How to achieve smooth and seamless stucco across whole surface?

Question

I did my stucco all by myself, (foolishly) relying on intuition how to do it, thinking I could just iron it out with a trowel. It doesn't look smooth. How can stucco be applied so it looks smooth across the whole wall without being uneven? I used regular bags of mortar/stucco from a big box store and was doing small increments each time because I was doing it all by myself. This one wall was probably done over 5-6 days of work in small increments. The seams used to be much worse but I spent countless hours ironing them out with a 4.5" grinder and a special diamond polishing blade. Still, it looks nowhere near as smooth as many European buildings where stucco is a lot more common than here in the States.

Is there a top coat that I can apply in one day with a paint roller that would fill in the rough surface and make it all look smooth? Like epoxy or really thick paint. It has gray primer in the picture.

UPDATE: If I finish painting this (has primer now), and if someone in the (near) future decided to do apply that top coat, would the paint being on be a problem for the top coat to stick to as substrate? IOW, should i leave it unpainted to allow for this addition in the future?

Answer 1

To my knowledge, there isn't a paint or color coat thick enough to smooth that out. You need a texture coat of stucco to provide the finished surface.

Just like mudding or plastering, stucco is a mix of technique and art. It's difficult to get a smooth surface and there are people who are excellent at it and people who aren't. Luckily, tabeltop smooth isn't usually what you're going for with stucco anyway.

A stucco finish is generally 3 coats. The first is the scratch coat, which is rough, ugly, and only there to provide surface for the next coat to adhere. It is trowled directly onto the substrate (block or mesh). Think of tile mortar for this coat - it should have ridges, gouges, etc.

Second is the brown coat, which makes up the bulk of the thickness of the stucco surface. It is trowled onto the dried scratch coat with a smooth trowel. Smooth this coat out flatter than the scratch coat, but it doesn't need to be perfect. Think of drywall mud prior to sanding. You'll still see imperfections if you look for them, but it's "mostly" there. This appears to be the stage where your wall stopped.

Finally (which is the coat you appear to be missing), the finish/texture coat is applied. Apply this coat thin with a smooth trowel then float it flat with a rubber float while it's wet. Finally, just as it is starting to lighten from drying it is rubbed with a wet sponge to redistribute the cement, expose some of the sand, and flatten the surface. Each pass leaves you with a flatter surface - I think you just didn't do all the passes.

Check a section of your primed wall to see if mortar will adhere to the primer. If it does, you can add the texture coat right on top.