Masonry Walls

Masonry is defined as the building of structures from individual units laid in and bound together by mortar. Inspectors find both solid masonry walls and veneer masonry in the houses they inspect. Each has a number of common defects.

Solid Masonry Walls

Many older homes throughout the country are constructed of full-thickness brick masonry or stone. Newer homes in the south often are constructed of concrete masonry units (blocks) at the first floor and wood frame at the second. In both cases, cracks are common. Almost all masonry will crack. Typically, cracking is due to shrinkage in the mortars and normal settling of the house. The inspector must determine whether or not the cracks are defects. Of course, large cracks or cracks with movement are candidates for further evaluation because they allow water to intrude and have the potential for structural consequences.

Generally, most inspectors believe cracks larger than 1⁄8 to 1/4 inch in masonry walls should be evaluated further. Additionally, a number of small cracks that add up to 1/4 inch or more may indicate more than usual movement. Any cracks with lateral (horizontal or vertical offset) movement should be investigated by a professional such as a structural engineer.

It is important to be observant for other evidence of movement that may be causative or consequential to the cracking observed in the masonry wall. This may include wracking of window frames or door frames, trimmed or rubbing interior doors, interior cracks, sloping floors, etc. These indicators, plus consideration of the age of the home and material being inspected, may indicate more than normal movement and require the services of a structural engineer.

Bulges are easier than cracks to assess because any bulge in a masonry wall is evidence of movement; therefore, due to the potential for dramatic failure, further evaluation is recommended as soon as possible.

Other areas to inspect closely in solid masonry walls are penetrations, such as windows and doors. Most solid masonry walls are not barrier walls. In other words, they will allow some moisture penetration, and they depend on the multiple wythes to allow water to drain to the bottom and escape. Due to this characteristic, any horizontal interruptions in the wall, such as the top frame of windows or doors, can cause moisture to slow in its downward path. This slow-moving moisture will be absorbed by wood frames, leading to their deterioration. Also, some moisture may enter the interior. In solid masonry walls, check closely the top of window and door frames, looking for deterioration and/or evidence of water penetration into the house.

Older solid brick and stone masonry (particularly brick) walls were usually strengthened with mortar. This mortar was a lime-based material and typically somewhat soft. It is porous and will allow moisture to escape between the bricks or stone. Often, old lime mortar deteriorates and typical maintenance is to rake out the old, loose mortar and install new. This is known as pointing. If the same type of mortar is not used (newer, plastic cement mortars are hard and less porous), the masonry units would absorb moisture and begin to “spall” (sections of the face would pop off). If deterioration is noticed in the mortar, be sure to recommend to the client that a professional with knowledge of vintage masonry buildings be consulted to determine the best course of repair.

Veneers

Veneers can be any material, but most often are brick or faux stone. Anchored veneers are heavy materials such as full-thickness brick and require a foundation. The veneer is anchored to the wood-frame walls with metal straps placed at 24 inches on-center each way. These materials are installed with an approximately 1-2 inch air space between them and the wood-frame walls to allow moisture to weep toward the bottom, where it may exit the wall through weep holes. Typically, weep holes are placed a maximum of 33 inches on center per the IRC (Residential Building Code); however, the Brick Industry Association recommends 24 inches for weeps (holes) and 16 inches for wicks (tubes with porous wicking material inside designed to help prevent entry of pests and
improve moisture movement out of the wall). These weep holes should be above-grade.

Adhered veneers are glued to the building with plastic mortars, such as thin-set. First, building paper and a metal lath are applied to the exterior of the wood framing. Next, a scratch coat of plaster (stucco) about 3/8-inch thick is installed. Once this material is dry, the adhered veneer is glued on and the joints are mortared. This type of installation does not require a separate foundation ledge for the veneer, but moisture should have an exit at the bottom of the wall. Usually, the adhesive bed is left open at the bottom of the wall or a weep screed is installed to direct water to the exterior.

Typical conditions requiring evaluation and repair found in anchored veneers are lack of weep holes, blocked weep holes and moisture intrusion into the house due to the lack of moisture exit. Occasionally, inspectors will encounter anchored veneer walls with sections displaced because moisture behind the wall was unable to exit and freezing caused movement, obviously a reportable condition. Metal lintels or headers typically are installed to support the masonry veneer above the penetrations. Often, these lintels develop surface rusting, a normal occurrence. Excessive rusting and movement of the veneer should be noted for further evaluation. There is almost always cracking of the mortar at the metal lintel. This is normal and should not be filled with caulking; it is the exit for moisture.

Glossary

Lintel
A beam placed perpendicular to wall studs above doors, windows or other openings to carry the weight of structural loads.

Weep holes or weeper holes
Small openings left in the outer wall of masonry construction as an outlet for water inside a building to move outside the wall and evaporate.

Weep Screed
Metal flashing used to allow moisture drainage in porous walls.

Wracking
The distortion of normally square or rectangle openings into trapezoidal shapes due to structural distress.

Wythe
Vertical masonry section, which is one unit thick in walls or as the dividing partition between two flues in a single chimney.

 

*Source: ASHI Reporter, June 2010