urethane exterior paints

[Noel]

I will be painting my 70 year old house this summer, and I'm confused about these new urethane paints. What I'm confused about if surface prep. I will need to scrape and sand for sure. But priming? It seems to me that putting a urethane topcoat over an acrylic primer defeats the purpose of these hi tech, breathable urethane paints? Yet, the paint makes recommend primer. I will have a mix of wood siding surfaces, such as new bare wood, old gray weathered siding, and spots of previous topcoats, some latex, some oil. I read one popular home improvement web site where the guy said that the label on the paint he used said "do not power wash". He also said how hard it was to clean his hands. Which lead me to believe that the paint wasn't acrylic latex.  Anyway, what do you suggest with these new paints? Any brand suggestions?  

[admin]

Noel,

Urethane House Paints are very new , so new in fact that they have not yet endured a practical test of time. The makers of these paints make some very bold statements as to the bonding power and endurance of the coating. Which may or may not prove to be true. I can not help but be reminded of the "Spray On Siding" fiasco.
That being said:
Urethane Paints contain both acrylic and polyurethane resins so an acrylic primer would be the proper undercoat.The makers of the paint do NOT recommend cleaning or power washing the house before you paint....this sends the message that they are concerned that the coating will NOT tolerate "back" moisture.
I would not recommend applying ANY paint or primer to a dirty or mildewed surface.The best option would be to power wash and allow the house to dry for at least a week or more, prime the entire house with an acrylic primer then apply the finish.

Best Regards,
Admin  pro painter

[the PAINTSMITH]

I have some limited experience with the "alkyd enhanced" acrylics, and it brings a smile to my face to hear someone how hard it was to clean up...I made the mistake of running the stuff through an airless pump. I wound up replacing the line as the junk that coagulated inside kept breaking loose and plugging the gun...They say to use a series of mineral spirits and soapy water to clean up, but they don't say for how many weeks or months. The brushes I used, though not unusable, have become permanently tinted the color of the paint.

I will say this...The last time I sprayed the stuff was three years ago on a farmhouse...The homeowner told me recently that the paintjob still looks like it was applied yesterday...