What are the code requirements for installing manufactured stone on the exterior of the wood stud wall of a house?

Tuesday, January 22, 2019

It is called “adhered masonry veneer” at Section 1405.10 of the Florida Building Code (FBC), and the International Building Code (IBC) is similar. The water-resistive barrier and lath are the same as for stucco. But here are the specific differences with manufactured stone:

1) Flashing - Should comply with Section 1405.4, with the addition of the following.

1405. Flashing at foundation.
A corrosion-resistant screed or flashing of a minimum 0.019-inch (0.48 mm) or 26 gage galvanized or plastic with a minimum vertical attachment flange of 31/2 inches (89 mm) shall be installed to extend not lessthan 1 inch (25 mm) below the foundation plate line on exteriorstud walls in accordance with Section 1405.4. The water-resistive barrier shall lap over the exterior of the attachment flange of the screed or flashing. 

2) Clearances - Minimum 4 inches above ground, 2 inches above paved surfaces, or 1/2 inch above exterior walking surface that is supported by same foundation as exterior wall.

1405.10.1.3 Clearances.
On exterior stud walls, adhered masonry veneer shall be 
installed not less than 4 inches (102 mm) above the earth, or not less than 2 inches (51 mm) above paved areas, or not less than 1/2 inch (12.7 mm) above exterior walking surfaces that are supported by the same foundation that 
supports the exterior wall.

    At some homes, we see that there once was 4” between the bottom of the stone and ground, but infill of soil and mulch for landscaping has reduced or eliminated it.

3) Scratch coat and adhering veneer - Minimum 1/2” scrach coat, completely covering the lathing and scored horizontally, followed by minimum 1/2” setting bed of mortar.

1405. Scratch coat.
A nominal 1/2-inch-thick (12.7 mm) layer of mortar complying with the material requirements of Sections 2103 and 2512.2 shall be applied, encapsulating the lathing. The surface of this mortar shall be scored horizontally, resulting in a scratch coat, with a minimum of 3/8” setting bed after manufactured stone is applied.

1405. Adhering veneer.
The masonry veneer units shall be adhered to the mortar scratch coat with a nominal 1/2-inch-thick (12.7 mm) setting bed of mortar complying with Sections 2103 and 2512.2 applied to create a full setting bed for the back of the masonry veneer units. The masonry veneer units shall be worked into the setting bed resulting in a nominal 3/8-inch (9.5 mm) setting bed after the masonry veneer units are applied.

Heres an example of an inadequate scratch coat and adhering veneer below.

    The building science guru Joe Lstiburek likes to call manufactured stone veneers “lumpy stucco,” because it's really just stucco with stuff stuck into the second, setting bed layer. Once you think of it that way, all the code requirements begin to make sense.

    Also, see our blog post What is the average life expectancy of manufactured stone?

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To learn more about exterior walls and structures, see these other blog posts:

What is the average lifespan of a house foundation?

What causes vertical cracks in fiber cement siding planks?

What causes raised white lines of residue on a block wall that are crusty and crumbling? 

What is the difference between soil subsidence, heave, creep, and settlement? 

How much ventilation is required for the under-floor crawl space of a home? 

 What causes stair-step cracks in a block or brick wall?

What causes a horizontal crack in a block or brick wall? 

How can I tell if a diagonal crack in drywall at the corner of a window or door indicates a structural problem?

What causes the surface of old bricks to erode away into sandy powder? 

What are the pros and cons of concrete block versus wood frame construction?

Should I buy a house with a crawl space? 

Why is my stucco cracking?

There's cracks running along the home's concrete tie beam. What's wrong? 

What would cause long horizontal lines of brick mortar to fall out?

How do I recognize structural problems in a retaining wall? 

What is engineered wood siding?

Should I buy a house that has had foundation repair? 

What is a "continuous load path”?

Should I buy a house with asbestos siding?   

How can I tell if cracks in the garage floor are a problem or not? 

What do you look for when inspecting vinyl siding?

Why is housewrap installed on exterior walls under the siding? 

How do I recognize serious structural problems in a house?

Why did so many concrete block homes collapse in Mexico Beach during Hurricane Michael? 

How can I tell if the concrete block walls of my house have vertical steel and concrete reinforcement?

Should I buy a house with structural problems? 

What are those powdery white areas on my brick walls?

What causes cracks in the walls and floors of a house?

How can I tell if the exterior walls of a house are concrete block (CBS) or wood or brick?

What are the common problems of different types of house foundations? 

• What are the warning signs of a dangerous deck?

      Visit our EXTERIOR WALLS AND STRUCTURE page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles. 

Diagrams - Installation Guide and Detailing Options for Compliance with ASTM C1780 for Adhered Manufactured Stone Veneer, Masonry Veneer Manufacturer’s Association

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