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Silicone caulking causes problems

QuestionOur 1920 house has semi-textured lath-and-plaster walls. In one room we used a steamer to remove wallpaper but damaged the thin layer of drywall compound that had been applied to smooth out the textured wall surfaces. The damaged areas can be repaired, but we were surprised to find what appears to be white rubber/silicone bathroom caulking compound spread out on all the inside corners and up against all the trim. We would like to paint these walls, but wonder if we can spackle and/or paint over this caulking or if we need to remove it. If it requires removal, is there a better way than to scrape it off and cause more wall damage?

AnswerI have never understood why individuals use silicone caulk to repair wall cracks or fill gaps between wall surfaces and trim. It requires more work in the long run and paint and other sealing compounds don't adhere to its surface.

Now that I've gotten that off my chest, I can answer your question. If the compound is truly 100 percent silicone, you cannot spackle or paint over it. Test the compound by applying a latex paint to the surface. A silicone surface will cause brushed-on paint to bead up and skip across the surface.

The best way to remove silicone is to apply plain old elbow grease. Yes, you could damage the surface, but you have mentioned that the wall surfaces are already damaged. A couple of tools could help you remove silicone and hopefully minimize wall damage in the process. Hyde makes a 6-IN-1 Painter's Tool that has a sharp scraper blade and a sharp point to help open cracks for patching. The other tool, Hyde's 4-inch Wallpaper Shaver, has a replaceable blade and is sharp enough to get underneath the silicone's feathered edge.

Silicone sealing compound is difficult to remove because it has to be scraped first and then rubbed off. Wear close-fitting gloves, preferably white cotton because dyed gloves could leave marks on the surface and create additional problems.

Because your skim-coated lath-and-plaster walls have been damaged, you'll want to carefully prepare them for painting. Look for cracks, especially where walls meet the ceiling, and repair them with joint tape and drywall joint compound. Taped areas will need one coat of joint compound and two (or possibly three) topping coats to bring the area flush out to the existing walls and/or ceiling.

Fill hairline cracks, frequently found where base moldings and casings meet the walls, with white latex (not silicone) caulk. Two or three thin coats may be required, so use your finger to blend in the caulk and finish with a soft sponge and warm water. Deep craters will require taping.

Fill small nail holes with joint compound and tape larger holes. Fill and sand any gouges, nicks, and other defects. Finally, skim coat wall and ceiling surfaces with joint compound and sand with a wallboard sander. Stanley's dust-free hand sander attaches to a wet-and-dry vacuum and controls dust. Use a unit with a double filter and an extra hose to vent the exhaust to the exterior. This will help to eliminate dust blowing back into the home.

Latex base primers and paints can sometimes cause calcimine in plaster walls to bleed through the joint compound to the finish paint, so I recommend that you paint new areas with a stain killer or white shellac before priming. I recommend two primer products by Zinsser, and my personal favorite is their shellac-based product, B-I-N. Cover Stain, their oil-based product, runs a close second. Both products are a little pricey but they are great products and available at your local home center. You can learn more about them at www.zinsser.com.

When you are completely satisfied with the prep work, move on to the single most important step in the process: priming. Priming is a key step to achieving great results because latex finish paint requires a heavily pigmented white latex primer (not a wall sealer).

If you use one of the Zinsser primer products, it's not necessary to use another primer because both Zinsser products prime and seal. However, if you still want to apply an additional primer, Zinsser offers Bulls-Eye, a water-based primer-sealer and stain killer. It's a tintable white product, which is nice if the walls will be painted in a color.

I recommend that you use a wallboard sander to sand the walls and ceiling after priming and then wipe them down with a damp sponge. The primer will reveal any remaining defects in the wall so make any necessary repairs and reprime.

I use a 3/4" lamb's wool roller because it adds some texture. Saturate the roller with paint and roll it over the entire wall including any newly-taped areas near or on the ceiling. Wait about five minutes and backroll the area with the same roller without any additional paint. The idea is to raise the paint surface while it is tacky to create texture.

You might have to repeat the procedure a few times, allowing a day between coats to dry. Once you achieve the desired texture, apply the finish coats, again using a lamb's wool roller. I prefer this method to spray-on textures because it produces more subtle results. This is also a great way to blend new surfaces to old.

The last step—the finish coat—is very important to pull the entire project together, and I encourage you to not skimp on paint quality. Begin with the ceiling, then paint the walls, and finish with the moldings and doors.

If the ceiling is a different color than the walls, paint around the perimeter of the ceiling using a 2" trim brush (also known as "cutting the inside edges"). Carefully blend the paint on the outside edge of the brush toward the ceiling center so you don't leave any brush strokes. Then use your 3/4" nap lamb's wool roller to apply the finish paint, overlapping the roller marks and brush strokes.

I find I achieve best results by applying a full roller in one direction. Use the same techniques for the walls, and be sure to paint moldings with the grain.

While the job is technically complete, don't rush to put everything back into the room. Instead, allow the paint to cure at least 2 to 3 days. This is one project that you and your family will benefit from for many years.

Copyright © 2004, 2006, & 2007 LAF/C.R.S., Inc. All rights reserved.
Question answered by Leon A. Frechette.

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C.R.S., Inc. · Spokane, Washington · USA

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