Common Woods and Grades

• Lumberyards sell their wood in varying grades according to the condition of the wood, moisture content and frequency of defects such as knots or warping. "Low grade," "poor" or "fair" classifications require more maintenance. Cedar, redwood, cypress, white and sugar pines are excellent choices. Ponderosa pine, hemlock, spruce and lodgepole pine are fair choices. Bottoming out at poor grade include southern pine, Douglas fir, red pine and western larch.
  
  

The Problem With Pine

• Many builders use fair grade pine wood for framing exterior structures. Pine is abundant, inexpensive and very manageable for the multitudes of cuts and fasteners required for most front porch structures. Pine, a resinous softwood, has a large grain, and the knots often bleed small amounts of resin for several years. The resin may ooze through inferior-grade white paint, producing shadowy, oval-shaped yellow stains on the white painted surfaces.
  
  

Other Wood Types

• Less common, some front porches are constructed of poplar, redwood and cedar wood. Poplar is an excellent replacement for pine. Its tight grain and dense, compact cell structure provide a smooth, solid surface for white paint. Poplar, redwood and cedar are more expensive than the typical pine wood, however, and many homeowners opt for the higher-maintenance pine. As with pine, redwood and cedar woods bleed resins, called tannins. Meticulous application with an oil-based primer and high-quality paint usually resolve most tannin issues.
  
  

Proper Primer Preparation

• Many front porches are constructed of pine, yet oozing resin does not seem to be overtly problematic for homeowners. The cure for resinous knots rests in high-quality primer and paint with careful application. Primer provides a superior base for white paint. An oil-based primer is the best choice for resinous softwoods. The oils soak into the large pores and harden to form a thin tough coating over the wood. Unfortunately, oil primers release volatile organic compounds (VOC) and dry slowly. Latex primers dry very quickly and are water soluble but may not protect against bleeding knots from low-grade woods. When choosing white paint, select a paint high in resins with 100 percent acrylic content. For best results, use only oil-based paints on oil-based primers and latex-based paints on latex-based primers.