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  1. #1
    Join Date
    May 2011
    Posts
    24

    Default Priming and Painting over Existing Paint?

    All the painters that I've spoken to (Including Rhino Shield....whom I'm not going to use) have advocated leaving the non-damaged paint in place and priming and painting over it.

    *dazed and confused*

    Help me here--->First assumption check: Doesn't the adherence of new paint depend upon the adherence of the first layer? If so, doesn't that just make the new primer & paint fall off on the old paints "schedule"?

  2. #2
    Join Date
    Aug 2007
    Location
    Portland, Oregon, formerly of Chicago
    Posts
    1,584

    Default Re: Priming and Painting over Existing Paint?

    TGM,

    To a certain extent, you are correct that the new paint is only as well adhered as is the old paint underneath it. However, the remaining old paint did manage to somehow stay stuck.

    Your alternative to going over the old paint is: to strip the house siding, replace the siding, or go to vinyl or aluminum siding. All of these alternatives are relatively expensive.

    Unless the house has obviously had repeated problems with drastic peeling over the years, I would go with a thorough prep job, followed by spot priming of bare wood, a general priming of the house with acrylic based primer and finally, a finish coat of acrylic house paint. The primer is best tinted toward the finish color.

    Be advised that dark colors are more prone to aggravating peeling by virtue of the higher temperatures when the sun beats on a dark color. Peeling to bare wood is almost always a sign of moisture problems as interior generated moisture tries to migrate to the exterior. The sun converts that moisture to vapor pressure and literally pushes the paint off the wood surface.

    There are many factors which aggravate this moisture tranfer such as high interior humidity in the house in winter in cold northern climes. You might want to investigate such remedies.

  3. #3
    Join Date
    Jan 2010
    Location
    Northern Virginia
    Posts
    975

    Default Re: Priming and Painting over Existing Paint?

    Paint applied to wood siding has everything working against it: A dead organic substrate that is prone to water absorption and decay, moisture from inside and out, and the effects of sunlight, temperature changes on two cycles (day/night and seasonal). Then, the paint's own chemical makeup works against it as it ages.
    Old oil paint eventually loses flexibility through all these aging factors and cracks away from the substrate. That's alligatoring.
    Peeling is almost always a signal of improper application or a moisture problem.
    By improper application, I mean painting while the siding is damp, failure to allow the primer to dry, or a primer/substrate adhesion fault from inadequate prep (dirt, failure to sand).
    Occasionally there is an incompatibility from primer to substrate or primer to finish paint.
    Moisture problems include any kind of leak/other source resulting in wet water or vapor wetting the underside of the siding. The moisture moving through the siding causes the bond at the lowest layer to fail.
    Casey
    Remove not the ancient landmark, which your fathers have set.

  4. #4
    Join Date
    Jul 2010
    Posts
    62

    Default Re: Priming and Painting over Existing Paint?

    Leaving the old paint on is definitely your cheapest option. As long as it's prepped well and a quality exterior paint is applied it should be fine.

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