So you have successfully dampproofed your basement, but you now face another question, how long until it needs to be done again. In most cases, you should be able to measure the time in between dampproofing in years, with the average being about 10 years. If your home is built on earth that is often saturated in water, such as marshy areas, your dampproofing won’t last nearly as long. There’s little to counteract this besides dampproof every fall before the wetter seasons arrive. Also, the more comprehensive and professional your approach to dampproofing is, the longer it will last. If you’ve only done the basics to protect your basement, expect to dampproof often.