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Stucco Mortar Mix OK to drill Tapcon screws into?


MiamiCuse's Avatar
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11-18-12, 06:18 PM   #1  
Stucco Mortar Mix OK to drill Tapcon screws into?

I have "pockets" on my exterior concrete block walls that I have previously hollowed out. Those could be voids left my old electrical boxes or drain pipes that I have since relocated...or new voids opened up in order to tie a new fixture into existing vent stacks.

I hired a concrete contractor to repair these walls.

Large voids he filled in with concrete mix, solid fill.

Smaller voids like electrical boxes and such, he stuff newspaper into adjacent hollow blocks to avoid, then fill with stucco mortar mix. Specifically the "SAKRETE 60 lb. Mortar Mix Type S".

My question is, when I am attaching wood furring strips to the concrete walls, is it OK to drill holes into the patched areas filled with stucco mortar mix and drive Tapcon screws into them? Or should I avoid those patches and only drill where I have original blocks?

The reason I am asking is if I take a scrapper blade I can shave a thin layer of sand off the stucco. I wonder if it really has any "bite"?

 
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chandler's Avatar
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11-19-12, 03:40 AM   #2  
He didn't remove adjacent stucco finish and frame in the voids?? I can't imagine using mortar mix to completely fill a void on a wall. Too heavy. I am afraid you will have cracks and failures, but maybe he knew what he was doing, since he was on site and we aren't. Don't drill into the void fill area. There is nothing there for your screws to bite into and it will weaken the fill. Why are you attaching furring strips?

 
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11-19-12, 05:34 PM   #3  
On some large voids, such as a 24H"x 18"W void where we knocked open the inside half of an 8" thick concrete wall (the exterior wall is 12" thick, an 8" thick block plus a 4" thick block), in order to expose a 2" vertical pipe so as to tie in a new drain, we formed the wall and pour in concrete mix. That's rock solid. On floor openings we use 1/2" rebar epoxy into existing plus wire mesh and pour in concrete.

On smaller voids he simply fill in stucco sand mix. Due to the blocks being hollow, he would stuff newspaper or rocks into adjacent cells, and fill in stucco mix into that cell. These are small holes like 4"x4" or 6"x3" sizes.

I am attaching furring strips on the inside of the wall to furr out 3/4" for conduits and pipes, then I will attach sheet rock on those. These furring strips sometimes cross over these existing patches and I was wondering if I should stay away from those or drive Tapcons into them IF they happen to be where I space the screws.

 
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11-19-12, 08:05 PM   #4  
Doesn't sound like a problem to me. I like to run a bead of construction adhesive when attaching wood to concrete. Once it sets, you don't have to worry too much about the fasteners holding.

 
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11-20-12, 03:40 AM   #5  
I concur. I was thinking this was an exterior wall. I forgot your house was block. Yeah, using a good adhesive like PL Advanced or equivalent will eliminate a bunch of fasteners, especially over the questionable areas.

 
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