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Hardcoat Stucco is a waterproof product, if installed properly, but improperly installed stucco and stucco cracks are not
waterproof and will leak causing rot and possible mold problems in the house.

Key problem areas in hardcoat stucco are:
Missing or improperly installed window and door flashings and casings.
No weep screeds at base of wood frame walls, and they should terminate 8 inches above finished grade.
Horizontal returns without proper drainage and control joints.
Missing drainage at porch beams and arches.
Improperly installed wire lath, with improper building paper installations.
Missing control/expansion joints (144 sf, no more than 18ft, no more than length to width ratio of 2 ½  to 1.)
Stucco is not coping and should not be installed on top of any wall.
No weep screeds at first or second story of wood over masonry.

The International Code Council (ICC), (BOCA, ICBO & SBCCI), The American Society of Testing Materials (ASTM) and the
Portland Cement Association require a thickness of 7/8 inch stucco over solid framing, using expanded wire lath. (3/8 base
coat – 3/8 brown coat – 1/8 finish coat, not including texture) The wire lath for the stucco should be nailed every 6 inches to the studs. There should be 2 layers of water resistant house wrap or asphalt felts installed under the wire lath. These felts should overlay the weep screeds. There should be weep screeds installed at the bottom of all framing and casing beads installed around all windows and doors to allow for proper drainage. The casing beads are required because stucco doesn’t stick to windows or trim. The joint between the window and the casing bead for the stucco should be filled with a backer rod and caulked. Window sill flashings are required to be sloped to drain and should be lapped over the building paper.

Water Penetration: Minor cracking is not likely to contribute to water intrusion; however, large cracks may allow water to reach the back plane of plaster. A properly installed weather barrier will direct this incidental water to the bottom of the wall and allow it to exit properly at the weep screed.

Inspecting the exterior stucco walls of new & newer existing homes, I typically see most hardcoat stucco, installed improperly. All vertical panels must drain, therefore, if weep screeds are not installed as specified water will remain behind the stucco and cause rot, mildew and mold. Improperly installed stucco, gives the homeowner an inferior wall finish with a reduced life expectancy and an easier access for water to enter the building through the wall finishes.

Most builders recommend that the stucco be sealed. Sealing of the stucco with a good masonry sealer or an elastomeric paint will possibly extend the life expectancy, however, this is a band-aid with minimal effectiveness and should not be accepted in place of properly installed stucco.

Buyers should insist on properly installed stucco. The wire lath should be properly secured and the flashings and weep screeds installed as required. If inferior conditions exist, buyers should request that the home/building be re-stuccoed as per Code.

International One and Two Family Dwelling Code, International Code Council (ICC)
ASTM C-926 – ASTM C-1063
Portland Cement Association

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