Selected Answers

From Jose Avendano of KTA-Tator, Inc. on April 30, 2015:
There is not an exact number of times, because it ...read more There is not an exact number of times, because it depends on paint and substrate condition. I recommend consulting SSPC-TU 3, "Overcoating," to determine the pertinence of this procedure.

From Andy Bozeman of ABP on April 30, 2015:
So, there I was in 1979, trying to open a new home ...read more So, there I was in 1979, trying to open a new home design office in a an old house, already 100 years old - the house, not me. I was 26. The single-room office walls were real plaster, and painted hot pink. I wanted Thunder Gray. I started on an exterior wall, a wall imperceptibly dampened by a hidden roof leak. I carefully and properly applied two coats of heavily pigmented latex, Thunder Gray, so-rich-looking-you-could-dip-it-with-a-spoon paint. It was beautiful. I went home happy. I arrived the next morning to discover the first evidence that my new paint had met the old dampness in the old damp walls under the old damp roof leak. Damp! (used here as an expletive). Thunder Gray sheets a square foot in size were peeling off the walls. But the New Thunder Gray held fast to the old Hot Pink. But, then in turn the Pink held onto Hot Teal, and Teal onto Cobalt, cobalt onto Rose Red, and on and on through twelve layers of Victorian versions of neon-like pastels, to finally reveal virgin plaster. Damp! (not an expletive this time - it was just wet). Young, just starting out, nearly penniless, I spent the last of my start-up money damp-proofing the gaps, and repainted. It wasn't as pretty as I wanted, but a few framed drawings hid the worst of it. So my experience says, that though it’s not good practice, twelve paint layers applied over one hundred years might be the limit. Your experience may vary. Thanks for reading.

From Warren Brand of Chicago Corrosion Group on April 30, 2015:
As long as its appearance and performance characte ...read more As long as its appearance and performance characteristics are acceptable to the owner, the building can continue to be repainted.

From Rodney White of Independent Consultant on April 29, 2015:
The question as presented is much too broad to giv ...read more The question as presented is much too broad to give a practical answer. Strictly speaking, any new paint placed on top of an aged coating will not perform as designed. A paint is designed to "fail" at a controlled rate. Therefore, assuming that the existing coatings (to be painted over) have some age on them, they have already partially failed, rendering a new coating on top to be only partially effective in its designed performance. Given design parameters such as adhesion, cohesion, and bond strength,  only a surface completely devoid of aged coatings can be coated with a system and expected to perform "properly."