aci-530.1 3.3 b

huangyhg

aci-530.1 3.3 b.
aci-530.1 3.3 b. placing mortar and units
b. unless otherwise required, tool joint with a round jointer when the mortar is thumbprint hard.
are veneered (sheet-rock, brick, whatever) cmu walls exempt from joint tooling?

check out our whitepaper library.
compaction of joints by tooling is for watertightness and appearance.  if the joint is veneered, there is no advantage in tooling.
untooled joints cause cursing and slowdowns when attaching a veneer to a face with mortar pultrusions.  tooling is standard and you should fire the mason who skips this requirement.  
most codes now require the masonry to have waterproofing or dampproofing on the face prior to veneer application.  untooled joints create waterproofing issues with coverage and poor surface texture....
striking is necessary, tooling is desirable
i have seen cmu struck off flush (and not tooled) when sheet rock or some other finish is placed over it.
ron:
what kind of waterproofing issues arise with untooled joints?
untooled joints provide small pathways for water to penetrate. also, even if waterproofing is applied to the ouside face of the block, untooled joints create a higher likelihood that the a pathway for water will still exist. once moisture gets in, it will wick through the block and set off problems such as saturation of interior surfaces, mold, etc.
i think of it like poking holes in flashing...is it highly likely that the inside will flood from this? no. but is it possible that problems could arise? absolutely. it's simply much easier to follow aci, tool the joints, and do all the other things that are recommended/required.
jike...the act of tooling closes the surface pores to some degree and inhibits the migration of water into the joint.  it doesn't stop it but it does slow it down so that less gets in than if you had untooled joints.
msucog's post explains it well.