Types Of Treated Lumber
There are three main families of treated lumber used in construction: Borate, Alkaline Copper Quat (ACQ) and other rot-resistant treatments, and Non-Com.
Borate: This newer process is primarily used in the Colorado area for sill plate use only (2x4 and 2x6) and available only in construction grades. Long-term storage should be, at minimum, wrapping the material in a watertight manner and keeping the material well off the ground to prevent migration of the borate treatment. There is no need to end coat after cutting. Exposure to the weather during a “normal” construction process is allowable for the material, but as with all construction, we suggest the building is dried in as soon as possible. No special fastener requirements are listed.
PTI: This is the newest process available and most of our treated lumber inventory has been changed to this new treatment. This treatment currently can be used for the bulk of exterior wood uses – everything except in-ground applications. This formulation has a lower environmental impact throughout its production, distribution and installation than other treatment alternatives. PTI is a GreenSpec® environmentally preferable product. Out-of-ground uses include: deck framing, fence boards, exterior trim, outdoor furniture, arbors and trellises. The most visible advantage to PTI is its color. By itself, the Wolman PTI preservative leaves wood its natural color. However, to distinguish treated from untreated material a cedar-tan pigment has been added to the solution. The resulting color better matches today’s favorite decking alternatives including composite decking, cedar and redwood. It can also be very readily stained or painted without special precautions. Stainless steel or hot dipped galvanized fasteners should ALWAYS be used with this product. The only exception is when fasteners (bolts) are ½” or greater in diameter; even then, these should be zinc plated (see below for more information). End cuts should be end coated. Other cuts may be restricted., specifically ripping boards voids any decay protection &/or warranty. PTI carries a limited lifetime warranty.
ACQ Exterior: As this process is treatment for exterior applications, no special covering precautions need be taken. All end-cuts should be treated with end-coat solution. Generally, other cutting (specifically ripping) should be avoided. Stainless steel or hot dipped galvanized fasteners should ALWAYS be used with this product. The only exception is when fasteners (bolts) are ½” or greater in diameter; even then, these should be zinc plated (see below for more information). Storage of ACQ treated lumber should be off the ground, stacked flat and neatly to minimize warpage and discoloration. Banding is desirable in warmer weather to reduce cupping and twisting until use. This treatment is very common and is widely available in both boards and plywoods in most construction sizes and grades. This type of treatment in a higher penetration level is used for “all wood” foundations.
Non-Com: (aka PyroGuard and other trade names, non-combustible, fire-resistant) this lumber should always be kept in a dry environment. Short-term storage under cover, off-ground prior to installation is acceptable. Again, exposure to the elements during the normal construction cycle is within guidelines. This product is NOT for direct exterior exposure. There are non-combustible products that are truly exterior graded. End cuts do not have to be end coated. Other cuts may be restricted, specifically ripping boards voids any fire protection &/or warranty. Non-Com is used for fire/building code purposes where a fire-resistant construction is desired. This lumber will eventually burn; however it has been treated such that when exposed to high heat, it will “sweat” so that combustion is harder to start and slower once begun. You can verify this treatment by the stamp on each board/ panel. The wood itself appears only slightly different from plain wood, in a slightly more yellow color and what looks to be a salt residue in places on individual pieces. No specific fasteners are required when using this product. Non-com plywoods are available in both CDX and ACX grades; 2x framing lumber is available in most lengths in 2x4 through 2x12. The type that Front Range Lumber stocks is very red in color, readily distinguishing itself from other woods.
CCA (Chromated Copper Arsenate): This is a generally outdated method of treating lumber and plywood for rot/insect resistance. It has been replaced by ACQ. It is still allowed for a few, narrowly defined uses. Most insurance companies will no longer provide coverage if you do sell/use this product.
Treated lumber and plywoods require the use of upgraded joist hangers and fasteners. The chemicals uses in this treatment process will corrode normal metals faster. Simpson, the leading hanger manufacturer, makes a whole series of hangers named Z-max for exterior construction. The Z-MAX coating assures a better galvanizing process to offset the corrosive effects of treatment. Use ONLY Z-MAX hangers on any treated lumber. Be sure to fill ALL the nail holes on all hangers to pass inspections and utilize the full strength of your hangers. The best fasteners to use on these products are stainless steel, which of course are the most expensive. A very reasonable and acceptable alternative is any nail, screw or bolt that has been hot dipped galvanized or other coatings that retard corrosion. Finally, information available to us is that any bolt with a ½” or greater diameter has enough bulk to it to not require special coatings. Newer treatment processes may allow for “normal” hangers and fasteners to be used, however, we recommend that a “Z-Max” type of coating continue to be used on ALL exterior applications. The extra cost is very much worth the extra protection. Again, Simpson Strong-tie advises the use of Z-Max hangers on all exterior installations.
Most treated lumber does not come in different grades, the exception being plywood, which will come in both ACX and CDX grades. Virtually all treated lumber is considered for construction only - that grade does not take appearance into consideration. In most cases (except deck framing), the treated wood used will be covered by trim, drywall, paint, etc. Front Range Lumber does have some of its own wood treated, translating into a better quality than widely available. Available readily is a “5/4” decking products that is graded for appearance.
Health & Safety
Health concerns for ALL treated lumber are present if used unwisely. Follow common sense instructions like the following and refer to a complete MSDS for full details. We will supply Material Safety Data Sheets on request.
- Wash hands and face after using treated lumber, wear gloves. Wash up before handling food and drinks (or using tobacco products).
- Do not burn scraps. Clean up all scraps and sawdust and dispose of in ordinary trash collections.
- As with all wood products, use of a dust mask is recommended.
- Keep children away from scraps and sawdust.
- Keep all food and drink away from treated lumber.
- Cut and machine wood in a well ventilated area.