I recently had to intercede in a building project, and research stucco code and best practice. Here’s what I wrote up for the GC. I post it in hopes it is useful to others:
Installation is to follow ASTM C1063, and proceed as highlighted below:
Existing stucco to be removed 6" around each corner, within 6" of the existing parapet, and to grade.
Fasten any loose siding boards prior to continuing.
Add parapet flashing, as far as practical under the existing paper.
All flashing and paper must lap, in the manner of shingles.
Flash penetrations with QuickFlash products.
Use two layers of Grade D building paper, lapped vertically and staggered horizontally.
Lath must be furred out 1/4" from the wall:
– Self-furred woven stucco lath must be used dimple side toward wall. Staples must be in dimples vertically, and every 16" horizontally.
– Flat woven ‘chicken wire’ lath must secured with FastenSeal nails, every 7" or better vertically, every 16" horizontally. Lath must be 20 gauge galvanized.
– Diamond lathe must be self-furred with dimples to the wall, with each dimple filled with a FastenSeal screw.
Most fasteners must embed 3/4" into the existing studs. Snap a chalk line if needed.
Lath & paper must butt to window, overlapping window flashing. No lath or paper is to foul the stucco mold.
Bare wood directly touching stucco must be primed with at least two layers of exterior grade primer.
At corners, use pre-made corner mesh.
At the seam to old stucco, roughen the edges, and apply concrete bonding agent (on this job old wire is rotten).
Paper must extend to fully down to the weep screed detail, depending on wall section.
Weep screed need not extend around corners, instead match existing detail.
I recently had to intercede in a building project, and research stucco code and best practice. Here’s what I wrote up for the GC. I post it in hopes it is useful to others:
Installation is to follow ASTM C1063, and proceed as highlighted below:
Existing stucco to be removed 6" around each corner, within 6" of the existing parapet, and to grade.
Fasten any loose siding boards prior to continuing.
Add parapet flashing, as far as practical under the existing paper.
All flashing and paper must lap, in the manner of shingles.
Flash penetrations with QuickFlash products.
Use two layers of Grade D building paper, lapped vertically and staggered horizontally.
Lath must be furred out 1/4" from the wall:
– Self-furred woven stucco lath must be used dimple side toward wall. Staples must be in dimples vertically, and every 16" horizontally.
– Flat woven ‘chicken wire’ lath must secured with FastenSeal nails, every 7" or better vertically, every 16" horizontally. Lath must be 20 gauge galvanized.
– Diamond lathe must be self-furred with dimples to the wall, with each dimple filled with a FastenSeal screw.Really?
Most fasteners must embed 3/4" into the existing studs. Snap a chalk line if needed.
Lath & paper must butt to window, overlapping window flashing. No lath or paper is to foul the stucco mold.
Bare wood directly touching stucco must be primed with at least two layers of exterior grade primer.
At corners, use pre-made corner mesh.
At the seam to old stucco, roughen the edges, and apply concrete bonding agent (on this job old wire is rotten).
Paper must extend to fully down to the weep screed detail, depending on wall section.
Weep screed need not extend around corners, instead match existing detail.
I based that on Alabama Metal Industries Corporation’s installation specifications for self-furred diamond metal lathe, which has a surface studded in dimples. You’re supposed to fasten at the dimples only. (The guide warns ‘not to negate the furring mechanism’). In our case I specified FastenSeal screws because they’re inexpensive, code compliant, and, well, have caulk. Also the siding in this case is all wobbly (the prior wall failure left all the wood OK, but the nails are all rusty and many of them just snap off) so the extra security of screws seemed useful.
The GC could choose any code compliant style of lath, but could not choose to to simply power staple the mesh flat to the wall with 100’s of staples like before.
I also replaced the line reading ‘two layers of paint’ with a clause about ‘sticky flashing’. This retrofit job has untreated plywood furrnig outside the WRB, that would otherwise directly contact the stucco.