When do you need to seal concrete? Anytime you're laying down something impermeable. Concrete is constantly pulling moisture up from the ground and if you have something like carpet, it allows the moisture to flow through and doesn't create problems. However, if you go with something like LVP which doesn't allow mositure to travel through easily, it will create mold on the underside so you must seal the concrete. I recommend checking out the sealer from @happyfeet_international . It goes on nice