Crack House
May 14, 2016 10:47 AM   Subscribe

I've got a couple of tricky paint repair jobs to do at my house, and would like some advice on how to proceed.

Paint job no. 1: I painted the hallways of my house about five years ago. Since then, the wall by the front door has developed cracks -- I assume because of the exposure to cold and heat. How can I repair the wall so that this won't happen again?

Paint job no. 2. This is the bottom right corner of the medicine cabinet in my bathroom. The enamel has cracked and chipped and the exposed metal is rusty. Is there any way to resurface it? I can't spare the money for a new cabinet, and in general I always prefer to repairing over replacing in order to save things from going into a landfill.
posted by orange swan to Home & Garden (10 answers total)
The cracks look like a moisture problem underneath the paint, so I can't help there. Someone with drywall experience might be able to help, as it might be a moisture barrier issue.

But I have successfully repainted metal cabinets using Rust-Oleum enamel paint. I used a sponge brush to avoid brush marks. You can sand it a little, then wipe with a tack cloth, let dry fully. I used sandpaper with a little water to help smooth any edges, then wiped clean and let dry. It won't look 100% if you only cover those spots and the edges, but it will stop the rust from spreading. Besides, it's inside the cabinet. Of course, make sure there is no continued water dripping into that area, but at least a dab of enamel paint will protect the metal.
posted by Marie Mon Dieu at 11:04 AM on May 14, 2016

The cracking in job no. 1 is usually* caused by moisture getting behind the paint: the muffin shapes are the layer of paint lifting from the substrate, the cracks are where the paint film can stretch no further. You can scrape, sand and repaint but the problem will reoccur if the source of the moisture isn't tracked down and fixed. Is this room a bathroom or some other potentially poorly-ventilated high-humdity room? It's worrisome to me that this is occurring at what looks to be fairly high up on a wall because that could indicate water getting in through the ceiling (roof or plumbing).

*The other cause is too thick of a coat of paint applied or multiple layers of paint applied over paint which hadn't had time to adequately dry, however, that usually just leaves cracks, not the muffining you have.
posted by jamaro at 11:15 AM on May 14, 2016

Yeah the first one is a moisture issue that looks like it is going to be annoying, and will probably involve tearing all the drywall off of that wall. You should poke the wall with a screwdriver- can it go right through? Do you know if there is plaster or drywall?
posted by rockindata at 11:16 AM on May 14, 2016

1. looks like moisture, but I notice another patch under the coat rack that had similar peeling. is the wall plaster or drywall? it's possible that these are improperly primed plaster patches. if you are sure there isn't a leak, scrape and make sure to prime with a primer/sealer type paint before you repaint.

2. medicine cabinets usual come out of the wall pretty easily. there should be two screwson the inside holding it in. take it out, sand away the rust and use rust oleum spray paint.
posted by at 11:28 AM on May 14, 2016 [1 favorite]

I believe the surface underneath the paint is a "skim coat" of plaster, and the wall underneath seems very firm and whole and dry. I've peeked underneath the cracks, and it's just the top layers that have cracked, while the wall underneath seems to be completely free of cracks. I did put on quite a few layers of paint, as I had trouble getting the paint colour right, and I think I painted the wall a total of five times. However, the entire hallway got the same five coats, and has not cracked anywhere else.
posted by orange swan at 11:32 AM on May 14, 2016

I've peeked underneath the cracks, and it's just the top layers that have cracked
Is there still paint on the walls behind the cracks? If the paint is lifting up between layers, then there's also an incompatibility between the coats of paint. Common causes are painting oil over latex, using budget paint or improper surface prep (such as not thoroughly cleaning the surface of greases before painting).

Plaster or drywall might not show visible signs of moisture damage at all. Plaster and drywall is porous, paint is not, thus moisture evaporating out of the plaster is being trapped behind the paint and lifting it. Think of this as an early warning system: there's a moisture problem somewhere and it should be fixed because it's pointing out a bigger problem than just a paint flaw. I'd try probing the walls with something thin and sharp to look for areas where the walls are softer (you're going to have to prep and repaint anyway, the probe holes can be patched at that time) and also checking the attic/crawlspace above for signs of moisture wicking along wood. If none of the above pans out, look into improving the ventilation in that room or put a dehumidifier in there.
posted by jamaro at 12:09 PM on May 14, 2016 [2 favorites]

Is there still paint on the walls behind the cracks?

No, there isn't. It looks to me like all the paint layers and possibly the skim coating have cracked, because the wall I'm seeing behind what's peeling away does not look like the skim coating I painted over.
posted by orange swan at 12:21 PM on May 14, 2016

For the cabinet, scrape off as much loose paint as you can, wire brushes work well for this. Let toilet bowl cleaner sit on the rusty spots to help dissolve some of the rust. Sand, clean, dry. Then use spray paint marketed for appliances.
posted by txtwinkletoes at 1:57 PM on May 14, 2016 [1 favorite]

To my eye, the cracking you're seeing on paint job 1 is absolutely due to moisture of some sort. HOWEVER, it may be historical water damage that is only now rearing its head. I've only ever seen this type of thing on plaster/cement walls, not drywall. Were I in your position, knowing what I know, I'd scrape the shit out of it and see what's going on underneath all that paint. scrape it down to the wall. If there's a paper layer behind there, you've got drywall, but again, I don't see that being likely.

What I imagine you'll see is that the material behind the paint is starting to crack/bubble up itself and if you pick at it, it will come off in flakes of various sizes, aand underneath you will find basically loose sand which you can easily clean away.. this is the plaster/cement/whatever that has been damaged by moisture and is essentially eroding away. Scrape/poke/wipe/brush all this shit off until all that's left is solid wall.. Sometimes you end up having to go all the way back to the cinderblocks, in which case repair is going to require something like SikaTop (made by Sika), which is not something for the do-it-yourselfer to muck with typically. Once you've covered up the cinderblocks, you should leave an eighth of an inch for the final plaster coat which you would feather out to match with the existing, good (painted) wall.

If the cause of the moisture problem was fixed in the past, you can now repair the wall by using a durable "mud" mixture like duraroc 90 or sheetrock 90. This takes some skill however and generally won't look terribly good unless you have done significant plaster/mud work before. It really is an art to blend a patch into an existing wall.

If the next day after you apply your plaster/mud coat, you see it bubbling up on you, that is a strong indicator that the moisture issue is still occurring, in which case you need to figure out why and where the moisture is coming from, and stop it, otherwise you'll constantly be re-patching this wall.

If you are renting, this is something that your landlord/super should be paying a professional to fix for you.
posted by some loser at 6:42 PM on May 14, 2016

My house is plaster-based as well, and I've had some issues like what you show.

The moisture-based cracking/bulging near your door looks like what happened when the previous owner of our house painted latex paint over a previous, unknown coat (likely chalk paint or improperly cleaned oil-based paint) and then added another coat over the cracking paint. It happened because the plaster keeps the base coat dry, then the second coat expands/contracts from heat/moisture cycles, and the third coat keeps the pieces from just breaking off.

You likely don't have an underlying structural issue, just paint incompatibility.

The way we fixed it in our house was to remove paint down past the issue layer (bare plaster if possible) and then prime and repaint.
posted by bookdragoness at 5:04 PM on May 16, 2016

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