Stone is an ancient form of masonry. In theory, stone will last a lifetime. Stone exteriors work best when installed with old-fashioned techniques. Problems can occur when mixing stone masonry with new building techniques. For example, many homeowners want the look of stone without paying the cost to get a properly built stone exterior. They choose to go with stone veneer over a modern stud frame. This will likely fail over time.

Water is stone masonry's worst enemy because freeze-thaw cycles can cause cracks. Properly sealed stone masonry prevents problems. Every year, check your building's masonry exterior four hours after a heavy rainstorm. Any dark patches on the wall means that water soaked into the surface. This is a future problem that needs fixing.

Concrete block masonry is more common with industrial buildings. It should last 50 to 80 years, and you'll need to fix the joints after 25 years. Unlike brick, concrete blocks are not waterproof. You'll need to apply a water seal every 10 years. The best water seals are silane and siloxane. You can apply them by spray, and they soak into the surface of the wall like stain.

Here are some of the problems you may encounter:

• Bulges in concrete come from excessive pressure on the back side of a wall.
• Concrete cracks happen because of horizontal or vertical stress to a masonry surface. (This is why rebar is used to strengthen concrete.)
• Discoloration is caused by water penetration or is an indication that water is entering but evaporating.
• Deteriorating mortar joints are generally due to age or water penetration.
• Leaning walls are usually due to the lack of sufficient footing (additional concrete added to the bottom of a wall to strengthen it) or to more horizontal pressure at the top of the wall than the bottom.
• Brick, stone or blocks come apart from age and deterioration of mortar between masonry units.
• Sinking or settling in masonry is due to improper compaction of soil beneath the masonry or improper drainage around masonry.
• Leaching water is moisture that slowly finds its way through the masonry wall via cracks, holes and mortar joints, usually because of improper or deteriorating waterproofing.

-- Tips courtesy of HomeAdvisor.com