STUCCO FAILURES and REMEDIATION Roger G. Morse AIA

Transcription

1 STUCCO FAILURES and REMEDIATION Roger G. Morse AIA Morse Zehnter Associates Rensselaer Technology Park 165 Jordan Road Troy, NY

2 Florida Environment Hot Humid High ground water Irrigation Mold, rot, rust, corrosion, insect infestation

3 Florida Moisture Dynamics Water intrusion in order of magnitude Liquid water Air infiltration Water vapor diffusion Typically water vapor becomes part of cooling load Risk of condensation

4 Florida Building Construction Single Wythe Masonry Stucco exterior Drywall interior

5 Roof

6 Window

7 Base Of Wall STUCCO PAINT MORTAR JOINTS STRUCK FLUSH L.W. CONC. BLOCK AIR SPACE OR INSULATION PAINT GYP. BOARD MORTAR DROPPINGS WOOD FURRING CONCRETE SLAB DRAWING 2: Base of Exterior Wall of Typical Florida Building

8 Moisture Pathways Florida House Water intrusion in order of magnitude Liquid water Air infiltration Water vapor diffusion

9 Moisture Pathways Base Of Wall

10 Moisture Pathways Window Head

11 Moisture Pathways Top of Wall/Roof

12 Stucco as Waterproofing Specified thickness typically 5 / 8 to ¾ Frequently ¼ or less thick Microcracking Map cracking Stress cracks Shrinkage cracks Expansion joints

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15 Map Cracking

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18 Settlement Crack

19 Shrinkage Crack

20 Shrinkage Cracks

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23 Typical Arrangement of Control Joints MITERED CONTROL JOINT VERTICAL CONTROL JOINT CORNER BEAD HORIZONTAL CONTROL JOINT

24 Control Joint Cross Section MASONRY STUCCO PAINT METAL OR PLASTIC CONTROL JOINT VOID BEHIND CONTROL JOINT DRAWING 5: Control Joint Cross Section

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31 Stucco Accessories

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36 Unprotected Top Edge of Stucco

37 Horizontal CJ Intersects Window Corner Bead

38 Sealants

39 Efflorescence from water Penetration

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44 Water Blister in Paint

45 Water Blister in Paint

46 Summing Up Construction Moisture RH higher immediately after construction Rain during construction Base of wall more wet due to gravity No vapor retarder RH becomes part of cooling load Components of the outside wall, such as wood trim and gypsum board, Windows leak more water than walls Stucco not waterproof Stucco accessories provide water pathways

47 Stucco Advantages Rugged Fire resistant Resists hurricane damage Effective air barrier

48 Stucco Limitations Does not provide water/moisture barrier Water entry can result in IAQ issues Mold Bacteria Insects Water entry can result in material damage Rotting Corrosion Delamination Swelling

49 Fragile Depends on moisture storage capacity of masonry and concrete Frequently found moisture levels near problem levels Particularly at base of walls Can be tipped over edge by small amount of additional water Sprinkler misdirected Window leak Sealant defect Heavy rain Higher incidence of damage where stucco alone is relied on for moisture management

50 New Construction Weep holes at the base of walls Use of less moisture-sensitive interior materials at the base of walls mold/moisture resistant drywall, pressure treated wood, non-corroding metals such as aluminum and stainless steel materials, synthetic carpet tile. Water-resistive coatings on the inside of walls, particularly at the base of the wall. Monitoring of the moisture content of slabs and masonry dry before installation of drywall, insulation, and interior finishes particularly finishes such as ceramic tile, that restrict drying.

51 Stucco Remediation Install drainage plane New stucco Weeps

52 Stucco Amelioration Reduce water intake Patch missing or loose stucco Repair cracks Restoration and/or installation of sealants Restoration and/or installation of coatings Remediation of accessories Retrofitting of weep holes.

53 Mitered Control Joint VERTICAL JOINTS OPEN TO WATER INTRUSION HORIZONTAL JOINT EMPTIES INTO VERTICAL JOINT DRAWING 6: Mitered Control Joint

54 Remediation of Mitered Control Joint VERTICAL CAP CONTINUOUS THROUGH INTERSECTION VERTICAL CONTROL JOINT HORIZONTAL CONTROL JOINT BUTT HORIZONTAL JOINT COVER TO VERTICAL. COMPLETELY FILL SPACE BELOW COVERS WITH SEALANT. DRAWING 7A: Remediation of Mitered Control Joint

55 Remediation Of Horizontal Control Joint MASONRY SAW CUT INTO CMU INSTALL NEW CAP WITH HOOKED END NEW DRIP EDGE OVER EXPOSED JOINT STAINLESS STEEL SCREW AT 16" O.C. HEMMED EDGE DRILL NEW ¼" Ø DIAMETER WEEP HOLE AT 16" O.C. INSTALL SCREEN ACCESSORY

56 Remediation Of Vertical Control Joint MASONRY FILL WITH LOW VISCOSITY SEALANT ⅜" SEALANT HEMMED EDGE BED IN SEALANT FILL WITH SEALANT STAINLESS STEEL SCREW AT 16" O.C. DRAWING 7C: Remediation of Vertical Control Joint

57 Retrofit Of Weep Hole STUCCO PAINT MORTAR JOINTS STRUCK FLUSH L.W. CONC. BLOCK WEEP ACCESSORY AIR SPACE OR INSULATION PAINT GYP. BOARD MORTAR DROPPINGS WOOD FURRING CONCRETE SLAB CLEAR MORTAR DROPPINGS AT WEEP DRAWING 8: Retrofit of Weep

58 STUCCO FAILURES and REMEDIATION Roger G. Morse AIA Morse Zehnter Associates Rensselaer Technology Park 165 Jordan Road Troy, NY