A technical review of proper masonry detailing
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A Technical Review of Proper Masonry Detailing. Matthew A. Dettman, P.E. Overview. Water Penetration Resistance Wall Systems Flashing and Weep holes Coatings Differential Movement Cracking Movement Joints. Problems related to water penetration. Water entry into interior Efflorescence

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Overview l.jpg
Overview

  • Water Penetration Resistance

    • Wall Systems

    • Flashing and Weep holes

    • Coatings

  • Differential Movement

    • Cracking

    • Movement Joints


Problems related to water penetration l.jpg
Problems related to water penetration

  • Water entry into interior

  • Efflorescence

  • Spalling

  • Corrosion

  • Reduced insulating capacity

  • Staining / Mold / Mildew


Keys to providing water penetration resistance l.jpg
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

  • 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

  • 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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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

Galvanized 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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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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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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Typical Spacing and Locations of Expansion Joints

  • Long Walls

  • Corners

  • Setbacks & Offsets

  • Parapet walls

  • Beneath shelf angles






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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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Bond Beams

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



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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> 0.002 - see Table 4.

  • See Table 3 for As/An = 0.0007 minimum requirement.

  • Minimum reinforcement ratio need not apply if length is < ½ maximum length shown in table.

  • CCC’s 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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1

Table 3—Maximum Spacing of Hor. Reinf. for A

>

0.0007A

s

n

Maximum spacing of horizontal reinforcement, in. (mm)

Reinforcement size

Wall

thick

in.

4x

4 x 8

4 x 9

2x

2 x 8

2 x 9

#5

#4

#3

3/16

gage

gage

3/16

gage

gage

Ungrouted or partially grouted walls

6

144

128

64

72

56

48

40

24

24

8

144

96

40

64

48

40

32

24

16

10

136

80

32

56

40

32

16

16

16

12

120

72

24

48

40

32

16

16

16

1. A

includes cross-sectional area of grout in bond beams.

n


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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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