To sheath or not to sheath

Many manufacturers, for residnetial applications in particular, are requiring solid decking and underlayment before the roofing is installed. Just the same, I am wondering whether your attic has soffit vents for intake and a roof ridge vent for exhaust. If not, installing good ventilation could eliminate the problems you have had.

thanks.......I was planning to put gable vents in each end of the house but maybe that may not be a good idea since that may disturb the flow. I have seen condensation on the inside of my porch which has wood roof inside and metal on the outside, so I do understand what you are saying. We just had a 40 degree swing in a few hours a week or so ago and everything showed condensation including the wood. I have been here 14 years and never seen it so bad. Just scared me a bit. But when I went in the attic this week there were a few wet spots but notthing soaking so maybe again my problem is not as bad as some folks and mother nature is the culprit right now. No plants or other issues you mentioned but I may still l llo into removing the metal and putting down sheating. Also what type of contractor would do the foam spraying on the undersode of the metal? do you think it would be cost effective to go that root or will that casue other issues later? thanks again for your help.

Condensation occurs when the dewpoint is reached. Dewpoint is based upon the amount of moisture in the air. Reducing the amount of moisture in the air makes it less likely to hit dewpoint. Good ventilation will help to carry out moisture and it will also help to keep the attic cooler. Both of these things help to avoid condensation. Adding decking beneath the roofing also acts as an insulator. The bottom of the decking will not get as cold as the bottom of the metal roofing will. However, just the same, I have seen condensation on the bottom side of decking too. It sounds like you have full soffit vents and a ridge vent. As long as the airflow is not restricted and as long as you do not have other vents in place elsewhere which would dissrupt the airflow, you should be doing a good job of getting airflow through the attic. Are there sources of excessive moisture in the home? This would be things like exhaust fans lacking or not vented to the outside, a lot of houseplants, a ventless gas stove, water in the crawlspace or basement, etc. If anything like this exists, correcting it could help dramatically.