When we bought our house, there had been a family room addition put up in 1996 (now 14 years old). Just this year, the studs are starting to bulge and the seams are showing pretty prominently. The ceiling pitch is about a 33 degree angle toward the outer wall. We do get a lot of moisture and have a sump pump system in our basement. There are no gutters on the addition... water slides down roof and drips down the edge into a perimeter pit filled with gravel and lined with plastic. What causes/cures should I look for?
A picture would be great of what you are describing.
Though from what you describe moisture sounds like the culprit though this can be from vapor due to improper flashing/no vapor barrier behind the siding, or standing water since you mention there is a plastic liner under your gravel bed. This would form a moat of standing water during high rainfalls and constant dampness not too mention it would be wise to install gutters and drainage away from the foundation.
Sounds like multiple issues, all water related.
Install gutters on the addition and regrade the land so the water drains away from the structure. The leaders should be at least 3 feet long.
Studs are wall framing members. Is this what you're referring to? Or are you referring to the ceiling joists?
Any framing member that has started to warp after 14 stable years is being subjected to moisture. You need to find the source and stop it.
Just read the heading. As these are ceiling joists, the roof system is leaking. Either flashing, shingles, fascia or vents.