| Author |
Message |
Robin E. Snyder
Senior Member
Username: robin
Post Number: 70
Registered: 08-2004
| | Posted on Monday, November 27, 2006 - 11:39 pm: |    |
Is there a specific product for application on the underside of concrete slabs to provide a smooth surface? Would you use a skim coat of plaster, or does someone manufacturer a product for this purpose? Thanks! |
Ralph Liebing, RA, CSI
Senior Member
Username: rliebing
Post Number: 498
Registered: 02-2003
| | Posted on Tuesday, November 28, 2006 - 06:58 am: | |
Two possibilities--
Block filler, or a fairly thick coating of a dry-fall paint. |
George A. Everding, AIA, CSI, CCS, CCCA
Senior Member
Username: geverding
Post Number: 235
Registered: 11-2004
| | Posted on Tuesday, November 28, 2006 - 11:19 am: | |
How about one of the concrete repair product manufacturers? Euclid Chemical, Dayton Superior, Sika Corporation spring to mind immediately, but there are dozens of others who make specialty concrete coating products. |
Robert W. Johnson
Senior Member
Username: bob_johnson
Post Number: 112
Registered: 08-2004
| | Posted on Tuesday, November 28, 2006 - 11:30 am: | |
You can also do it with a skim coat of gypsum board joint compound especially if you are trying to match adjacent gypsum board surfaces. You can specify the same level of finish as on the gypsum board.
It is best if you have also included some finish requirements for the formed concrete surface to eliminate major defects in the substrate. |
Jerome J. Lazar, RA, CCS, CSI, SCIP
Senior Member
Username: lazarcitec
Post Number: 276
Registered: 05-2003
| | Posted on Tuesday, November 28, 2006 - 01:24 pm: | |
Robert
You can not use a gypsum compound on concrete as you will void the warranty from the joint compound manufacturer. USG makes a product called Cover Coat (vinyl-based) that we use on many of our residential projects where the concrete slab is the finished ceiling. Woncote made by Premix is another product. If the concrete is irregular, we do specify an epoxy mortar to level the concrete - this is all based on an interior application, Robin did not say whether it was interior or exterior? |
Robin E. Snyder
Senior Member
Username: robin
Post Number: 71
Registered: 08-2004
| | Posted on Tuesday, November 28, 2006 - 02:45 pm: | |
It is the underslabs at a parking garage and also at balconies. |
Jerome J. Lazar, RA, CCS, CSI, SCIP
Senior Member
Username: lazarcitec
Post Number: 278
Registered: 05-2003
| | Posted on Tuesday, November 28, 2006 - 03:20 pm: | |
Well Robin you should not use any gypsum based or interior product in an open PG - we have had luck with a product manuf. by BASF's Chemrex division -Thorocoat, it is 100% acrylic, breathable, and high-build, available in a varity of colors...but honestly in most PG's it gets VE'd and left natural, sealed with a penetrating water repellent if necessary, unless the surface is highly irregular, than once again an epoxy mortar (BASF's Emaco is a good product) works great as you can feather it down to 1/8" and work overhead - since its epoxy you do need proper ventilation.
For Concrete Balconies - depending on the irregularities in the surface, we specify the same coating (Torocoat - which also is available in a textured product), except we recommend that the Concrete forming specs include a requirement that on high rise work, new plywood forms be used every 5 floors, this will keep the underside looking less raggard.
http://www.chemrex.com/documents/tct_tdg.pdf |
Nathan Woods, CCCA, LEED AP
Senior Member
Username: nwoods
Post Number: 139
Registered: 08-2005
| | Posted on Tuesday, November 28, 2006 - 06:25 pm: | |
The products used to "sack and patch" tilt-up buildings would be ideal. I like JetSet:
http://www.jetsetcement.com/ |
Wayne Yancey
Senior Member
Username: wyancey
Post Number: 221
Registered: 05-2005
| | Posted on Wednesday, November 29, 2006 - 02:18 pm: | |
One of our condo clients uses USG Sheetrock Brand Lightweight Setting-Type Joint Compound (Easy Sand) in 1/8" thickness over USG Sheetrock Brand First-Coat Ready-mixed.
Easy Sand is available in a wide variety of setting times (8-360 minutes).
Quality of concrete forms under slab is also important. ACI A347R, Class A.
Wayne |
Mark Gilligan SE, CSI
Senior Member
Username: markgilligan
Post Number: 111
Registered: 05-2005
| | Posted on Thursday, November 30, 2006 - 12:22 am: | |
Wayne
I believe that ACI has moved the tolerances for concrete forms out of ACI 347R and into ACI 117.
ACI's position is that ACI 347 is a Guide and it is not written in enforcable language. Thus ACI 347 should not be referenced in project specifications.
ACI 117 is a standard that defines the various tolerances for concrete and reinforcing. |
Wayne Yancey
Senior Member
Username: wyancey
Post Number: 222
Registered: 05-2005
| | Posted on Thursday, November 30, 2006 - 03:30 pm: | |
Mark,
Thanks for the input.
The source of my information in my previous posting is from AIA MasterSpec support Document for Section 033000_FL, August/September 2006 update. The following is a partial quote from this support document.
"ACI 347R, Guide to Formwork for Concrete, recommends materials, applications, and specifications for concrete forming. Among other topics, ACI 347R discusses issues such as the Contractor's design responsibility, loading information needed by the Contractor, submittals, and shoring responsibilities."
"ACI 347R recommends limits for tolerances and surface irregularities in the completed concrete work. Tolerances recommended by ACI 347R, and mandated by ACI 301, follow ACI 117 limits. For surface irregularities, ACI 117 recognizes four surface classes from ACI 347R but expects the design professional to designate where each applies. ACI 301 sets Class A as the default class for surfaces permanently exposed to public view and Class C as the default class for surfaces that will be permanently concealed, unless otherwise required by the Contract Documents."
"Surface irregularities are designated by ACI 347R as either "gradual" or "abrupt." Offsets and fins at formed joints are considered abrupt irregularities. Warping and planar variations are considered gradual irregularities, measured with a 60-inch long straightedge for plane surfaces or a template for curved surfaces. The four surface classes defined in ACI 347R, with their suggested uses, are as follows:
Class A: For surfaces prominently exposed to public view, where appearance is especially important. Class A permits gradual or abrupt irregularities of 1/8 inch.
Class B: For coarse-textured surfaces to receive plaster, stucco, or wainscoting. Class B permits gradual or abrupt irregularities of 1/4 inch.
Class C: For permanently exposed surfaces without additional finish. Class C permits gradual or abrupt irregularities of 1/2 inch.
Class D: For surfaces, usually permanently concealed, where roughness is not objectionable. Class D permits gradual or abrupt irregularities of 1 inch.
The following is an excerpt from Part 3 of 033000_F, Article 3.1,
A. Design, erect, shore, brace, and maintain formwork, according to ACI 301, to support vertical, lateral, static, and dynamic loads, and construction loads that might be applied, until structure can support such loads.
B. Construct formwork so concrete members and structures are of size, shape, alignment, elevation, and position indicated, within tolerance limits of ACI 117.
C. Limit concrete surface irregularities, designated by ACI 347R as abrupt or gradual, as follows:
It is paragraph C. that provides options for surface irregularities
Wayne |
Mark Gilligan SE, CSI
Senior Member
Username: markgilligan
Post Number: 112
Registered: 05-2005
| | Posted on Friday, December 01, 2006 - 01:37 am: | |
I looked in the 2006 ACI Manual of Concrete Practice which contains the latest versions of ACI documents. I then looked at the source documents.
ACI 117-90 defines Class A,B,C,&D form tolerances.
ACI 347-04 discusses the tolerances for formwork and points the reader to ACI 117, but ACI clearly states that ACI 347 is not a standard and should not be referenced in project specificaitons. ACI 347 is intended to be used as a background reference to help you understand the issues.
ACI 301-05 references ACI 117-90 but it does not reference ACI 347.
Based on these facts it is wrong to reference ACI 347 in project specifications. MasterSpec is 16 years behind the times.
Every time I have had an opportunity to review a MasterSpec master I have found similar disconnects. As a result I have not been impressed with their structural specifications. |
Kenneth C. Crocco
Senior Member
Username: kcrocco
Post Number: 65
Registered: 04-2003
| | Posted on Friday, December 01, 2006 - 11:36 am: | |
I don't think you're interpreting Masterspec correctly. The text says "designated by ACI 347R as abrupt or gradual". Masterspec is simply using terms from an ACI recommendation for definition; it is not using 347 as a reference standard. The limitation criteria for irregularities are listed below this statement.
I don't think the problem is that Masterspec is behind the times. Sometimes standards can be viewed as the end-all. They clearly are not. When ACI came forth with the masonry standard it was years before things were cleaned up. I don't think the problem is out of date specifications, but rather it is getting standards, codes, and commercial master specifications in sync. I am aware of other examples where they are not in sync, (aluminum windows glazing, and my favorite, fire containment.) and we all just have to do the best we can. (but this is certainly a topic for another time; sorry about that.) |
Wayne Yancey
Senior Member
Username: wyancey
Post Number: 224
Registered: 05-2005
| | Posted on Friday, December 01, 2006 - 07:37 pm: | |
Mark,
Thanks for the additional research. I guess I am victim of garbage in garbage out. I will be more dilgent in the future. It is obvious my employer needs to spring for the ACI 117-90 and 301-05.
Thanks
Wayne |
|
4specs.com Home Page