Originally Posted By: jpope This post was automatically imported from our archived forum.
A less expensive method would be to tap on the blocks with the handle of your screwdriver You’ve been around construction long enough Kevin, I’m sure you know what hollow blocks sound like.
Was this a basement or just a crawl?
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Originally Posted By: kmcmahon This post was automatically imported from our archived forum.
Just a crawlspace but a concrete floor. Didn’t even think about tapping on it.
That said, I've never seen an installation of block with no mortar between the joints before with only filled cells, so I don't know if this is acceptable construction practice for a foundation wall:?: (I have seen it for landscaping)
Originally Posted By: roconnor This post was automatically imported from our archived forum.
Without mortar joints the wall would have very low bending resistance (similar to a wall with a large horizontal crack at mid height)
Reinforced grouted cell masonry would be very unlikely for typical residental construction ... and I would seriously doubt it would ever be done without bed or head joints ... 
I would flag it ... just my opinion and 2-nickels ...
-- Robert O'Connor, PE
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I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: kmcmahon This post was automatically imported from our archived forum.
Apparently the block is called Michigan Block and is an interlocking block they use in mines. Apparently this block doesn’t need mortared joints and you just waterproof the exterior to keep water out. Homeowner stated that it didn’t work too well and he had seepage in the lower 3 rows so he tuckpointed those. He said that did the trick.
Originally Posted By: jpeck This post was automatically imported from our archived forum.
Besides interlocking block, there are surface bonding systems (yuck!). (But that is not one of them, as there is no surface bonding coating on the visible side. Still … Yuck!)
Originally Posted By: kmcmahon This post was automatically imported from our archived forum.
Thanks for the link!
The problem lies with the foundation location itself. It is in an area that has many cranberry marshes and the growers are constantly raising and lowering the water levels in the ponds thus affecting groundwater in surrounding areas. These blocks are not meant to be saturated like that, therein lies the problem the current homeowner had of seepage thru the joints. Even with a layer of damproofing, it has to be done perfect or you have problems.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
Any interlocking or dry set blocks just rely on the weight to remain in place. Not so good for a foundation wall retaining more than a nominal amount of soil, or a wall subject to high wind loads [or earthquake loads … neither of which would be acceptable under high loads]. It would still need to be set in a mortar bed joint or grouted with rebar to have any substantial bending resistance …
– Robert O’Connor, PE
Eagle Engineering ?
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I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: dhartke This post was automatically imported from our archived forum.
Kevin,
Many years ago I drove a concrete mix truck. Frequently I delivered "block fill", a concrete mix that used #12 stone instead of #5 and added more water for easier flow. The contractors made trough-like funnels that set on top of the finished block walls and rebar was inserted vertically in the open tops of the block every couple of feet. It significantly added strength to a conventional block wall.
I don't know anything about a mortarless block system but I can imagine using "block fill" with it and you might have something.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
David … good description of what is called “reinforced grouted masonry” construction, which is required in high wind/seismic/design load areas. But I have never seen that with dry set CMU without bed joints in over 20 years of design and construction experience … doesn’t mean it has never been done …
One more reason why you can not make an evaluation call just based on a visual non-destructive inspection ...
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
You’ve been around construction long enough Kevin, I’m sure you know what hollow blocks sound like.