Years ago I had shelves put up in the garage. The shelves are attached to 2x4 pieces that were nailed to the cement block itself (not into the mortar). Two of the 2x4 pieces came off the wall and the shelves are only attached on one side now and hanging on the other side to the detached 2x4 that came off. I believe some sort of nail gun was used to drive the nails through the 2x4 and block because the nails have an orange plastic casing around them.
It obviously didn't work well because the nails didn't penetrate the cement block deep enough and eventually pulled away from the cement leaving small craters where the nail was attached to the block.
There were problems in the past with water leaking and it may have been through the mortar joints but not sure. Is there a problem with using masonry screws to re-attach the boards and screwing them directly into the mortar? Could this cause the wall to leak? It is an underground wall.
Thanks in advance for any suggestions. Really need to fix this asap before the shelves completely come down.

If there are no water marks on block in area were u want to put shelf, the probability of water coming in would be very low. I personally would use lead shields and lag bolts.

Chuck

I don't think there are any water marks - will have to check. I'm in a situation where lead shields would be difficult because one side is still attached firmly to the cement. I'm thinking of using Heavy Duty Tapcon Concrete Anchors (blue screws). I will also use these to reinforce the side that did not detach. I'm also thinking it should hold in the mortar if the screw is long enough.

I have only used those anchors on concrete. Mortar is softer and may not hold, but this would depend on the amount of weight u put on shelf.

Chuck

If the shelves are going to be loaded heavily, use toggle bolts. Drill a hole in the block void, insert the toggle, silicone caulk around the hole and screw the toggle tight. Lead anchors work but shouldn't be used in block because in expanding, they can crack the block. Toggle bolts do not put expansion pressure on the block.

All the advice you are giving me is good BUT... the issue is still that one side is still attached. The side that came off is barely an inch away from the wall. And although the shelves are leaning, nothing has fallen off (even the milk crate filled with misc. items and kind of heavy). Plus, this is something I have to do myself. I figure: one hand holding the 2x4 the other hand drilling the screw right through into the mortar. I bought the heavy duty Tapcon concrete anchors that will put almost 2" into the mortar. I also figure that if for some reason one screw loosened and moved, it's not going anywhere. I plan on putting at least 2 screws (maybe more) per 2x4 depending on how they are positioned on the wall.
I did read something about mortar nails that are specifically made for this purpose but didn't see them come up on a search at Home Depot. I'm not sure that would be a way to go due to the hammering - think that would just loosen or detach the other side that's still anchored to the wall.

CDS

Doesn't sound like the shelves are too long. How long and wide are they?

The screws are long enough and should work fine. I am picturing a shelf about 8 feet long.

Chuck

Naw... the shelves are not long or wide. Wide enough for a milk crate and 4 to 6 feet long. The 4 foot shelves are attached to the same 2x4 so both are leaning. The 6 foot shelves are attached separately to 2x4s - one is leaning the other didn't come loose at all and those are on the same wall. What is very strange is that the 4 feet and 6 feet shelves are on different walls and they both came loose on one side at the same time. Like there was a minor earthquake or something AND we don't have earthquakes here!

If the 2x4 is a leg(vertical) Then 2 screws will be fine.

If 2x4 is a ledger strip(horizontal) then I would suggest to put screws about 16 inches apart.

Chuck

Yes - they are all vertical legs. I was planning a screw in each mortar section behind the board. Some have 2, some 3 mortar joints.

M.P.