2009 IBS - High Performance Masonry Walls

High Performance Residential Masonry Walls in the 21 st Century Presented by: Mike Coulton Director of Product Development Benjamin Obdyke Incorporated

AGENDA
It’s about moisture management
Why now?
Case study
Solution options
Selecting the right solutions
© 2008 Benjamin Obdyke Incorporated

Introduction
Need to incorporate good moisture management solutions
Ward off problems – occupant health mold, rot, sustainability
Energy efficiency of wall
Code changes – compliance

Why Now?
We’ve been building masonry walls for centuries - why water problems now?
Mass walls vs. veneer on wood framing
Insulation practices – Energy crisis #1 (1970s) and #2 (2000s)

Why Now?
Brick, stucco, stone walls have always absorbed lots of moisture – very porous
Before tight envelopes (insulation and water/air resistive barriers):
Winter – dried inside to outside
Summer – dried outside to inside

Why Now?
Tightened building envelopes are great for saving energy, but bad for “drying” walls out
OSB vs. planks or even plywood
Water-resistive (not water-proof) and air-resistive barriers

The Need
Preserving the life of exterior framing and sheathing – sustainability.
Reducing liability for callbacks, remediation, and litigation costs when moisture damage occurs.

The Need
Complying with growing code requirements:
IRC - Wall that “drains”
Water resistive barrier requirement
State code requirements (MN, OR?)
Canadian codes

Code Changes / Requirements
2006 IRC Section 703.1
“ The exterior wall envelope shall be designed and constructed in a manner that prevents the accumulation of water within the wall assembly by providing a water-resistant barrier behind the exterior veneer as required by Section 703.2, and a means of draining water that enters the assembly to the exterior .”

2006 IRC Section 703.2
“ One layer of No. 15 asphalt felt, free from holes and breaks, complying with ASTM D 226 for Type I felt or other approved water-resistive barrier shall be applied over studs or sheathing of all exterior walls.”
Code Changes / Requirements © 2008 Benjamin Obdyke Incorporated

2005 NBC of Canada Section 9.27.2.2
“… exterior walls exposed to precipitation shall be protected against precipitation ingress by an exterior cladding assembly consisting of a first plane of protection and a second plane of protection incorporating a capillary break ...”

2005 NBC of Canada Section 9.27.2.2 (cont.)
“… a cladding assembly is deemed to have a capillary break between the cladding and the backing assembly where …there is a drained and vented air space not less than 10mm deep behind the cladding, over the full height of the wall…”

Case Study
Homes on Philadelphia “Main Line”
Built within last 10 years
Moisture Problems
Remediation

Case Study
Cost to remediate $75,000 to $300,000+
Tear off cladding, WRB, sheathing, insulation, some framing
Do all this while occupied

Case Study
Costs to prevent up-front
$1000 to $5000

Brick Veneer
What can we learn from brick veneer?

Brick Veneer
Built with a space between cladding and sheathing
Built with drainage at bottom (need to keep clear)
Still uses WRB (one layer)

Rainscreens
A technique for controlling rain entry in an exterior wall
Involves locating an air space wide enough for capillary break immediately behind the exterior cladding

Rainscreens
When combined with openings at top and bottom, it creates a pressure equalized/moderated space to reduce forces leading to water entry
Water that does enter behind the cladding is not in direct contact with sheathing wall

Rainscreens
The capillary break space – at least 3/16” – can prevent surfactants from damaging the water resistive barrier
Residual moisture is dried by air movement (ventilation drying)

Rainscreens
Ventilation drying can also assist in removing moisture vapor from inside the building moving outward and from solar drive from wet claddings moving inward (remember those 2-way water resistive barriers)

Rainscreens
Brick veneer construction
Strapping or furring strips
Void space technology (“drainage mats”, “ventilation mats”, “rolled rainscreens”) – 21 st century

Rainscreens
The chief advantage of strapping is in material costs – furring strips are less expensive than manufactured rainscreen products
Installing these strips is labor-intensive and therefore strapping may ultimately be more costly than void space products

Rainscreens
Strapping covers about 15% of the wall surface leading to trapped moisture
Void space products are applied continuously protecting the entire surface area of the wall and providing a level surface for masonry application
Combination products provide the rainscreen in same installation step as the housewrap, reducing labor

Applications
How is this technology used in masonry walls?

Applications – Brick Veneer
Natural rainscreen
Must keep weep system “open” and avoid clogging with mortar droppings
Used to pull 1x or 2x board on wires up through wall or pour in pea gravel.
21 st century – void space products at bottom of walls

Applications – Stucco, Manufactured/Veneer Stone
Create a rainscreen wall with void-space rolled mats
Roll out like a WRB
Uniform thickness over wall
Creates capillary break to separate cladding from sheathing
Promotes drainage and drying

Conclusions
Walls no longer dry by themselves
Heightened concern over moisture liability and changing codes

Conclusions
Building science agrees that rainscreen wall is best wall system and NAHB recent white paper recognizes.
Learn from brick veneer - create a space between the cladding and the WRB/sheathing/framing

Conclusions
Advances in technology have broadened the range of solutions available to you to prevent problems
Upfront cost $1000 to $5000 vs. $75,000 to $300,000+ after the fact

Thank you

2009 IBS - High Performance Masonry Walls

by benjaminobdyke on Mar 03, 2009

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2009 IBS - High Performance Masonry Walls — Presentation Transcript