Precast Stone & Water Damages

Is Precast Stone Veneer the New Synthetic Stucco Water Damage Nightmare?

By Paul King-Licensed General Contractor & Licensed Home Inspector

Precast or manufactured stone veneer has become extremely popular in recent years. After all it’s a beautiful product, it makes the home look grand and structurally sound (in my opinion), and is a nice alternative to brick, cement fiber, vinyl, stucco or wood.

Many builders like at as well because it is less expensive than brick, but many are able to charge buyers the same price as a brick veneer so they can increase their profit margins.

Personally, I like the product so much that the next home I build for my family will be partially clad with precast stone veneer.

Since moving back to the Carolinas several years ago I have inspected thousands of homes, hundreds clad with precast stone and the popularity of the product is increasing. Unfortunately, the vast majority of the installations of precast stone veneer and its related components we’ve inspected do not come close to meeting code requirements. Despite overwhelming evidence some builders and precast stone subcontractors are trying to convince buyers there are no issues and pushing new home buyers to believe the installations are fine. Unfortunately, from what we’ve seen many buyers end up believing that the precast stone was correctly installed and do not demand the builder to sure the issue. Knowledgeable private inspectors are often accused of being incorrect, after all when someone says something along the line of “...that’s the way we always do it...” or “...it passed code so it must be correct…” many reasonable people will buy the statement. Sadly the trusting buyers that believe that statement are likely to wind up with severe water damage, compromised structural components, and possible mold growth inside walls that will require replacement of the precast stone veneer, framing, insulation, sheetrock, etc in a matter of a few years. Also, by the time they uncover the problem the structural damages are likely to be severe.

I took the photos above from outside and inside a beautiful custom built home less than two year's old home where the exterior wall was clad with precast stone veneer. The installation is typical of what we see locally, the exterior walls looked beautiful and showed no visible evidence of problems. The interior walls showed no indications of problems, only a small stain became evident in a corner of the baseboard. When the sheetrock was cut away from the interior walls and the insulation was moved over the entire wall sheathing was saturated with water; an inspection of the bandsill and foundation plate in the crawlspace indicated water damages as well. Most homeowners, contractors, and inspectors do not see the problem until the sheetrock walls show evidence of moisture and by the time the moisture gets that far the structural damage is typically extensive. In the case of this home the repairs were several thousands of dollars.

Some people say the problem is that there are minimal building codes that builders must adhere to, but actually there are plenty, many of which have been in existence for quite some time. Failure to following these codes as well as the stone manufacturer’s installation and or flashing instructions are typically the root causes that lead to that vast majority of all of the problems. For starters people need to realize that building codes “establish minimum regulations”, meaning codes are absolute minimums that must be met. Both North Carolina and South Carolina have currently adopted 2003 International Residential Code and 2003 International Building Code; North Carolina code has some minor revisions to International Code. 2006 IRC and IBC have been published for years so one could easily come to the conclusion that any revisions in 2006 codes should be known by builders and specialty contractors and that a standard of care and good construction practices would entice contractors to adhere to the 2006 code revisions despite their yet being adopted.

Unless otherwise noted any codes will be 2006 NC Residential Code/2003 IRC and/or 2006 NC Building Code/2003 IBC.

The International Code Council has published “ICC-AC51-ACCEPTANCE CRITERIA FOR PRECAST STONE VENEER” for several years in an attempt to clarify what codes should be followed.

In ICC-AC51 you have the following:

·         “Section 1.2 …The veneer system is considered a variation of exterior plaster regulated by IBC Section 2512, IRC Section 703.6,…and a variation of adhered masonry veneer regulated by IBC section 1405.9…”

·         “Section 2.1.1 Installation Instructions.”

·         “Section 2.1.2.1 Installation under the IBC & IRC: The installation instructions must comply with IBC Sections 1403.2 and 2512.1…” “Except when installation is over concrete or masonry walls, a water-restrictive barrier is required under the precast stone veneer system. The water-restrictive barrier shall comply with IBC Sections 1404.2 and 2510.6 or with IRC Sections R703.2 and R703.6.3, as applicable.”

·         “Section 6.0 Evaluation Report Recognition”

·         “6.3 Requirements for water-restrictive barrier, flashing, and weep screeds. For installations under the IBC and IRC, weep screeds shall have weep holes at least 3/16 inch (4.8 mm) in diameter, spaced less than 33 inches on center, in accordance with Section 6.1.5.2 of ACI 530.”

What do the NC & ICC Codes say?

“R102.4 Referenced codes and Standards. The codes and standards referenced in this code shall be considered part of the requirements of this to the prescribed extent of each such reference. Where differences occur between provisions of this code and referenced codes and standards, the provisions of this code shall apply. Exception: Where enforcement of a code provision would violate the conditions of the listing of the equipment or appliance the conditions of the listing and manufacturer’s instructions shall apply.” Most construction professionals believe this to say, if there is a manufacturers installation instructions they must be followed. Unfortunately many of the precast stone manufacturers do not have ICC acceptance and have not printed installation instructions. According to one industry source less than 5% of all precast stone manufacturers have ICC acceptance for their products.

“R703.6 Exterior plaster.”

“R703.6.1 Lath.” Lath should not be visible in a non-destructive/typical inspection of a completed home. If any lath is visible the veneer is not properly installed.

“R703.6.2.1 & IBC 2512.1.2 Weep Screeds. A minimum 0.019-inch (0.48mm)( No. 26 galvanized sheet gauge), corrosion-resistant weep screed or plastic weep screed, with a minimum vertical attachment flange of 3 ½ inches (89mm) shall be provided at or below the foundation plate line on exterior stud walls in accordance with ASTM C 926. The weep screed shall be placed a minimum of 4 inches (102mm) above the earth or 2 inches (51mm) above paved areas and shall be of a type that will allow trapped water to drain to the exterior of the building. The weather-resistant barrier shall lap the attachment flange. The exterior lath shall cover and terminate on the attachment flange of the weep screed.” The vast majority of the precast stone veneer installations we have inspected have no weep screed installed and the stone is installed to the ground and paving, a clearly visible omission of code requirements.

“R703.6.2 Plaster & 2512.1.1 On-grade floor slab. “…On wood frame construction with an on-grade floor slab system, exterior plaster shall be applied in such a manner as to cover, but not extend below, lath, paper, and screed.” The lath and paper should not be visible during inspection of a completed home, but if the weep screed is omitted as typically found, this code provision cannot be met.

2006 IRC although not yet adopted locally, adds a new requirement. “R703.6.3 Water-Restrictive Barriers. Water-restrictive barriers shall be installed as required in section R703.2 and, where applied over wood-based sheathing, shall include a water-restrictive vapor barrier with a performance at least equivalent to two layers of Grade D paper. Exception. Where the water restrictive barrier that is applied over wood-base sheathing has a water resistance equal to or greater than that of 60 minute Grade D paper and is separated from the stucco by an intervening, substantially, non-water absorbing layer or designed drainage space.” The publication “Significant Changes to the IRC 2006 Edition” by Hamid Naderi, P.E. & Douglas W. Thornburg, AIA states “Experience has shown that the typical method of protection for exterior wood sheathing has created problems for some types of exterior plaster. Grade D paper appears to have the proper permeability characteristics to prevent entrapment of moisture, thereby eliminating most of such moisture-related problems behind plaster applications.” The few manufactured stone companies that publish installation instructions require two overlapped layers of Grade D paper. Unfortunately this cannot be inspected unless an under construction inspection is performed during a very short window and most builders are not likely to stop construction so you can schedule a private inspection of this step.

“R703.8 Flashing. Approved corrosion-resistant flashing shall be provided in the exterior wall envelope in such a manner as to prevent entry of water into the wall cavity or penetration of water to the building structural framing components. The flashing shall extend to the surface of the exterior wall finish and shall be installed to prevent water from reentering the exterior wall envelope. Approved corrosion-resistant flashings shall be installed at all of the following locations:

1.     At top of all exterior window and door openings in such a manner as to be leakproof, except that self-flashing windows having a continuous lap of not less than 1 1/8 inches (28 mm) over the sheathing material around the perimeter of the opening, including corners, do not require additional flashing; jamb flashing may also be omitted when specifically approved by the building official.

2.     At the intersection of chimneys or other masonry construction with frame or stucco walls, with projecting lips on both sides under stucco copings.

3.     Under and at the ends of masonry, wood or metal copings and sills.

4.     Continuously above all projecting wood trim.

5.     Where exterior porches, decks, or stairs attach to a wall or floor assembly of wood frame construction.

6.     At wall and roof intersections.

7.     At built-in gutters.”

2006 North Carolina R703.8 adds “Install flashing per ASTM E 2112 Standard Practice for Installation of Exterior Windows, Doors, and Skylights, or in accordance with the manufacturer’s supplied written instructions. Aluminum flashing may not be used in contact with cementitious material except at counter flashing.” Many of these code provisions are typically not met.

“1403.2 Weather Protection. Exterior walls shall provide the building with a weather-resistant exterior wall envelope. The exterior wall envelope shall include flashing, as described in section 1405.3. The exterior wall envelope shall be designed and constructed in such a manner as to prevent the accumulation of water within the wall assembly by providing a water-restrictive barrier behind the exterior veneer, as described in section 1404.2 and a means for draining water that enters the assembly to the exterior of the veneer, unless it is determined that penetration of water behind the veneer shall not be detrimental to the building performance….” This cannot be fully evaluated in a completed home.

“1404.2 Water-resistive barrier. A minimum of one layer of No. 15 asphalt felt, complying with ASTM D 226 for Type 1 felt, shall be attached to the sheathing, with flashing as described in Section 1405.3, in such a manner as to provide a continuous water-restrictive barrier behind the exterior wall veneer.” This cannot be inspected in a completed home.

“2510.6 Weather-resistant barriers. Weather resistant barriers shall be installed as required in section 1404.2 and, where applied over wood based sheathing, shall include a weather-resistant vapor-permeable barrier with a performance at least equivalent to two layers of Grade D paper.” This cannot be inspected in a completed home.

While some items cannot be inspected in a completed home without being destructive many of the code provisions can be inspected. If the installer/contractor, who one would consider to be a professional in that specific trade, was unaware of the code provisions and often times the manufacturers installation instructions or just simply ignored them with regards to what can be visibly inspected in completed construction how confident can we be that they followed all of the code provisions and manufacturers installations instructions for the components that cannot be inspected without being destructive?

If they disagree with what has been made obvious it should raise concern that there are hidden issues as well.

Why, may you ask, would a precast stone sub contractor try to convince a buyer or homeowner that their installation was correct? The cure would involve tearing off the much and possibly even all of the veneer. That may expose water damage and deterioration. Everything removed would have to be thrown away and a new installation would have to be performed. Neighbors with precast stone would see the repair and/or hear of the repair and want their home corrected as well. If the precast stone contractor has failed to install the veneer on thousands of homes what is the possibility of them being able to afford return to all of those homes and correct their mistakes without going bankrupt?

Two of the higher quality, larger precast stone manufacturers are Owens Corning Cultured Stone and Centurion Stone; they are also two of the most commonly installed brands locally. Listed below are links to their ICC evaluation reports and installation and or flashing instructions.