My house is what is commonly know as Santa Fe (mission revival) style, with flat roofs and parapet walls. I bought the place from an owner-builder who spared little expense, however, I know from talking to neighbors that he was always upset with the job done by the origianl stucco contractor.
Since I perrsonally did an extensive addition and thus removed some of the stucco to do so, I know how the exterior walls were constructed. The basic wall structure is 8″ CMU leveled on the inside with mortor and skimmed with Imperial plaster.
The exterior side is insulated with 2″ rigid foam (4 x 8) sheets, then covered with three-coat stucco on wire mesh. Unfortunately, there was no taping of the joints between foam sheets and local code doesn’t require a waterproof membrane under stucco when applied to CMU walls so there is none.
Due to the extreme temperature variations, particularly on the west-facing walls (here in Tucson) and the stress risers in the stucco due to the untaped gap in the insulation there is a lot of cracking along joint lines. It may be hard to believe that in a climate where we got 6″ of rain last year, water is an issue, but I am plagued by bubbling paint and cracked plaster on the interior side.
I have discounted the obvious idea that I have either roof leaks or leaks on the tops of the parapets since the (finished) ceilings are rough-saw Pondersoa beams and planks that would immediiately show water stains. (I know this from a leak on a porch.)
Several years ago I had a coating of Dryvit Weatherlast applied, that according to the distributor would solve my problem. I won’t go into the ugliness of this issue other than to say the guy who did the job estimated that it would take 150 gals of material and he actually applied 75 of it. I’ve also been told that this wasn’t the material of choice in the first place. It did appear to work for a while, however, for whatever reason(s) the cracks and water problems have returned and it’s time to do something else.
Short of stripping the whole mess, which would likely damage the built-up roofing material on the top of the parapets, and starting over does anyone have any bright ideas?
Replies
Two coats of an acrylic ter-polymer elastomeric will do the trick. Make sure to use a premium quality elastomeric at a spread rate of 75 to 100 square feet per gallon. Two coats of elastomeric will fill cracks the thickness of a credit card. Anything wider should be grooved out and caulked with elastomeric caulking first, or fiberglass taped in a bed of elastomeric patching compound. We've waterproofed a number of buildings using this method and it works great. One word of caution though, make sure that your roof and gutters are in good condition, otherwise water infiltrating behind the elastomeric coating will cause large bubbles that will be full of water. Hope this helps.
re:Two coats of an acrylic
Thanks ppd. As per my original post, the roof is flat and no gutters. The worst wall does have a scupper (canale) near a corner and I originally thought this was where the problem originated. This has been sealed several times with mesh and roofing elastomeric as I renew the white coating about every three years. The last time was about two years ago while I replaced the roof-mounted heat pump.
I'll give your method serious consideration. Do you have a brand name in mind?
Several years ago I had a coating of Dryvit Weatherlast applied, that according to the distributor would solve my problem.
HAHAHAHA
I've also been told that this wasn't the material of choice in the first place.
It would be my last choice.
Taping the foam wouldn't have helped with the cracking problem, but it would have kept the water out. Stucco over foam is a no no. Some felt paper between the two might have worked. Stucco expansion joints over each joint in the foam would have worked, but it's too late for real stucco expansion joints.
The only solution I can dream up without R&R'ing the whole shebang is external expansion jointsover each joint in the foam. You'll have to contract with a sheetmetal bending house to have them made. They look like a W with wings.
i_//_i (outside on bottom)
Where the tiny vertical tabs ("i") fit in litlle slots cut into the Brown coat on each side of the large cut completely through the stucco that the W fits in. Remove the color coat between slots and the large cut. Make the W part about 3/4 to 1" wide and almost as deep as the stucco.The wings width is about the same. The vertical tabs only need to be about 1/8" tall and their slots abut 5/32" deep. Use a thin guage (<=24) galvanized sheet. Cut the wide cut 1/8" wider than the W.
Put a bead of adhesive in each tab slot and another in the corner of the wing and tab, and press in place. Tape down until the adhesive sets. Paint to fit.
You'll probably want to make up wall caps to match for the parapets.