Substandard drywall left our paint patchy. How can we fix it?

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Question : We had an extension built on our house a few years ago. The contractor used a paint sprayer to prime the walls with white paint, leaving us to paint them with our own choice of colors. The gun he used was inconsistent and although the walls looked good from a distance, up close and to the touch, they were rough in many places and we had to sand them down. We have since painted several times, but we can see flashing where the sanded areas have a different sheen than the unsanded areas. We tried using matte/matte paint but it didn’t help. Are we going to have to pay to have them re-plastered/skimmed again, or is there another solution?

A: Coating the walls with a thin coat of drywall finishing mix is ​​indeed a way to create a smooth surface for a great painting job. But before you invest in this, try applying primer to a section of wall where the flashing seems most obvious. Once the primer is dry, go over this section with regular paint and see if it looks uniform enough for your liking. If so, paint all 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 odors, filling small gaps, or preventing further chipping as paint begins to come off. Assuming your walls are now smooth, you only need one primer: something that will seal the surface so it’s uniformly porous. You can use a polyvinyl acetate – or PVA – primer, such as Valspar PVA Primer ($14.98 per gallon at Lowe’s). This is a water-based primer typically used on new drywall, where the joints are covered with drywall mud and the sections covered only with bare paper. PVA primer makes these walls uniformly porous and should accomplish the same thing on your walls. It also flows easily and is self-leveling, making it easier to apply than some thicker primers. And it’s relatively inexpensive, a reason to choose it over other primers that also seal but have extra features you don’t need. Kilz All-Purpose Interior/Exterior Primer, for example, blocks stains as well as seals — and costs $23.98 a gallon at Lowe’s.

How you apply paint over primer also makes a difference in creating a wall with an even shine. Resist the urge to go over the paint several times to make sure you haven’t skimped on any spots. Water-based paint dries very quickly on the surface, but it takes longer to dry all the way through. If you continue to go over a newly painted area, you will dig into the film layer and it will not dry to an even finish, regardless of how the surface was prepared. It still makes sense to remove drips – these show if they dry as is – but instead of going back and forth to make one coat of paint look perfectly even, plan to apply two coats.

Paint the edges first, a process known as trimming. Use a brush or paint pad, not a roller, to ensure you only get paint on the walls, not the ceiling or baseboards. (You may want to mask off the edges of the ceiling and baseboards with painter’s tape first.) Use a roller to paint the main portion of the walls. Apply the paint in 3-by-3-foot sections, using a zigzag pattern to quickly apply the paint to the wall. Then, even it out by rolling up and down. Complete the upper part of the wall, then immediately paint the lower part in the same way. Finally, run the roller up and down in one pass, but only once. Then move a little to the right or left and do the same with the neighboring area. Once you’ve done this across the entire 3-foot-wide area, repeat the zigzag steps on the next section of wall.

On a hot, dry day, you may find that the roller drags as you make the final floor-to-ceiling pass in a section. If this happens, paint in narrower strips – perhaps 2 feet wide. Always try to apply paint to the next section while the previous area is still wet. Any place where you layer dry paint with wet paint is likely to be visible, especially on the second coat. If you need a break, do so when you reach a corner and cover the tools and paint with plastic wrap or plastic bags so they don’t dry out before returning to work.

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If priming a test area and then painting it does not create a uniform surface, your other option is to apply a finish coat. If you hire someone, look for a painter rather than someone who only does drywall work, and consider having them carry out the work down to the final coats of paint. The last thing you need at this point is for different professionals to blame each other for the outcome of the work. You also don’t want to dictate too many details about how the work should be done, because there are different paths to good work. Check references and hire someone who does a good job; then let them follow the procedure they know works.

Or you might consider doing the siding yourself. A good YouTube video shows how to apply a light finishing mix using a paint roller, followed by passes with a drywall trowel 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 this happens, simply wait for the compound to dry completely, then remove the ridges with the edge of a drywall knife or trowel. If you see small holes in the finishing mixture, fill them with the same mixture and let the wall dry. Rather than sanding the finishing mixture, prevent dust by scrubbing the wall vigorously with a barely damp cloth. Let the wall dry, then prime and paint.

Do you have a problem at home? Send your questions to [email protected]. Put “How to” in the subject line, tell us where you live, and try to include a photo.

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