As you probably know, trim is normally installed first and then then stucco is applied around it. From an aesthetic viewpoint, adding trim afterwards can be an issue since it will stick out further from the surface and, since stucco has a rough texture, you will get gaps that have to be filled. From a technical standpoint I don't think you would want to nail anything as the nail holes could be a source for leaks. I have seen stone (both tiles and veneers like brick and ledgestone) successfully applied directly to stucco using fortified thinset. If you don't penetrate the stucco surface I don't know why you would be creating a leak risk. Stucco is not waterproof and will absorb water during a heavy rain. For that reason they install a weep screed at the bottom of stucco walls which allows any absorbed moisture to escape.

Thank you so much for your reply - the stone sounds like a good idea - our builder mentioned that as a possible option - we are not sure why he failed to put appropriate trim on the house initially (except perhaps cost) and really want to add it now. Will update with the final results - thanks for your input!

If you have true stucco (cement) or synthetic (EIFS), it should not mater, the out lined procedure should be the same. Normally on hard coat (cement stucco), it is an acceptable practice to use the synthetic foam to create the trim details, and the same goes for the EIFS system.

Procedures to apply trim (assuming the current "stucco" abuts the windows)

1. Figure out designs (MAKE SURE TO INCORPORATE A 15 DEGREE BEVEL ON THE TOP OF ALL FLAT SURFACES AND ON ANY BOTTOM LEDGES THAT POTENTIALLY COULD HOLD WATER)

2. Tape and plastic the windows or door opening.

3. Cut foam shapes and attach using a base coat adhesive (stucco contractor will (should) know what this is. Make sure all joints are tight (just as if it were wood, no gaps)

4. Apply "duct tape around the perimeter of the new trim to protect the existing wall surface, keep this tape aprox. 1/8 -1/4 of an inch away from the new trim detail, this is where the base coat and new finish will connect to the existing wall surface. DONÂT "TRY" AND COVER THE TAPE WITH THE BASE COAT OR THE FINISH, AS THIS WILL MAKE IT HARDER TO REMOVE THE TAPE WHEN FINISHED.

5. After these have had a day for drying, it is now time to "rasp" (sand) them and fine tune them, making sure that the outside edges are true and straight and that the surface area "facing you" is smooth etc.)

6. Proceed to base coat on top of new trim using the same material as you used to "stick" the foam and imbed reinforcing mesh on all exposed areas. Smooth every thing out (you are allowed to see the design of the mesh telegraphing (slightly) through the base coat but you should not actually be able to "see" the mesh its self. double coat it if this is the case. (The base coat and mesh is what gives the trim its strength)

7. After base coat is dry, apply a bead of sealant to the top of the trim where it meets the existing wall, tool it with your finger in both directions to make sure you have a good bond, do not use a silicon based product, use a (most expensive one you can find $ 5-10) latex or preferably a polyurethane product, color should be close to finish color, but shouldnÂt matter to much because when things are dry stucco finish coat will go directly on top of this.
8. Apply finish color

9. Slowly remove plastic and tape after finish has dried (6-10 hours)

10. Apply a good quality matching caulk to the inside connection where the new trim meets the existing window

11. Every application is different, so some things may need modification, and make sure not to caulk any "weep" areas that are designed to allow any incidental moister out.

Good luck, sounds like alot but it is easily done and should not pose any threats to the current conditions

PS do not attempt any of this if temps are not going to be above 45-48- degrees for at least a min of 8 hours!!!!!

the4of_us hit it the nail right on the head. Decorative stucco elements should be adhered chemically (cement), not mechanically (nails).
Just to add: you'll want the caulking/sealant to be LOW-MODULUS.

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