Leaking stucco walls
Hi RT Bullard
I'm have a small 2-story stucco house in Albuquerque NM. The stucco was painted with "elasomeric paint" by the previous owner - I have had this house for a year. It was built about 1984 and is slab on grade. The last rainstorm resulted in water puddles appearing at the concrete foundation stems from under the sill board in the garage and apparently also within the house (dampness near the outside wall moulding on the floor. This was a mystery because the roof is 2 years old, there is no measurable wetness at the top of the open framing garage wall that has the puddle. There was no evidence of water or soil pooling outside above the level of the foundation's sillboard.
A day later, I attempted to repair a hole in my wall to close off an improperly flashed vent hole and found that the tarpaper under the stucco was very thin and rotted near the sillboard. There was not too much wood rot damage but one could see it starting. The sillboard was slightly damp here.
I suspect that I have a combination of three problems causing water intrusion.
1. No weep screeds to terminate the bottom of the stucco coat - this is common in older construction. here.
2. painted stucco that's trapping water that does find its way into the stucco and generating water pressure at the lower portion of the outside wall.
3. Old, thin tarpaper that's been damaged by the above.
I suspect that my only real solution is to have someone strip off all the stucco, old lath, and old tarpaper and repaper and restucco the whole works. I will replace the windows at this time too. Should I replace the fiber board with treated and/or exterior plywood too?
This is a flat roof house with no eves and has parapets. What would you say is the best practice for restucco? Am I going to extremes by having all the stucco removed or is this necessary to prevent future long term problems?
Thanks for bearing with me and thanks in advance for your advice.
There could be sources for the leak above the sill plate. The sill plate is the horizontal 2 by 4 on the concrete slab that is supporting the house.
Above is a picture of a foundation weep screed. These were made for slab houses. The screed has a flange that provides flashing that prevents water from penetrating and sitting on the concrete and being absorbed into the sill plate.
The flange of the weep screed is overlapped with tarpaper. The joint between the concrete and the wood framing should always be covered with a flashing or at least overlapped with tarpaper.
The weep holes at the bottom provide drainage for water that penetrates the stucco. The most critical thing is that the joint between the slab and the wood framing needs flashing or at least overlapped with tar paper.
The fact the tarpaper is thin and weak shows it has been saturated with water.
What I think:
Water can still penetrate stucco even if it is painted. A source of our work is flashing stucco that has been painted.
The most important thing is to cut off the bottom and put on a weep screed. If it isn't possible to overlap the tar paper, the top can be taped to the old tar paper.
I think the leak may be coming from above, maybe from the parapet, either the coping at the top or the flashing on the inside of the parapet. Here's what I said about parapet walls in July of 2024:
Speaking from experience, we have patched stucco at the bottom slab level, to find a hole on the roof caused the problem. This is common in Reston, Virginia townhouses. The edge of the parapet wasn't flashed well, leaving a hole on the edge of the roof. The water ran all the way down to the slab and eventually damaged the stucco.
You may be able to make repairs. My old adage is, when in doubt tear it out. If you go to this extreme, you want to make sure everthing has good flashing and good tarpaper. It is important the windows have flashing over top, angled down away from the wall.
Hope this helps. Thanks for visiting my site.