Does stucco need expansion joints?

Tuesday, December 10, 2019

Stucco does not require expansion/contraction joints (also called control joints) when directly applied to concrete, concrete block, or other masonry, except where there is a change from one material to another.

    Stucco on wood frame construction is another story, because stucco has a different rate of expansion/contraction than the underlying wood framing. Wood is more responsive to changes in moisture, while stucco expands and contracts primarily based on temperature. So the two layers have conflicting patterns of movement and flexible joints are necessary.  Here are the standards, based on ASTM Standard C1063:

•• Maximum18 feet length of any stucco panel.
•• Maximum 144 square feet area per stucco panel, reduced to 100 square feet for horizontal, curved, or angular areas.
•• Length-to-width ratio of stucco panel cannot exceed 2.5 to 1.

    The home shown at the top of the page has a concrete block first floor and wood frame second, but lacks necessary expansion joints at second floor level. The photo was taken when the home was new, but many of these homes with inadequately installed stucco end up like the photo below after 7 to 10 years. Go to our blog post Why is my stucco cracking? for more details.

    And here’s a closeup of an expansion joint, with a hairline crack stopped by the joint.

    Also, see our blog posts How can I tell if a crack in a stucco wall is a structural problem and what is causing it? and Is the stucco on a wood frame house allowed to extend down into the ground? 

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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? 

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 serious structural problems in a house?

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?

How can I tell whether my house foundation problems are caused by a sinkhole or expansive clay soil?

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