Q: Does caulking expire in the tube?

A: Word on the street is that after 18 months, it should be used quickly or tossed. Because I am such a damned miser, I have tried innumerable times to use caulking manufactured back from the days of disco. Sometimes treasures are found on a back shelf, and you can't just throw them away! Maybe this tube will be the one exception to the rule.

But let me tell you: No matter how hard you try to pry it out with a nail, how far you cut the tip back, how hard you step on the tube, how long you soak it in warm water or how hard you beat it with a hammer, there are no exceptions. None. Use it or lose it.

Q: I noticed a blister of paint where our ceiling and wall meet. It was noticeably cool to the touch compared with the nearby wall. Above this location is where the furnace vents. A roofer could not see much wrong with the roofing or flashing, but he suspected it might be condensation on the metal chimney pipe inside the attic space. Because of the cathedral ceiling, there is no way to access this space.

Any suggestions? I suspect one way to check is to wait until we don't need the furnace operating and see if the blister is cool/wet after rains. But with wet insulation, it may be damp for months. Should I cut open the drywall and check for mold?

A: The roofer has checked it out and sees nothing wrong, thereby eliminating the low-hanging fruit, unfortunately. Of course, the vent cap and pipe themselves are large potential culprits, and need to be looked at very carefully from above, particularly the storm collar just below the cap. Frequently they leak and need silicone sealant.

My second thought is overall lack of venting in the cathedral ceiling. Have the roofer look at that. If it is not adequately vented, that cold pipe (when the furnace is not running) will be attracting condensation, then dripping down into your ceiling. Conversely, if the pipe is located in an exterior wall, adjacent to a roof vent, you will also be suffering from condensation because of too much venting. No misprint. It's a delicate balance.

The cold you feel on the ceiling could be moisture, or it could simply be lack of insulation in the area — you should have no insulation within a few inches of that exhaust pipe for fire safety. But it may need some insulating structure built around it to protect it from the direct shot of cold air while still inside enclosed space.

In any event, cut into the ceiling. The exhaust pipe may actually be partly detached, which would be a good explanation for everything. Busting in should tell you everything you need to know and assure you there is no lurking mold.

Darrell Hay is a local home inspector and manages several rental properties. Send home-maintenance questions to dhay@seattletimes.com. Sorry, no personal replies.