Exterior Stain over Primer Peeling BAD!
I have Cedar Shake Siding stained a dark oxford or chocolate brown. When house was about 20 years old, I had it sealed with an Oil based Primer, then stained a Juniper Blue with a Latex stain. Seven years later, it was in need of a spruce up due to some blistering and peeling and limited mildew damage. I cleaned the mildew areas with a special mildew killer, sc****d re-sealed with a good quality Primer and applied the same Stain after adding some mold inhibitor to it. In less than a year it is peeling right down to the original Cedar shake BIG TIME! What did I do wrong? How should I re-do this for a more permanent solution? The original coating lasted for about 7 years. Mine lasted about 7 months.
Re: Exterior Stain over Primer Peeling BAD!
Chance, when peeling is down to bare wood, the culprit is usually moisture involvement. You state the house was already 20 years old when you had it primed with an oil primer and stained with a latex product. Over the years, homes which had never had serious peeling problem, sometimes get the coat that "breaks the camels back". That is, a house that could still respire through 2 or 3 coats can no longer let water vapor pass through one more coat. I probably would not have given the siding a general priming with oil, but just spot primed the bare wood to control tannic bleeding. Oil paints in general inhibit water vapor transfer much more than latex products. There are now water based primers which will stop tannic bleed provided you let them cure a day before top coating. Kilz Premium is one of them.
AS to mildew additives, most quality exterior paints and stains already contain mildecides. I would simply make sure that the siding was treated first to remove the mildew and algae. Clorox works about as well as all the fancy products on the market. I do like a prouct called Jomax for this purpose however.