This doesn’t look right to me.
This is a barn roof that was recently re-shingled.
If it is only cosmetic then great but I am concerned that it is indicative of soft decking and the roller coaster effect will wear prematurely.
Thanks in advance
Looks like a potentially serious problem to me. Don’t walk on it! Looks like the roof was sheathed with 1/4" hardboard. Get that thing checked out by a roofing contractor. And not the one who installed it!
Thanks for your response. I am taking your advice.
I believe that the 24" between trusses needs thicker decking, hence the sag.
I’m concerned about voiding the shingle warranty, ability to support snow or someone walking, premature wear and leaks, and code.
Local code references the 2009 IBC but I have trouble navigating to the specific page.
sag doesn’t look as bad from the side but still bad.
http://https://lh3.googleusercontent.com/g1gewwvE9okl4gzMONfUO4lWqPdtKuZBPdegk7nYXfUy2xpEv3CXIsKy92pFdFfCWfbiN3HrJTDKnYYf_DH5hbRxjTo_gLOQ1oI5YwCgB3kpERE2G29AZct-Trbovv275HFEuNbtHz1nZb6GSTbjRiSZHeeIFpZbba_rXokz3LAWbHhgFkFjPtJnD2Dz8FQjbVRHbD3IG-ynOATDpL9Va_C0OTuEM2s1TkemECGY9AWwbm5jEXAlr5t-sOwne5D2IWMHPa_9Xxj3Tw5S4W685bRNgLkS8_gU4p-ROsQf9ha24lsCLJhTbyw30Q3NK9LYAW75R7QfdvT8HdBX8GwJMEQ-bjH7RgXGRIQt6oGjNtk_zR3FpIN0dHnFWciP_e5PUKO5MTdiBKF0axIX8fI_GuNmU7XRFzMcoGBU7F0jVEHso_HVtKMT72uKZZaSVmzHealm1r4Ud4shu6oawBtrVsXAWaltlFpgsavZ4Uc8WjMQ82tjuXaLu2nJEtWQfgMGk1eHHG58NWkrB-h9DJKYo9iJUFx4vtywdEOLgCU6_22SkpWFuPWoeA7oS5F1hPJVI1Kp=w1280-h960-no
In my opinion water damage looks severe and this should have been replaced
24" on center is standard truss spacing. Minimum is 3/8" plywood but much more common is 7/16 OSB or plywood (typically called half-inch.
That photo appears to show the underside of badly damaged roof sheathing, as if sheathing had no protection at all from weather for an extended period of time during which it rained a lot. But why is there blue sky in the photo? It looks like a box-out for a skylight.
I can’t imagine any decent roofing contractor installing shingles over roof sheathing that looks like that sheathing does, and if the sheathing damage occurred after shingles were installed, the shingles weren’t installed correctly.
I’m not familiar with those shingles but most shingles have about a 5 1/2" exposure. Those look like about twice that.
I would also question the placement of the insulation against the underside of what appears to be the roof sheathing.
That would only be acceptable in a home with a vaulted ceiling, and even then there should be a 2" air channel to ventilate the sheathing.
I would question everything there including the electrical overhead mast, and the ridge of the roof should be straight regardless of the sheathing thickness and I also never seen this type of roof covering.
This is FUBAR in my opinion. 
Please allow me to share a couple more images.
(Sorry about the size, I’m not very good using Google+ as a web host.)
My roofer is upset because I am voicing objections to paying him for this portion.
I’m pretty sure this original piece was only replaced because one of the crew busted through.
The more I see in the Pic’s the worse it looks! Your last photo of the roof edge to the wall below and the lower roof…and ridge caps - OMG!
Shingles on th sidewall appear to been installed using the racking method, which is only an approved method for a small number of shingle models. Joints should typically show a stairstep pattern.
In addition to what appears to be excessive exposure, there’s a trough at the roof edge that will pool water, increasing the chance of leakage. Roof edge flashing is incomplete, and sidewall flashing is missing. Looks like maybe the skylight is missing flashing.
The section of sheathing shows dark stains from corroded nail heads… evidence of significant exposure to moisture.
And Marcel’s obviously right about the “hack a hole in the siding and bend the mast” method of installing the electrical mast.
Undulation of the roof plane due to normal deflection over structural timbers. Some defects in the pointing between slates. Evidence elsewhere suggests that there may be
cracking to some of the ridge tiles. One should consult damage restorartion team in oredr to fix it up and get the best result . You can visit to http://priorityservicesgroup.com/ and check their services.
- Not slate.
- Not tile.
- Not normal.
- Nor are you.
So many visible defects. Recommend further evaluation of structure by a qualified contractor and further evaluation of roof covering by a qualified roofer.