How to repair/waterproof small cracks on exterior stucco?

[nospam.house]

I have a 50 year old single story home with stucco on the exterior. There's been a lot of rain lately. I noticed the southern facing wall in the garage became wet after a very windy rain day when the wind was blowing the rain toward the exterior wall.

The garage walls have no interior drywall. I noticed the weather paper behind the stucco became wet in some areas. One of the beams became very wet. I did some investigation, the water is not leaking from the roof, but got in from the side, as the top of the wall is dry.

After the rain has passed. I went outside and noticed some clear wet path along the exterior drywall, like someone has painted the wall with water mark. Look closer, and I see that every one of these path, the drywall has cracked. It's interesting that in areas not cracked, it looks dry. On the inside, the crack is approximately where the water has gotten inside and the weather paper becomes wet.

How do I fix this? The crack seems to be too small to be patched by stucco mix, yet water still finds their way inside. Can I patch it up with calking? The weather paper is not in its prime conditions, but fixing it seems to be rather hard, since the beams are in the way...

Thanks!

[Shelly]

I have successfully used stucco patch many times:

[Mike Paulsen]

Look into elastomeric paint. You may need some putty-grade for filling the larger cracks before painting. Be sure to properly prepare the wall, including applying the recommended primer.

[Robert Allison]

For hairline cracks on stucco here are the proper methods to repair and waterproof:

Truly hairline cracks can be left as they are.

Cracks of 1/16" should be filled with a one part urethane caulk or equivalent (not silicone). Caulk should be squeezed into the crack as much as possible and tooled flush with surface.

Cracks greater than 1/16" should be V-grooved with a v groove masonry grinding wheel, then filled flush with the surface. I like to use Vulkem 116 for this, but any equivalent caulk will work.

When caulk has cured to paintability, paint the entire surface of the stucco with an elastomeric paint.

You could use a Siloxane paint, but I prefer the elastomeric.

You should have no more problems with water intrusion. It helps to power wash stucco before painting, unless it is less than a year old. Don't blast it, just wash it.

[Norminn]

Our condo in Florida is stuccon on concrete block. When it was painted, the contractor used a brushable caulk on all the cracks. Cracks were all hairline or very fine. The brushable caulk should be available at good paint stores - it has flex, so cracks don't reopen. Six years ago, and we have no cracks showing through the paint.

FWIW, after the hurricanes here, there were articles about water driven THROUGH these walls - cb/stucco is the only building style these days here. Older homes, with more coats of paint, were less apt to have the problem.

[nospam.house]

Thanks everyone for the suggestions!

While we are on the subject of calking. What type of calking should I use to repair cracked concrete walkway in the backyard?

I bought some blue-looking ready-mix cement filler stuff at home depot. It worked for a while but the stuff hardens, and after a year, the crack widened or moved and it no longer works.

At commercial places, they seem to fill the low spot on concrete joins (or where they draw the lines ) with a dark paste/rubber like compound. What is it?

Thanks again!

Raymond

[DanG]

The old method was to clean the joints real well, usually with a blow pipe, and then use a crack pot and pour the joints and cracks with hot tar.

The more modern method is to make sure the joint is cleaned very well to expose good sound concrete on each side so the caulk can adhere to this concrete only. Backer rod is installed to prevent a 3 sided bond and to control the shape of the caulk. Each type of caulk has rated stretch percentages based on the proper rectangular joint shape that is wider than it is tall. Use a high grade of polyurethane caulk like Vulkem or Sonneborn NP1 (or SL1 if the pavement is fairly level).

There are some new hot applied silicone products, but they would be beyond a DIY approach.