Friday, February 15, 2013

Adhered Manufactured Stone Veneer (Part 1)

JNX-clusives

Chips Off the Old Block
and other ruminations about masonry 

by
Larry D. Jenks











 

Manufactured Stone Veneer

Some of you probably recall the early days of exterior insulation and finishing systems (EIFS). EIFS was first used in North America in the 1960s, and became very popular in the mid-1970s. I worked with Richard (Dick) Crowther in those days, a pioneer in energy-conscious and energy-conserving architectural design, predating the work of the USGBC by some 20 years. One of the design idioms that became the hallmark of Crowtherian designs was the idea of exterior insulation. Dick was a vocal proponent of exterior insulation because it mitigated the thermal bridging that was common in buildings that featured only batt insulation between the wall studs.

I had the opportunity to work on many leading-edge energy conserving designs, most of which were residential. But I worked on one very special commercial building -- the national headquarters for The Hotsy Corporation.


The Hotsy Corporation National Headquarters

This building, built in 1977, was loaded with energy-conserving features and many opportunities for interior daylighting. And it was designed using state-of-the-art EIFS materials and details. However, the state-of-the-art for EIFS in 1977 was, unfortunately, not very advanced. These early EIFS systems trapped water that leaked in around doors and windows. The moisture damage that was concealed behind EIFS cladding systems was first discovered in this country in 1995, in Wilmington, North Carolina.

[Buildings] clad with EIFS ... have a very strong tendency to retain moisture between the sheathing of the home and the finish system. The design of EIFS, unlike other systems (brick, stone, siding, etc.), does not allow the moisture to drain out. The problem is water intrusion and entrapment in the wall cavities. The moisture can sit in contact with the sheathing for a prolonged period and rotting may result. Damage can be serious.

 
While a brick or stone wall will contain an internal drainage plane behind it and weep holes along the bottom edge to allow for water drainage, moisture intruding into the EIFS wall cavities is more damaging because it cannot readily escape back out through the waterproof EIFS exterior as quickly as it can through brick veneer, stone, or cement stucco, leaving the internal sheathing and wood framing vulnerable to rot and decay. (EIFS  Facts, Douglas Pencille)

The solutions to this problem were many-fold, but foremost among them was a philosophical change from the belief that EIFS could be a successful “barrier” or "face-sealed" system to the realization that it really needed to be a “drainage” system.  Now the
EIFS state-of-the-art mandates that drainage methodologies be used, except in limited (mostly hot and dry) locations.
 

Why am I discussing EIFS in an article about manufactured stone veneer? The reason is simple. MSV (Manufactured Stone Veneer is called by many names in the industry, but probably a more appropriate term would be Adhered Manufactured Stone Masonry Veneer [AMSMV], although the issues pertain to the use of real stone veneer as well) is following a path that is very similar to the path followed by the EIFS industry. And very interestingly, the state of North Carolina seems to be taking the lead in addressing the issues thru its inspection system. But I am certain that jurisdictions in Colorado are right there beside them.
Manufactured Stone Veneer


MSV units
The problems that we are seeing with MSV really pertain only to buildings where it is applied over water-sensitive materials used in the exterior building envelope (exterior gypsum board, oriented strand board (OSB) or plywood sheathing, metal or wood studs, or fiberglass cavity insulation). When MSV is installed correctly over concrete or masonry, problems are rare. When problems do arise, they seem to stem from the fact that the system was viewed initially as a masonry veneer system rather than an adhered system. 

Masonry veneer systems have been developed and refined for many years, and some of the recommendations we take for granted today came about as responses to problems that were discovered in the early years. One of those “recommendations” (I use the term “recommendations” with caution because if you were to fail to adhere to the "recommendations" and a problem were to develop, you would be very far out on a very thin branch with no help in sight) is the use of an air space behind the brick veneer, and then a drainage plane covering the water-sensitive materials. MSV systems are commonly installed with no air space. Metal lath (or sometimes in residential construction, a woven-wire  lath also known as chicken wire) is stapled thru a building paper or asphaltic building felt (this is the Water Resistive Barrier --WRB) Then the mortar scratch coat is applied to the metal lath to hold the veneer stones. It is is applied in contact with that WRB. When it rains, the system becomes saturated, and water migrates towards the WRB via suction. But since there is no air space to enable drainage, the water is held against the paper drainage plane. In a masonry system, the weather resistive barrier may get wet, but the air space allows the system to both drain along the drainage plane, as well as access to air to help dry it out. In an MSV system, once it gets to the WRB, to paraphrase Richard Gere in An Officer and a Gentleman, it‘s "got nowhere else to go." Eventually, the current thinking is that it will be absorbed by the mortar and concrete materials, from which it can evaporate, or it will make its way down to the weep screed, where it should be able to exit the system.

In the next installment, I’ll talk more about what is required to make the MSV system more effective at resisting water intrusion. In the meantime, I believe you my find it interesting to review the Masonry Veneer Manufacturers' Association (MVMA) testing to determine the effectiveness of MVS systems in preventing water intrusion. The following tests were conducted by Architectural Testing, Inc. on a veneer system without a rainscreen (a path for water to escape and air to enter) and also with a rainscreen. The tests were conducted according to the protocols in ASTM Standard E331. Neither system suffered any failures.

In a publication entitled Adhered Natural Stone Veneer Installation Guide (see below) authored jointly by the Rocky Mountain Masonry Institute, Atkinson-Noland Engineers, and Robinson Brick Company, the issue of using rain screens is not addressed in detail. The publication says only that the use of rainscreens is optional. However, a number of authorities having jurisdiction around the country require the use of rainscreens in manufactured stone veneer systems.
 
Masonry Veneer Manufacturers' Association 
Water Penetration Test -- No Rainscreen



Masonry Veneer Manufacturers' Association 
Water Penetration Test -- With Rainscreen 












Masonry Veneer Installation Guide 

 














NOTE: This document was prepared by the JNX Group, LLC and is disseminated for informational purposes only. Nothing contained herein is intended to revoke or change the requirements or specifications of  individual manufacturers or local, state and federal building officials that have jurisdiction in your area. Any question, or inquiry, as to the requirements or specifications of a manufacturer, should be directed to the manufacturer concerned. The user is responsible for for assuring compliance with all applicable laws and regulations.

The information provided here is provided for informational purposes only, and includes the opinions of the author. Nothing contained herein shall be interpreted as an endorsement of any particular product or manufacturer, or as a warranty by JNX Group, LLC, either express or implied, including but not limited to the implied warranties of merchantability, fitness for a particular purpose or non-infringement. In no event shall JNX Group, LLC be responsible for any damages whatsoever, including special, indirect, consequential or incidental damages or damages for loss of profits, revenue, use or data, whether claimed in contract, tort or otherwise. 

 

Thursday, February 14, 2013

Adhered Manufactured Stone Veneer (Part 2)


JNX-clusives

Chips Off the Old Block
and other ruminations about masonry 

by
Larry D. Jenks











 

Manufactured Stone Veneer

Perhaps the problems encountered by the EIFS industry are making me extraordinarily apprehensive about the current recommended installation protocols of the Adhered Manufactured Stone Veneer industry. Or, possibly those problems are making me appropriately apprehensive.

I recently read the Adhered Natural Stone Installation Guide, (written by Diane Travis of the Rocky Mountain Masonry Institute, Mike Schuller of Atkinson-Noland and Associates, the Building Stone Institute, and Robinson Brick),  as well as many other installation guides and Manufactured Stone Nightmares by Dennis McCoy. Everything I have read makes direct comparisons to the water intrusion problems discovered in the EIFS industry in the ‘90s. I have also read the MVMA Installation Guide, the MVMA Technical Bulletins on water penetration tests (see the links in my last installment), and I am troubled by a couple of things.

First, I have been unable to find the results any tests that might have been done on EIFS systems before the need for a drainage system was discovered (if you know of any, please let me know). I suspect that this is because there were no tests done at that time.

Second, the testing performed by Architectural Testing, Inc. and reported in the MVMA technical bulletins used the protocols from ASTM E331. ASTM E 331 requires the system to survive testing for a period of 2 hours in order to receive a “no failures” evaluation. I am troubled by this because I suspect that if the old EIFS systems had been subjected to a test that lasted only 2 hours, that it might well have received a “no failures” evaluation as well.  It seems to me that the failures in the EIFS systems occurred over much longer periods of time.

Therefore, I find myself wondering whether there any long-term tests being done on the adhered (manufactured or) natural stone veneer systems to determine the long-term success of this system to prevent water intrusion, especially in the absence of a rainscreen or drainage plane. I know that some Authorities Having Jurisdiction are requiring the drainage plane approach, while many others do not. Further, I can find very little information from manufacturers about the wisdom of using the rainscreen, except from the rainscreen manufacturers. Adhered Natural Stone Installation Guide says only that the rainscreen approach is “optional”.

Adhered Natural Stone Installation Guide
I am concerned that we may be in a sort of limbo period where the system is new enough that internal problems have not yet been discovered, and that, over time, the Adhered Manufactured Stone Veneer system will come to the same conclusions that the EIFS industry has come to.

So, I guess my question is this... What reason is there to believe that the AMSV system where the mortar scratch coat is in contact with the water-resistant barrier can be successful for the long term? And a follow-up question... How effective is the drainage that occurs without a drainage plane (given that the EIFS problems seem to be traceable to the fact that water was held in place against the WRB for long periods of time, eventually causing the WRB to fail)?

This installment is long enough, so I'll provide some installation details in my next installment. However, if you are a homeowner with the Adhered Manufactured Stone Veneer (AMSV) system in place on your house, I would encourage you to check to see if it is a draining type application. You can tell fairly easily --

  1. First, check to see if the AMSV stops at least 4" above the grade, or 2" above any pavement.
  2. Second, look up at the bottom of the application (you may have to use a mirror) -- you should see a piece of galvanized metal with holes in it, like this...
If you see the bottom of the manufactured stone, or mortar, or both -- your home almost assuredly does not use a drainage system. I would encourage you to check out the underlying materials to determine whether moisture is present. If moisture is present, you can't address it soon enough.



 











NOTE: This document was prepared by the JNX Group, LLC and is disseminated for informational purposes only. Nothing contained herein is intended to revoke or change the requirements or specifications of the individual manufacturers or local, state and federal building officials that have jurisdiction in your area. Any question, or inquiry, as to the requirements or specifications of a manufacturer, should be directed to the manufacturer concerned. The user is responsible for for assuring compliance with all applicable laws and regulations.

The information provided here is provided for informational purposes only, and includes the opinions of the author. Nothing contained herein shall be interpreted as an endorsement of any particular product or manufacturer, or as a warranty by JNX Group, LLC, either express or implied, including but not limited to the implied warranties of merchantability, fitness for a particular purpose or non-infringement. In no event shall JNX Group, LLC be responsible for any damages whatsoever, including special, indirect, consequential or incidental damages or damages for loss of profits, revenue, use or data, whether claimed in contract, tort or otherwise. 

Wednesday, February 13, 2013

Adhered Manufactured Stone Veneer (Part 3)


JNX-clusives

Chips Off the Old Block
and other ruminations about masonry 

by
Larry D. Jenks











 

Manufactured Stone Veneer

In my last installment, I promised to provide some installation details for the Adhered Manufactured Stone Veneer system. I have read many from a variety of different manufacturers, and I am going to summarize them for you here... with this caveat -- the Adhered Manufactured Stone Veneer (AMSV) industry is not currently recommending the use of a drainage plane in their installations. The final word on this has not yet been written, but I find it difficult to recommend the system without one. So the drawings I have provided here show one -- in this case, it is Sure Cavity by Masonry Technologies, Incorporated, which is a recycled plastic material with a built-in filter fabric that looks like this...

  There are other manufacturers that make drainage plane (and drainage mat) products, such as DC14 Drainage Mat manufactured by Greenguard, or fibrous entangled filament drainage mats. You can choose one that you like.




 

Adhered Manufactured Stone Veneer Installation Recommendations

(taken from the Masonry Veneer Manufacturers Association Installation Guide, 3rd Edition)

(These recommendations apply to wood framed exterior walls made with moisture sensitive- materials; the application is slightly different when applied to concrete or masonry walls, but I am not going to address those applications in this installment)

The first thing that a drainage systems needs is a slotted (or draining) weep screed. I like the ones made from galvanized sheet metal, but others made from plastics are also available. A draining weep screed looks like this...
 
According to the  Masonry Veneer Manufacturers Association (MVMA), the weep screed should be installed so that the bottom of the AMSV system is at least 4" above the surrounding grade.
  


 













Then a 2-ply water resistant barrier should be installed. The plies should be installed in a shingle-lapped manner, overlapped by 2" (6" at the vertical joints).
Figure 3-- Add 2 layers of Water Resistant Barrier


Then the drainage plane or drainage mat, or rainscreen should be installed over the water resistant barrier...
Figure 4-- Add rain screen drainage plane



Figure 5-- Enlarged view of rainscreen drainage plane





Figure 6-- Filter fabric comes already installed on rainscreen drainage plane


The MTI drainage rainscreen is already covered with a filter fabric to keep the mortar scratch coat from filling the drainage cavities.


Then metal lath is installed. I have seen many installations on houses around where I live that have used chicken wire, but I have found no recommendations from any source that recommend that.
Figure 7



Now the wall is ready for the mortar scratch coat, or setting bed. This is what holds the manufactured stone in place. 
Figure 8



Then the manufactured stone must be installed with great care and skill...
Figure 9




Please give me a call if you would like to discuss this further. I'm always happy to talk with you about these kinds of things (or a little baseball, too).

Until next time...

NOTE: This document was prepared by the JNX Group, LLC and is disseminated for informational purposes only. Nothing contained herein is intended to revoke or change the requirements or specifications of the individual manufacturers or local, state and federal building officials that have jurisdiction in your area. Any question, or inquiry, as to the requirements or specifications of a manufacturer, should be directed to the manufacturer concerned. The user is responsible for for assuring compliance with all applicable laws and regulations.

The information provided here is provided for informational purposes only, and includes the opinions of the author. Nothing contained herein shall be interpreted as an endorsement of any particular product or manufacturer, or as a warranty by JNX Group, LLC, either express or implied, including but not limited to the implied warranties of merchantability, fitness for a particular purpose or non-infringement. In no event shall JNX Group, LLC be responsible for any damages whatsoever, including special, indirect, consequential or incidental damages or damages for loss of profits, revenue, use or data, whether claimed in contract, tort or otherwise.


Drawings copyright JNX Group, LLC. All rights reserved.

Tuesday, February 12, 2013

Adhered Manufactured Concrete Stone Veneer (Part 4)

JNX-clusives

Chips Off the Old Block
and other ruminations about masonry 

by
Larry D. Jenks











 

Adhered Manufactured Concrete Stone Veneer

 Since my last installment, I have exchanged some thoughts with my friends Diane Travis, Technical Director at the Rocky Mountain Masonry Institute, and Mike Schuller of Atkinson-Noland + Associates. I will try to provide a synopsis of those discussions for you to ponder.

The main thing that makes an Adhered Manufactured Concrete Stone Veneer (AMCSV) different than EIFS from a moisture intrusion perspective is that the AMCSV system will  absorb water that comes in contact with it, and keep it from penetrating unbridled to the Water Resistive Barrier (WRB). That gives it time to evaporate. The EIFS systems, including the drainage systems I discussed briefly earlier, don't have water-absorbing materials, and water continues to migrate through the finish materials to the WRB. If a drainage system is not provided, the water stays held against the WRB, and eventually causes it to fail.

Here's what the IBC says about all of this...

According to the International Building Code (paragraph 1403.2 Weather Protection):
“The exterior wall envelope shall be designed and constructed in such a manner as to prevent the accumulation of water within the wall assembly by providing a water-resistive barrier behind the exterior veneer, as described in Section 1404.2 and a means for draining water that enters the assembly to the exterior of the veneer…”

The Commentary to the Code explains further:

“The method to provide the means of drainage is a performance criterion and must be evaluated based upon the ability to allow moisture that may penetrate behind the exterior wall covering to drain back to the exterior.  This may be as complicated as a rain-screen pressure-equalized type of exterior assembly or as simple as providing discontinuities or gaps between the surface of the substrate and the back side of the finish, such as through the use of non-corrodible furring.”
This says, to me, that a provision must be made to allow water to drain back out of the system. The code doesn't say anything about the ability of the system to achieve evaporation. But also keep in mind that in many parts of Colorado and the southwest, moisture events can be few and far between. In these cases, there is likely to be ample opportunity for adequate evaporation to occur. That said, rain screens or drainage mats add time and costs to projects, and their use should be weighed carefully. But clearly, the drainage mechanism can be a simple one, such as a dimpled mat. This strikes me as something you would want to discuss with your local Authority Having Jurisdiction (AHJ) before making your final decision. So please let me know if you find an AHJ that does not require some kind of drainage mechanism. The status of this system seems to be in flux, and we all need to monitor its evolution. While this plays out, my recommendation would be to play it safe. It may be short-sighted to opt for the pretty, the fast, and the cheap. You can quote me on that (but Diane said it first).



Thursday, February 23, 2012

Chips Off the Old Block -- Tooling Mortar Joints


JNX-clusives

Chips Off the Old Block
and other ruminations about masonry, by

Larry D. Jenks



















Tooling Mortar Joints
Before we get too far into the topic of tooling mortar joints, let's pause for a moment to remind ourselves why we even care about mortar joints. Of course, mortar joints will affect the appearance of our masonry walls, so we obviously need to pay attention to them for that reason.
But more importantly, the mortar joints are the first line of defense against water penetration. To reduce water penetration through the wall, there is no substitute for the proper filling of the mortar joints. 


Improperly filled joints... 
  • reduce masonry strength 
  • result in leaky walls 
  • are susceptible to freezing and thawing damage 
  • contribute to disintegration and cracking
  • reduce sound insulation
  • contribute to corrosion of embedded steel elements 
  • may contribute to disintegration and cracking due to water penetration and subsequent freezing and thawing.
Figure A: Tooling a concave mortar joint
If integral water repellent is being used, as it will be for most single-wythe walls, the water repellent will reduce the absorptivity of the block, so tooled and compressed joints become even more critical. Integral water repellents make masonry materials hydrophobic, thereby significantly decreasing their water absorption and wicking characteristics. While these admixtures can limit the amount of water that can pass through units and mortar, they have little impact on moisture entering through relatively large cracks and voids in the wall. Therefore, even with the incorporation of integral water repellents, proper detailing of control joints and quality workmanship to preclude beeholes and unfilled or inadequate mortar joints is still essential. 



A Specification Section on Procedures for Laying Unit Masonry
As I discovered last time when I searched YouTube for videos showing the proper techniques for laying masonry, masons may have a different understanding of how various elements of the process should be carried out. The ways that they have been doing things for a generation or two may not be exactly what you are looking for in order to attain good moisture penetration resistance. A section in the masonry specifications describing the procedure for "Laying Walls and Partitions" can help. Such a specification could read: 

A. Laying Procedure: 
  1. Hollow Units: In starter courses and elsewhere as noted, lay units fully bedded in mortar under both shells and webs. Other units shall be laid with fully bedded face shells, but mortar shall extend through the unit on web edges where anchors or ties occur. All head-joints, except in control joints requiring a control joint key, shall be filled solidly with mortar for a distance in from the face of the unit not less than the thickness of the longitudinal face shell. Place mortar on webs where required to contain grout in partially grouted walls. 
  2. Solid Units: Spread the mortar bed full width and relatively smooth. Do not furrow. Do not fill head joints by slushing, instead butter the end of each unit with mortar and shove it into place to completely fill the head joints.
During inclement weather, tops of unfinished walls must be covered at the end of the work day. The cover should extend two feet down both sides of the masonry and be securely help in place. After completion of the walls, immediately install the wall cap to prevent excessive amounts of water from directly entering the masonry.

Bibliography

International Masonry Institute

TECHNICAL NOTES on Brick Construction 7The Brick Industry AssociationWater Penetration Resistance - Design and Detailingwww.gobrick.com
TECHNICAL NOTES on Brick Construction 7BThe Brick Industry AssociationWater Penetration Resistance - Construction and Workmanship www.gobrick.com
Mortar Joints -- How Full is Full?
Rocky Mountain Institute
Rain Resistant Architectural Concrete MasonryNWCMA (Northwest Concrete Masonry Association)TEK Note November 2000http://www.nwcma.org/ 
NCMA TEK 19-2ADesign for Dry Single-Wythe-Wythe Concrete Masonry WallsNational Concrete Masonry Association 1998http://www.ncma.org/Pages/default.aspx 
NCMA TEK 3-8AConcrete Masonry ConstructionNational Concrete Masonry Association 2001http://www.ncma.org/Pages/default.aspx 
NCMA TEK 19-07Characteristics of Concrete Masonry Units with Integral Water RepellentNational Concrete Masonry Association 2008http://www.ncma.org/Pages/default.aspx 



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