Answers to Interior Walls Questions #2

Q. I have a home built in the 50's. In the living room on an outside wall, there is a large nasty crack from a piano window almost to the floor. The crack/wall is bubbly. How can I tell if this is just a simple fix to the plaster or could it be a more serious problem?

A. It might be water leakage behind the window. Check for leakage first. You could get some Dura-bond 90 mix it up and applied to fill the crack.

Q. I have one of those honey-do jobs, replacing Marlite wall paneling in a laundry room with plasterboard. My problem is the outside wall is blocked with an entry door, so framing the wall out to nail the plasterboard is out of the question. On that wall can I use thinner plasterboard and maybe glue it to the block wall, since that's how the Marlite was put up?

A. Go ahead and glue it. That will work fine.

Q. I did a good job taping my drywall in my laundry room. I did three coats and the walls and ceiling feels nice and smooth. My problem is the inside corners on the wall and ceiling. I got the tape coat on nice and smooth. I'm doing the second coat on one edge, letting it dry, and then doing the second edge. I read online that it is easier for Diyer to let it dry, and then you don't stand the chance of ruining your work. But I just can't seem to get the tape to cover. After the second coat is it still showing through. Any suggestions?

A. A third coat should help. Completely covering the tape isn't as important as getting a smooth finish. If a little tape shows but can't be felt, it shouldn't show after painting.

Q. I'm papering my seams now and I find that after the first coat of mud, the paper isn't stuck down in some places. Do you have any ideas of what I can do?

A. If it is a corner joint, it will probably be OK. If it is a flat taped joint and the paper is bulged out, you will most likely need to re-tape it. Like you said, give it time to dry first as there is always enough work to do with out making more.

Q. I have heard different opinions, but which is better to use, sandpaper or sanding screens for finishing the drywall seams?

A. If you go with the screen, get at least rough grit so you don't leave scratches if this is the finish coat. Screens are good if you have a lot to do because they do not clog up.

Read this: "Sanding drywall seams involves two steps: Make a first pass using a pole sander with a universal joint and fitted with 120-grit sandpaper. Then sand by hand using 150-grit sandpaper. For this step, fold the sandpaper in quarters, or attach it to a sanding block. As an alternative to this two-step process, you can sand using a fine screen mounted on a handle, or wet-sand (a dustless approach) using a small-celled polyurethane sponge designed for this purpose. Wet sanding with one of these sponges does not yield so fine a finish as dry sanding to 150-grit, but in situations that don't permit dust, it makes a good substitute for the pole-sanding/hand-sanding technique. If you're particularly sensitive to dust or happen to have the equipment handy, you can use a commercial sanding machine with a wet/dry vacuum attachment for nearly dust-free sanding.

If possible, seal off your work area to keep dust from drifting into finished rooms. To accomplish this, set up a dust barrier of polyethylene sheets between the workspace and all clean areas, and seal all edges with masking tape. Keep in mind that joint-compound dust is very fine-grained and can escape through tiny cracks between doors and jambs or around unsealed dust barriers. For your own safety, wear a dust mask and safety goggles while working. You might also want to wear a hat to keep much of the dust out of your hair.

Sanding Drywall Seams: Lighting the work area carefully is essential to good finish sanding. If you shine light directly on a drywall joint, imperfections may not show up. Move the light to the side of the drywall, or shine it from above or below, and you're more likely to detect creases, recesses, bulges, and other defects. For this purpose, acquire a portable, high-powered light source, such as a halogen lamp. Place it on a stand in order to free up both hands, or carry a portable light in one hand and sandpaper in the other as you return to survey the joints and spot-sand any imperfections."

Q. I just purchased 10 sheets of Georgia-Pacific "Plybead" to install on my back porch ceiling. This will be applied over the top of (underneath actually) finished drywall. I think it was blue board, but I'm not sure. At some point in the past, I had seen an installation technique that used construction adhesive applied around the perimeter and 6" beads, 6" apart through the field. I purchased 10 tubes of "Liquid Nails" and planned to tack with my finish nails as well. Well, I can't find that site again. I contacted Georgia-Pacific and they don't recommend the liquid nails. I am afraid the heads on the 16 GA. finish nails may not hold by themselves. By the way, the "Plybead" is real plywood, a little more than 1/4" thick.

A. Use paneling adhesive and brad nails. 16 GA work fine.

Q. The framing is out of plumb and cannot be corrected. The new drywall over the bump creates a hump going up the wall. Can I sand through the drywall to make the wall surface plumb and then coat with a skim coat, tape, texture etc. to form a perfectly plumb surface ready for paint?

A. It sounds as if what you are describing is an improperly taped and finished ripper and not the underlying framing. If you elect to sand, do not fracture the paper surface, just remove as much of the dried mud and tape as is necessary to refinish.

Q. I have a section of the wall in my home where you can see the outline/edges of the piece of drywall. How do I refinish these edges?

A. Apply a coat or two of joint compound.

Q. In the next week or so, I am going to install an in-wall ironing board in the master bedroom. Do I need to cut the space out in between the studs? Should I drill a hole first, and then cut the opening out with a drywall saw or will a jigsaw be easier and quicker? Also, should I screw in a few screws and leave them sticking out enough for "handles" so I have something to grab as I am cutting the last of the four sides, so the cutout does not fall into the wall when it is completely cut?

A. Start out with the drywall saw and see how it goes. Look for any electrical outlets on the wall. After you do that than you should be safe with a hole cut above 32 inches, although, you never know what is behind a wall. Your best bet is to probably go down to the city hall of records or even the county assessor's office and look for a set of plans for the house. Other than that, it is trial and error. The screws are a good idea since the cutout piece may fall down inside the wall. Measure carefully and cut slowly, and it will go just fine. Put a drop cloth on the floor under your cut. You will make quite a bit of dust and it is easier to clean up if you can roll it up in something and carry it outside.

Q. I'd just like to know before I start painting, if it is best to sand the wall by hand or could I use a power tool such as a palm sander? There is "ripple" effect on the wall. Is the "screen" required? What is the purpose of the screen? I have seen some drywall hand sanders at home improvement stores, and some of them come with the screen and some do not. I have also seen another type of hand sander. It's like a sponge material, "medium" grit on one side and "fine" on the other side. Is this type of hand sander worth getting? I am currently sanding the drywalls in my house, but I have noticed that some areas of the drywall are smooth and some are semi-smooth. The semi-smooth parts are like the chocolate bar "Oreo." Is there a way to sand down the semi-smooth area?

A. Hand sanding works fine. A palm sander could do too much damage. Use a sanding pole with a medium or fine grit sanding screen attached. This works very nicely on bumps, hairs, grits of dirt, and off the wall. Use the pole because it allows you to do an entire room quickly, without the aid of a ladder.

You said you have ripples in the wall. The best way to fix this is by using joint compound to fill the low spots, as opposed to trying to sand them all down flat. The sanding sponge works well for small applications. You can use them for sanding doors and frames, small bits of woodwork, etc., but for the body of the walls do not use it, since it takes a long time. The screens do a great job and are quick and easy. An advantage of the screen is that it does not clog like the sponge. With a pole sander and a screen, you will have the whole room done before you get one wall done with the sponge.

The marks could be:
1. Wrong grit - screens have different grits like sandpaper. You would not expect a smooth surface from coarse grit sandpaper.
2. Too much pressure - screens work quickly so too much pressure will cut in too deeply. Screens need very little pressure to work.
3. Used your hand instead of a block or pole. Using a block or sanding pole will keep the screen flat.

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