There are four primary types of treated lumber sold to lumberyards and the big-box stores in Central Florida.
Micronized Copper Azole is the predominant treated product sold and it comes in three basic strengths of treating process—above ground, ground contact, and in-ground contact. Galvanized or coated fasteners are required in construction using MCA.
Borate treated lumber, which is a product developed for construction that protects the home against termites, including Formosan, as well as carpenter ants and fungal decay. Borate is a naturally occurring mineral, which is lethal to insects. It is harmless and noncorrosive, so common fasteners can be used in construction.
Micronized Copper Quaternary is the treating process that replaced Chromated Copper Arsenate in the mid-2000s when advocacy groups questioned the safety of CCA treated wood for projects involving children. Although CCA treated wood was eventually deemed safe, the industry moved to MCQ because the damage was done. Unfortunately, MCQ is highly corrosive and errors in fastener selection make the product untenable for most builders.
Chromated Copper Arsenate continues to be available in certain treated wood products for agriculture and posts because of its long-term durability and performance. Safety concerns in handling CCA have been alleviated. However, coated or stainless-steel fasteners are required when used in construction.
The big issue occurs when a lumberyard sells MCA above-ground treated lumber to a consumer or builder and it is used improperly. Above-ground contact treated lumber must be used in projects six inches above the ground and not above any standing water source. Plus, the above-ground treated lumber must be well drained and cannot take continuous standing water.
Think about this — we live in Florida and there is water and rain everywhere. Despite this, some lumberyards and big-box stores are only selling above-ground contact treated lumber because of the lower prices. Even worse, the wrong fasteners are being used on the treated lumber, which can create rust issues. This is the reason why the number of decks and treated lumber failures in Florida have risen.
Not all treated lumber is the same.
The main questions you should ask before using treated lumber in a project are:
- Is this product treated for my project application? If you live in Florida, insist that you are sold ground-contact treated lumber, because of the heavy moisture issues and climate.
- What type of fasteners and hangers should I use with the treated wood that is required for my project? If aluminum is being used on your project, make sure proper precaution is taken, since many types of treated lumber are highly corrosive to aluminum windows and sidings.
- Insist on a copy of the manufacturer’s treated warranty and then pull some identifying tags off the treated lumber and put it together with your sales receipt for safe keeping. If you have a treated lumber failure, most manufacturers are very good with their warranties if you can prove when it was purchased, it is their brand and it was properly installed.
Gone are the days of going to the lumberyard and just ordering treated lumber — it’s gotten complicated. The problem has worsened because many lumberyards and big-box stores have clerks who don’t know the difference and are giving either no advice or bad advice to customers.
For the best results on your next outdoor project, make sure you buy the right treated lumber.