| Author |
Message |
Jerome J. Lazar, RA, CCS, CSI, SCIP
Senior Member
Username: lazarcitec
Post Number: 314
Registered: 05-2003
| | Posted on Wednesday, February 07, 2007 - 11:02 am: |    |
Paper backed stucco lath
Pros and Cons?
SE US |
Anne Whitacre, FCSI CCS
Senior Member
Username: awhitacre
Post Number: 446
Registered: 07-2002
| | Posted on Wednesday, February 07, 2007 - 12:18 pm: | |
I haven't had any problem with it, and its common in the northwest. the OSB, on the other hand, is just asking for trouble in my experience. it degrades pretty quickly in the northwest area and loses strength. typical backer for stucco in Seattle area is densglass or if you need shear, plywood. |
Nathan Woods, CCCA, LEED AP
Senior Member
Username: nwoods
Post Number: 166
Registered: 08-2005
| | Posted on Wednesday, February 07, 2007 - 12:24 pm: | |
I'm generally opposed to it. I think having individual sheets of building paper allows better laps, more flexibility to cover special joints, corners, etc...and allows better control around window openings.
I have also "heard" of complaints from installers that the paper is often punctured, ripped or torn as the mesh is unrolled and applied.
Disclaimer, I am not an installer, I have never been an installer, and am unlikely to ever be an installer, so take my comments with a grain of salt. I suggest talking to some of the larger plaster contractors in your area to get their feedback.
Be sure to ask, "If price was not a factor, which would you use..." |
Wayne Yancey
Senior Member
Username: wyancey
Post Number: 271
Registered: 05-2005
| | Posted on Wednesday, February 07, 2007 - 01:49 pm: | |
Paper backed stucco lath without the redundancy of a separate water-resistive barrier or drainage cavity is not wise.
I assume (please correct me if I am wrong) the SE US is a high risk climate.
Builders do not consider long term costs or long term risks so they will always favor the lowest cost option as long as it will not attract lawsuits.
Stucco thickness is probably not a significant factor. Since stucco is porous, and always cracks, water will get through, and fairly quickly. The key issue is how the water that gets through is handled (i.e. gets out).
To strap or not to strap?
The key advantage of using a drainage material under stucco is that it provides a capillarity break as well as a drainage path.
I like the thinking behind the new National Building Code of Canada requirements for high risk climates.
9.27.2.2.5 requires that in climates like British Columbia’s Lower Mainland, the “exterior walls exposed to precipitation shall be protected against precipitation ingress with an exterior cladding assembly consisting of a first plane of protection and a second plane of protection incorporating a capillary break”.
Proposed Sentence 9.27.2.2(1) states that “a cladding assembly is deemed to have a capillary break between the cladding and the back-up assembly where:
a) there is a clear air space not less than 10 mm (3/8 inch) in depth between the cladding and the inner boundary of the second plane of protection for the full height and width of the wall,
b) an open drainage material not less than 10mm (3/8 inch)thick and with a cross-sectional area that is not less than 80% open, is installed between the cladding and the back-up for the full height and width of the wall,
c) the cladding is loosely fastened to the backup and there is a clear air space behind each cladding component that is
i) continuous for the full width of the component,
ii) not less than 10 mm (3/8 inch) in depth at the bottom of the component, and
iii) not less than 6 mm (1/4 inch) in depth over not less than 90 mm (3 1/2 inch) for every 230 mm (9 inches) of exposed height of the component.
I live and work in a high risk climate (PNW. The past 4 months have lived up to and exceeded that reputation. It drove Anne W to lotus land. I would not consider a cladding that does not conform to the above requirements.
Detail, details, details. Lots of details.
Wayne |
Anonymous
| | Posted on Wednesday, February 07, 2007 - 02:32 pm: | |
The Canadians have it totally wrong - the CA code requirement is a knee jerk reaction to the problems they have had with leaky EIFS cladding, the large majority due to installation errors - well documented by Canadian building "scientists."
The scientific studies that I am aware of show that two layers of weather resistant barrier is more than adequate to provide necessary drainage behind cladding - I have one from the Canadian Home Mortgage group that corrorborates this.
The Northwest Wall and Ceiling bureau will also corroborate this, and they are considered the experts in the west (stateside, anyway) for stucco assemblies. They can also provide you with expertise for other climate regions. They also feel that the Canadians are way out of whack with their prescriptive requirements.
Lstiburek has also got some really great scientific advice about stucco cladding and proper detailing. You can check his stuff out at buildingscience.com. He also thinks that the Canadians are way overboard with their code requirements... |
Jerome J. Lazar, RA, CCS, CSI, SCIP
Senior Member
Username: lazarcitec
Post Number: 315
Registered: 05-2003
| | Posted on Wednesday, February 07, 2007 - 02:55 pm: | |
Yes Anonymous, Lstiburek does have some valid opinions, some of which I agree with, I just wish my clients would read his stuff, so what I am looking for in this thread is some other opinions or insight, for those who don't know Lstiburek, here is a link to one of his better papers:
http://www.buildingscienceconsulting.com/resources/walls/Water_Management_Details-Housewraps_Flashings_Windows.pdf |
Steven Bruneel, AIA, CSI-CDT, LEED-AP
Senior Member
Username: redseca2
Post Number: 17
Registered: 12-2006
| | Posted on Wednesday, February 07, 2007 - 03:37 pm: | |
We have been all over this with waterproofing consultants and our current thinking is:
Dens Glass Sheathing
Tape joints and penetrations with a peal-n-stick product.
Two layers of of high grade 60-pound paper, creating a drainage channel.
All horizontal trims designed to allow weeping from panel above.
Brown and Scratch coat.
Topcoat usually from an EIFS manufacturer |
Anonymous
| | Posted on Wednesday, February 07, 2007 - 05:26 pm: | |
What is "high grade 60-pound paper" pray tell? |
Nathan Woods, CCCA, LEED AP
Senior Member
Username: nwoods
Post Number: 169
Registered: 08-2005
| | Posted on Wednesday, February 07, 2007 - 05:33 pm: | |
JumboTex-60, Grade D Bldg Paper from FortiFiber
http://www.fortifiber.com/FBSG/HTML_FFACTS/library_60_minute.html |
Bob Woodburn
Senior Member
Username: bwoodburn
Post Number: 158
Registered: 01-2005
| | Posted on Wednesday, February 07, 2007 - 06:00 pm: | |
Oh--"60 minute" Grade D paper, not "60 pound" (or "number 60"...)
Never heard of building paper designated in minutes before.
(Whatever happened to grades A, B and C?) |
Nathan Woods, CCCA, LEED AP
Senior Member
Username: nwoods
Post Number: 170
Registered: 08-2005
| | Posted on Wednesday, February 07, 2007 - 06:03 pm: | |
Those grades exist, but are for shorter durations of water impermeability, often used in interior applications? I think I've seen Class B (20min?) in countertop tile assemblies. |
Jim Brittell
Senior Member
Username: jwbrittell
Post Number: 31
Registered: 08-2004
| | Posted on Wednesday, February 07, 2007 - 07:26 pm: | |
Jerome,
I suggest looking at ASTM E 2266-04 "Standard Guide for Design and Construction of Low-Rise Frame Building Wall Systems to Resist Water Intrusion" (that's easy for them to say...)
There's nothing particularly new about their recommendations, but it's convenient to have an ASTM standard to point to and say "do this..." The list of referenced documents (both ASTM and industry standards organizations is 2 pages long. Many of the points discussed above are addressed in the guide. |
Dave Metzger
Senior Member
Username: davemetzger
Post Number: 185
Registered: 07-2001
| | Posted on Wednesday, February 07, 2007 - 07:26 pm: | |
We have used Jumbo-Tex 60 Minute, shop-attached to a ventilating drainage mat, in roll form. It is sold under the name Home Slicker plus Super Jumbo Tex 60 Minute, by Benjamin Obdyke. |
Richard Howard, AIA CSI CCS
Senior Member
Username: rick_howard
Post Number: 112
Registered: 07-2003
| | Posted on Thursday, February 08, 2007 - 09:42 am: | |
The standard for building paper is Federal Specification UU-B-790-a "Building Paper, Vegetable Fiber: (Kraft, Waterproofed, Water Repellant and Fire Resistant)." It covers several different grades, the most commonly used being Type I, Grade D, Style 2. Grade D is water-vapor permeable Kraft paper and is available with water resistance of 10, 30 and 60 minutes. IBC calls for the equivalent of at least two layers of Grade D paper installed over wood-based sheathing (OSB or plywood). Over other sheathing materials, such as gypsum sheathing, Dens-glas type panels, or cement board, the code requires the equivalent of one layer of 15-lb asphalt-saturated felt. Providing two layers of paper under stucco is strongly recommended to assure a drainage plane if one layer is adhered to the cement base coat. Stucco should not be considered a barrier-type of cladding. Management of water should be designed into the wall system.
Grade B paper is water-vapor retardant and resists water penetration for 16 hours. This would be acceptable in warm, normally-dry climates, but not where the stucco is subject to freezing or constantly wet for long periods because it could trap moisture in the wall assembly.
The use of Grade D paper is not common in sone parts of the country. Local installers can tell you what is commonly done in the area of the project. As always, only the local authority having jurisdiction can determine what is acceptable as "equivalent" for what is called out in the building code. |
Wayne Yancey
Senior Member
Username: wyancey
Post Number: 273
Registered: 05-2005
| | Posted on Thursday, February 08, 2007 - 11:14 am: | |
I agree, Dr. Joe (a fellow Canadian) has differing opinions regarding exterior claddings and vapor barriers/retarders. I graduated from the Morrison Hershfield school of building science. MH are the pre-emminent building science specialists in Canada and have been for many years. MH has butted heads with the Northwest Wall and Ceiling Bureau on this and other issues, but NWWCB is not the designer of record sealing the documents.
I agree, a rainscreen or drained cavity is not required for all exposure conditions for each project. However, it does have it's place amoung the choices offered for water and water vapor (water vapor released from the interior) management.
Dr. Joe's positon on rain screen is contrary to Canadian practices in certain high risk climate areas such as the lower mainland of BC and the Pacific NW. Rainscreen may not be required in dryer and colder climates such as in the western states east of the Rockies and Cascades. Dr. Joe knows his opinions are not popular in Canada and has stated publically (with tongue in cheek) that he will loose his Canadian citezenship and that we veiw him as a traitor any way becuase he moved to Boston. I am a traitor also because I moved to Seattle.
Both systems are valid as part of the risk assessment. I have done projects in the PNW utilizing both rainscreen and concealed barrier, based on the severity of the exposure, and without rainscreen on severe exposure conditions by utilizing additional layers of WRB. First cost plays a part in the decision process.
Rainscreen is just another trick in our bag of tricks that we can pull out when requried. Whatever it takes. Neither system is the fnal solution. To bluntly stated "The Canadians have it totally wrong" is shortsighted and narrow minded.
For futher reading check out the CMHC Best Practice Guide - Building Technology, WOOD-FRAMED ENVELOPES IN THE COASTAL CLIMATE OF BRITISH COLUMBIA.
Dr. Joe says this about plastic interior vapor barriers "...that stupid (and boy to I mean stupid except in 9000 heating degree day climates) plastic intieror vapor barrier,.... In otherwords, OK for regions above the Arctic Circle.
Wayne (another totally wrong Canadian). |
(Unregistered Guest)
Unregistered guest
| | Posted on Thursday, February 08, 2007 - 12:50 pm: | |
MH, as is true with other building "scientists", is typically not the 'designer of record sealing documents' either, but a consultant to the designer of record. MHs liability is very limited in comparison to that of the designer of record (take a look at one of their standard forms of agreement). |
Wayne Yancey
Senior Member
Username: wyancey
Post Number: 276
Registered: 05-2005
| | Posted on Thursday, February 08, 2007 - 02:03 pm: | |
Dear Unregistered Guest,
On the contrary, on assessment and rehab projects MH, or other building envelope specialist are THE "Designer or Architect of Record". They seal and sign the Construction Documents, building permit documents, issue documents for bidding, receive and evaluate bids, and if required by their Contract, CA services. In accordance with WA law (Chapter 64.55 RCW, formerly known as EHB 1848), they must perform observations during the course of construction, and sign-off at closeout. I have done a handful of such projects from Bremerton to Bellevue to Kirkland to Seattle. They also provide the same service in Portland but not under legislation as rigid as Chapter 64.55 RCW.
Yes, they also provide design assist to the architect of record with limited liability, usually to the limit of their fees.
Please get registered.
Wayne (registered member) |
Anonymous
| | Posted on Thursday, February 08, 2007 - 05:00 pm: | |
Rehab contracts and HB1848 are two separate things. Envelope consultants may indeed prepare and stamp documents for rehabilitation work, but for HB1848, if an envelope consultant is retained by the Owner (the bill does not require this to be an envelope consultant, btw), the only requirement of the consultant is to verify that the project was built in substantial accordance with the Contract Documents - typically prepared by the architect. There is no other liability to the consultant in the bill, as written. |
Wayne Yancey
Senior Member
Username: wyancey
Post Number: 277
Registered: 05-2005
| | Posted on Thursday, February 08, 2007 - 05:31 pm: | |
Dear Anonymous,
To my knowledge, Architects in my region do not delve into assessment and rehab projects. In my time in this specialty field, we never competed against an Architect. Traditionally, these projects are left to the building envelope specialists who are retained directly by the Owner or by the plaintiffs (Owner's) lawyer. Apartment to condo conversions also apply.
Chapter 64.55 RCW, formerly known as EHB 1848 includes new construction, rehab work, and apartment to condo conversions.
You are correct. Chapter 64.55 RCW does not require the building envelope consultant to prepare the CD's but the A/E that does must have adequate and varifiable experience for rehab work. The A/E (or Owner) usually retains the services of the building envelope consultant for design assist
Rehab contracts, apartment to condo conversions, and HB1848 are NOT separate things. |
Anonymous
| | Posted on Thursday, February 08, 2007 - 06:05 pm: | |
HB1848 is specific to condos and apartments that will be, or may be, converted into condos.
Rahab work is not limited to condos and apartments.
"Envelope consultants" and building "scientists" are NOT required to be retained by an Owner to satisfy requirements of HB 1848.
Consutlants hired by Owners to satisfy requirements of HB1848 are required only to certify that construction was carried out in substantial compliance with the Contract Documents.
The Owner is free to hire any properly credentialed design professional for rehabilitation projects, and many architects do this without "envelope specialist" or building "scientist" appearing anywhere in their marketing brochures. I can name several in your area that regularly engage in this sort of work, tho you may not have ever competed with them. Believe me, it's not just the MHs of the world that are retained to provide these types of services.
Anon |
Helaine K. (Holly) Robinson CSI CCS CCCA
Senior Member
Username: hollyrob
Post Number: 265
Registered: 07-2003
| | Posted on Thursday, February 08, 2007 - 06:21 pm: | |
I thought Rahab was a prostitute in the Bible! |
Wayne Yancey
Senior Member
Username: wyancey
Post Number: 278
Registered: 05-2005
| | Posted on Thursday, February 08, 2007 - 07:25 pm: | |
Dear Anonymous,
I think we agree.
I was referring only to and limiting my comments to projects that fall under the umbrella of Chapter 64.55 RCW (EHB 1848) where the building envelope consultant is the A/E of record; sealing and signing the CD's.
Rehab projects and adaptive reuse projects do not apply as you point out.
Wayne |
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