stucco over exisisting smooth stucco

[michelevit]

I am 95 percent done with my pizza oven and
have applied a smooth colored stucco over insulating perlite.

I underestimated how much stucco to purchase and
have a bald spot on the back of my oven.

I purchased another sack of stucco (and color)

Will the new stucco adhere to the existing smooth and hardened stucco?
or -
Should I roughen up the existing stucco with an angle grinder type tool to
give the new stucco something to bite into? The existing stucco is a smooth
finish.

I am worried about the new stucco and existing stucco
matching color. I purchased the colorant and stucco from
the same store, but I?m paranoid that they wont match perfectly if
I just blend it.

I?d like to just apply another thin coat of
stucco over the existing smooth finish but am worried that
the new stucco wont adhere to the existing smooth stucco.

Any advice or suggestions is greatly appreciated. I am building a 36 inch
interior dome, with three inches of ceramic blankets, 6 inches of perlite.
The oven is built on a stout steel stand which I intend on moving
with me as I inevitably outgrow our small 2 bedroom home.

[jrparks]

Re: stucco over exisisting smooth stucco

Hi michelevit,
I believe there are specialty product that you paint on prior, which allow the stucco to adhere properly. You should ask at a concrete product supply store.
Cheers,

[gjbingham]

Re: stucco over exisisting smooth stucco

I think JR is correct above, but I question how much these products help. Here's a link to the type of product I believe he is referring to:

QUIKRETE - Concrete Bonding Adhesive

Personally, I would roughen up the existing surface surrounding the area you are going to finish. I think you're pretty much stuck crossing your fingers about matching the color. I don't see that you have any alternative other than recoating the entire dome with another layer of stucco, or painting it if the patch doesn't suit your QA standards.

[david s]

Re: stucco over exisisting smooth stucco

If you're worried about the colour match you can easily make up a thinner mixture (more water) and paint it over the whole lot. It will tend to dry almost as soon as you apply it so dampening the already hard stucco first works well.

[michelevit]

Re: stucco over exisisting smooth stucco

i think that is what i'll do. Its been raining for days now and I haven't had
a chance to work on the oven. Which is in turn led me to just ponder
over it and worry about stupid things like color matching.

Worst case scenario is the stucco doesnt match or stick to the existing
smooth surface. I can just roughen it up with my angle grider
and start again.

Thanks for all the advice.

[michelevit]

Re: stucco over exisisting smooth stucco

the weather was nice on sunday and i mixed my entire bag of stucco
and colorant.

turns out even though I purchased from the same store and identical product the new stucco color did not match the existing color.
I just covered the entire oven again.

Lesson learned- buy enough stucco the first time.

Now that the finish is done, I'm starting the tools and the insulated
door.

Thanks for all the great advice and providing this forum.
I have learned a great deal from just lurking.

[michelevit]

Re: stucco over exisisting smooth stucco

I applied the stucco.
Turns out the color did not match at all, so I reapplied it over the entire
dome. It seems to stick just find over the existing smooth stucco. The new
coat is probally 1/4 inch. It is defintaley a different shade. Lesson to be learned. Stucco all at once if you are doing a color stucco.

Thanks for all your advice. We'll be firing it up this Saturday night
for an informal christening.

[david s]

Re: stucco over exisisting smooth stucco

You will increase its strength and reduce its tendency to crack if you wait for several days before firing. Also keeping it slightly damp,maybe spray some water on it, will help too.

[Balthazar]

Re: stucco over exisisting smooth stucco

I used an acrylic based stucco/render on my WFO. Being acrylic based it flexes with the weather changes and doesn't crack.
You can easily add another layer without a problem as it keys to itself really well. I then just painted over it with an acrylic "Tuscan" style exterior acrylic. I could have tinted the render, but decided to paint it with a blend of colours.

[suez]

Re: stucco over exisisting smooth stucco

i just came across a thumbnail pic of your oven-this is what i want! this is a perfect oven with gauge and pipe etc-it looks like the right size-can you give me your oven floor size (4ftx4ft)ex: or anytype of info on what you used or how you did that-i love it!

[Balthazar]

Re: stucco over exisisting smooth stucco

i just came across a thumbnail pic of your oven-this is what i want! this is a perfect oven with gauge and pipe etc-it looks like the right size-can you give me your oven floor size (4ftx4ft)ex: or anytype of info on what you used or how you did that-i love it!

Thanks, I'm glad you like it
Ok...here's the abbreviated version of what I did:

The overall dimensions of the floor including the surrounding pavers is 1500mm x 1300mm. The internal firebricks cover an area of 1100mm x 800mm and I then just laid the surrounding pavers. (had to make sure the thicknesses were the same of course). Internal height of the dome is 400mm.
The dome itself was cast over a sand and styrene mold/timber door mold. I used refractory cement with stainless steel needles for reinforcement, at a thickness of 50mm. I then covered it with two layers of 25mm ceramic blanket, held to the dome with chicken wire and wire.
I then added 50mm-75mm thickness of a mixture of vermiculite and cement fondue and finished that off with the exterior acrylic render as stated in my previous post.
The gauge is from a commercial pizza oven store(300mm probe), and I used a steel rod of the same thickness as the gauge when casting the dome. Then just removed it when the dome had set and used high temp silicone to fix in the actual gauge.
I have several pics of the oven in various stages of completion if you want me to post them.