Q: The cold months are slowly killing the stone on the exterior of my house and the outdoor fireplace original to my home, built in the 1920s. Is there anything I can do to winterize the stone to protect it from crumbling?
A: Since your stone fireplace is always subject to the elements, the stone will suffer from time and wear. Our part of the country has notoriously harsh winters and scorching summers which are hard on even the most durable of materials. The damage you are experiencing is caused primarily in the winter by the freeze-thaw cycle. Moisture enters the masonry structure (through rain, snow, etc.), then freezes and expands as temperatures fall. In the warmth of the sun (during the day) the moisture thaws, then freezes again at night. This cycle causes the masonry to crack and “spall,” which allows room for more moisture to enter.In an effort to slow this process, I would recommend consulting a masonry restoration professional to inspect the structure. Have the cracks caulked, the mortar patched and any other repairs made to the surface. Then, have a water repellent applied to the fireplace. Do not use a sealant. A sealant may trap moisture in the masonry and can cause more harm than good. Water repellents allow the masonry to “breathe” and aid in the natural migration of water.
Read more here: http://www.kansascity.com/2012/11/07/3903418/handyman-cold-stone-solutions.html#storylink=cpy