While I was repairing shingle siding on a house last fall, my client asked me to look at some rot damage on her screen porch and give her an estimate to repair it. At first glance, the porch appeared to be in good condition, but with visible damage at the base of some of the posts. Then closer inspection revealed that previous repair attempts had masked the extent of the problem, and that the framing would need to be replaced.
My proposed solution involved removing the aluminum screen panels and the porch framing they were attached to, replacing the framing with new material, and trimming the porch exterior with low-maintenance PVC. The project would also include repainting and rescreening the existing panels, which were otherwise in good condition, and replacing the old screen door with a new unit.
The porch began life sometime in the 1970s, when the split-level home was built, as an uncovered porch framed on top of a small concrete slab leading into the back of the house. At some point—possibly when the backyard pool was installed—the small porch and slab had been replaced with a larger slab on grade and screen porch overlooking the pool.
It appeared that untreated fir had been used to frame the porch, including the 4x4 corner post and intermediate posts. Fir, particularly the heartwood, has rot-resistant qualities but will eventually rot when bearing directly on a concrete slab that occasionally gets wet. Some pressure-treated material had been used to make repairs to the framing but mostly as applied patches to the sill plates rather than as replacements (Figure 1).
The concrete slab was in good condition and had been finished with an epoxy floor coating. It looked like the coating might have contributed to the rot problem, as the seam between the coating and the framing appeared to have the potential to trap water blowing in through the screens instead of allowing it to spread out over the floor and dry.