Stucco Thickness

[builtright3]

Just curious to know;

I notice that Chief always defaults stucco thickness to be 1 1/8" when stucco molding is 1".

Is stucco different thicknesses depending on the area?

[CharlesVolz]

I use 7/8" for 3-coat system for the lathe/stucco per ASTM C926 Table 4 summarized here:

 

[builtright3]

8 minutes ago, CharlesVolz said:

I use 7/8" for 3-coat system for the lathe/stucco per ASTM C926 Table 4 summarized here:

 

That's what I have always done is 7/8". However It always usually ends up being 1" on finish

Not sure where Chief gets 1 1/8"

Edited May 3, 2019 by builtright3
Clarification

[CharlesVolz]

Same place they get 3" for brick thickness.

[tommy1]

1 hour ago, builtright3 said:

That's what I have always done is 7/8". However It always usually ends up being 1" on finish

Not sure where Chief gets 1 1/8"

Good to know. Thank you.

[Kbird1]

Some maybe 7/8" ( that is minimum I think ) but not all, some like Rock Dash and some of the other heavy finishes can be thicker easily.....

 

M.

[builtright3]

The mill core (J Metal) that we use is 7/8" but they screed the brown coat to it and than the color added will make it one inch.

Not sure why I'm even processing this after almost 40 years in construction. I guess because I'm full time doing drawings and design now and I like to be accurate.

[CharlesVolz]

The ASTM 926 uses the language "nominal" to allow for some variation:

 

Quote

What is the correct thickness of stucco?

Stucco thickness depends on the backup system and on whether or not lath is present. In ASTM C926, the Standard Specification for Application of Portland Cement-Based Plaster, thicknesses are provided for scratch, brown, and finish coats.

 

Over frame construction, lath must be used. Over solid substrates—which include concrete masonry, cast-in-place concrete, and precast concrete—lath is sometimes used. When lath is present, three-coat plaster is recommended. Note that frame construction—metal or wood studs—may or may not have sheathing present, but that plaster thickness is independent of sheathing. With lath, total plaster thickness is 7/8 inch.

 

Three-coat work can also be specified for solid plaster bases without metal lath. The correct thickness is then 5/8 inch.

 

Two-coat applications are only for use over solid plaster bases without metal lath. For unit masonry, that thickness is ½ inch. For cast-in-place or precast concrete, the thickness for two-coat work is 3/8 inch. These are direct-applied systems, meaning that there is no metal lath involved.

It is important to note that the committee in charge of ASTM C 926, the reference document for this application, has decided to keep the term “nominal thickness” in the title of the table for two- and three-coat work. This term takes into account that walls are built to certain tolerances and may not be exactly plumb or plane. The reference to a nominal thickness allows for small variations from an exact dimension. The intent of the specified thickness is to provide a reasonable system that, over many years, has proven itself to be weather resistant and durable. Local building officials should be consulted for further information about variations from the specified thickness.

 

See www.astm.org for information about ordering a copy of ASTM C926, which contains the recommendations for both vertical and horizontal plaster thickness over metal plaster bases and solid plaster bases.

 

I am sure stucco that is way too thick could cause problems but what stucco contractor is going to do that?

[builtright3]

10 hours ago, CharlesVolz said:

The ASTM 926 uses the language "nominal" to allow for some variation:

 

 

I am sure stucco that is way too thick could cause problems but what stucco contractor is going to do that?

 

Yes, I'm aware. Back to my original question. Why does CA set their default at 1-1/8"? Not important just curious to know where it was pulled from. I build on the west cost (California) so is this a east cost standard? Maybe because of the cold? Not sure?