Painting Tips by a Professional

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Preparing Walls for Painting Efficiently

For re-painting walls, below you’ll find all the steps you need for preparing walls for painting, from before you start up to the finished product. We will review all the potential problems you might encounter.

If you’re painting brand new dry-wall, we have a post just for that.

Preparing Walls for Painting: Prepping Old Walls

Are Walls in good condition? Keep reading.

Problems? See the next section, but in both cases, you want your walls gently sanded and cleaned.

Many walls we work on were painted by DIY-ers who used cheap rollers that shed lint into the paint, leaving a gritty surface. We give that a sanding (mostly from eye-level down to knee-level), and then wipe with a damp cloth. Most walls have pin/nail holes and we write about that in #4 below, but generally, you can start to paint most pre-painted walls with little prep. The other DIY sites will not say this to cover their butts, but it’s true. Let’s not lose sight of the forest.

When do you need to prime?

When you are going to paint new walls, red walls or old yeller, uh, I mean yellow, or unless you are changing TO NEW red or yellow—you need a primer. Somehow the chemistry (pigments) in red and yellow paints are problems. When you buy your primer for red paint: have it tinted gray. Primer for yellow: no tinting. Ask advice from the store. Read my post on paint-and-primer-in-one and when not to use it.

Other than that, you only need a primer coat when changing from a very dark surface to a much lighter one. The better lines of paint have no problem covering in 2 coats. Don’t believe the ads you have seen about how our great paint covers in one coat. Bunk.

Problems are not problems

“Problems” are not really difficult (except the last one in the list – oh boy.)

Problem #1: Water Stains. (Read this and #2) If you had a plumbing or roof leak (now repaired right?), you have to put a stain-blocking primer on the water damage.  such stains bleed through every single coat of paint you could apply. Amazon sells Kilz and so do most paint stores. Other products are called Bin, and so on. Use the knowledge of paint store managers, or talk to me here, and I’ll reply asap.

Problem #2: Water Damage. Sometimes water will ruin the ‘rock’ of your wallboard. It will turn soft and powdery. No worries. It’s messy, but it’s not rocket science. Just dig out the soft rock, and fill the hole with a pre-mixed drywall compound (“mud”). (It lasts forever in a plastic tub if you keep the lid clean and tight). This stuff shrinks so we only use it when we have to. For deep holes, you’ll need several coats of mud. Sand between coats somewhat and sand well after the last coat. Use the rough grit sandpaper (about 80 grit) to go fast and fine-tune with 150 or so. I’d recommend an assortment pack. For massive holes, sell the house. Not an option? It’s ok, you just need to do a patch. See the next ‘problem’.

Problem #3: You will need some drywall “joint” tape and the compound mentioned in this paragraph, as well as a wide knife. A low-cost set of knives is here.

Cut a scrap piece of drywall in something close to a square that’s just bigger than the hole.  With a pencil (never ink) trace your new patch over the old hole. Cut the pencil line with a sharp knife and remove the old wall. If there is a stud, you can use it to screw in your new piece, but if not just find a strip of wood (a painting stir stick will work, but something bigger is better), and fasten it to the backside of the hole as you see in the photo (this is simulating a stud and will give you something to screw your new piece into).  It is just a matter of holding the stick behind the wall as your screw goes through it: if you have a clamp or a teenager, that will help to hold it as you screw. Fit your new piece in and screw it in and lightly cover edges with ‘mud’. Then lay your tape of patch material over that and then another coat of mud over the tape.  If you don’t use tape, the seam will crack later.  That will probably shrink and maybe crack a bit as it dries, so you’ll need at least one more coat, sanding between coats.  Save the fine tune-sanding work for the final dry mud.  Whew.  Done.  Prime and paint.  All too much? See my first short story at the bottom of this page.

drywall patch photo
Preparing Walls for Painting Efficiently

Problem #4: nail pops. The nails or screws that hold the ‘rock’ up to the walls frequently crack and pop out (mostly from temperature changes outside, not from ‘house settling’). Slamming a door will pop them too: vibrations from that loud music you play. Not really. Just scrape the loose stuff out with your putty knife (or 5-in-1) and hit it with this spackle. We use non-shrink, lightweight spackle because it dries in only hours, or less depending on the depth of the hole.  (“Mud” takes overnight). Your wide knife from the above will work but a medium-size knife is what we use, or if nothing is around I’ll just use my 5-in-1.  Apply, let dry, give a quicksand, prime with regular wall paint (not proper! but ok) if you have no primer handy, and you are done.

Problem #5: pin and nail holes. We don’t do much here, just like finger-painting in kindergarten, we just our finger, spread a bit of lightweight spackle (described above) and wipe with the palm of the hand. No need to prime.

Problem #6: glue type gunk. We just remove with a knife and use a little paint thinner on a rag. If you have a real problem, write to me.

Problem #7: paint beads up like water on a waxed car. 

water wax beads photo

Ok, you have a serious problem. It is probably grease or even tar from a smoker.  (See not so funny cavitation  story below* ) This beading is known as cavitation. The paint cannot adhere. You are going to have to get your hands dirty, but as they say, if there is no solution, don’t worry. If there is a solution, don’t worry. Here the solution is a solution.  Tri-Sodium Phosphate (TSP) is your new best friend. It comes as a liquid or as a powder you mix with water. It’s not very toxic, but WEAR EYE PROTECTION and water-proof gloves. It is basically soap plus Moxy. Really, the phosphates are just something they used to put in detergent, but it was having a bad effect on the environment. If you have any mildew or mold, don’t go with bleach: Bleach can actually make the mold spores retreat deeper into the surface. Try BioBarrier.

Short Story on Preparing Walls for Painting

That’s it but here is a short story: My father showed me how to just stuff a hole in a wall with newspaper until the paper was fairly tight, just keep pushing in the paper until there is no more room in the hole. With the paper just below the surface of the wall, he would layer the mud in coat by coat.  It’s easy but slow. Works!

*A short story about cavitation: We were assigned a studio apartment in an urban setting (near NYC).  We had done literally hundreds of these: 2 per day. This one was very different. Brown walls need 2 coats of off-white. Let’s go in. The stink, oh god the stink.  Anyway, let’s start painting.  Oh, the cavitation, the cavitation.  We packed up and left.  The cause? Smoker. 20 years in that hole.  The brown walls? They used to be white. That what’s happen sometimes when you are preparing walls for painting.

If you have any comments or questions about preparing walls for painting, please write in the comment section.  I’ll reply asap!


12 thoughts on “Preparing Walls for Painting Efficiently”

    • Hi. If you use the right primer for the situation, no. If you use a product that does not have the stain-blocking ability for the stains you have, yes you will have to use more primer, and better primer. If you like, write again here and let me know what you have…if you like, send a photo and description. Good luck.

  1. no, I’m good thanks. since im not pro, i had primed an apt and after a visual inspection i had just thought that it looked like it would have benefitted from another coat of primer. obviously, an amateur mistake. thanks fr taking the time out to answer my question.

  2. Hi. I love you! Thank you so much for all your information and the work that went into it. I wish I had found you at the very beginning of my project. It would have saved me much time and attempts at making decisions. Fortunately I haven’t  purchased anything yet.
    Question regarding filling of holes.
    The walls I will be painting  have a massive amount of anchor holes and much of them are 3/8″ diameter after removal. Since I will be hanging artwork eventually I am concerned about what filler product I should use for strength in case I end up wanting to hang something in the same area. What product would you suggest?

    • Hi. Thanks for the nice words… What I would do is either use a ball-peen hammer to knock the anchors just under the surface, then fill the hole or pull it and fill the larger hole. It would not matter so much if you want to put a screw or nail right in the spot where there is a plastic or metal anchor: the shaft would just go to one side. I would say you’re safe 999 times out of 1000.
      For the best look later, use drywall compound, ie mud. It sands smoother and harder than the 2nd choice, lightweight quick-dry spackle.
      I’ll get to your other question on that post re. trim.
      Thanks again.

  3. Thank you for all this information!
    Question: the walls I will be painting have many anchor holes. Many are 5/8″ in diameter. Is the lightweight spackle you mention the correct product to use for these?
    Thank you in advance.

  4. Hi. I have never painted my walls (20 years) and there were many imperfections which have now been fixed with mud and sanding. The walls are white now and I’m planning on painting them a colour. Do I need to prime first?

  5. I am using your tip from you tube on “How to use a shop vac to catch drywall dust”. I just had to stop sanding to let you know how awesome this tip is! The idea of all the fine dust flying around was literally a roadblock to continuing my project and now I hardly have to deal with any!


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