Q. My shower stall was tiled three years ago. Is it too late to seal the grout? Also, one grout joint in a corner has cracked, from the floor to the ceiling. How can I fix it so it won’t crack again?

You can seal the grout the day after you applied it or 100 years later, if it is still there. If it isn’t dirty, seal all three sides of the shower. That will make the grout water-resistant, if not waterproof, and help prevent the growth of mold and dirt. If it is dirty, clean thoroughly with bleach and water, rinse, and seal. Any of the clear masonry or tile sealers will work; most such sealers have to be reapplied once a year.

As for that crack in the corner, it cracked because the grout was not compacted heavily enough. Tilers are good tilers but mediocre grouters. The corner is a bigger pain than the flat surfaces because there is often a bigger empty space behind them. You can do this yourself: Dig out all of the old grout. Use a utility knife or any sharp instrument. Buy sanded grout in a hardware store and insert it into the crack with a squeegee, and press it in well so that it is completely compact. Then smooth it off and forget about it until a day or two later, when you can seal it.

I am not a big fan of using caulking with ceramic tile, but this particular corner may be just the place for caulking instead of grouting. You can try it, anyway; put a bead of adhesive caulk (Phenoseal and Polyseamseal are two good brands) in the corner (after digging out all the old grout), then press it in and smooth it off.

Q. I am having fiberglass shingles installed. I have two gable vents at each end of the house, and a roofer cut in a ridge vent. One roofer said I need soffit vents; another said I didn’t. Another said either to take away the ridge vent or keep it. Now what do I do?

One of the reasons for all that confusion is that a ridge vent and soffit vents will work to best advantage in ventilating the attic. No other vents are needed; in fact, those gable vents are interfering with the efficiency of ridge and soffit vents. So close the gable vents and install a continuous screened strip the full length of each soffit. The soffit vents and ridge vent will provide bottom-to-top ventilation, the best way.

Q. I tried scraping off green moss from my driveway with an ice scraper, but it did not work. What am I doing wrong?

Did this ”moss” have a thickness? If so, it is moss, and should scrape off easily. If not, it is algae, which can be power-washed off. Or treat it with a solution of 1 part bleach and 3 parts water, scrub and rinse. If necessary, treat with another dose of the bleach solution.

Q. The parting beads of my double-hung windows are rotting, but their size, 5/16 inch by 1 1/2 inches wide, are not available. Why can’t I get such a size?

Because they are not parting beads, which keep the lower sash separate from the upper sash and which fit in a groove the full length of each jamb. I think they are side stops, which go the full height of the window on the jamb, preventing the lower sash from popping out. You can get stock stops that are 1/2 inch thick and 1 1/2 inches wide. Nail or screw them on.