Ed is a do-it-yourselfer who is happy to share some of his ideas and experiences in this monthly column.
No matter how your porch was built, or how old or new it is, it should shed water. Many of the old-timers, who seem way smarter than we are today, cared less about how a porch with a slope looked than how water ran off of it. All you need to do is look at some old, well-built porches, and you can see the disparity between the handrail/banister (level) and the porch walking surface (sloping). Water running off not only means that porch wood will last longer, but it also means that whatever is below that porch (perhaps a basement) will likely stay drier.
Many of my articles are based on work done at the old office and superintendant’s house at the Oak Park Cemetery (New Castle, PA), including this one. Look carefully at the way someone over the years simply installed plywood over the rebuilt joists and the front porch.
The problem manifested itself in that the basement area under the porch often showed signs of wetness – not from any wall leakage, but from rain puddling on the level porch and seeping through plywood joints (and maybe the plywood itself). The plywood was “treated” and actually not in bad shape. It was just installed flat, so windblown rain onto the porch simply did not run off. If you use the internet and look up what a porch flooring slope should be, you’ll find all sorts of answers. My take is that you should get whatever you can, so long as it looks good, and more is better. I’d say a minimum of an inch per 10 feet, though, which is hardly noticeable. Again looking at what I had to work with, and using the existing plywood as a base, I decided to sacrifice a bit of house exposure, and raise the house end of the porch, rather than lower the outboard end of the porch. Does that make sense? I knew there would be less of a “stepdown” from the house door onto the porch, which could create its own problems (like snow buildup) but the width of the porch pretty much minimized that issue. SO, I decided to install new kiln-dried, pressure-treated tongue-and-groove flooring right over the existing plywood. To facilitate a slope, I installed featherboards which would support the new flooring. You might be able to tell from the photo that each featherboard going in the direction from the porch edge to the house is slightly taller, or is shimmed to a higher height.
Solidly anchored in place and spaced at 16” on center, those variable-height risers would provide a slope for porch flooring secured to them. I took it a step further, and decided to make this porch, which has two spots for ingress/egress (after I removed an errant section of railing once put in place) slope in two directions. The section with access from the west slopes from the house west to the porch edge, and the section with north access slopes to the north. To make an aesthetically pleasing transition, I installed a 45-degree joint at the porch corner.
One of my favorite sayings is that “Everything is more difficult, takes longer, and costs more than you first think.” In this case, you’ll see that by installing ¾” thick boards OVER the existing porch, and gaining the proper pitch, I had to use a cutoff saw and carefully remove just enough of the lower projection on each mini-section of handrail. Without doing so, the new porch surface would just not fit in place. Hopefully the ornate metal gods will forgive this transgression. Putting the porch on grade did solve the basement water problem!
I hope all your projects go well. Thanks for reading, and happy restoring!
Ed