Your basement's biggest threat is water damage. Because basements are located below ground, they are susceptible to flooding and are likely the first place that plumbing damage and mold growth will manifest. Basement waterproofing can prevent water from entering and damaging your basement, and there are a few clear signs that can indicate to you if you are in need of having such waterproofing installed.
If you notice a musty, earthy odor in your basement, especially if it occurs with greater intensity after it rains or when the temperature increases, you may want to look into basement waterproofing. The smell is likely coming from unseen mold and mildew growth, which is a serious health concern and can quickly spread throughout the rest of your basement if not properly dealt with.
Physical signs of dampness are perhaps the clearest indication that you need to consider installing a waterproofing membrane in your basement. Discoloration is the surest sign that water has managed to make its way onto a surface in your basement, regardless of if the surface is actually wet at the time. Further, if you have wooden floors or paneling in your basement, or wallpaper or paint on the walls, look out for signs of warping, bubbling, peeling or similar damages, as these can indicate prolonged exposure to moisture.
If the concrete of your home's foundation is exposed in your basement, keep an eye out for any signs of cracks. Even hairline fractures that only cover a small portion of the wall at first can quickly spread into much more serious breaks that threaten the structural stability of your home. These cracks are almost always due to water pressure and present a clear path for additional water to enter your home, effectively creating a positive feedback loop that will undermine the strength of your foundation and increase the likelihood of water damage in your basement.
In a similar vein to the above points, if you have wood panels or drywall walls in your basement, keep an eye out for actual bowing or warping of the material. This represents water that has managed to make its way behind the wall itself, causing the wall to begin to bow inwards. This is a serious sign of water damage, and likely means that excessive amounts of water are managing to make their way into your basement. These bulging walls also present the ideal place for mold and mildew to begin growth.
If you believe you need waterproofing in your basement, talk to a company like John's Waterproofing for more information.