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medicdave 06-13-2008 07:58 PM

Wall prep question - still having trouble!
Howdy - First time poster, thanks in advance to anyone able to lend some advice!

I'm doing some interior painting in a large room that previously had a high/low color scheme separated by chair rail. I've removed the chair rail and mudded over the "trough" it left behind. So I'm left with three textures:
  1. The upper wall, which is glossy paint with visible vertical brush strokes
  2. The middle, where the freshly-sanded mud is smooth
  3. The bottom, which is a flat-finish paint
After all's said and done, I want the whole wall to have a flat finish, and since we'll be rolling the new paint on, no brush strokes. I figured it would be enough to prime and paint it, but now I'm concerned the texture differences will show through.

Do I need to sand the whole wall? Is there such a thing as a "filling" primer that will spread out and smooth the brush strokes on the upper portion of the wall? I tried Googling around, but didn't find too much.

Thanks a bunch,

slickshift 06-13-2008 08:41 PM

Your concerns are justified
The brushmarks may show through
(though how much depends on how bad they are)

Best to hit it with a power sander, random orbital type before priming
Most high build primers are meant to be sprayed, but your local Paint Store may have a brush-on type
For example, Benjamin Moore's "First Coat" primer (really an underbody) has a slightly higher build (than regular primer) and can still be brushed on

Then two coats of rolled on premium paint and the marks should be much less visible

Alternate to the sanding would be a "skim coat" of joint compound over the area, but as the brush marks are in shiny paint, that would entail sanding and priming then skim coating....

medicdave 06-13-2008 08:48 PM

Cool, thanks - I will check in with the paint folks when we go shopping, and see if they have any suitable products. Also will check with the local Benjamin Moore place.

Can always do some pole sanding ahead of time as well, to take down the highest ridges. We don't have a random orbital sander, but I imagine they're not too bad to rent...

Thanks again!

slickshift 06-13-2008 08:54 PM

A sanding screen on a pole may help quite a bit w/o actually buying/renting an orbital palm sander

medicdave 06-15-2008 08:11 PM

Wall prep question - yellow alert!
Hi Again...

We rented a Porter Cable drywall sander from the local home improvement warehouse, and took some 150-grit to the upper wall. It did an OK job of removing the highest "ridges" of the brush marks there, but we're still left with 3 very distinct texture zones!

I'm getting pretty concerned that we're going to end up with very odd looking walls after we paint. The plan now is to go back to the store tomorrow and get some toothier sandpaper - probably a 40 or 50 grit - and take it to the top portion of the wall. Then go over the whole thing with an 80-grit-or-so to even it out, and then 150 all around too. Just recalling lots of progressive sanding in grade-school wood shop class...

Then hit it with whatever kind of high-build primer I can get my hands on that can be rolled on (the "First Coat" type sounds promising) and hopefully the texture will end up looking somewhat normal...

Does this sound like a reasonable approach? Is there anything else I should be trying?


slickshift 06-15-2008 08:56 PM

It's either that or skim coat it with joint compound
...or both
Skim coating is not really an easy DIY thing to just pick up
But if the 50/80 grit still isn't doing the job, then you may need to consider it

sirwired 06-16-2008 04:52 AM

Wow! What did they use as a paint brush there? A toothbrush? Yeah, sounds like time for a skim coat. I don't think even a high-build primer is going to save you there...


medicdave 06-16-2008 05:04 AM

I was thinking maybe the previous owner used a 3/8" grout trowel...

50/80 grit goes on today, if no help, then we'll call in the pros for a skim coat.


slickshift 06-16-2008 07:07 AM

Yeah I think that more of a textured strie finish rather than brush marks

If you need to consider a skim coat, to DIY you would have to coat the entire area with a layer or two of joint compound using large putty knifes, and then sand it smooth
Usually if one doesn't have a lot of experience with joint compound, it takes a few (3,4) coats and a lot of sanding (as newbies tend to build it up too high and create much work sanding it down)
But if the area is not too big, it might not be too bad for DIY
(though a pro would be in and out pretty quick if time is a concern)

medicdave 06-16-2008 07:42 AM

Thanks for the ongoing advice stream! This is a pretty big area (21x17'-ish room) so skim coating is probably too big an endeavor for us first-timers.

One alternative a colleague suggested this morning is using a mild orange-peel texture. If the 50-grit paper doesn't take down the brush strokes completely-enough for the Moore primer to make up the difference, we could spray orange peel to get an consistent wall texture from top to bottom. We have a compressor so we'd just need the spray gun and the material.

I've seen various opinions on the paintability of orange peel - colleague here said he had no problem roller-painting over it, but some of the web sites say it can't be painted without risking damage... Opinions? Anyone know of any brands marketed as paintable?


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