Natural Stone – Thin Veneer
Preparing the Wall Surface
Unsealed Masonry: Stone veneer can be installed directly over cleaned, unsealed masonry walls using metal lath fastened to the existing structure. Fasten the lath with masonry nails or masonry screws.
Sealed Masonry: If you can sand blast or otherwise remove the sealer, install the veneer as you would over unsealed masonry. If the sealer can not be removed:
- Use masonry nails or masonry screws to fasten metal lath to the existing structure.
- Apply a scratch coat of mortar mix (at least 1/2″ thick) to the metal lath. Be sure to work the mortar mix into the lath.
- As the mortar begins to set, use a brush to rough up the scratch coat and allow the coat to set completely. The roughness provides a good bonding surface for the mortar used to adhere the stones.
- Wood: Nail double D paper to the wood to create a vapor barrier. Then apply metal lath and a scratch coat of mortar as above.
Laying the Stone
- In a wheelbarrow or mud box, mix a bag of mortar to roughly the consistency of mashed potatoes.
- Apply a thin coat (1/4″ to 1/2″ thick) of mortar to the entire wall. Let this base coat dry for 12-24 hours. After 12-24 hours, come back to begin laying the stone.
- Butter the back of a stone with about 1/2″ of mortar.
- Press the stone into the bottom of the wall. Wiggle the stone slightly back and forth until it seats against the wall. Take care not to press all the mortar mix from between the stone and the wall.
- Continue laying the bottom course to the end of the wall. Note that as you lay large stones, it may be necessary to place smaller stones in gaps and along uneven edges to fill in the wall. It may also be necessary to use the brick chisel to cut stones at the ends of the wall. Selecting good stones for the edges before you start on the wall reduces the need for chiseling and makes your work look more natural.
- Apply the next courses in the same manner as the first. Be sure to interlock each course so that the joints are staggered from course to course.
- If you are veneering the foundation of a structure, flash the top course to keep water from getting behind the stone. If you are veneering a garden wall, stop slightly short of or even with the top of the wall. Cap the wall with stone laid horizontally across its top, or a natural cutstone wall cap.
- Once the mortar has hardened some, but not completely set, use a jointer or the point of your trowel to dress the joints.
- Clean any mortar from the face of the stones with a stiff-bristled brush. Do not allow mortar to set on the face of the stone.