Prevent Peeling Paint on Parging
LESLIE: Tom in Pennsylvania has a painting question. What’s going on?
TOM IN PENNSYLVANIA: Well listen, I have a bi-level and the outside block wall is kind of sandy and I did some repair on it because some of the parging – it’s not a true stucco but a parging – flaked off and I mixed up some cement and I put it on there and I actually painted it with an outside mason paint. But it seems like a year later actually the half of the bi-level that’s insulated and heated – because I put a family room on that side –
TOM IN PENNSYLVANIA: — it seems like all the paint is peeling off; not on the other side where there’s really no heat, just a regular basin with a washer and dryer. I did insulate it. You know, there’s tongue-and-groove wood inside there. Is there anything I can put on the outside?
TOM: (overlapping voices) What side of the house is the paint peeling off on? Is it the north or the south?
TOM IN PENNSYLVANIA: On the south.
TOM: OK, well you’ve got a lot more sun there so that could be part of the problem.
TOM IN PENNSYLVANIA: Yes, but it’s just on the one half. It seemed like the other half that I painted didn’t flake off at all.
TOM: Did the parging repair stick? Is any of the parging falling off?
TOM IN PENNSYLVANIA: No, the parging repair did stick.
TOM IN PENNSYLVANIA: It’s the original parging; it’s just real sandy. And I did know that when they built the house – because I had it built – they did the parging during the wintertime and I thought maybe that somehow it kind of froze a little bit and didn’t cure right. But, like I said, when I did paint it, the parts that fell off were flaky; real – the parge is real sandy.
TOM: Well, did you prime this before you put the paint on that new surface?
TOM IN PENNSYLVANIA: No, I didn’t use any primer at all.
TOM IN PENNSYLVANIA: The paint that I used was a primer and masonry paint in one.
TOM: OK. Well, if the paint is peeling you have an adhesion issue and you have to understand that when paint is designed that it’s either designed to be a primer, which is very adhesive, or to be a topcoat, which has a lot more color in it. And while there may be some products out there that mix both together, I think you’re always better off – especially if you have a difficult masonry surface – of using a primer first, preferably an oil-based primer and oil surface like a KILZ or Bin or something like that, and then you could put a topcoat over that. I think, in this situation, since you’ve tried the masonry product that’s a two-in-one, that what you really probably should do here is wire-brush all of that stuff off that’s really loose – get as much of it off as you can; prime the surface; let it really dry and really adhere. In fact, you know, if it’s cold and damp I would not do this; I’d wait for a nice, warm, dry day.
LESLIE: You have to wait for it really to dry out.
TOM IN PENNSYLVANIA: Right, right.
TOM: Especially with masonry because, you know, it’s so spongy in terms of its ability to hold water.
LESLIE: And it may look like it’s dry but it could – you know, it’s very hydroscopic so it’s going to suck water through from the soil; it’s going to really maintain that water. So wait for, you know, it to be dry for a few days.
TOM IN PENNSYLVANIA: Right.
TOM: You know when the perfect time is to do this? On a – maybe a not terribly hot but just a slightly warm summer day on the south side; wait for the sun to go down – about 4:00 in the afternoon – and it’s not in direct sunlight but the masonry surface is nice and dry and a bit warm. That would be the perfect time to paint this and you’ll get really good adhesion and I think it’s going to last a lot longer.
TOM IN PENNSYLVANIA: Yeah, I did do that when I did initially do it. You know, it was dry. In fact, I went out and I pressure-washed the whole thing.
TOM: After you pressure-washed it, how long did you wait?
TOM IN PENNSYLVANIA: Oh, I waited a week …
TOM IN PENNSYLVANIA: … for it to dry. I mean it dried. It was in August and it dried.
TOM: Right, but again, you used a two-in-one paint that was primer and paint mixed together. I’m suggesting to you that the best thing to do is to do a separate primer coat and then a topcoat. I think you’re always going to better off doing it that way, Tom.
TOM IN PENNSYLVANIA: OK. Is that like a thermal seal, bonding seal or just a primer?
TOM: Primer. Standard, exterior-grade primer. Use an oil-based KILZ, for example.
TOM IN PENNSYLVANIA: OK.
TOM: Will work very well. OK?
TOM IN PENNSYLVANIA: Alright, I appreciate it. Thank you very much.
TOM: Tom, thanks so much for calling us at 888-MONEY-PIT.