I replaced my roof in the fall.I replaced any plywood that needed it.One spot was very rotted and I noticed that the insulation was damp and there was some mildew on the sheetrock ceiling. I pulled the insulation but did not replace it.when the roof was done,I took down the bad ceiling and found that the brand new plywood was damp,not dripping, but damp.The ceiling was dry.I have a 3/12 pitch so I did the whole thing in I/W,covered by 3-tab shingles,used baffles in the soffit,and ridge vent the entire length.I know that i have warm air seeping into the ceiling in places and this was one of them.Could it be condensation?I can’t figure out where it could possibly be leaking from.I did the job myself,i am not a roofer,but i do my homework before i tackle most projects.I consider myself pretty handy,but this one’s got me stumped.Thanks for any help.

Your lack of insulation or insulation quality will reflect moisture, colder the climate the more condensation to be expected.

Full I & W is a moisture trap in itself. At least you vented the attic best you could.

Air sealing kitchen and bathroom exhaust vents (hopefully if going through the attic they actually make it outside) will also cause excessive moisture.

Hope this helps.

Something could be accidently venting into that area as well. Like maybe a vent hose came off a dryer vent, bathroom vent, or kitchen vent?

thanks guys,I guess i’ll have to just seal up the inside as best i can,and in the spring,and see if i can vent it better.any suggestions on extra vent options?I have a manufactured. hm. 75’x28’.with about a 2’ space between the ceiling and roof deck(not an attic).the soffit is vented,and i replaced all the bath and kitchen vents and made sure they vent out the roof.

Make sure all the soffet vent can vent freely & not stuffed with insulation. Also, do you have ridgevent? Make sure its properly cut in & not a fake out. Soffet vent wont work without ridge vent as well.

Moisture and the lack of venting is the enemy of all roofs.

What is your venting arrangement like and pictures are helpful.

Any attic space where a 3/12 pitch roof comes into play, you will have venting difficulties. Depending on the truss system you have, you will have an average of 4-6 inches where intake air can flow through.

You said you used baffles??? If you used them, it would allow intake for that bay only…then after 3 ft…the moving air will mix in with the existing air.

**Problem #1…**The bay to the left and right (of the baffle) will have the natural moisture seeping through from the living space…but the air is not moving at this point

**Problem #2…**If these areas have a bathroom or laundry room, then the threat level of moisture increases dramatically

**Problem #3…**Because of the low ceiling between sheet rock and underside of plywood (4-6 inches)…insulation may be coming in contact with the plywood…this will definitely cause moisture build-up (warm moist insulation touching a cold moist plywood will make the moist vapor reach its dew point…hence…condesations!)

I did install a ridge vent.I cut it 1-1/2"on either side of the ridge board the entire length of the house.when i tore off the old roof,there were only 3 four foot long slits cut in the ridge.the rest was shingled over (under the old ridge vent).so what i thought was 70’ of vent,was really only12’.all the bays around my house do not have baffles,only where i had to replace the deck.My plan is to go around and slide baffles up into the bays through the soffits that dont have any.Im sure there are spots where the insulation is touching on the edge.I also found that my furnace chimney has about 2" of open space around it where it goes through the ceiling(furnace is on main floor in a utility closet).A ton of hot air is escaping(I’ve sealed it).

Thats good you cut it yourself, so you know thats done. What about your soffet vents? are they the 2 inch round or 3 round or continuous?

the soffits are continuous.they are white panels, held up between the f-channel and the facia,with a bunch of tiny holes in it.they come in long panels,which you cut to size and snap-n-click together.if i pull them down i can slide baffles up between the insulation, and the roof deck.sry no pics

It sure sounds like you covered all your bases on ventilation.

first i would ask if they had new windows put in. Reason why it will insulate the house alot more than before. The ice and water on the whole house is a concern since the roof does breath and since that’s why we use felt. This could be a multitude of things. I am not going to guess i like the facts and what i know. Ventilation always is a problem and this is a true statistics 78% of the time.

really enjoyed everyones responses. good stuff.

personally i try Not to have 1.5 inches per side for ridge vent.
attempted 3 inches total turns into 4 inches or more in spots and it just turns into leaky.

I have seen ridge vent leak.
I make sure that hole is no more than 3 inches.
Not saying this is your issue. I just want to bring it up as a possibility because i do believe it is a isssue.

I cant count how many cathedral ceilings i have seen with stained ridges with ridge vent that didnt have any stains before the ridge vent but had zero ventilation. sigh.

That is really amazing and interesting post thanks for sharing.