Leland Moore
General Contractor

Pressure Treated Lumber

Pressure Treated Lumber:
Has become very common in today’s building practices. Revolutionized by Dr. Karl Wolman over 80 years ago.  Deck substructures (the structural framing componentPressure Treated lumber Photo of the deck) is probably the most common place you might find pressure treated lumber in residential construction. Although it can be used as surface decking plank it's not as cosmetically appealing as a lot of other choices, and is probably not the best choice if you have young children.  

Pressure-Treating lumber is a process designed to deeply impregnate lumber with chemical preservatives to prevent insect infestation, rot and fungal decay. The intent is to give strong woods like Oak, Southern Yellow Pine and Coastal Douglas Fir the same rot/insect resistance that softer woods like cedar, redwood and cypress naturally possess.

There are the three classes of preservatives typically used when pressure-treating wood.
Creosote   Waterborne   Oil-borne

First introduced by the Swedes a process designed to deeply impregnate wood with creosote in a  pressurized tank, which would be the preferred treatment except that creosote is actively carcinogenic as well as very flammable. In a pressurized tank, kiln-dried lumber is loaded and a vacuum is drawn, this pulls any air out of the wood's cells. The treating chemical (creosote, originally) is then introduced into the tank, and the tank is pressurized for a number of hours. They then drain the tank and again draw a vacuum to pull excess chemicals out of the wood.

Introduced by Dr. Karl Wolman over 80 years ago this process, pressure-treating lumber with Chromated Copper Arsenate (CCA), other wise known as the Wolman solution includes 50 percent copper oxide, 30 percent chromium oxide and 20 percent arsenic oxide in water which became the standard for protecting and preserving most wood exposed to outdoor weather. Pressure from the (EPA) caused a voluntary industry transition in the year 2003. Today CCA is no longer being produced for residential or general consumer use. A number of alternative preservatives are available. These include Alkaline Copper Quat Type C (ACQ-C), Alkaline Copper Quat Type D, Carbonate formulation (ACQ-D Carbonate), Copper Azole Types A and B (CBA-A and CA-B), as well as Sodium Borate (SBX/DOT) and Zinc Borate preservatives. 

Oil-borne (penta)
Some different oil-borne preservatives that are used are; Chlorpyrifos/IBPC, Copper Naphthenate and Pentachlorphenol. One advantage of these treatments is that they do not create swelling in the wood, but there is generally an added cost over water-borne treatments as well as availability in some regions.

Pressure-Treated Wood is measured in Retention level

Retention level

This refers to the amount of preservative that remains in the wood after the treatment process is complete. It is measured on a weight basis and is typically expressed as pounds of preservative per cubic foot (pcf) of wood. There are a number of typical retention levels available. Generally, the harsher the condition the wood is exposed to, the higher the retention level must be.
For Above Ground use/exposures the following retentions are typical: (i.e. wood not in contact with soil)
0.25 pcf for ACQ, CCA-C, MCQ
0.20 pcf for CBA-A
0.10 pcf for CA-B
For Ground Contact use / exposures the following retentions are typical: (i.e. wood in contact with soil)
0.40 pcf for ACQ, CCA-C, MCQ
0.41 pcf for CBA-A
0.21 pcf for CA-B


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General Contractor

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Primary metro Denver, Colorado Area cities and counties Served: Arvada, Broomfield, Centennial, Douglas county, Evergreen, Genesee, Golden, Highlands Ranch, Jefferson county, Lakewood, Littleton, Lone Tree, Morrison, Westminster and Wheat Ridge
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