Exterior paint freshly bubbling on wood siding after primer/painted

We have an 80+ year old house with original (I'm guessing pine) siding (it's pretty soft). Doesn't look like it has been painted more than a few times in that time span. The surface was pretty rough, with a lot of sections where they painted over the scrapped areas, making big depressions, etc. We did our best to scrap everywhere and use wood filler (Dap Plastic wood) on the transitions to smooth out these sections. Did a fine sanding, and then put on Kilz primer (over the whole house, whether wood filler, bare wood, or previous paint). Today after putting on our first coating of exterior paint primer we are already getting bubbling within 12 hours, even in completely new places that look like they were Kilz primer over the original paint (which was in good shape).
The surface looked pretty good with the primer on (smoothing out the surface a good bit, and no issues of bubbling). Now it looks awful again. It looks like many of these new bubbles are happening all the way down to the wood/original paint surface, not just between the primer and new coat of exterior paint.

Any thoughts? Super frustrating as we have spent weeks prepping and thought we were doing everything as correctly as we could.

 

There are about 7 kinds of Kilz primer and you didn't say specifically which one you used.


Image credit: Lowes dot com

 

Kilz 2 primer

Sherwin Williams store seems to think that the primer we used was "too adherent" and once the exterior coat went on it was enough to pull the original paint off the soft wood (not rotten wood, just soft). So we may need to do a lot more prep over and use a less adherent primer. UGH.

 

That's about the dumbest thing I have ever heard come out of a SW store.

IMO you probably have old linseed oils on the old siding that didn't appreciate the latex primer and paint. Either poor adhesion or moisture behind the paint can drive it off. Hard to say when we can't see the prep you did. If you washed the siding at all or if it rained on it, its likely inadequate dry time.

Vapor drive from the sun can drive moisture into the wood and that loosens poorly adhered paint. Plus Kilz2 is not one of my favorites, and it could be the problem. If the old paint was oil based and they used linseed oil in the past, I'd recommend SW oil based exterior primer followed by a quality latex topcoat.

 

Thanks. It has been incredibly dry (especially considering we live in Seattle) the last 2-3 weeks, so I don't think moisture is a big issue. There was no bubbling issue with the primer on (and some sections had just primer on for over a week). It just all happened when the first exterior latex coat was on.

Now we have to figure out what do do next. Do we try to scrape off as much of the single coat and primer as we can (in a few sections where we have already scrapped off the bubbles it comes off pretty easily down to the bare wood)? And what to do for the sections that just have the Kilz on them now (the taller stuff hasn't been painted yet, just has the primer)?

 

Kilz2 isn't a very good primer, I never use it.

I've had good results with both A-100 oil and latex primers from SWP.

I'd probably aggressively sand [80 grit] and then reprime, probably with oil base.

 

Kilz 2 is the last primer I would ever use. Oil based primer would have been a better choice than latex and then follow up with a quality latex topcoat.

 

You didn't state what paint was used?

 

It was a Valspar SeasonFlex Paint/Primer latex exterior paint.

 

"I'd probably aggressively sand [80 grit] and then reprime, probably with oil base."

Sand down both the sections with primer and paint and the sections with just primer, I'm assuming?

 

anywhere it's bubbling up or you think it might

 

So it's okay to just put the new oil-based primer over the other latex?
I'm thinking a test wall is a good idea at this point.

It's wild how I can find a little bubble, and then end up peeling/scrapping of a big chunk of the old paint/primer/new paint all the way back down to the wood.

 

Applying oil primer over exterior latex isn't a great idea but sometimes you don't have a lot of choices. A quality exterior latex primer in some ways would be better .... but oil base has better adhesion properties.

 

Sorry, I also meant is it okay to put oil-based primer directly onto latex primer?

 

Yes. The problem is, you used an inferior latex primer; I would be inclined to remove as much of it as possible.