In exterior applications, is it better to use mortar between brick pavers or to place pavers without mortar?
No simple answer to this question applies to all uses of pavers in all parts of the country. In general, brick paving without mortar is more appropriate for northern climates, where mortar can deteriorate rapidly due to freeze-thaw action. Brick paving without mortar and with a good subsurface drainage system holds less water and performs better. Mortarless paving systems have other advantages, which also are factors in southern climates. Mortarless brick pavements accommodate thermal and moisture expansion between individual pavers, reducing the need for expansion joints. They also accommodate small amounts of differential settlement without cracking. Mortarless brick pavements have some disadvantages, however. Dirt that collects in joints between pavers can support plant growth. Also, if the exterior paving is an extension of an interior brick floor, it may not be architecturally appropriate to change from a mortared system inside to a mortarless system outside.