Stone and brick are assailed by multiple forces over time, and the extent of a structure’s resistance to them is dependent on how well designed it is.
A robustly built building may be able to bear up indefinitely against such forces, while a structure with a bad foundation, which does not shed water well, absorb movements and expansions, or is made from shoddy materials, will quickly deteriorate and require maintenance.
Most Common Causes of Masonry Deterioration
- 1. Excess moisture in masonry that leads to damaging freeze/thaw cycles and soluble salt crystallization action.
2. Water flow through walls giving rise to damage of supporting structure (wood rot or metal corrosion), differential settlement, and structural decay
3. Improper methods of repair such as sandblasting
4. Abrasion from windborne particles
5. Shifts in the underlying soil or foundation
6. Accidental impacts (falling trees, renovation tool slips, etc)
7. Acid Rain or air pollution leading to corroding and disintegrating materials
8. Moss and Lichen (secrete acids which cause chemical deterioration)
It is important to determine the cause of the problem in your masonry. Just as in a medical diagnosis, you don’t want to treat the superficial symptoms of the disease, but rather the underlying problem. For example, if there appears to be damage from moisture, you need to find out if it is due to a leaky roof, or if your foundation needs to be waterproofed.
The renovation required will also depend on the material involved. Cracked bricks are most easily replaced, but cracks in stone should be filled with grout or repaired with epoxy in preference to their replacement. Cracks in mortar joints are to be repointed.
A skilled masonry craftsman or inspector is usually able to make a good analysis of what needs to be repaired by a thorough visual inspection of a house and it’s foundation. For more involved cases where the problem’s source cannot be readily determined, further investigation and testing by a specialized restoration professional may be required. There are various masonry deterioration testing and monitoring methods.
Soil borings can establish if ground water problems are involved or not. Small test pits are dug at various times during the year and examined to gauge the level of ground water in relation to foundation footing.
The physical and chemical composition of stones, mortar and bricks are tested for age and composition. Moisture levels within these materials are also monitored by moisture sensors.
Salt deposits on or within masonry material are analyzed to assist in finding their source, which could be from de-icing salts, chlorides, or fertilizers.
Infrared thermography is used to measure the amount of heat transmitted through walls, which can pinpoint air leakage and heat loss areas.
Crack movement and progression can also be monitored and analyzed through various methods. Applying plaster to areas adjacent to the crack to see if it breaks down over time, scoring fine lines across brass strips attached to each side of the crack, and other specialized methods are used.
Efflorescence is brushed away and the area is monitored to see if the efflorescence returns and how quickly.
It can be necessary to repeat the inspections and testing over a period of time to get the overall picture of the problems on larger building, particularly with moisture problems which may change with the seasons. Periods of heavy rainfall, freezing and thawing and high winds, all can have their own unique stresses on a structure.
Finally, a general inspection should be carried out periodically on every building; once every five years is recommended.
Photo by Buffa, Creative Commons Attribution License