Crumbling stucco

[install4you]

Hello to everyone and a constant thanks to anyone who has offered me advice.

I tagged this on the end of another post but I think I can't count on that for help.

The back wall of my house under the canteliver is swirled mortar stucco on block. The house is 45 years old & the stucco has deteriorated to crumbling in places. I'm using a 1300 psi pressure washer to clean for painting & it knocked some stucco off. I anticipated this & planned on that low pressure to knock off loose paint & bad stucco without excess damage.
>>How aggressive should I get cleaning the loose stuff off before I apply patches? I don't want to go too far or do to little. I can use a wire brush on a grinder but that takes a lot of time. In the worst places the pressure washer will actually chew the old mortar out from under the paint without knocking off the paint. The soft stucco doesn't come off in big flakes so chipping with a mason's hammer does little. I want to find the balance between perfection and planning on 20 more years in this house. Then I'll be 93 & be moving on.

 

[speed fighter]

I'd also be using pressure washer to find the weak spots.

Just continue with the pressure washer on the worst spots until it stops chewing things out or use a stiff wire brush by hand or on the grinder for the final cleanup of dust and loose debris in the cutout areas to ensure your new patch material bonds only to the firm, existing block or very solid stucco edge. You are aiming for a solid, clean, concave depression that will mechanically lock the new stucco patch in place, which is the best compromise between a perfect repair and a twenty-year life expectancy.

 

[install4you]

Thanks for reply. I responded more in the thread about forgetting to pre-wet the wall.
I ended up with places to patch ranging from pencil eraser size up to a couple of square feet. Used about all of an 80# bag of mortar mix.

 

[t1m davis]

>>How aggressive should I get cleaning the loose stuff off before I apply patches? I don't want to go too far or do to little. I can use a wire brush on a grinder but that takes a lot of time. In the worst places the pressure washer will actually chew the old mortar out from under the paint without knocking off the paint. The soft stucco doesn't come off in big flakes so chipping with a mason's hammer does little. I want to find the balance between perfection and planning on 20 more years in this house. Then I'll be 93 & be moving on.

well, you should be aggressive enough to remove all material that is not soundly adhered to the block wall, but careful not to damage the underlying solid structure.
Any stucco that is loose, crumbling, or bulging needs to go, even if it seems to be just cosmetic