There are two schools of thought regarding limestone and sandstone. One idea for how to seal natural stones is to seal them when they are horizontal and leave them unsealed when they are vertical. Other people believe that the stones should be sealed regardless of where and how they are being used. You should consult with your building stone supplier before making any decisions about sealing your stone. An expert will know exactly how to care for your stone.
How to Seal Natural Limestone and Sandstone
Once you have the best sealer available, again consult an expert, you will want to test it on a small section that is not noticeable. If this works, begin sealing the stone.