I am installing an air conditioner into the side of my house.The hole is 24x17 inches. So I cut the hole and I am stuccoing it to give it a clean look. I have papered,wired,brown coated everything. I applied the stucco and finished it off to match the old stucco.I let it dry for a week and used the garden hose to wash off any loose material.A lot of the finish coat started coming off to the point that I now have to go back and patch it again. Some of the stucco that is being repaired/replaced is a very thin coat and the rest is between 1/8 to 1/4 inch to make it match. I have done this to about 14 windows I replaced over the the years and I don't remember this happening. It has been a while.Do I have to add some kind of adhesive with the stucco to get it to hold to the house?