Stone veneer on exterior retaining wall

[Jc67roch]

Client wishes to install a stone veneer (3-4" thick) on an existing 12" cmu fully grouted retaining wall which is roughly 4 feet in height above grade. The wall reportedly has a drainage system behind it. Should I recommended installing the veneer with an air gap and ties to the masonry so that any cracking doesn't reflect thru and the stone and cmu backup wall can move independently? Or is it OK to set the veneer in mortar with a scratch coat directly to the cmu retaining wall? Thoughts? Wall will be capped and weatherproofed on the top (with flashing).

 

[concretemasonry]

A wall that has a veneer connected to the basic structural wall may tend to act as composite bonded masonry and any deflection of the main structural element and and movement (vertical, horizontally or diagonally) could the telegraphed to the "veneer" that actually becomes a visual low strength width of the structural wall depending on the construction sequence.

A veneer that is attached by "scratch coat" is just an applied veneer and is not structural, but does see the reaction of the controlling structural element (a 12" grouted CMU) and respond to those effects.

If there is common footing to bear the veneer on, the isolation air gap will minimize the deflection of the main wall far better than a composite acting wall. The air gap also allows the possibility of draining excess moisture (efflorescence) on the face if the basic structure is not drained as well as rumored.

Dick



Engineer and international traveler interested in construction techniques, problems and proper design.

 

[WiSEiwish]

What size veneer? Are they large panels, or is it rubble stone? Larger panels may require anchorage like what is supplied by Hohmann and Barnard which may necessitate a larger gap.