STUCCO 1

[delt]

I cannot find information on several items concerning stucco.

1. What is a typical unit weight for stucco? Is it the same as for concrete?

2. How thick is stucco usually placed? Is 7/8" thick out of the ordinary?

3. Is there a limiting deflection for headers that support stucco walls? Is it similar to that for brick lintels (l/600)?

Any assistance would be appreciated.

 

[JAE]

Try:

http://www.lahabrastucco.com/

http://www.elrey.com

7/8" thick stucco weighs 10 psf. (per Timber Construction Manual, AITC)

 

[Ron]

delt...
Good conventional stucco (portland cement plaster) is going the way of dinosaurs. That's unfortunate,because it can be an excellent surface finishing material.

True stucco (without lath) should be placed in 3 successive layers known as the scratch coat (this is the stronger one, placed first and deeply scored to cause initial, closely spaced cracking), the brown coat (less cement in this layer thus the aggregate imparts a "brown" tint to the mix..this layer also has less shrinkage than the scratch coat and absorbs some of the shrinkage stresses, thus reducing (at least theoretically) the cracks at this level. These two layers are followed by a finish layer, similar in mix character to either the scratch or brown, depending upon desired finish texture.

The following layer thicknesses are used:
scratch-3/8"
brown-3/8"
finish-1/8"-1/4"

If using lath, the thickness can be reduced to about 5/8" total.

The unit weight of stucco is about the same as concrete/grout/mortar. Somewhere between 120 and 140 pcf.
This puts the value at about that which JAE gave, perhaps a bit more depending on mix constituent weights.

I would limit deflection to l/600 as brick. Also, be sure to accommodate overall shrinkage with properly spaced joints. Refer to ASTM C926-98a "Standard Specification for Application of Portland Cement-Based Plaster".