Decay Prevention in Wooden Steps and Porches Through Proper Design and Protective Treatments

When wood is used for structures of known high decay hazard, such as southern pine porches and steps in the South, it is safest to use lumber commercially impregnated with a suitable preservative. It must be remembered, however, that some commercially-treated lumber cannot be painted or only with partial satisfaction. If suitable impregnated lumber is not available and sapwood lumber is protected by an on-the-job application only a surface treatment can be expected. Consequently, the following precautions are necessary: 1) Cut all wood to size and shape before treatment. If any subsequent cutting must be done, treat all cut surfaces, at least with a copious brush application. 2) Use a preservative with a moisture repellent added because these have been shown to be more effective in dip treatments. For small jobs, a ready-to-use treating solution is best. The label should be checked to see that it contains 5 percent pentachlorophenol or 20 percent copper naphthenate (often expressed as 2 percent metallic copper). If the solution is water repellent, the label should state that water repellent solids were added. If a concentrate is used, be sure to dilute with the proper amount of mineral spirits (cleaning type) to give the concentration shown above. The label should state that the solution will leave a paintable surface. 4) If painting is not contemplated and for wood items in which some creeping of the preservative would not be important, use a heavier oil carrier, as a number 2 fuel oil. These give somewhat better protection than light paintable solutions. 5) If possible, use a soak of at least 10 minutes. No preservative known will produce a miracle; the degree of protection will depend on the amount of preservative gotten into the wood and the depth of its penetration. 6) After the oil has dried from the treated wood, paint all exposed surfaces with a standard oil paint or enamel to reduce checking and the chances of internal infections. It is safest to allow a few days to a week for drying before painting. 7) Supplement the preservative treatment with designs that remove the greatest decay hazards. 8) On-the-job dips and short-period soaks are not recommended for wood to be used in contact with the ground.

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