If your crawl space has a persistent moisture problem, you fortunately have many solutions for dealing with it. In addition to treating the root problem, there are several tools that can continue to remove excess moisture.
Find out why your crawl space has a moisture problem in the first place. Common sources of moisture include:
Floor drains backing up
A leak in the roof
Inspect the exterior of your home as well to find a possible source of moisture. Dig around your foundation to find an area that is very moist. You might have a downspout that is directing moisture near your foundation because of a poor design or because the downspout is leaking. If the downspout is too short, you can get an extender so the moisture from your roof is carried farther away from your foundation. Even if your home seems to slope away from your foundation, the water may still find that the path of least resistance is toward your crawl space.
If you do not treat the root cause of the moisture, every other measure will simply be a band-aid. However, you may simply live in a high-humidity area. If this is the case, you will simply need to manage your moisture problem in the long-term.
A sump pump, especially a completely submersible sump pump, can remove a considerable amount of water from your crawl space. This device uses a float arm that activates the sump pump when the water causes the float arm to rise above a certain point. You will need to place the sump pump in a sump, which is a hole in the ground. You will want the sump to be near the part of the crawl space that collects the most water.
After you have installed a sump pump, you will want to install a vapor barrier. Vapor barriers are made from six millimeter polyethylene sheets. You will need to separate these sheets, cover the foundation walls with these sheets and tape the seams together using duct tape. However, if you have termites, you will not want to run the vapor barrier all the way up to the floor joists because the vapor barriers will make it easier for the termites to construct hidden mud tunnels.
A dehumidifier is another useful tool for keeping your crawl space dry and it is also easy to use. All you have to do is regularly remove the water that is collected by the dehumidifier. Otherwise, it reduces moisture entirely on its own.
If the damage in your crawl space is significant, it might be a better idea to work with a professional crawl space repair company to get everything taken care of.