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High Performance Exterior Masonry Wall Design and
Detailing for Water Resistance, Thermal Control
and Crack Control
MASONRY SEMINARMasonry Institute of Iowa
Thursday, March 2, 2017
W. Mark McGinley, Ph. D., PE FASTM
IntroductionThe presentation will address the following learning objectives:• Describe the functions of exterior wall
systems and discuss their behavior as it relates to their function as a building envelope. Address moisture, air, vapor and vapor and thermal barriers.
• Present fault tolerant masonry detailing for moisture penetration, vapor transmission, etc
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Introduction• Present an overview of masonry crack
control and detailing for differential movements.
• Discuss thermal resistance, U and R values and thermal mass effects on energy use in walls systems.
• Present a number of “high” performanceexterior masonry wall configurations andcosts.
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Exterior Wall SystemsFunctions
• Resist loads• Control movement of air• Control movement of
moisture (and vapor)• Control thermal movements• Control sound• Control fire – Masonry does
so inherently• Others
Must do so in a aesthetically pleasing, durable,cost effective manner 4
Drainage Walls – Moisture Resistance
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Single wythes ofmasonry can leak
Drainage Walls
OTHER TYPE BARRIER WALLAll Single wythe
To be effective moisture barrier must detail forFault Tolerance at Critical Locations
Extend flashing on sill up behind window
Make Cavity at least 2 in – Free to allow for tolerance and mortar fins-code – 1” Consider Extending flashing to shelf angle instead under sill brick –short heights –BIA.org -
Positively Anchor Sill
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Show and detail end dams where needed
Step flashing down
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Design for Fault Tolerance
at Critical Locations
Design for Fault Tolerance atCritical Locations
Stainless steel edge 8
Detail and show how to attached flashing to backing system
Extend flashing or you likely have brick staining
If you don’t like drip edge look Alternative way to provide this
PermaBarrier
more later
Be Careful Using Standard Details
PoorWet Bat. insulation
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This is what can be built if you are not careful with details
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Back to Envelope Function: Thermal/Air MovementsThree major mechanisms of thermal energy loss/gain through exterior wall systems:
- Conduction– Radiation- Convection
Lump these into an overall heat transfer coefficient U - See earlier talk - more later
Note R= 1/U11
Thermal Resistance
For conductive Thermal movements -Do one of:
a) Meet prescriptive R , U values in Energy code
b) Do a detailed energy analysis (LEED)
c) Comply with ASHREA 90.1 – Prescriptive& Detailed analysis
See my earlier Talk
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Thermal/Air MovementsAlso a significant amount of heat energy can move through wall systems via air movement in the wall systems. –up to 30%?
So ASHREA 90.1- IBC –Bldgs. must have an air barrier and it must be continuous – JOINTS & PENETRATIONS ARE VERYIMPORTANT – Must be flexible &strong enough to resist pressures.
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ASHREA 90.1 Walls – (Not windows or doors)can be air barriers if they:
(a)Have materials that have an air permeance not exceeding 0.004 cfm/ft2 under a pressure differential of 0.3” w.g. (1.57psf) OR
(b) Assemblies that have average air leakage not toexceed 0.04 cfm/ft2 under a pressure differential of 0.3”w.g. (1.57psf). OR
(c) Building demonstrates air leakage rates of ≤ 0.40cfm/ft2 at a pressure differential of 0.3” w.g. (1.57 psf)(2.0 L/s.m2 @ 75 Pa)
Exception: Buildings in Zones 1, 2, and 3 constructed with mass walls are exempt.
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Vapor ControlWater vapor moves from high to lowvapor pressure: Temp and RH relateda) Put vapor barrier on warm side of
insulation when cooling degree days are greater than heating degree days andhave a vapor permeable Air/moisture barrier.
b) In mixed climates and some wall systems its hard to find warm side- Do not have two vapor retarders!
c) Some times better to have no vapor barrier. Know condensation point!
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Movements in Clay MasonryMovements are produced by:• Thermal differences• Shrinkage• Moisture Expansion• Elastic- deformation both of the masonry
and any supporting structural systems• Creep• Foundation Settlements
See BIA Tech Notes 18 and 18A and NCMATEK Notes 10-1A , 10-2A, 10-3
Movements of Clay Masonry Assemblies Irreversible Moisture
Expansion
Brick are the smallest when cooled from the kiln. Expansion ranges from 0.0002 to 0.0009 in/in Codes gives ke= 0.0003 in/in.
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Control of Movements of Clay Masonry Assemblies (WALLS)
Clay masonry wall panels generally expand if unrestrained.
There is usually no problem in these wallsif they are allowed to move freely.
However, rarely are these wallsunrestrained unless properly detailed.
Control of Movements of ClayMasonry Assemblies (WALLS)
Clay masonry can expand significantlyBenson Conv.Sealant
forced out
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Control of Movements of Clay Masonry Walls
There is two ways in which the designer can deal with this expansion:1. Design the masonry and surroundingelements to resist the stress induced
by the restrained masonry. TECHNote 182. Design the systems so that masonrycan move freely. See TECH Note 18A
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Expansion Joints in Clay MasonryThe primary function of this joint is allow free expansion of the masonry but must also resists water penetration and air movement
Note that expansion joints and control joints not the same
BIA Tech note 18A Vertical Expansion Joints
Note that most sealants require a backer rod and the sealant depth should be about ½ the width of the joint (min ¼”) – Types include urethanes, silicones, polysulfides.
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Expansion Joints Clay Masonry
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Vertical Expansion Joints in Clay Masonry
A conservative estimate of verticalexpansion joint spacing, Se, can be madeusing wej
e (ke k f kt t)100S
w = is the width of the joint (in)
ej = the extensibility of the sealant (%)
Tech note 18 and 18 A suggest equation above can be reduced to
0.09j
e
weS
Vertical Expansion Joints inClay Masonry
For Example: for a 50% sealant, 3/8” joint, and 3/8” joint with the simplified equation:
Se = 17’-4”
½” joint would have a spacing of 23’- 2”
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Placement - Vertical Expansion Joints- Clay Masonry
Consideration should be given for vertical expansion joints at:Corners Offsets OpeningsWall intersections Changes in wall heights Parapets
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Placement of Vertical Expansion Jointsin Clay Masonry
Corners Place jointsnear corner or cracks will developBIATechNote 18A
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Placement of Vertical ExpansionJoints in Clay Masonry
Walls do moveFoundation was bonded to wall and went with movementFlashing canstop this
Corner opening cracks
Placement of Vertical Expansion Joints in Clay Masonry
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You even get this with opening near the corner
Shalimar
Not an expansion joint just caulk
Placement of Vertical ExpansionJoints in Clay Masonry
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Be careful with support at corners
Backing wall
Must have at least two ties on each Leg of column cover
Placement of Vertical ExpansionJoints in Clay Masonry
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OffsetsThis is sort of acorner and an offset movementBenton Cov.
Placement of Vertical Expansion Joints in Clay Masonry
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Placement of Vertical ExpansionJoints in Clay Masonry
Openings
No expansion joint creates crack as shown (TMS)These arenot due tosettlement(up) Sections with openings
move less and providerestraint to upper portions
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Placement of Vertical Expansion Joints in Clay Masonry
Placement of Vertical Expansion Joints in Clay Masonry
Openings
There are openings above and below and a solid section between the edge column section is connected to both and creates distress due to differential movement
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Placement of Vertical Expansion Joints in Clay Masonry
Openings
You should place a vertical expansion joint atopening edges - note if a loose angle is used it must be allowed to expand independent of brick - note min 4”bearing length of angleNeed to put on both sides if large opening or lintel supported on backing
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Placement of Vertical Expansion Joints in Clay Masonry
Intersections and junctions
You should place a vertical expansion joint at changes in heights, thickness an types of walls and on walls that undergo differential warming
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Placement of Vertical Expansion Joints in Clay Masonry
The parapet wall is exposed on three sidesand usually moves more than other walls. Also a parapet has much less dead load restraint.The usual rule of thumb is reduce thespacing of vertical expansion joints inparapet to ½ elsewhere.
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Placement of Vertical ExpansionJoints in Clay Masonry
Hidden jointscan
improve Aesthetics
Horizontal Expansion Joints inClay Masonry
Brick moves up
Frame shortens
Horizontal expansion joints typically placed below shelf angles
They should be sized for the masonry and frame movements
Ensures Masonry Non loadbearing39
Note that the total joint size must include the angle thickness and it will be very difficult to get a 3/8” thickness
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The space below the shelf angle must be free to move and is the critical dimension for the joint size
Horizontal Expansion Joints in Clay Masonry
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Can hide the joint with lipped brick – BUT THESE CAN CHIP BADLY
What’s wrong withthis detail?
Placement of HorizontalExpansion Joints in Clay Masonry
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Problems – Closed mortar joints - Harbor
Placement of Horizontal Expansion Joints in Clay Masonry
Popped out –no ties
Crackedaway
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Problems – Closed mortar joints – BentonConv
Placement of Horizontal Expansion Joints in Clay Masonry
Spalled Faces
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Shrinkage (contraction)Control in Concrete MasonryUsually shrinkage in concrete masonry only a problem if restrained - NCMA Tek 10-1A, 10-2C, 10-3.
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Control joints - creates a weakness in the masonry wall and allows thecracks to form in the joint NCMA Tek Note 10-2A
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Control joints - BOND BEAMS – need specialdetailing
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Control Joints in ConcreteMasonry
Use control joints with a minimum amount of reinforcing shown in Table 1 of NCMA Tek 10-2 C - based on experience may be adjusted
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Control Joints in Concrete Masonry Placement NCMA Tek Note 10-2A
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Some Other ConsiderationsDifferential Movements of Masonry andthe structure can be an issue:•Don’t rigidly connect masonry that is supported on the structure to masonry that is supported on the ground.•Allow the exterior wythe of masonry tomove independently.•Use adjustable ties with enough travel
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Ties
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Some Other Considerations
Differential Movements of different masonry elements is an issue:
Be careful of movement of different color, and or types of masonry, they move differently
Also separate load bearing andnon load bearing walls
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Some Other ConsiderationsConcrete block and brick - different color
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Some Other Considerations
Had controljoints but too farapart.
No cracking in dark CMU but cracking in lighter CMU
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Some Other Considerations
Separate dissimilar materials
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Some Other ConsiderationsCoping is very important ( joints need sealing)
Movement of outer wythe will add up and be the worst at copingMay pop the coping and or roll over the parapet Recommend a flexible coping or expansion joint & TWF
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Some Other ConsiderationsDETAILS – DETAILS – DETAILSVery important that joints go through all systems
High Performance Masonry Walls?
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NCMA- TEK 6-1B
ICF From WebMasonry Cavity Wall
I was asked a while back whether you can design a high performance masonry wall – Like ICF
The answer is yes !!!!!
. Data from Sherman Carter Barnhart –Architects
Typical ICF system – R 23 –has an integral Air/moisture and vapor barrier – also structural
~ $31.4/SF (KY-values)
Note - This is 16”+ thick wall
If this ICF Wall defines high performance Can a masonry wall be designed to perform similarly?
YES 59
.Try rigid insulation board in the cavity – Initially assume polyisocyanurate 3”Note the R value ranges from 24.3 to about 25.8 depending on the density of the materials and the temperature in the air spaceThe air/vapor barrier on the masonry wall can be achieved by a spray-on mastic or trowel-on material behind the insulationOr – use foil faced insulation and taped seams – note that R value goes up to 25.8 to 28.3 with the foil facing in cavity.
R-Value =24.3
Spray or trowel-on air barrier or seal insulation seams
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8-in. concrete masonry backup wythe, grouted48 in. o.c. vertically and 12 ft o.c. horizontally
3 in. polyisocyanuraterigid board insulation1 in. airspace4-in. clay brick veneer
Point- the insulation, air barrier, vapor barrier and moisture barrier protectedin cavity
. Try more conventional rigid insulation board in the cavity –Say assume 3.5”polyurethane, R~22
Note if 3” of insulation is used R value ranges from 18.7 to about19.8 depending on the density ofthe materials and the
The air barrier on the masonry wall can be achieved by a spray on mastic behind the insulation or tape/seal seams.
Spray on mastic will also formwater/vapor barrier.
312 in. extruded polystyrene temperature in the air space
rigid board insulation
8-in. concrete masonrybackup wythe, grouted48 in. o.c. vertically and12 ft o.c. horizontally
1 in. airspace4-in. clay brick veneer
R-Value =21.7PossibleSpray or trowel-on barrier
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Point- the insulation, air barrier, vapor barrier and moisture barrier protectedin cavity
. OR - Try spray on closed cell Polyurethane foam Insulation
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Spray foam forms Moisture/Air/Vapor Barriers- Joints critical – Inspection by AABA certified individuals- (BASF-walltite)
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.Try 3” of spray foam insulation in the cavity – R-6.8/inch
Note if 3” of insulation is used R value ranges from 23.4 to about25.7 depending on the density of the materials and the temperature in the air space
The air/moisture/vapor barrier on the masonry wall is integrally contained in the insulation system
8-in. concrete masonry backup wythe, grouted 48 in. o.c. vertically and 12 ft o.c. horizontally
3 in. spray polyurethane foaminsulation1 in. airspace
4-in. clay brickveneer
R-Value = 23.4
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SUS.TAINABLE DESIGN “DOING MORE WITH LESS”– OR AT LEAST DOING THE SAME WITH LESS Perhaps most effective walls have R 14 to 15 – (colder climates R)
R-Value =14.2
8-in. concrete masonry backup wythe, grouted 48 in. o.c. vertically and 12 ft o.c. horizontally
2 in. extruded polystyrene rigid board insulation1 in. airspace4-in. clay brick veneer
R-Value = 15.1
8-in. concrete masonry backup wythe, grouted 48 in. o.c. vertically and 12 ft o.c. horizontally
1.5 in. polyisocyanurate rigid board insulation1 in. airspace
4-in. clay brick veneer65
R-Value = 14.2
48 in. o.c. vertically and 12 ft o.c. horizontally
2 in. extruded polystyrene rigid board insulation1 in. airspace4-in. clay brick veneer
Thermal massStudies at ORNL and elsewhere have shown the best performance in mass walls is obtained by putting the mass on the interior of the insulation
The mass on theinterior of insulation and exposed to regulated temp helps mitigate interior temp variations and shifts peak loading – saves energy and peak
8-in. concrete masonry shaves –possiblebackup wythe, grouted thermal storage use
Insulating mass from interior allows internal loads to spike temps and reduces effect of mass –up to 5% 66
Cost of this wall isapproximately :
$28.50/ft2 to 30.6/ft2 (KY values) Based on prevailing wages with spray-on air barrier
8-in. concrete masonry backup wythe, grouted48 in. o.c. vertically and12 ft o.c. horizontally
3 in. polyisocyanurate rigid board insulation1 in. airspace
4-in. clay brick veneer
R-Value =24.3
.Wall Costs
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312 in. extruded polystyrene
rigid board insulation 1 in. airspace
8-in. concrete masonry backup wythe, grouted 48 in. o.c. vertically and 12 ft o.c. horizontally
4-in. clay brick veneer
. R-Value =21.7 PossibleSpray ortroweledbarrier
Cost of this wall is approximately about the same
$28.50/ft2 to 30.0/ft2
(KY Values)Based on prevailing wages with spray-on air barrier
Remember ICF Cost~$31.4/ft2
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.Try 3” of spray foam insulation in the cavity – R-6.8/inch
Cost of moisture/air barrier is about ~$1.10/ft2 and the cost of the 3” polyiso. insulation ~
2$2.50/ft so
Spray insulation this is aboutthe same cost as the polyiso.foil faced board.
8-in. concrete masonry backup wythe, grouted 48 in. o.c. vertically and 12 ft o.c. horizontally
3 in. spray polyurethane foaminsulation1 in. airspace
4-in. clay brickveneer
R-Value =23.4
Cost of Spay insulation – General valuesf 1.0 inches = R- 6.3 Budget $1.80/sq.ft.
1.5 inches = R- 9.45 Budget $2.20/sq.ft.2.0 inches = R-12.60 Budget $2.80/sq.ft.2.5 inches = R-15.75 Budget $3.40/sq.ft3.0 inches = R-18.90 Budget $4.00/sq.ft
With joint sealing and opening flashing– about $4- 6/ft2
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R-Value = 14.2
8-in. concrete masonry backup wythe, grouted 48 in. o.c. vertically and 12 ft o.c. horizontally
2 in. extruded polystyrene rigid board insulation1 in. airspace4-in. clay brick veneer
.Wall CostsMore conventional configurationshould be closer to about$28.5/ft2 - $29 (KY Values)
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J.B
.SPE
EDSC
HO
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OF
ENG
INEE
RIN
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THANK YOU !
QUESTIONS?
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