How to Spackle Walls

Spackle, sometimes called spackling or spackling compound, is a sticky, whitish paste made with gypsum and various synthetic additives, such as vinyl or acrylic. There are powdered forms that you mix with water, but most homeowners reach for one of the handy tubs or tubes of premixed spackle. If you keep the lid closed tightly when not in use, spackle in tubs can stay moist for up to a year. You can usually re-wet aging spackle by mixing in a little water, as long as it's not too dried out.

There are many formulas of spackle, but most fall into two broad categories: lightweight and vinyl. Lightweight can be considered the "instant" version of spackle, along the lines of instant oatmeal or instant pudding; it's fast, but it's also kind of fluffy and lacks substance. Vinyl spackle is the general-purpose version. It dries more slowly than lightweight formulas, but it goes on smoother, sticks better, and is more versatile and suitable for more situations.

Spackle is the ultimate hole-filler: nail and screw holes, dings, dents, gouges, chips, etc. It also fills small cracks up to about 1/4 inch wide and can hide ugly joints in painted woodwork (although sometimes caulk is a better choice for this). Spackle sticks to bare or painted drywall, plaster or wood surfaces. It will fill deep holes if they are small, but it's best to apply it no more than 1/4 thick at a time and to let it dry between layers. Applying spackle too thickly leads to cracks and excessive shrinkage.

Many spackle formulas are touted as "no-shrink," which is a good thing, when available. But regardless of what the packaging says, shrinkage is usually a function of thickness. The thicker the application, the more shrinkage you should expect. Follow the manufacturer's directions for the best results. To combat shrinkage, you can simply overfill the hole slightly and sand it flush after it has dried. Better to apply too much than too little.

Lightweight spackle is designed for very small holes, like nail holes in trim and holes left from removing nails, thumbtacks or hangers in walls. It's less effective for broader patches that need to be smoothed out and leveled. For all other jobs, including holes up to 3/4 inch deep, standard vinyl spackle is the way to go. It spreads well with a putty knife and can be "feathered" into the surrounding surface by making it ultra-thin along the edges.

For tiny holes, you can apply lightweight spackle with just a finger, but generally, it's best to apply any spackle with a putty knife.

1. Scoop a small amount of spackle onto the edge or corner of the knife blade, then press the spackle into the hole or crack, with the putty knife pressed almost flat to the wall while swiping over the hole.
   
2. Scrape off the excess spackle onto the edge of the tub (or use a "palate" made from a wood scrap) so the blade is clean, then make a second pass over the hole, holding the knife at an angle, to smooth the patch and scrape off excess spackle. It's okay if the hole is slightly overfilled,
   
3. Let the spackle dry, as directed. Some lightweight spackle changes color to indicate it is dry and ready for paint.
   
4. Inspect the patch: If it isn't up to full thickness, add a second coat, as needed. If it's too full, making a bump in the wall surface, sand it lightly with a 150-grit sanding sponge or sandpaper until it is flush or flat.
   
5. Wipe off all sanding dust with a clean rag. All spackle is ready to be primed or painted as soon as it's dry.

Spackle is very similar to drywall compound (a.k.a. drywall mud), and sometimes people say spackle when they actually mean mud. Like spackle, drywall mud can be used to fill holes and cracks in drywall, plaster and wood, but mud is thinner and takes longer to dry than spackle. Mud is designed to finish drywall joints that are covered with joint tape. Spackle doesn't work as well in this application, especially over long runs of tape, such as with new drywall installation.

As mentioned, spackle can fill small holes (up to 1 inch, or so, in diameter) in plaster, but for larger holes, a better option is patching plaster. Patching plaster builds up better than spackle and is less likely to crack. Large holes in drywall should be filled with a patch of drywall and receive seam tape along the edges of the patch. The tape can be finished with spackle or drywall mud.

Spackle doesn't expand and contract very much, so it's not a good choice for areas that require flexibility. This includes joints between dissimilar materials, like drywall and wood or ceramic tile, or joints in wood that open up in winter (when the wood shrinks). The appropriate choice in these cases is caulk, not spackle. Likewise, spackle should never be used as a sealant, either indoors or outdoors, or in areas that may get wet. Those are also jobs for the right type of caulk.