More about old bricks
hello there!
My wife and I own a brick house built circa 1850. The brick is in poor condition. About half of the bricks are spalling and the mortar has eroded considerably.
We would like to stucco the exterior ourselves rather than pay for re-pointing of the brick.
Can we stucco directly on top of the brick since there is a lot of relief? Would you recommend we use a wire mesh anyway? If so, what kind of wire mesh? What sort of stucco would you recommend ?
I wanted to elaborate on stucco over brick, particularly old bricks from the 1800's and before.
Newer bricks, that is since about 1900, are excellent to stucco over, unless the surface is slick. If the surface of the bricks is slick, they can be roughed up using a chipping hammer or a hatchet, making chips to open pores on the brick. If the surface is rough, and the bricks are hard and what I call modern bricks, mortar will bond fine without any preparation.
Putting metal lath on brick will only weaken the bond, believe it or not.
Our method of stucco on old bricks from the 1800's is as follows: Note the bricks are usually soft and crumbly. This is normal because the kilns used back then just weren't very hot. The bricks do deteriorate and spall easily.
The reason mortar doesn't bond to old bricks is the bricks have too much suction. That is. the bricks are porous and absorb water rapidly, or too fast. What we want is enough suction to absorb the mortar. Too much suction will absorb the water out of the mortar instead of absorbing the mortar causing the bond to fail. Wetting the bricks with a hose helps some, but if you notice the water is absorbed into the brick as fast as you can wet them. On hot days, we soak the bricks with a hose a few times the evening before we put on the scratch coat.
The next morning, we kill most of the suction by splashing the wall with acrylic admixture, mixed half and half with water. A little goes a long ways. This soaks in immediately.
The next step is mix mortar for our scratch coat with our half acrylic and half water. This provides a very solid permanent bond. If you chip this mortar off the wall it will take part of the brick with it.
It works best to dry mix the mortar first in a mortar box, then shovel the mortar into buckets with the acrylic mix and mix with a drill. This mortar is sticky, so mixing with a drill allows the mortar to spread easy.
I mentioned this method in my chapter: CHAPTER 7: BONDING MORTAR-PLASTER AND CEMENT.
More about stucco over bricks here: Stucco over brick.