Specifications for stucco

Ask the pros- June, 2002
By Reggie Bullard




                     Specifications for lath and stucco

I have a Specification I wrote that was partly copied from the
specifications of Portland Cement Assoc. from 1929. 
I found it from the web and have used it  for submittals. It is what we use.  Also, note there are no expansion joints because they didn't have them in 1929 and I don't see why they do now.
 I did government work for years and had ambiguous specifications that at times were impossible to follow or simply ridiculous. As a warning to the plastering contractor, since these government specs are part of the bidding documents, you can be held to use them any time. You may have my specs approved instead, and edit them to suit your needs and preferences.
I had these on my RTBullard site for a long time and am amazed how many people use them. 
The most important thing that I left out is that this work must be done by skilled, experienced plasterers.
You can copy and paste the info below or download a pdf file by clicking here.
Without further adieu, my Specifications for lath and stucco:

                    Specifications for lath and stucco

Tar paper or suitable vapor barrier shall be used on bare wood surfaces.
Galvanized self-furring lath shall be used on all wood framing. Fasteners shall be spaced no more than 12” on center.
Portland cement stucco shall be applied in a 3-coat method to a nominal ¾” thickness.

Scratch coat shall be applied to cover Lath and cross-raked to provide an adequate key for the basecoat.
Scratch coat shall set at least 2 days before the application of brown coat.
Brown coat shall be straightened to a reasonably straight and true surface and surface floated and left rough with open pores for and adequate bond of the finish. Brown coat shall cure at least 3 days before application of finish coat.
Finish coat shall be white Portland cement, lime and sand with a color if desired. Finish coat shall be a nominal 1/8” and floated or textured as desired.
American Portland Cement Stucco Specifications (c. 1929)

Base Coats: 

5 pounds, dry, hydrated lime 

1 bag Portland cement (94 lb.) 

Not less than 3 cubic feet  sand (passed through a #8 screen) 
There are about 5 shovels to a cubic foot. We use about 4
cubic feet, but no more than 5 cubic feet on porous surfaces
like block.
Water to make a workable mix. 

Finish Coat: 

Use WHITE Portland cement in the mix in the same proportions as above. 

To color the stucco, add not more than 10 pounds pigment for each bag of cement contained in the mix.