We are building a project with 9’ 4” walls. The walls have vertical steel in poured cells at 16” on center and a single 8”x8” bond beam one course down from the top of the wall. The top course is regular block with only every other core grouted above the vertical poured cells. We would like to pour this wall in a single 9’ 4” lift however the building official is telling us we must pour the wall in 5’ 4” lifts because of the bond beam one course down from the top.
The salient code section governing this discussion is out of TMS 402-2016 Section 3.2.1 and TMS 602-2016 Section 3.5 D – Grout lift height. A copy of these code sections is attached to this blog (I hope). Since the 2008 TMS 402/602 we have been allowed to grout up to 12’ 8” in a single lift if three conditions were met: 1) the masonry was at least 4 hours old, 2) the grout was fluid – 10-11 inches and 3) there were no intermediate bond beams to be grouted where we would need the grout to flow horizontally to fill the bond beams.
The next section of the code (3.5 D.1.b) tells us that if the first 2 conditions are met and we have intermediate bond beams we can grout to the bottom of the lowest bond beam above 5’ 4”. In this case that would be 9’ 4” subtract 16” or 8’ of height. So, by the book, we would place an 8’ lift then come back with a second pass and grout the bond beam and the course above.
The normal spacing of vertical and horizontal bond beams is 48” oc throughout the seismic regions of the country. In Florida we do not have the minimum 48”x48” seismic grid requirement and our bond beams are normally at the top of the wall. Thus, the code is written to ensure that the grout will flow at least 24” into any horizontal bond beam. In this particular case the grout need only flow 4” horizontally into the horizontal bond beam (remember the poured cells are only 16” on center).
It would be my hope that in this particular case common sense would prevail and the inspector or EOR would ignore the intermediate bond beam realizing that 1) it is virtually at the top of the wall and 2) the horizontal flow is MUCH, MUCH less than the distance that the code is set up to accommodate.
Failing common sense, section 3.2.1 of TMS 402-2016 provides for a solution through the use of a demo panel showing that the variance from the code does not affect the ability of the contractor to solidly grout the spaces in the wall receiving grout. The commentary to Section 3.2.1 gives additional guidance on the demo panel.
Jerry Painter, FASTM
Don Beers, PE, GC