huangyhg

cmu foundation walls
i have a slab on grade building with masonry foundation walls bearing on concrete footing. the masonry walls have #4 dowels at 48" o.c.. the masonry walls will be below grade 36" for frost protection and not subject to lateral forces. the rebar is in there to just tie the masonry to the concrete footing.
my question is: do the masonry walls have to be grouted solid or is it ok to only fill the cores that have the rebar?
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we specify any cmu below grade to be grouted solid.
no good reason to grout the walls solid.
there is no structural reason, but it is a good place to dump the excess if you used grout and not concrete.
if you are really worried about uplift it is a plus, but with verticals at 48" you still have the footing and associated loads.
you will get a variety of answers. i like them filled with grout to prevent the cores from filling up with water and freezing.
jike is correct. your wall does not have strength concerns but practices. ever think to fill the voids with insulation material to prevent cold floor around the perimeter?
the plant site that i am at has cmu walls with every 3 block filled with concrete/grout and rebar in it.
grouting the cells below grade prevents water ponding and freeze/thaw issues. definitely a sound construction technique that i've seen used many times.
there is not much worse than partially filled grouted walls that are grouted without any controls. the results give no benefit and possible problems. - sort of like "belt and suspenders" not as good as a belt or suspenders.
for controlled, specified grouting, smart engineers will use blocks with cores that align to facilitate proper, complete filling with 8" - 11" slump grout. normal three core or two core block (even with flush ends) do not align well enough. engineers/inspectors make a big deal out of mortar projections into the core space when grouting, but permit units that cause the same or worse situations. conventional 2 core block with open ends (half cores) will leak leak grout, creating a semi-solid pyramid around the rebar if it ends up having good bond. in any case the rare problem of water accululation still existes. if concrete is used instesd of grout, you are just permitting a location to dump unconsolidated left over concrete.
you can do it, but it is not professional or correct.
in 40 years i have not seen too many problems (except for remodeling/alterations) and later utility access.
forgive the tiraid, but i have seen too many good uses of masonry internationally and hate to see u.s. engineers habitually misuse it.
dick

in our office, we always call out fully grouted masonry walls below ground.
i would also recommend fill solid with 3000 psi pea gravel. it does not have to be grout/concrete. there are so many reasons why you want to have cmu wall inside the soil to be filled solid.
the prudent thing is to grout all cells below grade, preferably to a foot above grade. you are leaving yourself open to too many problems to list here just to save the client a few bucks.

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