Can You Put Mortar Over Stone Walls?

Stone Wall Basics

• Two primary types of stone walls exist, those made from numerous stones bound together with an adhesive building material, and those made from large slabs of stone material such as concrete. Stone walls made from individual pieces such as bricks, cinder blocks and rocks almost always contain mortar. The mortar in these walls serves as the adhesive that holds the pieces of the wall together. You can apply mortar to both types of walls, though the procedure for doing so differs.

Mortar Over Stone Walls

• You can apply mortar directly to solid stone walls made from materials such as concrete or cinderblocks. You can do the same with stone walls made from bricks or rocks, though sources such as “The Complete Idiot’s Guide to Building Your Own Home” recommend placing a metal lath over the wall before covering it with mortar. Metal lath is a construction material that resembles chain-link fence. It provides a better surface material for mortar than a stone wall made from numerous individual stones.

Stucco vs. Mortar

• Technically speaking, stucco qualifies as a type of mortar. If you apply mortar to a stone wall as an adhesive material, it constitutes mortar. For instance, if you cover a stone wall in mortar and place bricks in the mortar, so your stone wall becomes a brick wall, you use mortar. However, if you cover a stone wall in mortar so that the mortar becomes the new surface material, your mortar is considered stucco. When purchasing material for covering your stone wall, keep this distinction in mind, as manufacturers produce mortar suited for the former purpose and stucco for the latter.

Additional Information

• Apply mortar in coats for the best finish and performance. Add a 1/4- to 1/2-inch thick scratch coat, or primer, before applying a thicker layer on top of this. You can add a third layer for extra thickness and protection, though two suffice. If you use mortar as a stucco to refinish a stone wall, purchase stucco in a color you can live with. You can paint stucco, but it’s tricky business and can result in numerous problems. Luckily, paint pigment comprises one of stucco’s ingredients, so you can get the color you want without worrying about painting.