A damp and musty smell in the basement is often always a sign of a waterproofing issue. Because basements are below ground structures, they are prone to water and moisture damage. Damp and musty smells indicate moisture infiltration and the growth of mold or mildew.
The best way to deal with damp and musty smells is to get in touch with a basement waterproofing contractor. They will inspect your basement and determine the best way to deal with moisture problems.

If there is an odor in your basement that is like that of sewage, you should deal with this as soon as possible. It could be sewer gas accumulating in your basement. This gas is both explosive and toxic especially when it is in a confined space such as your basement. The sewage odor could also be the result of sewage seeping into your basement.

The first step to take is to contact a professional basement waterproofing contractor. They will help you identify where the odor is coming from. You may need to hire a plumber to deal with the sewage leakage. Your waterproofing contractor will help waterproof your basement to prevent penetration of toxic gases and leaks in future.

The smell of ammonia is often an indicator of the presence of animal urine in your basement. This smell indicates that you have a pest infestation or that there are animals that are gaining access to your basement. The problem with animal urine is that it is a breeding ground for bacteria. It can also penetrate porous surfaces causing stains and a bad odor that are hard to get rid of.