Appication Of Synthetic Colorcoat Over Painted And Cracking Stucco

Silverback123

I have been encountering individuals that have been advised that their cracked and paint-peeling walls can be rejuvenated by a fresh coating of synthetic stucco. I advise them that a new coating is adhering to old paint that is already breaking down, and though it will now be encapsulated by the synthetic coating, it will also lose its bond to the Portland Cement base causing the acrilic coat to become loose where this delamination of old paint occurs, causing a greater problem and waste of money.
Another problem with synthetic coatings is that they seal the exterior of the cement walls as well does paint. If any moisture is trapped in the wall cavity, the synthetic coating will not allow moisture to be drawn out to the surface. This is a major cause of dry rot and mold. Portland Cement as a wall cladding is porous and meant to allow air infiltration which makes it breathable. This system of allowing water vapor to be drawn out to the surface and evaporated is defeated by paint of synthetic color coats.
I am wondering if any other Plastering Contractors encounter this situation, and how you deal with it. The misinformation is rampant on the web. Synthetic color coats are part of the EIFIS Sysem and not advised to apply over Portland Cement Systems in my opinion.

LocalSoljah

We do a lot of synthetic finishes over cement. If its a repair job I would recommend skimming the cement with basecoat first.

Tscarborough

Synthetic over cement is fine, and in fact, is how EIFS is done. What is NOT done is to apply ANY new finish coat, cementious or synthetic over crappy substrate.

Your options are to remove the paint, or lath and stucco over it. Those are the only 2 viable options.

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Silverback123

I acknowlege the fact that many contractors are making a quick buck by re-coating old cracked and peeling painted walls, but I still do not agree that it is the best method for the customer in the long run. Synthetics are mainly Acrilic Glues, aggregate, and color pigments. Moisture travels in and out of Portland Cement especially during high humidity conditions. The interior of a room contains moisture that can be drawn by the outside temperature through the walls. If the exterior of the walls have been sealed by synthetics, then it becomes trapped. A cement based color coat allows for moisture to excape to the exterior of the walls. In the case of deteriorating paint on the stucco, sandblasting is the best method, but waterblasting may remove enough of the paint to create a bond for new Portland based finish coat thereby retaining a breathable wall cladding. As for EIFIS, it is a complete system comprising of foam substrate, Portland enriched bonders such as PolyBond, and Fiber Mesh trowled into the bonder. The system is then completed with synthetic finish coat. A synthetic color coat over stucco is not considered EIFIS. It is my opinion that synthetics over Portland Cement may delaminate after a period of time, but that is only my opinion. Time will tell.

Tscarborough

The base coat of any and every EIFS system is portland cement based. Acrylic over a portland cement base is not an issue. Any re-finish over a poorly prepared base is.

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Tscarborough

What would you consider an appropriate time frame? 20 years? 30?

It is my opinion that synthetic stucco is garbage for many reasons, but it's ability to remain adhered to a portland base coat is not one of them.

__________________
It ain't Rocket Science unless you are building rockets.