Synthetic stucco is really EIFS (Exterior Insulation Finish System) and it a fiberglass mesh reinforced synthetic coating on extruded polystyrene insulation board. It had some serious problems in its early days because commercial builders used the unreinforced soft coat version instead of the reinforced hard coat system. It also got a bad name because it was used over housewrap with no drainage plane and a lot of OSB sheathing rotted especially in the Southeast.

Real stucco has one layer of wire lath and two layers of Portland cement-based plaster. Often an acrylic finish is added for added waterproofing and flexibility.

Both can fail miserably if not installed correctly.

Thanks mightyanvil! You're a fountain of knowledge. I really appreciate all that you contribute.

Best,

Bill

Here in Florida the hurricanes several years ago exposed the weakness of the 'one coat colored' stucco finish (the third kind). Wind-driven rain will pass right through it after a while (and also through the concrete block behind it). Many homes had their drywall ruined. A good coat of paint cures the problem but wasn't in the builder's plan at the time...relying on the color in the finish for the house color.

Sealed EIFS systems have failed across the continent. OTOH, a leading building scientist says that properly drained EIFS systems are fine.

For my part, a wall that has to be repaired if your child bounces a ball off it isn't my idea of "robust."

Here is a link that might be useful: Sealed vs. Drainable EIFS

Everything I have read about (real) Portland cement stucco states it's 3 coats -- a scratch coat, a brown coat and a finish coat that may have integrated color in it (ours was white).

It goes over metal lathe, which in turn has been applied over black building paper (called felt paper around here). The vapor-permeable, water-resistant building paper separates the plaster and lath from the water sensitive framing (or ICF wall in our case).

Done correctly, it lasts "forever" and looks great. Note: stucco is not waterproof and requires a proper drainage plain behind it and weep screeds at bottom of all walls.

Great info. I see stucco on alot of VERY high end (think million$) homes and figured it couldn't all be complete crap.

Anyone know how it compares in price per square foot versus brick?

Usually in Florida the standard finish is two coats...the scratch coat, applied over dampened block, then the brown coat that gets painted for waterproofing. Pretty much lasts until the building gets torn down. The three coat procedure with the included color doesn't perform too well here due to the high humidity causing mold and fungus growth on and in the surface. Plus you still have the problem of wind-blown rain penetration...but not as severe as the one coat. Much more durable with the stucco sealed with paint. Dallasbill's comment on drainage would be correct for stucco over frame.

In a real cement-based stucco system, the underlaymnet/weather barrier/air barrier that is placed over the sheathing should be a double layer so it can work properly as a drainage plane.

DuPont's StuccoWrap (wrinkled Tyvek) or DrainWrap (same product marketed for siding) with a cheap micro-perforated housewrap over it or two layers of building paper/felt should work fine.

Stucco did not stick to the old building felt made with cotton rag and high grade asphalt and because it wrinkled during installation it provided a drainage plane. Unfortunately, the stucco will stick to any modern single layer.

There have a lot of problems (especially in the Northwest) with single layer underlayments combined with poor window flashing and lack of kick-out flashing. (Contractors willing to use one layer of underlayment often also omit other waterproofing as well) A double layer of underlayment is now required by many states or local communities.

Here is a link that might be useful: stucco problems

Additional info

You can also search for EIFS failures too. the synthetic stuff has just as many problems.

It's as if builders just forgot how to keep water out of buildings.

Here is a link that might be useful: stucco problems

Manufacturers like STO offer a higher grade EIFS system for commercial projects that is rarely used for homes perhaps because home builders don't look far beyond conventional systems.

STO makes a liquid-applied vapor permeable weather/air barrier that is applied to the sheathing. It covers joints and wraps into openings which are reinforced with mesh tape. It's called GoldCoat and can be applied by sprayer or roller by anyone.

Huber makes a similar system but the sheathing is coated in the factory and the joints are sealed with tape in the field.

WR Grace makes a fluid-applied permeable air barrier called
Perm-A-Barrier® VP.

I would use one of these systems with StuccoWrap for any form of stucco.

Here is a link that might be useful: GoldCoat