Masonry rebar splice length vs grout lift height

[smvk3]

I have a project where I am using #6 and #7 rebar for an 8" CMU wall. The design code is 2006 IBC and the required masonry rebar lap splice length is 72d[sub]b[/sub] due to the stress in the bars. So for a #6 and #7 bar, the required lap splice length is 54" and 63", respectively.

The masonry contractor wishes to construct the wall in 48" lifts. I have a note on the drawings stating that the lap splice shall be within the grouted lift height for the wall, otherwise rebar couplers would have to be used. Therefore, the contractor would have to increase the height of his lifts from 48" to at least 56" for walls reinforced with #6 bars, and 64" for bars reinforced with #7 bars.

The contractor stated I am wrong and that the splices dont need to be within the grouted lift of the wall. However, I dont see how this would work as you could have up to three bars in one area due to overlapping splices.

Is the contractor right?

 

[tristrium]

Is it a bad thing to have splices extending across multiple lifts?

You will end up with a line of bars terminating at the same point as a construction joint otherwise.

Perhaps you could stagger the laps vertically and extend across lifts.

I have seen a wall blow out that was poured too soon after laying bricks, so be careful.

I am assuming you are talking vertical splices.

 

[Tomfh]

Why does it make a difference if a lift intersects a splice?

 

[smvk3]

Wouldn't each grout each lift interface represent a construction joint in the wall? Wouldn't you want to make sure you are developing the vertical reinforcing at the top and bottom of each grout lift/construction joint to maintain continuity in the wall?

 

[BridgeSmith]

I expect you know this, but grout, like concrete, is expected to carry only compression loads, not tension, including between the bars at the splice. So, I would have the same question as Tomfh; why would it matter if the splice crosses a joint in the grout?

Rod Smith, P.E., The artist formerly known as HotRod10

 

[phamENG]

I love continuity as much as the next guy, but I agree that it shouldn't matter from the splice's perspective. Even in a monolithic pour, you can get cracks in the splice region and we ignore them since they'll close up in compression when the splice is engaged. A cold joint is little more than an intentionally placed crack.

From a constructibility perspective, though, I'm not sure how it makes sense unless they're using much longer bars and either hefting the block up and over (I doubt it) or using H-Blocks to weave the blocks in and around the bars (also doubt it, but possible if you have a local supplier of that kind of block). Timing the rebar installation/tie off/inspection with the grouting would be a nightmare if you don't want to splice them in triplicate every other lift. Do you have bond beams in the wall for horizontal reinforcement or are you using joint reinforcement?