Dry stack CMU question

[abq1124]

If you dry stack CMU, how do you account for difference in length between the full block and half block? Do you end up trimming the last longer block, or do you leave some space between where a full block and half block join?

[concretemasonry]

When it comes to meeting a wall length or going between two ends or columns, nothing is perfect and that is one of the reasons why mortar is used. It permits adjusting for the usual dimensional variations encountered in construction.

When you dry stack the block, you will do any corners first and then lay in between the corners or between the corner and end of a wall. When you lay out your block for length on the first course, you will be able to determine what kind of difference there is that has to be adjusted for. If it is very slight, you can just adjust the spacing to make the vertical joints small and uniform. It is is large, you will just have to trim the block or use mortar for one large vertical joint.

You will always have to be prepared to use some mortar on the project. It is commonly needed for the first bedding joint, to adjust for wide vertical joints or to lay one course of block midway up the wall to adjust for variations, make the wall plumb and to make it more stable to complete dry stacking.

If dry stacking even became common, block producers could make special block for the system, but it has not been warrented. In some markets you may be able to get full 8" high block in addition to the modular 7 5/8" high block.

In many cases, people that have dry stacked have discovered that upon completion, they would lay block in mortar on their next project because of the speed and convenience (wall bracing, easier schedule, etc.).

Dick