15 Using mortars that ensure the long-term preservation of the masonry assembly, and are compatible in strength, porosity, absorption and vapor permeability with the existing masonry units. Pointing mortars should be weaker than the masonry units; bedding mortars should meet structural requirements, and the joint profile should be visually compatible with the masonry in color, texture and width

Repointing with mortar of a higher Portland cement content than in the original mortar. This can create a bond stronger than the historic material (brick or stone) and cause damage as a result of the different expansion coefficients and porosity of the materials.

Repointing with a synthetic caulking compound. Using a 'scrub coating technique to repoint instead of using traditional repointing methods
16 Duplicating original mortar joints in color, texture, width, and joint profile  
17  Replacing in kind extensively deteriorated or missing parts of masonry elements, based on documentary and physical evidence Using a substitute material for the replacement part that neither conveys the same appearance as the masonry element nor is physically or chemically compatible
Concrete    
2 Documenting the form, composition, strength, color, texture, details and condition of the concrete before undertaking an intervention. For example, identifying the particular characteristics and source of the type of aggregate used. Undertaking an intervention that affects concrete, without first documenting its existing character and condition.
3  Protecting and maintaining concrete by preventing moisture penetration; maintaining proper drainage: improving water-shedding; and by preventing damage due to the overuse of ice-clearing chemicals

Failing to identify, evaluate and treat the various causes of concrete deterioration

Applying water-repellent coatings to above-grade concrete to stop moisture penetration, when the problem could be solved by repairing failed flashings or other mechanical defects
11 Stabilizing deteriorated concrete elements by structural reinforcement and weather protection, or correcting unsafe conditions, as required, until repair work is undertaken.  
12 Repairing deteriorated concrete by patching or consolidating, using appropriate conservation methods

Repairing concrete without treating the cause of deterioration

Replacing an entire concrete element when selective repair or replacement is possible.

Using coatings or finishes to cover and hide surface repairs.
13 Minimizing damage to early concrete by limiting the size of the chipping equipment to better control the degree of removal, remembering that the compressive strength of early concrete may be much lower than modern concrete.