3-hole vs. 10-hole brick

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Author Message Paul Sweet (Unregistered Guest) Unregistered guest Posted on Friday, July 08, 2011 - 03:17 pm:    The mason for a large science building under construction is saying that he needs to increase the quantity of mortar mix from 7 bags to 10 bags per 1000 bricks because the selected bricks had 3 holes instead of 10. I can see where a slight increase might be reasonable, because mortar won’t bridge over the larger holes as well, and more would sag into them, but a 40% increase sounds high. Does anybody know of industry studies on the effect of number of holes vs. mortar quantities? The bricks are ASTM C216, so they are 75% solid no matter how many holes they have. Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 402 Registered: 10-2007 Posted on Friday, July 08, 2011 - 07:57 pm:    Run a test at the start of the work. weigh some bricks of each type w/o mortar. Have the workman install one bed joint and one head joint using 3 hole bricks and the same using 10 hole bricks. Weigh the assemblies and compute the difference in mortar weight in the two samples. The size of the hole might influence how far the mortar extends into the holes and hence the volume. George A. Everding, AIA, CSI, CCS, CCCA Senior Member Username: geverding Post Number: 602 Registered: 11-2004 Posted on Friday, July 08, 2011 - 08:08 pm:    Huh? Sounds like a bunch of hooey to me. Are they giving back a credit on the bricks because they have two-third fewer holes? I think your owner is being cheated, given the obvious design intent of providing decimal-based masonry units. Seriously, why is there an expectation of "x" number of holes, anyway? Surely it is not in the specification - if so, I'd love to see a copy of it. My understanding is that the cores in clay masonry depend on the die used to extrude the unit, and that is a manufacturer's decision. I doubt C216 says anything about the cores beyond the 75% requirement you pointed out. Sounds like someone sharpened his or her pencil a bit too much in bidding the masonry, and this is a ploy to staunch the financial bleeding. Regarding industry studies, try the BIA Tech Notes, or contact them directly. [In fact I am eagerly awaiting Mr. Trimble's comment if he is still lurking around these boards.] George A. Everding AIA CSI CCS CCCA Ingersoll Rand Security Technologies St. Louis, MO Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 403 Registered: 10-2007 Posted on Saturday, July 09, 2011 - 01:30 am:    George I Think the argument is that because the specs did not state the number of holes the contractor can base his quote on whatever brick he wants to use that meets the specifications. Then during CA the Architect/Owner tells him he has to use a sspecific brick that so happens to have 3 holes which costs more to buy and install. In this context the contractor probably has a decent claim. If the specs were written so that there were no price adjustments the Mason would have boosted his bid to cover the worst case which would mean that in many cases the Owner would pay more. In a situation such as this the trick is to understand what the contract required and what was the basis of the bid. Tim Werbstein, AIA, CSI, CCS Senior Member Username: tim_werbstein Post Number: 41 Registered: 09-2006 Posted on Monday, July 11, 2011 - 08:21 am:    Unlike laying 100% solid bricks, masons often lay cored brick by placing mortar along the two faces of the brick, not in the middle (where the holes are). There ought to be no difference in the quantity of mortar when laid this way. Curt Norton, CSI, CCS Senior Member Username: curtn Post Number: 176 Registered: 06-2002 Posted on Monday, July 11, 2011 - 09:02 am:    Face shell bedding is commonly used for CMU but it is not typical for exterior brick veneer. Full bed mortar is used for exterior veneer. I don't know of any reason why the mix would need to be stronger just because of the three holes. How stiff the mix is would make a bigger difference than the strength. David Axt, AIA, CCS, CSI Senior Member Username: david_axt Post Number: 1212 Registered: 03-2002 Posted on Monday, July 11, 2011 - 12:55 pm:    Here is information on cored bricks from Belden. "Orders for mortar have not increased, based on the brick percent solid. Monitoring of a variety of projects in several regions of the country has shown that mortar use has remained below seven bags/1000 brick for void area above 25% and below 30% of the bed area." http://www.masonryconstruction.com/industry-news-print.asp?sectionID=790&articleID=883613 Paul Gerber Senior Member Username: paulgerber Post Number: 75 Registered: 04-2010 Posted on Monday, July 11, 2011 - 02:34 pm:    When I first read this post this morning I was of the same opinion as the esteemed Mr. Everding, although I probably wouldn't have used the word "hooey" but something similar and a little more coarse. I have never heard of this sort of claim in my area, but I think I will give our CA guys a heads up to the potential. I too think that someone underestimated the amount of mortar he needed to perform the work or cut his margin a little too tight and is trying to find a way to recoup some cost/lost profit! David, thanks for the back-up information! Ride it like you stole it!!! Brian E. Trimble, CDT Senior Member Username: brian_e_trimble_cdt Post Number: 47 Registered: 08-2005 Posted on Monday, July 11, 2011 - 05:03 pm:    The article from Masonry Construction is the one I would have used in responding to this earlier. While larger cores may require a little more (undefined on purpose) mortar, it is usually not a significant amount. Mortar waste is often taken anywhere from 25 to 100%, so the coring often has little impact. Most C216 brick (cored up to 25%) are not face shell bedded. It's only when you start using C652 brick (cored over 25%) that face shell bedding is sometimes used, and that's usually on the structural brick units.