A Technical Review of Proper Masonry Detailing

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A Technical Review of Proper Masonry Detailing

• Matthew A. Dettman, P.E.

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Overview

• Water Penetration Resistance
• Wall Systems
• Flashing and Weep holes
• Coatings
• Differential Movement
• Cracking
• Movement Joints

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Problems related to water penetration

• Water entry into interior
• Efflorescence
• Spalling
• Corrosion
• Reduced insulating capacity
• Staining / Mold / Mildew

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Keys to Providing Water Penetration Resistance

• Quality Materials
• Good Construction
• Proper detailing
• Maintenance

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Keys to Providing Water Penetration Resistance

• Quality Materials
• Good Construction
• Proper detailing
• Maintenance

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Three Basic Wall Types

• Drainage Wall
• Barrier Wall
• Single Wythe Wall

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Drainage Wall
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Drainage Wall

• Water travels down back side of outer wythe,
  collected on flashing, and channeled to exterior
  through weep holes
• Examples
• Cavity walls
• Masonry veneer walls
• Rain screen walls

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Drainage Walls Requirements

• 2 to 4 ½ inch clear cavity
• Flashing and weep holes to channel out excessive
  water

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Rain Screen Wall

• Equalizes pressure within cavity
• Vents at top and bottom of wall or panel
• Flashing and weep holes
• Compartmentalized
• Allows for ventilation and evaporation

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Barrier Wall

• Collar joint between wythes acts a barrier to
  moisture along with the thickness of the wall
• Examples
• Brick and Block Composite Wall

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Barrier Wall

• Voids allow water penetration
• Must be filled solid with mortar or grout

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Single Wythe Walls
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Single Wythe

• Masonry units with coating or integral water
  repellent
• Mortar with integral water repellent
• Through-wall flashing
• Weep Holes
• Vents

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Flashing Details

• Locations
• Placement

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Flashing Locations

• base of wall
• sills
• heads of windows
• at shelf angles
• copings
• lower wall/ higher roof intersection
• other discontinuities in air space

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Good Flashing Detail
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Poor Detail
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Drip Edge
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SS Drip Edge
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Shelf Angles
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Flashing Single Wythe Walls
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Flashing with Shear Transfer
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Flashing Reinforced Wall
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End Dams
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Flashing Laps
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Drainage Materials
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Weep Holes
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Weep Tubes
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Vent Weep Holes
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Rope Wicks
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Flashing Materials

• Sheet Metal
• Composites
• Plastic and Rubber
• Compounds

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Sheet Metals
Advantages
Disadvantages
Material
Hard to solder and form Damaged by excessive
flexing and can stain Difficult to solder,
corrodes early in acidic and salty air
Durable, non staining Durable Easy to paint
and durable
Stainless Steel Cold-Rolled Copper Galvanize
d Steel
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Composites
Advantages
Disadvantages
Material
Difficult to solder, damaged by excessive
flexing, metal drip edge suggested Degrades in
UV light, more easily torn than metal
Flexible, durable, non-staining Easy to form
Lead-coated copper Copper laminates
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Plastics and Rubber Compounds
Advantages
Disadvantages
Material
Flexible, easy to form, non-staining Fully
adhered, separate lap adhesive not needed, self
healing, flexible, easy to form and join Easy to
form and join, non-staining, low cost
Aesthetics if not used with a metal drip edge,
full support recommended Full support required,
degrades in UV light, metal drip edge
required Easily damaged, full support required,
metal drip edge required, questionable durability
EPDM Rubberized asphalt PVC
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Bldg felt and poly sheeting
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Colorless Coatings

• Used for a variety of reasons
• Recommended for Concrete Masonry
• Questionable for Clay Masonry

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Possible Dangers

• Water can still penetrate
• Could cause spalling
• If efflorescence occurs under coating, it may be
  impossible to remove
• Recoating will be necessary

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Coating Types

• Colorless Coatings
• Paints

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Colorless Coatings

• Penetrating
• Silanes
• Siloxanes
• Film-forming
• Acrylics
• Stearates

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Coating Types

• Paints
• Cement based
• Latex
• Alkyd
• Oil-based Paints

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Differential Movement

• Movements
• Temperature Movement
• Moisture Movement
• Elastic Deformation
• Movement Joints
• Design
• Placement

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Causes of Cracking

• Differential Movement
• Restraint
• Settlement
• Elastic Deformations
• Creep

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Types of Movement
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Temperature Movement

• Coefficient of Thermal Expansion
• Brick 3.6 x 10-6
• Concrete Masonry 4.3 x 10-6
• Aluminum 12.8 x 10-6
• Steel 6.5 x 10-6

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Moisture Movement

• Brick - irreversible expansion
• Concrete masonry drying shrinkage and
  carbonation

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Types of Movement Joints

• Expansion Joint - Brick Masonry
• Control Joint - Concrete Masonry
• Building Joint - Structures

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Expansion Joint

• Used in Clay Masonry
• Used to separate brick into sections so cracking
  will not occur
• Horizontal / Vertical
• Entire joint is unobstructed and formed from a
  highly elastic, continuous material

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Types of Expansion Joints(Details)
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Expansion Joint
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Typical Spacing and Locations of Expansion Joints

• Long Walls
• Corners
• Setbacks Offsets
• Parapet walls
• Beneath shelf angles

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Expansion Joints at Corners
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Horizontal Expansion Joint
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False Horizontal EJ
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Hiding Expansion Joints
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Control Joint

• Used in Concrete Masonry
• Relieve horizontal tensile stresses
• Reduce restraint and permit longitudinal movement
• Separate dissimilar materials

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Types of Control Joints

• Pre-formed gasket
• Formed paper
• Special shape units

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Pre-formed Gasket
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Formed Paper (also known as Michigan Joint)
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Special Shape Unit
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Joint Reinforcement at CJ
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Bond Beams

• Do not cut bond beam reinforcement unless
  specifically indicated on the plans

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Control Joint Locations
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Control Joint Spacing

• Two methods
• Empirical
• based on historical performance
• Engineered
• based on a crack control coefficient

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Empirical Control Joint Criteria

• Spacing for above grade exposed concrete masonry
  walls
• Distance between joints is the lesser of
• Length to height ratio or
• 1 ½ 25 feet
• Notes
• Based on horizontal reinforcement of 0.025
  in.2/ft
• Applies to both Type I and Type II units
• Can be modified based on local experience

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Engineered Crack Control Criteria
Criteria for Controlling Cracking in Reinforced
Concrete Masonry Walls

Crack Control Coefficient in./in.
(mm/mm) ________________ __________
__________0.0010 ___ 0.0015 Maximum wall
_length, ft (m)_________25 (7.62)__20 (6.10)
panel dimensions_ length/height ratio_
_____2 ½ ______2___ Min. horizontal reinf. ratio
As/An 0.0007
0.0007 Notes As cross-sectional area of
steel, in2/ft (mm2/m) An net cross-sectional
area of masonry, in2/ft (mm2/m)
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Engineered Crack Control Criteria (cont.)

• Notes
• Need not apply if As/An gt 0.002 - see Table 4.
• See Table 3 for As/An 0.0007 minimum
  requirement.
• Minimum reinforcement ratio need not apply if
  length is lt ½ maximum length shown in table.
• CCCs less than 0.0010 may be available in some
  areas and spacing should be adjusted accordingly.
• Control joint spacing may be adjusted up or down
  based on local experience.

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Brick and Block Together

• Align Expansion Joints and Control Joints

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Bond Breaks

• Use to separate bands of different masonry types

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