I'm interested in Steel SIPS, rather than OSB, but maybe some of the same techniques apply. How would one attach foam details like quoins, half-columns, moulding, et cetera to the SIPS panels if stucco is the ext. finish? I'm guessing screws with plastic washers? And would the paper backed lath go over the SIPS, then the foam details on top of that? Or would the foam go on first and the paper backed lath go over all of it?

Typically the entire building would get a scratch coat over lath, foam trims are attached with adhesive and screws to temporarily hold, then finish coat stucco is applied

Do you normally install a drain plane under the stucco?  Do you use traditional (3 coat) stucco (brown coat also under the foam trims)?

we prefer paper backed lath and traditional 3 coat stucco (7/8" thick)

Chris, I know you've had problems with polymer-modified stucco, but that was applied directly to the steel wasn't it? I wonder how it would do applied to the paper backed lath.

Do you notice much cracking with traditional 3 coat stucco in your applications? I'm wondering about the expansion difference in the steel and Portland cement. I guess the lath allows them to move independently?

Jelly;

the syntetoc coatings are meant tp be applied @ about 1/8" thick with no wire.
In any event stucco over steel panels performs better than over wood as the expansion and contraction coefficients are similar

Chris,

How do Hardi board lap siding and stucco compare on price per sf fully finished over a steel SIP?  (Assuming single story with good access.)

Have you noticed any long term maintence differences between them?

Do you ever use white cement and pigment as the smooth coat to give a "no maintenance" finish?

Very respectfully,
Larry

Larry;

Hardi is slightly higher

Have not noticed any long term differences , but hardi has not been around that long

I have used the  white cement before, but since stucco cement is not water proof I still like a good coat of elastomeric paint for the finish

Thanks Chris,

The paint would kinda kill the advantage of white cement (grin).

Very respectfully,
Larry

Larry;

I totally undersatand where you are coming from in your thinking.

Some people are under the impression that cement stucco and tile grouts are waterproof .....they are not

Forgive me for what may seem like a boneheaded question, but is "white cement" something more than just cement which is white?

Many old Florida houses used white cement stucco so they did not need painting

Ok that's what I thought. It is one of the advantages of stucco - it can be tinted a variety of colors and never need painting. So what is the need for elastomeric paint, especially if there is a waterproof steel SIP behind it?

White cement is a different formulation of portland cement, which is typically grey.  You can't make grey cement white other than by painting over it, which will eventually require repainting.  White cement lets you get brighter, more pure colors (especially pastels), but it is more expensive than normal grey cement, so it's generally only used in decorative applications, usually as a thin top coat over cheaper grey cement/concrete underneath.

http://en.wikipedia.org/wiki/White_Portland_cement

Stucco can be tinted but, I have never seen a uniform tint job , you can see where each new batch was started on the wall

Elastomeric is my paint preference in Florida's tropical climate, I use it to keep the water from the imbedded steel lath not from the SIP

you can leave the stucco raw if you like, It's just not my preference

Waterproof?  There's no such thing as a waterproof building material.  Or at least, it won't remain water proof forever.  Think of all the fasteners penetrating that steel skin.  Think of the seams.  Sure tape over them, but what happens as the building settles due to foundation movement, thermal expansion, and material creep?  Nevermind windows and doors!  Water and especially water vapor will find a way through any tiny crack.  Nothing is waterproof once it's become part of a building out in the real world, not forever.

Water tolerant designs are better than water proof.  Keep out as much water as you can.  (Elastomeric paint does a good job of that.)  Provide an escape route (drainage and/or evaporation) for what inevitably gets through.  (Drainage plane behind the stucco -- e.g. metal lath over building paper over drainage mat, if you want to get fancy.)  Use materials that resist rot, corrosion, and freeze/thaw cycles.  (Galvalume rates pretty highly here, I guess.)

An alternative would be to not try to waterproof the stucco at all -- let it breathe.  Use only vapor permeable paints, or no paint at all, just pigmented stucco.  This way, whatever water and water vapor makes it through te stucco will dry back the way it came.  Water does not hurt stucco or cement unless it freezes before it gets to dry.  (So the suitability of this design depends on climate.)  You need a building wrap between the SIPs and stucco in this case, to keep water out of all those tiny holes made by seams and fasteners.  Make sure it is a good capillary break.  A drainage mat would provide extra protection.

rnortman, you're right, I used the wrong word when I said "waterproof" but it is my understanding that the steel SIP functions essentially as a drainage plane. We went round and round in another thread about the tiny holes all over the SIP face and whether water and water vapor would permeate the styrofoam inside of the steel SIP sandwich. But any building wrap is going to be applied with fasteners, making more holes in the SIP face, creating more of the problem that one is trying to solve in the first place (keep in mind I am not considering OSB SIPs here).

I'm in Louisiana now, but I've spent the last ten years in Germany where "stucco" is usually polymer-modified and applied with a nylon or fiberglass mesh in the first coat, then another coat on top of the mesh coat. The pigments are mixed in to the top coat and are very intense and very consistent. The polymers contribute some water resistance, too. This is usually applied directly to styrofoam, but in theory it seems like it would be good over a steel SIP, even if one used a lath underneath. But I would sure like to hear from someone who has really done it this way.