Stucco fireplace surround


  #1  
Old 10-19-01, 06:28 PM
Sonnie Layne
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Hey pro's,

I'm a renovator/restoration guy in Dallas. I've recently added a fireplace surround to a home. Southwestern design, all corners rounded, they wanted stucco finish. I've never done any stucco by definition, but have worked with other troweled mud finishes and set tile in wet beds, so I'm familiar with technique but that's about it.

After all the lath was up I used 3parts washed sand to 1part white mason's cement. Next I understand is the brown coat, is the recipe the same? I think I understand as well that the final coat will have to have the finest sand around, is that the difference? What should I ask for and what ratio of ingredients to use?

Thanks a jillion,
Sonnie Layne
 
  #2  
Old 10-24-01, 07:09 PM
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Generally sand for the scratch coat using masonry cement ranges from 2.5 to 4 (3 to 4 is the norm). The corresponding brown coat is 3 to 5 sand (4 is average). The ranges account for variations in avialable sand.

Traditional three coat work is rare. Scratch & brown is more common. The general idea of using finer sand is true. But no one, except maybe a rare odd ball, blends their own finish coats.

Finish coats can be purchased from a finish coat stucco supplier/blender. Common white finish coat as well as coloring agents can be purchased off the shelf at many building supply outlets. Save yourself some grief lessons...purchase the superior product.
 
  #3  
Old 10-25-01, 08:55 AM
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Talking

Oh c'mon, just fling it at the wall, get the money and get out.

Sorry slow day!
 
  #4  
Old 10-26-01, 12:51 AM
Sonnie Layne
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Thanks, I'll have another look for it. Hate to drive across the county for a few stinkin bags. I've already mixed some of the finish coat with different tints for the client's approval. Yeah, I'm an oddball, I still tint my own paint, .

Jim, you're having entirely too much fun!

Sonnie
 
  #5  
Old 10-27-01, 03:44 PM
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I had already deduced that you were the odd ball, and a relatively good craftsman in your own right.

Manufactured finish coats are superior to site mixed batches, however, if you insist purchase fine clean plasters or masons sand. Sacked or silo sand are preferable to sand that has had a loader blade filled with dirt rammed into the pile.

Two general grades of plasters sand exist, course and fine. The texture of the finish coat is in part controlled by the sand particle size and the graduation of. Avoid silty and sands with clay. Both tend to crack but for different reasons.

A few factors that affect color coats are uneven sand graduation, damp sand, poorly proportioned or blended ingredients, poorly mixed ingredients and unclean equipment, to much mix water or retempering, uneven suction of the base coat [base coat varies in thickness, different areas were darbied, rodded or troweled], application technique and curing.

The starting ratio is the same as the brown coat. If damp sand is used add 10% more to account for bulking and reduce mix water. If the brown coat was allowed to dry spraying acrylic admix on the surface will help bonding.
 
  #6  
Old 10-28-01, 10:17 AM
Sonnie Layne
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2000

Great info! I'm pretty familiar with many of the concepts as I've dabbled in cementitious products before on varying levels. Client wanted a smooth troweled effect on this stucco fireplace.

I finished today and they are tickled, I'm a little disappointed. The premixed finish I bought had to be custom tinted, which I managed, but I found the sand a little coarse to trowel out smooth.

Finally had to tell myself I was working with stucco and not plaster. Still I'm wondering about the dif it would make to use say silica sand in the mix and really get a finer finish. On the other hand, maybe I'd be better off with plaster for that fine a finish?

S

 
  #7  
Old 10-28-01, 02:53 PM
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Similar to plaster for a finer finish when site mixing use a portland lime mixture instead of masonry cement. Scratch & Brown: 1:1:6 Finish 1:2:9. Masonry cement is better suited for painting afterward. Portland lime achieves better bonding due to increased suction, and the lime definitely improves workability. The systems should not be inter-combine.

If too fine of sand is added it increase the need for mix water. In turn that increase plastic shrink cracking. [One of those grief lessons].

Realistically site mixed finish coats are more like random occurrences of success, especially when using proportions instead of weighing. Off the shelf finish coats are suitable for most jobs. If and when a finish coat of xx color and xx texture (smooth or otherwise) a batch plant or stucco supplier is your best bet. It's almost humanly impossible to match the controls employed during manufacture.

For example, if xx grind (fineness modulus) of cement is required for a specific mix design your chance of obtaining a single sack or smaller quantity is nil. Batch plants can obtain cement with any desired characteristic. The same applies to sand and admixes.

I live near to a batch plant. I have been there many times. The operation is computerized from start to finish (sand silos, drying ovens, screens, and onward). A wide variety of finish coats can be obtained. And it is very difficult to match or beat an engineered product.
 
  #8  
Old 10-29-01, 01:57 AM
Sonnie Layne
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I would agree totally.

I have found a great place for raw ingredients from a mason's supply house here in Dallas, but still, as you pointed out, the moisture is only one part of the problem. They might call it screened, for instance but to what grit??

At any rate, I'm heading back out to the site this morning, I'll have a talk with the client.

Won't be doing any work, as all the skin is gone from the tips of 4 fingers. Duhhhh! and I own gloves!!! Makes replying to emails pretty "touchy".

Thanks for being such a wealth of information. If you happen to know anything about making fake boulders, or tile work, or most anything else, I'd invite you to a cool forum. Hosted by John Bridge from Houston, he's the tile man, even wrote the book. A bunch of guys hang out there and have interesting topics. http://www.johnbridge.com

Thanks again for your input, do you work with cement products for a living or are you just that interested?

my best,
Sonnie
 
  #9  
Old 10-29-01, 07:07 PM
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If you want to play with a finish coat formulation use the sand graduation (sive sizes) for stucco basecoats as a starting point. Below are the percentages retained by weight (+- 2%) on each sieve.

[code]
Sieve Min. Max. U.S. stand. sive opening sizes
No. Inch Microns
4 0 0 .187 4760
8 10 10 .0937 2380
16 10 40 .0469 1190
30 30 65 .0232 590
50 70 90 .0117 297
100 95 100 .0059 149
[/code]

In general the min. values provide a finer finish. Increasing No. 50 to 80%, No. 30 to 35%, and No. 100 to 100%, and retaining No.16 at 10% may put you closer.

I work in commercial construction. My interest in mix design is in a minor part job related. On the other hand I tend to delve more deeply into subject matter than other people, because I see fundamentals as how to in disguise. And, who knows, one day, spurred by a word or an apple falling on my head, I may become rich.

Thanks, I'll drop by Johns site.
 
 

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