Stucco Leaks in the HVHZ: Diagnosis Before Repair
You are the general contractor for a 72-unit, six-story condominium in Miami-Dade County, inside the High-Velocity Hurricane Zone. Exterior walls are three-coat stucco over CMU on a cast-in-place frame; windows and balcony sliding doors carry Miami-Dade NOAs. The first strong rain of the season produces water intrusion in 14 units - concentrated at window and door perimeters, at the second-floor slab line, and along the base of walls where efflorescence and a hollow-sounding scratch coat are visible. Destructive openings show no water-resistive barrier behind the metal lath, lath fastened with 1-1/4-inch roofing nails at 12 inches on center, total stucco thickness of about 5/8 inch where the specification calls for 7/8 inch, no weep screed at the wall base, no pan flashing under the balcony doors, and sealant joints at floor lines that were never installed. The stucco subcontractor says stucco has never been waterproof and points at the window installer; the owner's attorney has served a Chapter 558 pre-suit notice.
1. How do you investigate this before anyone touches a caulk gun?
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Treat it as an evidence problem first and a repair problem second. Assemble the paper trail: approved submittals and shop drawings, the NOA numbers and their installation instructions, the stucco system specification, inspection reports, and RFIs from construction. Then compare what was specified and approved against what is in the wall.
Survey each leak pattern separately, because there are at least three mechanisms. Use pin meters and infrared to map moisture, then open the wall at each distinct location - window jamb, door threshold, slab line, wall base. Test the window and door perimeters with an AAMA 501.2 hose test to see whether the opening itself leaks, and flood-test the balcony deck to see whether water is coming under the threshold. Verify lath installation against ASTM C1063 (fastener type and length, spacing, penetration, clearance, weep screed) and the stucco against ASTM C926 (thickness, curing, scratch coat).
On the face of it, the absence of a water-resistive barrier behind the lath removes the drainage plane, so any water that passes the stucco has nowhere to go but inward; short roofing nails do not provide the specified corrosion-resistant attachment into CMU; missing pan flashing at a door is a direct path; and no sealant joint at the floor line leaves a moving joint unprotected. Confirm each with a test, not an opinion.
Use one investigator, photograph everything, and keep chain of custody - this file will be litigated.
2. Which of the observed conditions are code or standard violations in the HVHZ, and what does that mean for liability?
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Several of these are not judgment calls. In the HVHZ, exterior windows and doors must hold Miami-Dade NOAs or Florida product approval, and installation must follow the NOA's installation instructions - a NOA does not cover an installation that omits the flashing and pan the instructions require. The approved stucco assembly and the code's exterior envelope provisions require a water-resistive barrier behind the lath, lapped and integrated with flashing at openings and at the wall base; none is present. Missing pan flashing at balcony doors and no weep screed at the wall base violate the flashing and drainage requirements of the stucco standards (ASTM C1063/C926) and the code's weather-protection provisions. Lath fastened with 1-1/4-inch roofing nails at 12 inches on center does not meet the specified attachment for CMU, and 5/8-inch total thickness falls short of a 7/8-inch specification. The unsealed floor-line joints are a movement-joint failure.
The liability consequence: a building official's inspection and a certificate of occupancy do not relieve the contractor of the obligation to build to the approved documents. Because the deficiencies are objective code and standard violations rather than aesthetic complaints, the 'stucco is not waterproof' defense fails - the design assumes water gets behind the finish and relies on the drainage plane, flashing, and weep system that were omitted. Expect the stucco sub and the GC to be jointly exposed, with a contribution claim against any designer or inspector who signed off.
3. What repair approach do you propose, and how do you allocate cost and manage the 558 process?
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Repair, do not patch. For each affected zone, remove the stucco to the lath and the lath to the substrate, extending until you reach sound, dry material with no elevated moisture readings. Then rebuild the assembly as designed and approved: water-resistive barrier properly lapped and integrated with flashing, new lath with the specified corrosion-resistant fasteners at the specified spacing, pan flashing and sill flashing at every door and window, weep screed and casing beads at the base and openings, correct three-coat thickness, control joints at the specified spacings, and sealant joints at the floor lines and all dissimilar materials. Re-test the openings with AAMA 501.2 and water-test the rebuilt walls before the finish coat is closed out, and document with photos and meter readings at each stage.
Cost allocation: this is not a maintenance item. It is a construction defect inside the warranty period. As GC you owe the owner a conforming wall; you then pursue the stucco subcontractor under its indemnity and warranty, and evaluate a contribution claim against any design professional or inspector whose acceptance allowed the work to proceed. Notify your general liability and builder's risk carriers early and preserve the removed material.
On the 558 notice: respond within the statutory window with an inspection that includes your experts and the subs, do not make admissions, and use the process to get a joint condition survey. A written repair protocol sealed by the engineer of record is the strongest tool you have, both to fix the building and to cap the claim.