• Masonry Fences...Got Cracks?
  • STUCCO, a care-free exterior - or is it?

Masonry Fences...Got Cracks?
Pete Di Girolmao

Throughout the Valley, as in much of the Southwest, many residential developments have incorporated masonry walls around sites to address a desire for both security and a cohesive community identity. Masonry has been a choice for permanence, stability, and resistance to wind and sun. As site designs have become more sophisticated, these walls have increasingly incorporated decorative finishes and graphics to identify the community and provide a design theme.

Unfortunately, many of our walls seem to be displaying signs of impermanence as a result of persistent cracking, foiling the maintenance efforts of even the most persistent HOA or individual owner, and degrading the appearance of the community.

While there may be significant, major structural concerns underlying a specific project's cracking concerns, we have found that the majority of problems appear to be related to marginal construction of a tightly-designed (or 'value-engineered') masonry fence system - the "mortarless headjoint" type of wall or fence.

Basically "mortarless headjoint" masonry is a system developed by the masonry industry and intended for non-load-bearing, non-retaining fence walls. It is designed with an interlocking vertical joint between blocks that eliminates the need for mortar at that joint, leaving mortar required only at the long, horizontal joints. For a typical 6' wall, street reinforcing of the hollow concrete block occurs vertically at 4' intervals, and horizontally only at the topmost block with a bar or wire "ladder" type reinforcing. At regular intervals of 30-50', vertical expansion joints or pilasters are required to absorb movement from daily temperature swings. Details for this construction are specifically addressed by a handout from various local building departments.

While these walls have been designed and engineered to provide quicker, less expensive construction, they leave little or no margin for error by the builder, and often result in walls of increased flexibility - poor candidates for thin, rigid stucco color coats used as a finish for the block. Even with the necessary steel reinforcing in place, the required lapping of the bars or wire ladders is not consistently done or is insufficiently anchored by mortar. The often-seen result of this is a series of stair-step cracks along the wall. Inadequate expansion joint placement and detailing may also aggravate the cracking. Walls without the additional finish over the block tend to hide the cracks in the pattern of the exposed joints, but may still have the cracking problems.

Although actual "fall-over" failure of the wall is not usually a concern, the outlook for maintenance is not reassuring, as surface patching of the stucco finish or mortar cannot withstand the movement of the poorly-bonded block. Permanent repair would need to be addressed on a project-specific basis, and may incorporate varying degrees of reconstruction and/or alternative finishes to eliminate the recurring cracking.

Pete di Girolamo is a principal at Building Analysts, A subsidiary of Salerno/Livingston Architects

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STUCCO, a care-free exterior - or is it?
Pete di Girolamo

Las Vegas, like much of the Southwest, uses Stucco as the predominant exterior finish material on its homes and many commercial properties. Stucco easily accommodates the many expressions of Mediterranean, Southwestern, and various 'western hacienda' variations that are so often seen. Its workability allows a variety of decorative or utilitarian textures.

What is stucco?

Stucco is also called Cement Plaster, which better describes what it is: a mixture of cement, sand, and water applied as a wet paste, cured and dried to a hard, durable finish.

Historically, stucco has been applied as a 3-coat cement plaster material, approximately 7/8" thick, over wire lath and water resistant building paper. Within the last several years, however, new alternative stucco finish systems have become popular in the building industry, which allow faster material application and often accommodate increased exterior insulation. Here in the Valley you may be familiar with what is known as "one-coat" stucco that is a 3/8" stucco mix over light-gage wire lath and 1" foam sheet.

What maintenance is required of stucco finishes?

Stucco, properly applied, should be relatively care-free, other than occasional cleaning or power-washing.

Unfortunately, "the devil is in the details," and increased maintenance - and possibly repair - may be necessary as a result of building and site conditions, deficiencies in the material and construction, or both.

Keep concentrations of water from the roof or exterior balconies from flowing directly on to the stucco to avoid staining from dirt that has settled on these surfaces, and to avoid concentrations of water that may find their way to poorly-detailed window, trim, or other potential leak sources. Control irrigation that may repeatedly spray the base of stucco walls. Las Vegas water is particularly hard on stucco, and can weaken and erode the surface. Local winds often make this difficult, and drip alternatives may be preferable for plantings close to the wall.

Check to make sure the bottom of stucco walls are not in contact with earth or porch and patio slabs. Irrigation or storm water has been observed to 'wick' up several feet in a wall. Unfortunately, attention is often not paid to these details during original construction, but aware Homeowners can avoid adding patio slabs and landscape that create this problem.

We try and do all that, and we still have problems...

Even well-maintained, there are some problems too-often encountered with stucco construction:

As we described, stucco is a mix of ingredients, not unlike making bread, and proportions of those ingredients, their placement, and curing are all critical to a finish that is durable. If it is weak or porous, it may require remedial repair or replacement.

The stucco assembly is the primary weather barrier for your building's exterior walls. What makes it effective is the combined quality of the stucco material, lath attachment, and building paper underlayment. Two of these materials are hidden from view, and may be contributing to poor performance of the assembly with respect to cracking of the finish, leakage to the interior, or both.

In an effort to market more interesting and varied designs for housing and commercial construction, the building industry has introduced more variations in the surfaces of exteriors, incorporating pot shelves, raised bands, and "pop-outs" around windows – all made of stucco. These often require special materials or detailing to maintain the integrity of the building's weather barrier around these complex shapes, usually complicate the 'maintainability' of the finish, and may require remedial repair.

Stucco will always be one of our most versatile building materials, and will continue to be the predominate finish for the built environment in the Southwest - it deserves to have its needs and limitations respected.

Pete di Girolamo is a principal at Building Analysts, A subsidiary of Salerno/Livingston Architects

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