Ask the Experts - Questions and Answers
Can you use pressure treated lumber for raised garden beds?
While there is scientific consensus that it is safe to use for vegetable/garden beds, the information in this article explains what chemicals are used in Viance ground contact treated wood for residential use and the results of numerous scientific studies.
The American Wood Protection Association (AWPA) specifies the use of treated lumber for horticultural purposes to be Ground Contact. In the AWPA Book of Standards, copper azole (CA) and alkaline copper quaternary (ACQ) are listed preservatives for Ground Contact use in residential applications. CA and ACQ are both available from Viance under the brand name Preserve.
Do I need to treat the cut ends on my fence posts?
I just got a fence installed with ground contact pressure treated 4x4 posts. I think it is your Preserve. Do I need to treat the cut ends of the posts? They look to be green all the way through but I wanted to be sure.
Construction projects necessitate the need to cut and drill into wood. Building codes and the American Wood Protection Association (AWPA) Standard M4-15 require "all cuts, holes and injuries such as abrasions or holes from removal of nails and spikes which may penetrate the treated zone shall be field treated." The extra effort protects the longevity that the preservatives offer.
Copper naphthenate is one of the most used preservatives for cut ends and holes. The minimum recommendation is 2% copper metal with 1% copper naphthenate appropriate in those regions of the country where the higher concentration material is not readily available.
Another two preservatives, oxine copper and inorganic boron can be used for field treating in above ground applications. Oxine copper can be used for applications originally treated with oil-borne or waterborne preservatives. Oxine copper preservatives, containing the recommended minimum .675% oxine copper (0.12% copper metal), are available colorless or in various colors and have little odor, according to preservedwood.org. Inorganic boron can be used in applications originally treated with a waterborne treatment and in areas continuously protected from liquid water.
These topical preservatives are available in the retail market and can be purchased at local home centers, building material retailers and paint stores who stock products for wood decks or ordered online. Be sure to follow the preservative’s manufacturer's application instructions.
Can a fire retardant be added to Ecolife and still be effective?
The Ecolife treatment does not impart fire retardancy properties to decking.
Unfortunately there isn’t a treatment on the market for both durability and fire retardancy.
A fire retardant coating will likely wear off over time because it is not pressure impregnated. In addition, building codes do not recognize sprayed-on or brushed-on coatings as code approved fire retardants for wood products; they only recognize formulations that are vacuum/pressure impregnated products.
Most pressure treated fire retardants are for interior use only, i.e. our D-Blaze fire retardant treated wood product. However, there are some exterior fire retardants available but they don’t increase the weathering, durability, or insect/fungal protection of wood so they are usually only used on naturally durable species of decking like Redwood and Western Red Cedar. The availability is somewhat limited so you would have to check with your local retailer on availability.
Todd Schoffstoll, Western Regional Manager
Can treated wood be used for sill plates and interior applications?
Treated wood is intended for exterior use. However, all treated wood material for residential use can be used for indoor, outdoor or in play set construction.
Example: If the Ecolife product is going to be used 6” above the final grade and will be on a wood subfloor as a sill plate for the stud walls, then EcoLife treated wood is okay to use. Please read the Ecolife installation instructions and adhere to all fastener requirements.
Example: If the Ecolife treated lumber is going to be used on a concrete slab, then a foam sill seal must be used as a barrier between the concrete and the EcoLife treated wood. We recommend that Dow’s Sill Seal be used to provide this moisture protection. Please adhere to all of Dow’s installation instructions on proper installation. The installation instructions can be found on the product or on data sheets at your local Lowe's retailer. Be sure that the concrete building surface will be above the final grade and all water is diverted away from the slab. If you have any further question please let me know. Thank you again for your inquiry and happy building.
Jonathan Whitehead, Eastern Region Sales
Does Preserve ACQ protect against powderpost beetles?
This question comes from a homeowner in Washington state.
Based on a study performed by the International Research Group on Wood Preserveation, ACQ is effective in protecting wood against the Powderpost beetle.
Michael Merchant, Ph.D., Professor and Extension Urban Entomologist, with Texas AgriLife Extension Service states, "The most commonly infested woods include ash, oak, hickory and walnut." He also explains in an article on the Texas A& M website, that powderpost beetles pose little threat to the structural integrity of most homes because they are framed with softwood lumber, and thus not susceptible to attack. Removing infested wood and replacing it with treated wood will eliminate the problem in most cases.
Aaron Sooter, Technical Services Representative
What are the benefits of Ecolife®/Severe Weather® treated lumber compared to other wood treatments?
- The built-in wood stabilizer keeps boards straighter and minimizes cracking, checking and splitting.
- An environmentally advanced, non-metallic preservative, Ecolife (EL2) is extremely effective at .019 pcf retention, a fraction of competing products that use two times the chemicals to achieve adequate above ground product performance.
- The water repellent stabilizer is a built-in part of the preservative system and not an add-on that can vary by treater supplier.
- Fights exposure to the sun and rain and is used in building decks, railings, fence pickets, arbors, trellises, joists and beams.
- Less corrosive to connectors and fasteners and can be used in direct contact with aluminum products, even in continuously wet applications.
- Unsurpassed in effectiveness with virtually no warranty claims in its history.
- Designed for applications six inches or more off the ground.
What types of nails or screws do you recommend?
- Use code-approved hot-dipped galvanized or stainless steel corrosion-resistant fasteners and G185 hot-dipped galvanized connectors for exterior use.
- Do not mix metals. If using hot-dipped galvanized fasteners, use hot-dipped galvanized connectors. If using stainless steel fasteners, use stainless steel connectors.
- For coastal installations, use code-approved stainless steel.
How do I remove the grade stamp on my treated wood deck?
Light sanding will remove or lighten the grade stamp's appearance.
How long do I need to wait to stain or paint my treated wood deck?
- Allow treated wood to dry prior to application. Test the wood with a few drops of water to see if the wood is dry enough to readily absorb water.
- Typically, treated wood will be dry and ready for finishing 60 days after installation.
- Apply the stain to a small portion of the deck to ensure the wood is sufficiently dry.
- Follow the manufacturer's instructions.
What do you recommend I use to stain or paint my treated wood deck or fence?
- Use a good quality oil-based or water-based stain, or exterior wood water sealant product with UV protection to help prevent the wood from turning gray from exposure to the sun.
- Apply a water repellent sealer at least every two years.
- Follow the manufacturer's instructions.
What do I use to clean my treated wood deck?
- Clean annually and keep your deck free from dirt and debris.
- A solution of liquid detergent and water with a stiff brush will remove mildew and dirt.
- For hard to clean surfaces, use a deck brightener containing oxalic acid to retain the wood’s natural beauty.
- Never use household chloride bleaches or foaming cleaners as they can strip the preservatives and damage the wood fibers leaving an unnatural whitewashed appearance.
- Be careful if using a pressure-washer as excessive pressure may cause damage to the wood.
What are important installation tips when working with treated wood?
- Butt boards tightly together during installation as they will shrink slightly in width and thickness as they dry out.
- Pre-drill holes at the ends of boards to help prevent splitting.
- Use screws to improve holding performance.
- Install fasteners flush to the wood surface. Do not overdrive fastener.
- For ground contact support posts, install the un-cut ends in the ground.
How do I remove mold from my deck?
Mold that you find on pressure treated wood is not an indication of a fungal attack. Mold can grow on the surface of many products including wood (treated and untreated) due to exposure to moisture. To remove mold from your treated deck, use mild soap and water solution and a stiff brush.
Mold and mildew are present everywhere in our environment, both indoors and outdoors. Mold and mildew need four things to thrive: air, water, temperatures between 32 and 120°F, and a food source, conditions that are common wherever humans live, work, and play.
The best way to minimize mold and mildew growth is to control water and food sources. When it comes to mold or mildew on wood decking, water and organic matter are the primary conditions that enable mold and mildew colonies to thrive. To minimize these conditions, make sure water has the ability to flow away from the deck surface and areas surrounding the deck to lessen the absorption of water. Ensure there is adequate ventilation between deck boards and underneath the deck surface, so water can rapidly evaporate.
And since both mold and mildew feed on dead or decaying organic matter, so it is important to keep your deck clean of leaves and debris.
Cleaning Your Deck
To minimize mold on your decking, clean your deck as often as needed, at least twice each year. Climate conditions vary in different regions of the country and may necessitate more periodic cleaning.
Remove leaves, debris, and other organic materials that provide a food source for mold.
If mold is present, there are many commercial products available for cleaning mold. We recommend commercial cleaners containing oxalic acid. For best results, follow the manufacturer’s instructions and use cleaners within their stated shelf life. Do not mix recommended cleaning products together as harmful chemical reactions could occur.
We do not recommend household chloride bleaches or foaming cleaners as they can strip the preservatives and damage the wood fibers leaving an unnatural whitewashed appearance.
To maximize application coverage, remove excessive organic growth or clumps prior to applying the cleaner.
Coatings for High Mold-Prone Environments
For environments prone to high mold growth, there are commercially available coatings and finishes that seal the wood surface when applied and they should be maintained per the manufacturer’s instructions.
- Coatings should be applied within one week of cleaning for best results.
- Prior to coating, properly clean the decking, rinse thoroughly with water and allow to dry completely.
- Sweep off any pollen and debris.
Tips for Minimizing Mold
- Maintain a deck that is dry and clean.
- Ensure gutters / down-spouts and dryer vents do not discharge directly on decks.
- Ensure adequate ventilation under and between decking boards.
- Minimize water puddles under decks and the use of wet mulch up against the deck structure.
- Cleaning a deck just after the last of the major pollen events (when your car doesn't change color from the pollen anymore) will minimize the seasonal outbreak of mold and mildew.
- Periodically rinse off your deck using a garden hose with a spray nozzle, especially after the major pollen events. Skilled professionals may use pressure washers with wide fan tips but in the wrong hands, your deck can be damaged. Exercise extreme caution when using pressure washers.
- Ensure the gaps between the decking boards remain free of debris so that regular rain showers can remove pollen and organic debris between cleanings.
- Avoid fertilizer over-spray.
What are safe practices when working with treated wood?
- Wear gloves, goggles and dust mask when working with treated wood.
- Wash hands thoroughly with mild soap and water after working with treated wood.
- Do not burn or use treated wood debris as mulch.
- Do not use treated wood where it may come into direct or indirect contact with drinking water or a component of food, animal feed or beehives.
- Dispose of treated wood debris in accordance with local regulations.