Is it true that it's harder to get watertight joints in fluted block walls?
Yes. Flutes make it difficult to tool bed joints. Instead of trying to tool bed joints in the shape of the flutes, tool them at the back surface of the flutes. This causes two problems: the flutes project, making them more exposed to weather; and the projecting flutes create small ledges for water or ice to accumulate. Nevertheless, with the joints tooled in this way, the wall is less likely to deteriorate than if the joints are poorly tooled. Poor tooling results in greater water penetration. (Also be aware if the flutes aren't bedded in mortar, they shouldn't be considered when determining the wall's structural properties.) Norbert V. Krogstad is a senior engineer at Wiss, Janney, Elstner Associates, Inc., Northbrook, Illinois.