THE GREAT COVERUP
Subpar drywalling left our paint looking uneven. What can we do now to fix it?
Q We had an extension done to our home a couple of years ago. The contractor used a paint spray gun to prime the walls with white paint, leaving us to paint them with our own colour choice. The gun he used was inconsistent and while the walls looked fine from a distance, up close and to the touch they were rough in many spots and we had to sand them. Since then, we have painted multiple times but we can see flashing where areas that were sanded have a different sheen than the unsanded parts. We tried using matte/flat paint but that didn't help. Are we going to have to pay for them to be replastered/ skimmed again, or is there some other solution?
A Skim-coating the walls with a thin layer of drywall topping mix is indeed one way to create a smooth surface for a great paint job. But before you invest in that, try applying primer to a section of wall where the flashing seems most obvious. Once the primer dries, go over that section with regular paint and see if it looks uniform enough for your taste. If so, paint all the walls, including the test section, with primer and then paint.
There are different types of primers, each optimized for specific purposes, such as blocking stains or smells, filling small divots, or preventing further peeling of paint that's starting to come loose. Assuming your walls are now smooth, you need just one thing from a primer: something that will seal the surface so it is evenly porous. You could use a polyvinyl acetate — or PVA — primer, such as Valspar PVA primer. It's a water-based primer typically used on new drywall, which has seams covered with drywall mud and sections with just the bare paper covering. PVA primer makes these walls evenly porous, and it should accomplish the same thing on your walls. It also flows easily and is self-levelling, making it easier to apply than some thicker primers. And it's relatively inexpensive, one reason to pick it over other primers that also seal, but have added features you don't need. Kilz all-purpose interior/exterior primer, for example, blocks stains as well as seals — and it's $54.99 a gallon at Rona.
How you apply paint over the primer also makes a difference in creating a wall with an even sheen.
Resist the urge to go over paint repeatedly to ensure that you haven't skimped any spots. Water-based paint dries on the surface very quickly, but it takes longer for the whole thickness to dry. If you keep going over a newly painted area, you will dig into the film layer and it won't dry with a uniform finish, regardless of how the surface was prepared. It always makes sense to brush away drips — those do show if they dry as is — but instead of going back and forth to make one coat of paint look perfectly uniform, plan on applying two coats.
Paint the edges first, a process known as cutting in. Use a brush or paint pad for this, not a roller, to make sure you get paint only on the walls, not the ceiling or baseboards. (You might want to mask off the edges of the ceiling and baseboards with painter's tape first.) Use a roller to paint the main expanse of the walls. Apply the paint in 3-by-3-foot sections, using a zigzag pattern to get paint onto the wall quickly. Then even it out by rolling up and down. Do the top section of the wall, then immediately paint the section below in the same way. Finally, run the roller from the top to the bottom in one pass — but just one time. Then move a bit to the right or left and do the same thing to the neighbouring area. Once you've done that to the whole three-foot-wide area, repeat the zigzag steps on the next section of the wall.
On a hot, dry day, you may find the roller dragging as you do the final floor-to-ceiling pass in a section. If that happens, paint in narrower bands — maybe two feet wide.
Always try to apply paint to the next section while the previous area is still wet. Any place where you overlap dry paint with wet paint is likely to show, especially on the second coat. If you need a break, do it when you reach a corner, and cover the tools and paint with plastic wrap or plastic bags so they don't dry out before you get back to work.
If priming a test area and then painting it doesn't create a uniform surface, your other option is to skim-coat. If you hire someone, look for a painter rather than a person who does only drywall work, and consider having them see the job through to the final paint layers. The last thing you need at this point is to have different professionals blame one another for how the job turns out. You also don't want to dictate too many details in how the job should be done, because there are different paths to a good job. Check references and hire someone who does good work, then let them follow the procedure they know works.
Or you might consider doing the skim-coating yourself. One good Youtube video shows how to apply a lightweight topping mix using a paint roller, followed by passes with a drywall trowel that is maybe 10 to 14 inches wide. By pressing down on one side of the trowel and lifting the other side slightly, you can avoid creating ridges where passes overlap.
But if they do happen, just wait for the compound to dry completely and then knock off the ridges with the edge of a drywall knife or trowel.
If you see small holes in the topping mix, fill them with the same mixture and let the wall dry. Rather than sanding the topping mix, avoid dust by rubbing the wall vigorously with a barely damp rag. Let the wall dry, then prime and paint.