QUESTION: I have a shed-roofed porch (one slope butting into the wall of the house), nicely glassed in with windows, and with screens in summer. I am getting a lot of mold on the ceiling. How can I remove it and keep it away? The ceiling follows the slope of the roof, and it seems that a lot of warm, moist air gets trapped under the ceiling, which may be causing the mold. Is there a way to keep that air circulating or venting?

ANSWER: You hit the problem square on the head. First, treat the mold with Peter Hotton's favorite mold remedy: one part household bleach, three parts water. If there is a plasterboard ceiling under the shed (one slope) roof, rinse off the bleach, let it dry and paint the ceiling with Super White latex interior paint, made by Zinsser. It is a very hard, shiny finish, which makes it mold-resistant.Also, to keep that moist air moving, install a larger ceiling paddle fan. The fan will help diminish the mold, but not entirely.And here is what you can do to keep the mold from coming back. Ventilate the porch. Cut a 2-inch-wide strip from the ceiling where it meets the wall. Cut another 2-inch-wide strip from the roof above. It is a lot of work, but will do the trick. You will have to cut out the asphalt shingles and the flashing where the roof meets the wall.Now, install half a ridge vent. I don't think they make such things, but you can do it yourself with a standard ridge vent. Cut off one side of the ridge vent, leaving intact the plastic cover of that side. Set the intact vent on the roof, with the cover acting as flashing, set against the wall and under the bottom row of shingles.With this half ridge vent, air will circulate from the porch through the vent, and outside.

QUESTION: I am getting a hum from my fluorescent-tube light. It is not very big, and I have replaced the starter and changed the tube itself without success. Now what?

ANSWER: You have come to the last resort. Unless an electrician can fix it, replace the whole fixture. Don't forget to turn off the power when you do this.

QUESTION: I am putting up grab bars in my shower area. The ceramic tiles are on plasterboard, so I cannot locate the studs, even with a stud finder. Is there any other way to find the studs? Would it be possble to put up the grab bars with molly bolts driven through the tile and plasterbaord? Would this be strong enough?

ANSWER: Don't try the molly bolts. You will be putting weight on the grab bars, and in an emergency you might be grabbing it quickly and heavily. A bolt even in ceramic and plasterboard or plaster will not stand up to heavy pressure or sudden movement.I never had luck with the electronic stud finders. I have relied on the knuckle test.If the wall in question backs up to another room, you can locate the studs from the wall in that room. Then drive a long, thin drill bit beside that stud and through the wall and through the ceramic tile. Go gently through that dark wall to keep from pushing the tile off. Measure 16 inches from that mark to locate the next stud.A horizontal or vertical bar is OK. If your grab bar is too long and is not adjustable to make it horizontal, you could angle it so the end will be over a stud.Handyman on Call Peter Hotton is available 1-6 p.m. Tuesdays to answer questions. Call 617-929-2930. Hotton also chats online 2 to3 p.m. Thursdays. Go to www.boston.com. Hotton's e-mail is photton@globe.comBy The Boston Globe