rookie move...latex over oil

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Old 07-16-09, 07:36 PM
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rookie move...latex over oil

So i closed on my first house this morning. very excited, had the family over for a painting party this evening. got this first coat up in the dining and living rooms. about 8pm the neighbor comes by to introduce himself. he asks "oh hows the paint sticking?" we said just fine..."oh well the old owners had some professional come in years back and do everything in oil" we had no idea..this was an estate sale, so it was never mentioned...so now, how screwed am i. i havent moved into the house, so im afraid of the mess i'm getting into tomorrow. any help would be great!!
 
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Old 07-16-09, 07:44 PM
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You’re fine. Oil based paint can loosen latex paint. Latex paint will not loosen oil based paint. One thing you should do though is “rough up” the surface before painting in order to get better adhesion. You can use some light sand paper or even a Brillo pad.
 
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Old 07-16-09, 07:48 PM
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yeah, ive read everywhere that i "should have sanded or primed" but what about the paint thats already on the wall? do i need to scrape and sand it off? or wait to see if it cures and holds? i've read a ton of different opinions online and its getting confusing...some say start scraping, others say sand the first coat of latex and apply second..or prime over latex and try again
 
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Old 07-17-09, 03:48 AM
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I doubt primer over the latex would make much difference at this time. You say the walls were painted with oil base, were they shiny? If the walls were painted with flat oil base paint there shouldn't be a problem. I'm not sure if they still make flat oil wall paint - it's been over 30 yrs since I've used any.

I'm not sure where Robert gets his info On interiors there isn't any problem with applying oil base over latex but latex should never be applied over oil base enamel. It's the opposite on exteriors - no oil over latex but latex can go over weathered oil base.

If the walls were painted with an oil base enamel, you would have had coverage issues and the latex paint would be a little slow in drying. Have you painted all the walls? There is a sticky at the top of the painting forums that gives instructions to help determine the type of paint.
 
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Old 07-23-09, 07:59 AM
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Painting parties can be a tough one. Not sure where Mark or Robert get their information, but as long as the paint is tight, you will be fine with latex over whatever was there on your interior work. It is too late to suggest, washing, sanding, patching and priming, before painting at this point but you'll know next time. The reason using latex over oil on exteriors is not advised is that as latex dries, it kind of shrink dries much like the shrink wrap used in stores over vegatables and meat. If there is any loose or scaling paint you don't notice before painting, the latex will pull it of. I ususally recommend if an exterior is oil, to stay with oil, because if you should want to change to latex, you would have to prime the complete house with an oil base primer, before going with latex, even if the color is the same. If on the other hand and house has been painted with latex and the paint is tight, you are fine with oil, but as I said before, it's easier to stay with what you have.

Bill
 
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Old 07-23-09, 03:27 PM
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I know the weather in new england differs from that in the south but here if exterior oil base paint is well weathered it is acceptable to switch to latex. In fact, the further south you go, the better exterior latex will hold up as opposed to exterior oil.

I've come across a lot of peeling interior paint where others have painted latex over oil base enamel. I don't recall seeing problems when the oil enamel was first coated with a solvent based primer.
 
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Old 07-23-09, 08:37 PM
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I am assuming you did not degloss the oil enamel and painted directly over it without priming or dulling it.

Sometimes (but not often) you can get lucky and the latex paint will adhere to the oil enamel. If the oil enamel was a low luster, and you have a good adhering latex enamel on top -you might be lucky.

Most of the time you will not be lucky.

Latex paint will adhere to a flat oil paint without any problems because there is a lot of "tooth" for it to adhere to.

Latex paints are easily repelled by glossy surfaces and smooth tight paint films (such as oil enamels) which have nothing to grip to. Oil based paints on the other hand, are much more forgiving over glossy surfaces and will often adhere without priming.

The universal surface preparation rule is the surface must be: Clean - Dull - Dry. If the oil enamel was glossy, it will likely repel the latex paint.

It is not impossible for a latex paint to grip to a glossy surface by the way, and the newer "waterborne" enamels have much better adhesion to glossy surfaces than the older types of standard latex enamels. Case in point: There are waterbased primers (XIM UMA for one) that will bond to CLEAN glossy enamels, so the technology is there. Hopefully in a few years the latex paint not adhering to oil enamels problem will be a thing of the past. BUT "this is not that day". So for now, be diligent to either degloss or prime (or both) when using latex over oil - 9 1/2 times out of 10 - you will run into trouble if you don't.

How do you know about the adhesion of the paint already on the trim?? You must allow the paint to cure first (which may take three or four weeks), then you can do a "cross cut" adhesion test to see if it is adhering. If it fails the tape test miserably (and it probably will), you can pull off most of the paint with masking tape (there may be no need to strip the paint off - it will pull off with tape).

Note: The other issue that has come up in response to your post about latex pulling off oil paint is primarily an exterior problem where the shrinkage and strong pull of a dried latex paint will pull off marginally adhering old brittle oil paint. I don't think you need to be concerned about this in your situation.
 
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Old 07-31-09, 03:41 PM
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This isn't a reply but another question ... I have a similar problem at my house ... six months ago I had a guy paint all of the interior walls and trim (doors and window frames included). Now the paint is peeling back on every surface ... the slightest rubbing against a wall causes the paint to peel. I now know that the previous paint was oil-based enamel, and the recent painter put on two coats of latex paint. He said he "scuffed" the surface and put on a primer, but I'm not so sure he really did that. He said he would come back and re-do the job, but now I am afraid that he won't know what to do to fix it. Can he just scrape off the paint where it's peeling and apply a primer, then two new coats of paint?? Or does the latex paint have to be sanded off entirely??? And what specific primer would you recommend??
 
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Old 07-31-09, 06:04 PM
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Welcome to the forums mceachen2!

If the painter is willing to come back free of charge let him! If he deligently scrapes and sands, what latex is left should be adhered ok. Generally a solvent based primer is best although zinnser's gardz [latex] should be ok. I'm not sure that I'd trust a latex primer but I am old school
 
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