Scratch coat for stone veneer. Use Mortar or Stucco Mix?

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Old 10-18-06, 10:39 AM
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Question Scratch coat for stone veneer. Use Mortar or Stucco Mix?

I'm creating a new scratch coat base layer to which I'll later be applying Cultured Stone Veneer. Question is should I use Mortar mix or a Stucco?

Only technicality is that I am extending what was an old area of stucco higher on the house to form a new hip line. As such, I have a lower area with old stucco which has been stripped of paint and a new upper section that is prepped with backerboard, vapor barrior, stucco mesh. These two areas will be covered to create one even surface with a new scatch coat to apply the stone to. So Mortar or Stucco and why?

I plan to use a bonding agent to the old stucco, but I'm not too worried as I got down to the old raw stucco after I blasted away the old paint.

Thanks for any help
 
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Old 10-18-06, 03:03 PM
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"Stucco" is a wall system. "Mortar" is any material that is applied in a plastic state that subsequently hardens.

If you mean prebagged "stucco mix" VS prebagged "mortar mix", then there is very little to no difference between the two, other than the stucco mix will (should) have fibers in the blend. For small jobs, I just use a type S premixed mortar mix (4-5 bucks for 80# +7 bucks for enough fiber to do 42 bags) and add a small handful of fibers. That is much cheaper than buying stucco mix (12-15 bucks for 100#). The only time I would recommend premixed stucco is for the finish coat if you want an integrally colored finish. I would also ad the bonding agent into all of your mortar; no need to paint it onto the old.

What is the total square footage of area you will be covering, and how much of that is existing?
 
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Old 10-18-06, 03:46 PM
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SQ footage is approx 80-110(guesstimate) with a 60/40 distribution of new mesh surface waiting for a scratch coat mated above old stucco which was applied to the lowest 1-2 ft of the house below siding. (40% old stucco)

What i'm doing is unifying a common hip line accross the whole front of the house for purely cosmetic reasons. Then adding Cultured stone to update the look.

about 2.5 foot high accross the face of the house not including the garage.
 
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Old 10-18-06, 03:59 PM
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Did you break out some of the old stucco to tie the new mesh to it or are you planning on butting the new casing to the old casing?
 
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Old 10-18-06, 04:56 PM
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Thumbs up

Butting the two together, but took care to match the thickness so there is not a huge difference (depth not gap) The reason, was much of the old stucco is actually applied over the poured concrete foundation I am working up from that over the exterior studs that used to have old siding. This will be covered with stacked ledgestone look veneer. I'm not extreemly worried about cracking where the two areas meet. I just want to get a consistent new mortar layer on there to seat the stone. BTW location is Los Angeles so rain abatement is not a huge concern
 
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Old 10-18-06, 05:10 PM
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Yeah, the butt joint is no problem, but this is how I would handle that joint:

I prefer latex modified thinset to set the stone, both because I can work faster, and because it is better in every respect (flexural, compressive, and bond strength).

At the joint, I would begin there, and overlap the stone, top and bottom of the joint, attaching the stone to only one side of the joint. This will prevent any movement from cracking/dislodging the stones. If possible, do not tuckpoint that joint, but if you have to, try and make it a somewhat wide joint.

edit- here is a quick sketch of what I mean:

http://lizking.com/stuccojointdetail.jpg
 

Last edited by Tscarborough; 10-18-06 at 05:22 PM.
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Old 10-18-06, 06:42 PM
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awesome! Thanks for that info! I planned on disguising the whole thing with the stone anyway but this is great advice. I already have visions of all that stone popping off if I screw this up, but so far all my forays into concrete, mortar and stucco have turned out OK and still look good 2 years on.

BTW I plan to keep the house not flip it, so the advice on how to do things the "right" way are much appreciated.
 
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