Primer not sticking to new mold-resistant drywall

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Old 11-09-15, 01:58 PM
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Primer not sticking to new mold-resistant drywall

I'm a DIY'er doing a new room in the basement. I've drywalled the room with a mix of regular "white" drywall and "green" mold resistant drywall. I have primed the room but have concerns that the primer has not bonded properly to the greenboard.

Prior to priming, I wiped down the walls with dry towels to knock down the dust and then vacuumed lightly. I used a drywall primer recommended to me by my local Sherwin Williams store (Quali-kote which I gather is unique to Canada). While painting the ceiling I masked off some of the walls and found that wherever I stuck the green painters tape and then removed it, the primer is getting pulled off with the tape. I don't see the same problem on the regular white drywall.

It is now 2 weeks since priming and I can still pull off primer just by sticking a piece of tape on the wall and then pulling it off. Obviously I'm concerned about proceeding with painting a topcoat. I've spoken to both the Sherwin Williams dealer and the drywall rep and neither have any ideas why this might be happening. They also haven't been able to give me any good options other than trying another coat of primer (???) or "lightly sanding" and then trying a more expensive primer.

I'm stuck and confused what to do next. If I just paint it, will it seal somehow? Or do I need to remove everything somehow? Any advice is appreciated.


The drywall I used: https://www.usg.com/content/dam/USG_...eet-en-can.pdf
 
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Old 11-09-15, 02:23 PM
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Welcome to the forums!

I don't know what changes have been made to green board over the years but back when it was prevalent in bath rms there were always times when the primer wouldn't adhere like it should. It's been my understanding that they impregnate the drywall with a waxy like substance to make it water proof which also makes it harder for primer to make a good bond with the drywall.

Oil base primer does adhere to green board better than latex but applying it over the latex doesn't help much. I'd probably sand the wall with 80 grit and see how it looks. If sanding removes a lot of primer - use a better primer. Otherwise it's probably ok to paint.
 
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Old 11-09-15, 06:58 PM
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Thanks for the reply. The SW rep gave me a quart of their multipurpose primer to try on a small test area and see whether that helps. I have a hard time believing it will soak through the first coat and magically bond it all together but I've tried a small test area to see what happens. I did it in two small sections - one where I lightly sanded the 1st coat and a second without any additional prep. I'll give it a couple of days and try the tape test.

I'm not sure how I would have sanded this drywall prior to priming. I have some scraps here that I've just dragged the sandpaper over and it doesn't take much to rough up the paper surface. I'd be nervous about doing the entire surface - I'd probably have to do a skim coat of mud after. Ugh. In any event I asked the USG drywall rep directly whether this type of drywall requires any special prep or primer and he said no - it is finished exactly the same as their regular drywall. It does soak up less moisture and maybe the primer SW sold me just isn't suitable (although their rep didn't seem to think that was likely).

I've seen some mention on various painting forums of using Zinsser Gardz for problems that sound similar to mine. I gather I would paint the entire surface with it and then paint directly over that. Any opinions on whether that is a solution that could save me a lot of sanding and scraping?

Thanks very much for the help
 
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Old 11-10-15, 03:53 AM
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Stop using tape on drywall. It was never really meant for that to begin with. The tape will stick to the flat paint much better than it will stick to a paint with a sheen of any kind. Your wall, in the normal course of events, will never have tape stuck to it, so what you are witnessing is an unusual event. However, latex paint, regardless of sheen, remains flexible and therefore always has the potential of peeling if you apply adhesive tape to it and remove. Don't use tape as a substitute for taking your time and trying to cut in a nice line. Tape is meant to protect adjacent surfaces and it not meant to be used to cut a straight line. Yet, that is how most people use it. I would say you are fine to just continue painting without a bunch of additional prep.
 
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Old 11-10-15, 03:54 AM
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The main reason for sanding would be to remove any primer that isn't bonded well with the drywall. I've never known of any adhesion issues over the mudded joints, only on the areas of exposed green board.

Zinnser Gardz is a great water based sealer. Probably it's biggest use is over stripped wallpaper. It seals any leftover adhesive so it won't be an issue with the top coat. Prior to Gardz we always used an oil base primer for the same reason. Zinnser also sells a primer called Peel Stop might be beneficial in your situation although I don't recall ever having used it.

Personally I'd have more confidence in mechanically removing what I could [sanding] than just applying a sealer over the existing primer. Let us know how your test spots go.
 
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Old 11-10-15, 06:46 AM
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czizzi: Yeah I've wondered whether the tape test is fair or not but given it doesn't pull off the primer from the regular drywall I was concerned that I'm going to have a problem somewhere down the road. And my SW paint store manager had the same concern and recommended I not proceed. But I also wonder whether I'm overreacting or not. By the way, I wouldn't normally tape (especially a primer) but the ceiling was sprayed and I masked off the walls. I didn't want dusty overspray getting on the walls and end up having that cause me a problem.

marksr: I'll post back after a couple of days and let you know how it goes.

Thanks
 
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Old 11-11-15, 09:03 AM
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Some test results:

I had some scrap pieces of green board that had never been finished or exposed to drywall dust. I primed three different areas: One with the SW Quali-kote that is used in the room now, one with the SW multipurpose primer that SW recommended I try after the fact and one with Zinsser Bullseye 123. I allowed 36 hour dry time which maybe isn't enough but the tape test is pretty clear. Green painters tape pulls off the Quail-kote like it never had bonded. On the other hand, the tape doesn't pull off any primer with either of the other two.

This rules out drywall dust as the cause. And clearly if I'd used either of the other primers, I'd have no problem now. So much for going to a paint store to get good advice - I'm pretty annoyed about that.

I had also painted sample areas over the existing primed wall, lightly sanding in some areas and not sanding at all in others. Unexpectedly what I found is that the area that I lightly pre-sanded actually seems to show no improvement even though the better primer is used. But strangely the areas where I didn't sand at all show quite an improvement over the existing situation. It comes off but in much smaller flecks. I'm not sure if the top coat of better primer soaked through to help bond or whether this is simply due to a stronger mechanical layer now that I have two built-up layers. In any event, my initial test suggests that sanding is worse which just doesn't make sense to me. Maybe I didn't sand enough or maybe I should have wiped it down with a damp rag in addition to vacuuming?

I guess I'll be heading back to the SW store to show my results (bringing my sample with me) but I don't know what to expect.
 
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Old 11-11-15, 12:09 PM
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When you originally went to the paint store did they know that some of the drywall is green board?
 
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Old 11-11-15, 07:29 PM
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They knew it was new drywall installed in a basement. Basement mold is a problem in this area due to our extreme weather and so mold-resistant is advised for basements and I believe is quite common in basement developments (my home center advised me to use it as did the building inspector).

The datasheet for the drywall says finishing is the same as non-mold resistant drywall so I didn't think to bring it up. And when I went back to the paint store I told them the problem was only with the green drywall and they didn't know of any problems so I don't think they would have advised any different. The drywall rep told me the same thing - he says there are no special primer requirements and any drywall sealer/primer should be fine. But obviously it is different enough.
 
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Old 11-12-15, 03:21 AM
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I've not painted any new greenboard in decades so anyone that wasn't around back when it was prevalent might not know about any of the adhesion issues associated with it. Green board used to be mandated for bath rms but the building trade got away from that over 20 yrs ago.
 
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