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Q.I'd like to use a coated glass mat tile backerboard like DensShield in a shower stall, but would like to stop the tile about 78 inches above the floor rather than completely covering the walls and ceiling. Is it okay to continue the backerboard all the way up to the 8-foot-high ceiling — which would be covered with the same material — and then simply paint the nontiled areas? If so, how should the textured surface of the tile backer be prepped for a smooth, painted finish?

A.Charles Young, a technical service representative with Georgia-Pacific Gypsum in Atlanta, responds: In a typical residential shower, it is acceptable to skim-coat DensShield tile backer (Georgia-Pacific Gypsum, 800/225-6119, www.gp.com/build) with a setting-type joint compound — such as Durabond (USG, 800/874-4968, www.usg.com) or Georgia-Pacific's ToughRock 45 or 90 — to get a smooth, paintable surface in areas that aren't tiled.

Since these compounds set by a chemical reaction and are very hard when they cure, you might be tempted to use a sandable version. But sandable setting compounds are not recommended in this application, because they don't set as hard as regular formulations. Use 2-inch 10x10 glass-fiber mesh tape (not paper tape) at the corners and wherever DensShield butts into regular gypsum board outside the shower. Joints to be covered with tile should be skimmed with the same latex-modified thinset mortar or Type 1 mastic that will be used to set the tile; otherwise, skim the joints with setting compound.

The nontiled areas can be primed and painted with the same finish used on the other walls in the room as long as the primer and paint are suitable for high-moisture areas.