 for us (plus shipping) Available in 8, 10, 12, 14, 16ft lengths and many colors. This grade would work for baseboards.
Their Clearance dept might be useful, as we probably don’t care exactly what color it is, or even if it’s all the same color. Currently they have 2” x 6” x 12’ in white for $76.50 each ($1224 for 192 ft) and a grey board with peg joins 1 7/8’ x 5 7/8” x 12’ for $50 each, but they only have 9 left! 2” x 6” x 8‘ black (severe “dog-bone”, meaning the boards are thinner in the middle than along the edges. (Oops! We all have days like that) for $30.16 each – must buy all 36 pieces. We only need 24. email@example.com or call (610) 277-3900 for shipping info.
Markstaar 888-846-2693 Offering double discounts right now. Recycled lumber boards.
2” x 6” x 12’ $48.96; 2” x 6” x 8’ $32.64. (24 for $783.36) Black is cheapest.
Steel is available as either “hat” profile strips from greenhouse suppliers, or metal joists, 6″ wide, C-cross-section. They look easiest to use, but have zero insulating value.
I’ve found some steel joists on https://www.repurposedmaterialsinc.com/ . This is a fun website, saving all sorts of good stuff from going to the landfill.
- Hat channel Join by overlapping sections and using self-tapping screws. Tunnel Vision has an installation video on Hat Channel. $54.74 for a 12’3” length 5” wide. 18-gauge steel. ($875.84 plus shipping for 16 lengths) Truck delivery for full-length strips, or they will cut them in half for ground delivery.
Boot Strap Farmer also has a video with hat channel. 6.5’ lengths, $452.99 for a 10-pack. (65’). We’d need three 10-packs, $1358.97 plus shipping. And lots of joins. . .
- Square tubing
- Steel C-section joists
RepurposedMaterials is a fun website, saving all sorts of good stuff from going to the landfill. I need to compare prices, shipping and practicality. Steel is looking better right now. has different things at different times, naturally enough.
$78 for almost 20ft length. 12″ x 2″ 14 gauge C-shape plus curved over edges. We’d need 10 lengths and would spend $780 Plus Shipping
$48 for 20ft. 10″ x 1.25″ 18 gauge We’d spend $480 plus shipping from SC
$45. 20′ x 11-1/4″ x 1-1/2″. 18 gauge. Square cornered, no curved in edges. We’d spend $450 plus shipping.
|Wood||Recycled Plastic||Hat Channel||Repurposed joist|
|No maintenance||Saving waste
Price is good
Leaches? They say not
|Shipping might be high (heavy)|