Ignore the weird formatting (titles).This is reference to be installed in the InterNACHI Narrative Library:
INSPECTION OF BRICK EXTERIORS
Brick Veneer VS Solid Masonry walls
• Brick veneer walls are connected to wood framing with metal ties. Typically there is a 1” air gap between framing and brick.
• Brick above window and door openings is typically supported by a lintel (metal header).
• Brick veneer may bear upon a ledge cast into the foundation, or on angle steel bolted to the outside of the foundation wall.
• No headers (brick ends) will be visible in a veneer wall.
• Brick veneer walls typically have weep holes installed along the bottom course to allow any water that finds its way behind the veneer to escape.
Solid Brick Masonry
• Solid brick masonry typically consists of inner and outer brick walls (called “wythes”), connected to each other with header bricks. Header bricks are bricks turned 90 degrees so that one end of a header brick is mortared into the outer wythe and one end into the inner wythe.
• Metal ties are also used for this purpose although they are subject to long-term failure from corrosion.
• Window and door openings with arches above the openings instead of lintels indicates solid masonry walls.
With both types of walls, look for bulging where metal ties have failed.
CAUSES OF CRACKING
When forces act on a material or a structure that create stress, cracking is one of the methods that nature uses to relieve that stress.
Differential Soil Movement
Differential soil movement happens when:
- One part of a building remains stable while an adjacent part of the building moves. Heaving, settling and creep can all cause differential movement.
Heaving can be caused by:
- Saturated soil expanding as it turns to ice. You might see this where an exterior hose bib leaks where plumbing supply pipes have leaked, or where roof drainage discharges to the foundation.
- Expansive soils. Soils that expand in volume with increases in moisture content are typically clays. Clay deposits can be cover large areas and small deposits may exist randomly and affect only scattered homes in a small area.
Settling can be caused by:
- Inadequately compacted fill. Soil disturbed by the excavation process must be compacted to a density equal to that of the surrounding, undisturbed soil. If soil is inadequately compacted, the weight of the structure will force air out of the spaces between soil particles and settling will occur.
- Consolidation occurs when soil loses moisture, leaving air pockets between soil particles. Again, the weight of the structure will force air out of the spaces between soil particles and settling will occur.
- Fill impurities can consist of wood that will eventually decay, leaving a void in its place, or any other material that deterioration will reduce in size over time.
- Collapsible soils: Collapsible soils are those in which a significant portion of particles are loosely stacked and held together by thin binding agents like clay or other materials, all of which are water-sensitive. The particle structure is stable as long as it remains dry. Once water is introduced, the binder dissolves and the particle structure collapses, causing settling.
Lateral movement can be caused by:
- Soil creep: Soil creep happens when gravity slowly moves soil downhill. This can happen when, in order to create a buildable lot from a sloped lot, the builder brings in fill to level the lot. If the original lot was too steeply sloped, the fill may start sliding slowly downhill. Especially if the rate of creep beneath a structure foundation varies among different parts of the foundation, stresses may develop that are relieved by cracking.
Craze cracking is random hairline cracking, usually appearing on the face of glazed brick. It may be caused by poor manufacturing processes or as a result of freeze damage.
Cracking caused by soil movement is typically visible lower in the walls.
Stepped cracking in mortar is typically the result of foundation movement caused by differential soil movement. It will follow the rules for crack closures but is typically oriented diagonally. Cracks follow mortar lines because the mortar is weaker than the brick.
Differential soil movement can also cause straight cracking. If a type of mortar has been used that is stronger than the brick, cracks will propagate (grow) through the brick and mortar in relatively straight lines (not stepped cracking).
Cracking/Deterioration Above Arched Openings
Solid masonry (brick double wythe) walls often have arches supporting the wall areas above openings. Because of the increased stress in thee areas, over the long-term it’s common to see cracking in the arches and the wall areas above them. This is typically the result of mortar deterioration. It will continue to deteriorate unless it is stabilized by re-pointing or rebuilding, depending on the condition.
Cracks should be described in terms of “closures”.
Descending closure: crack is wider at the top.
Ascending closure: crack is wider at the bottom.
Both ascending and descending closures can be caused by either heaving or settling, depending on to which part of the foundation walls the vertical force is applied; at the corners or between corners.
• Heaving at a corner will cause an ascending closure (wider at the bottom).
• Heaving between corners will cause a descending closure (wider at the top).
• Settling at a corner will cause a descending closure (wider at the top).
• Settling between corners will cause an ascending closure (wider at the bottom).
Horizontal cracks may develop where mortar loses its bond to brick. Raking and re-pointing would be required for correction.
The primary cause of brick spalling is the use of mortar with excessive compressive strength. Mortar is typically made up of three dry components: a binder, an aggregate and lime. This is usually Portland cement, sand and hydrated lime. It’s the ratio that determines the strength, or ASTM classification, of the mortar.
Brick is a reservoir material, meaning that it can absorb and store significant amounts of water. If, while brick is full of water the outside temperature drops and the stored water turns to ice, brick will expand.
Under these conditions, softer, lime-based mortar will compress, accommodating the expansion without visible damage. Harder, portland cement-based mortar will not compress enough to accommodate this compression and the developing stress will cause the brick face to spall.
If the mortar joint is flush with the brick face, spalling brick will lose only its corners. If the joints are raked, so that the brick face extends out past the mortar termination, the brick face may shear off along a plane flush with the mortar termination, affecting brick across the entire wall, including all brick walls built with the same mortar.
The general term for this condition is “constrained expansion”, and it may also be caused by concentrated (point) loads.
A good mason should be able to mix a re-pointing mortar that will not jeopardize masonry. If the color or texture are more challenging, there are firms available online that will custom match mortar samples for under $200.
White stains are typically efflorescence. As water moves through masonry it dissolves mineral salts that it carries to the face of the masonry. As water evaporates from the face, the white, powdery residue accumulates on the surface. Efflorescence is typically a cosmetic issue, but is also a red flag that moisture moving through masonry may cause problems other than efflorescence.
Deposits of mineral salts located in the body of the brick but near the surface (called “subflorescence”) can cause spalling as the salt crystals expand with wetting. This process is influenced by the Saline Gradient: water moves from less salty areas toward saltier areas. In other words, salt attracts water. Larger deposits of mineral salts will have a stronger attraction for water. As water moves faster and faster through masonry, hydrostatic pressure develops. Water is moved through masonry by three different forces:
- Diffusion pressures are 3-5 pounds per square inch (psi).
- Capillary pressure reaches 300-500 psi.
- Osmosis is a stronger force, reaching 3,000-5,000 psi.
If the hydrostatic pressure exceeds the compressive strength of the brick, spalling may occur. Compressive strength of brick varies from about 3,000 psi to about 6,500 psi depending on clay characteristics and the manufacturing process.
When either of these conditions is visible, try to identify the source of moisture and recommend correction. The Standards of Practice do not require inspector to identify the source of problems, and it can increase your liability of you’re wrong, but sources are often obvious, and identification makes an inspector look good.
Other Stain Sources
Other sources of staining include rust, paint, smoke, mortar, etc. Most of these are cosmetic problems only.
Brick face may be eroded over time by improper cleaning, especially sandblasting. Sandblasting can cause severe erosion.
Mortar Joint Deterioration
Pointing mortar can be deteriorated by the action of wind or freezing moisture. It’s typically the lime binder that deteriorates. In extreme cases the bond between mortar and brick may fail completely.
Repointing or rebuilding will be necessary, depending on the severity of the problem.
Brick Window Sills
To help ensure that they shed water adequately, brick window sills should slope at least 15 degrees. Also, when they’re installed, the holes should be filled so that they can’t collect water. Sloped brick sills commonly suffer failure and should always be checked.