Screened-in porches provide relaxing outdoor shade and protection from insects. But any porch owner knows that most screens are too flimsy to protect against severe weather. After a rainstorm, your screened-in porch might be dripping wet. Unless you plan to convert the screened structure into a solid, walled part of the house, there is no way to keep every drop of rain out. But you can keep most of it out by doing a little weatherproofing.
Installing an extendable overhang is perhaps the easiest and most cost-effective way to keep massive amounts of rain out of your screened porch. While intense rainstorms with violent, horizontal winds might penetrate this defense, an extendable overhang will keep out virtually all vertical rain. The overhang should extend several feet beyond the normal roof of the porch, providing a buffer zone of protection. Expensive models require hand cranks and professional installation, but a quick do-it-yourself overhang is little more than a tarp attached to the existing ceiling and fastened to some sturdy poles. When you want to put away the temporary overhang, simply untie the tarp from the poles, roll it up and tie it off near the roof using a few low-cost ropes.
Use storm windows for your screened-in porch. Just as normal house windows have screens to let in a breeze on a sunny day, screened-porch windows can be covered with attachable glass to keep out weather during harsh storms. These windows attach to the screened-porch windows with small, locking clips. This option usually costs several hundred dollars, but it provides excellent rain protection. Screened-porch storm windows are not as sturdy or leak-free as regular house windows, but they provide some of the best protection available.
Install a drain in the floor of the porch. While this will not keep the rain out, it will prevent or mitigate rainwater damage. Some of the worst discoloration and seasonal wear to your porch's wood or concrete floor will be caused by water. In the case of a wooden porch, installing a drain is relatively simple and cheap; you simply cut a hole in the floor with a jigsaw, pop in a decorative drain cover, and run a gutter underneath the hole to let the water drain outside the porch rather than under it. If your porch has a concrete base, you'll want to consult a professional contractor to do the job.