Board Formed Concrete

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Author Message John Hunter Senior Member Username: johnhunter Post Number: 99 Registered: 12-2005 Posted on Tuesday, October 02, 2012 - 05:55 pm:    The design team wants to use horizontal board formed concrete for the architectural concrete walls for an upcoming project. After looking at formliners they've decided they want to use actual board forms. Does anyone have any suggestions on the best way to proceed in terms of specifying? My sense is it belongs in 03 3300 "Architectural Concrete" because it's really about the finish, but this is a new one on me. Thanks. Guest (Unregistered Guest) Unregistered guest Posted on Tuesday, October 02, 2012 - 08:15 pm:    Yes, architectural concrete section, but you'll need to determine the extent of grading rules defects for board lumber that impart same to formed surfaces (e.g., knots, splits, etc.). Do your designer's have a reference sample panel to match? Or are willing to pay for having one made by someone before bidding? Otherwise, you'd have to try to specify (i.e., describe) the aesthetic effect that designers want and probably specify mockups (probably several) to confirm acceptable finish appearance. William C. Pegues, FCSI, CCS Senior Member Username: wpegues Post Number: 875 Registered: 10-2002 Posted on Tuesday, October 02, 2012 - 10:17 pm:    Yes, I agree with Guest there. I have done this a number of times but its been some time. I can't stress enough how important getting a sample/mockup done in advance of 'bidding'. The owner needs to be on board, this is a fee he will need to pay up front. Then the designers work with a concrete installer that is not tied to the GC, he is working for the owner, and you get what you really want as that is his purpose - to provide what you want. Out of that, its also nice to get the mix used for the concrete so that you also get the coloration - changing sand source can get you a wide variety of color for instance. "natural" is whatever it turns out to be, sand and the other fines can be a lot of different colorations. And same for the boards used, and how out of plane one is from the next, and the randomness (or lack thereof) in the lengths, how much offset different ends are from each other (from alignment to really randomness like wood flooring). Three is a lot to think about that can vary widely. Also, you need to think about and understand larger aggregates - some like the greater irregularity they can cause as they lodge in a corner and create a bubble randomly. I have done some that are really very irregular to some that are very smooth and flat. The control is all in the up front mockup that then becomes what all the bidders must bid to match. And it becomes the control sample for the selected installer to create their own job mockup to show they can actually match it before they proceed to actually doing the work. Its really great fun to do this kind of thing, and once you go through it, you remember the process and the things that went right or wrong forever. William C. Pegues, FCSI, CCS, SCIP Affiliate WDG Architecture, Washington, DC | Dallas, TX Steven Bruneel, AIA, CSI-CDT, LEED-AP, EDAC Senior Member Username: redseca2 Post Number: 373 Registered: 12-2006 Posted on Wednesday, October 03, 2012 - 01:03 pm:    William has provided excellent advice. If you are able to get mockups prepared prior to bidding you might also consider having one or more mockups prepared using selected board look form liners. Each sample could be specified as a Bid Alternate, giving you and the Owner some hard numbers and choices to consider. scott piper (Unregistered Guest) Unregistered guest Posted on Wednesday, October 03, 2012 - 02:06 pm:    I would also add some additional language about vibration of the concrete during the pours to make sure you get the look you want and to make sure you can duplicate it over and over again. We have vibration language in our standrad spec but it is somewhat "boiler-plate" and in an instance like this that could prove to be insufficient. What works fine for typical foundation walls (a guy banging the side of the form with a hammer intermittently) probably won't work in this situation. Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 508 Registered: 10-2007 Posted on Wednesday, October 03, 2012 - 04:09 pm:    The problem with trying to specify vibration of the concrete is that it gets into the means and methods of construction. Since there are numerous parameters that go into getting the right look you will not be able to specify all of them. Thus if there is a problem the contractor will look at you and say they did it how you told them. As an alternate I have seen specification that require the mockup be constructed using the same forman and workers who will do the actual production work. Thus if there is a problem you can lay the problem at the feet of the contractor. scott piper (Unregistered Guest) Unregistered guest Posted on Wednesday, October 03, 2012 - 06:02 pm:    I agree that there are many ways to achieve the desired look. I was not suggesting that you specify the vibration method but rather that you modify the wording to make sure the contractor is aware that they must develop an acceptable means with the mock up and then repeat it through-out the project. Writing a specification that makes the contractor responsible for developing and implementing a system for proper vibration would not be means and methods. I realize my first post gave the wrong impression, Sorry about that. Louis Medcalf, FCSI, CCS Advanced Member Username: louis_medcalf Post Number: 5 Registered: 11-2010 Posted on Thursday, October 04, 2012 - 11:55 am:    Boards for this type of formwork are often washed with muriatic acid to emphasize grain. The surface then should be neutralized. You may want to say something about grain direction in adjacent boards and number or size of knots that are permissable or even desirable. Wayne Yancey Senior Member Username: wayne_yancey Post Number: 545 Registered: 01-2008 Posted on Thursday, October 04, 2012 - 12:04 pm:    It is important to set controls for the location of butt joints between adjacent boards, such as the number of board between joints occurring at the same bearing, to prevent the stair step look. A BIG frestanding mockup (or 2 of 3 or ...) is imperative to get it right. John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1450 Registered: 03-2002 Posted on Tuesday, October 09, 2012 - 03:57 pm:    Rough-sawn vs. surfaced would also have a pronounced effect on the grain visibility, and the consistency of thickness between individual boards. Gerard Sanchis Senior Member Username: gerard_sanchis Post Number: 84 Registered: 10-2009 Posted on Tuesday, October 16, 2012 - 10:24 pm:    Consider also the wood specie to be used and its sugar content. The latter affects concrete color. Be mindful of face texture and remember that in most cases you'll get one pour for the liner if it's real wood. It will loose part of its texture during de-forming and cleaning. Karen L. Zaterman, CCS, LEED-AP, SCIP Senior Member Username: kittiz Post Number: 97 Registered: 10-2005 Posted on Tuesday, October 16, 2012 - 11:16 pm:    Perhaps also the number of times the same board is re-used. Seems I recall that on a tour of the Caltrans District 7 building downtown L.A. Karen L. Zaterman, CSI, CCS, SCIP-Affil, LEED AP BD+C ken hercenberg Senior Member Username: khercenberg Post Number: 340 Registered: 12-2006 Posted on Wednesday, October 17, 2012 - 01:33 pm:    Don't forget your concrete mix and finishing methods. As a general rule, fly ash darkens concrete. Granulated slag lightens the color. You also want to determine in advance whether you want any patching, grinding, rubbing, etc. (hey, this is conversation, not a spec). Any time concrete is touched after the forms are pulled, it affects the look. A lot of designers I've worked with would rather see voids and bugholes; they don't even want to see a wet burlap rubbed finish let alone grout or brick. Very often, grinding is prohibited except in the most egregious case of fins and projections. Often mock-ups are ineffective as they are too small and the conditions are too contrived. I'd require a tour of previous projects where the Installer has provided similar looks. You want to know that yours isn't their first project doing this. After all, this is probably more important to your designer than it is to the client. Something the designer wants to reject may end up becoming an end product by an owner that wants to keep the project moving on schedule. Robin E. Snyder Senior Member Username: robin Post Number: 442 Registered: 08-2004 Posted on Wednesday, December 05, 2012 - 09:20 pm:    @John - did you ever develop a spec section for the board formed concrete? If so, would you be willing to share? Thanks! Robin@spectraspecs.com