Why was the use of CCA wood discontinued for residential construction?
CCA stands for Chromated Copper Arsenate. Over the past few years, there have
been an increased number of concerns about potential negative health effects of
this wood preservative containing arsenic. As a result, the wood-treatment industry voluntarily transitioned away from CCA-treated wood to alternative treatments for residential construction applications. CCA will remain in use for some industrial, agricultural, and marine applications.
What are the alternative wood-treatment preservatives?
ACQ (Alkaline Copper Quaternary), CA-B (Copper Azole), and ACZA (Ammoniacal Copper Zinc Arsenate) are the most common wood treatment chemicals that replaced CCA for residential applications. They are commercially available today. All three of them are more corrosive than CCA (Chromated Copper Arsenate).
Why do the new pressure-treatment preservatives (such as ACQ, CA-B, and ACZA) cause corrosion?
Galvanic corrosion occurs when two dissimilar metals come in contact in the presence of moisture. ACQ, CA-B, and ACZA are copper-based. Most metal deck components are galvanized, i.e. they are coated with zinc to improve their durability. When in direct contact and in the presence of moisture, the copper in the wood corrodes the zinc galvanizing layer.
How much more corrosive are the new pressure-treated wood preservatives (i.e. ACQ, CA-B, and ACZA)?
ACQ, CA-B, and ACZA are approximately 2.5 to 4 times more corrosive to galvanized metal connectors than the historically used CCA wood. (Results after 2 months of accelerated corrosion testing.)
Since CCA is also copper-based, why has there been no corrosion problems with the CCA treated wood?
Although CCA contains copper, it has other chemical components (chromate and arsenate) that are corrosion inhibitors. The inhibitors protect the zinc galvanizing layer from corrosion in the presence of copper.
What is the effect of using Grace Vycor® Deck Protector™ on the corrosion of galvanized metal connectors?
Separating the galvanized metal connectors (i.e. joist hangers) from the surface of ACQ, CA-B, and ACZA-treated wood with Grace Vycor Deck Protector can help reduce the corrosion rates of these connectors to the historically acceptable rates seen with CCA wood. CCA has been successfully used in the field for almost 70 years.
How long does it take for corrosion to occur?
There are a lot of variables that can affect the corrosion rates of metal, such as environmental conditions (temperature and rain/moisture), concentration of the chemical preservative in the wood, moisture content of the wood, exposure of the deck, type of connectors/fasteners used, etc. Under continuously wet laboratory conditions, corrosion of galvanized metal connectors in contact with ACQ, CA-B, and ACZA-treated wood can become visible in a very short period of time — weeks or months rather than years. Depending on the corrosiveness of the environment, this period may vary. Since corrosion begins from the inside of the joist hanger (at the point of contact with the wood), it is difficult to notice until it becomes quite advanced.
Refer to your connectors/fasteners manufacturer for specific recommendations.
Can I use felt, building paper, housewrap or similar materials as barriers to prevent corrosion?
No. These materials may not effectively separate the dissimilar metals in the wood and in the metal components. They offer NO protection at the key potential corrosion sites where fasteners penetrate the barrier.
Will all fully-adhered peel-and-stick membranes work to prevent corrosion?
No. Grace Vycor Deck Protector's corrosion reduction properties have been specifically tested for this application. Patent is pending. Other peel-and-stick membranes may not perform as well in exterior deck applications, making them ineffective corrosion barriers.
Talk to the barrier manufacturer to provide product-specific technical support data or to the metal manufacturer to recommend a barrier product.
Will the moisture inside the wood affect the corrosion rates?
Yes. The higher the moisture content, the faster the corrosion. However, corrosion will occur even in low moisture levels, making most decking susceptible to this problem.
Does Vycor Deck Protector protect the fastener inside the wood from corrosion?
The use of Grace Vycor Deck Protector can help reduce the corrosion of the nails at the wood interface (the most corrosion susceptible area of the fastener), by separating it from the galvanic effect of the large connector (i.e. joist hanger). Grace Vycor Deck Protector could also help drive down the corrosion rate of the nails inside the wood. Use hot-dip galvanized (HDG) fasteners per ASTM A153 when attaching galvanized metal connectors.
Use fasteners per the manufacturer's recommendation when attaching the surface decking boards to the supporting joists.
What fasteners should be used with Grace Vycor Deck Protector?
Use hot-dip galvanized (HDG) fasteners per ASTM A153 when attaching galvanized metal connectors. HDG fasteners optimize structural and corrosion
performance.
Use fasteners per the manufacturer's recommendation when attaching the surface decking boards to the supporting joists.
If the surface decking boards are also pressure-treated with ACQ, CA-B, and ACZA, would the fasteners attaching them to the joist corrode?
Yes. Fasteners made out of stainless steel or of a thicker galvanizing layer should be used to attach pressure-treated (PT) surface boards to PT joists. However, stainless steel and galvanized metal should not come in direct contact with each other; for instance, stainless steel fasteners should NOT be used with galvanized connectors/joist hangers. Otherwise, corrosion will be accelerated further.
Stainless steel fasteners are not required for attaching composite surface decking boards. Check with your decking manufacturer and/or metal component manufacturer for specific recommendation.
Can Grace Vycor Plus be used for corrosion protection?
Grace Vycor Deck Protector is the barrier membrane specifically formulated and tested to slow down corrosion rates of galvanized metal in contact with the pressure-treated structures. It also has an added skid resistance coating to help facilitate the application process. Although it is believed that Grace Vycor Plus may also be successful in reducing corrosion rates, no tests have been conducted at this time to prove its corrosion protection performance. Grace recommends that Grace Vycor Deck Protector is the barrier membrane used for corrosion protection.
How many rolls of Grace Vycor Deck Protector do I need for my deck?
For a 400 SF deck, one would need about 1 roll of 4" Grace Vycor Deck Protector for the ends of the joists and less than 1 roll of 9" Grace Vycor Flashing for the ledger board and the rim joists. Additional 4" material will be needed for the post caps (depending on the deck construction) or other areas where a barrier is required to separate the wood from the metal.
These estimates may vary, depending on the exact dimensions of the deck, as well as the usage rate.
How much money would Grace Vycor Deck Protector add to the cost of my deck?
For a 400 SF deck the material cost for Grace Vycor Deck Protector is approximately $50. This number may vary slightly depending on the exact dimensions of the deck, as well as the usage rate.
Do I need to mechanically fasten Grace Vycor Deck Protector to the joist?
If the wood substrate is wet or dirty, staples may be used to hold Grace Vycor Deck Protector in place until adhesion develops.
Where should I install Grace Vycor Deck Protector?
Grace Vycor Deck Protector should be installed in all applications where the wood could get wet and where the galvanized metal connectors come in contact with the pressure-treated wood. For specific details, please refer to our informational brochures.
Can Grace Vycor Deck Protector be used in all areas of the US?
Grace Vycor Deck Protector can be used in all areas of the US, except in the desert Southwest.
Can I use stainless steel joist hangers/fasteners with the new PT preservatives?
Yes. Stainless steel hangers and fasteners can be used. However, most metal components are not readily available in stainless steel which practically limits the use of stainless steel components. Do not use stainless steel fasteners with galvanized connectors and vice versa. Grace Vycor Deck Protector is not needed if stainless steel components are used.
Can Grace Vycor Deck Protector be left exposed to sunlight?
In general, typical deck applications (such as on ledger boards/rim joists or around joist hangers) may expose Grace Vycor Deck Protector only to indirect sunlight (with limited intensity) and only for short periods of the day, if at all. Such UV exposure is acceptable; membrane could be, but does not have to be covered.
The product should not be left permanently exposed to direct sunlight. It is recommended that the membrane be trimmed around the connector to limit the direct UV exposure (for instance, at post bases). It is recommended that the product be covered within 30 days. However, exposures of up to 60 days may be acceptable when the membrane is applied for corrosion protection.
Where can I purchase Grace Vycor Deck Protector?
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you.
I am interested in stocking Grace Vycor Deck Protector. Who should I contact?
Call Grace toll free at (866) 333-SBM (3726).
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Where can I get pricing information for your products?
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Do you have any sales representative in my area that I can contact?
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Where can I get warranty information on your products?
Warranty is printed on product packaging. If you need further information, call 866-333-3726
Where can I call for technical / application questions?
For technical support call 866-333-3726.
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Where can I get Material Safety Data Sheets (MSDS)?
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here to locate an MSDS.