Pam has given great info on the roof inspection process.
In addition, here's what I do. As I enter the home, I give a quick look up to view the roof. What I'm looking for is any waving in the roof structure which would cause me to complete a really detailed (over and beyond the HUD "head and shoulders" requirement) inspection of the attic. I'm looking for water damaged or delaminated sheathing which would be evidenced by wavy shingles or visible sags between the roof rafters/trusses-signs the roof may have been installed over bad sheathing or that the attic has excess humidity from improperly vented bath fans or from the excessive use of portable humidifers for little children. You would also want to look for evidence of mold in the attic under this scenario of excess humidity. I am also looking for compostion roofs that may have been installed over non-conventional sheathing which may or may not have enough holding power for the nails-roofs installed over old cedar shakes or metal roofs generally have a wavy appearance from the outside. I also check for water leaks by the chimney and the plumbing vent stacks which indicates failed flashing.
Remember, this is probably the biggest complaint area from the new homeowner that HUD is going to receive so if you see any problems that would cause you to doubt the 2 year remaining life, check the appropriate VC box under (9), then explain the roof deficiency on Page 4 of the VC sheet under 9A,B,etc and call for a certification/inspection by a professional which states the roof has a two year remaining life. That way you're off the hook and the DEU is off the hook also. Learn to word VC conditions to your advantage to lessen your liability. When completing the CIR (repair inspection) for the roof VC, don't comment on the roof repair or the roof certification if they hand it to you, it's not your job. Just state, say under VC 9A: Underwriter to review the required roof certification for acceptability. Now your totally off the hook and the DEU is responsible for the roof certification's acceptability to HUD. If HUD is called with a complaint, you did your job. You called for the cert and made the DEU totally responsible for acceptability via your comment on the CIR.
Of course, we all must learn to look up at the ceiling in every room for water stains which would trigger an automatic roof certification, in my mind anyway. Basically, if the roof looks "sketchy" to you, you're looking for a good reason to throw the 2 year REL opinion onto an expert. Remember, you're not a roofing expert.
Also, the biggest mistake most FHA appraisers make is OK'ing a roof when they CAN'T see certain areas of the roof. Example would be a Cape COD, Salt Box, or Bungalow with a shed dormer. You can see part of the roof but not the dormer section as the pitch is too shallow to observe from the ground. Do not assume that the roof is in the same condition as the rest of the dwelling. If you can't see it, call for a roof certification and tell the DEU that you can not observe the condition of the roof in that area due to the low pitch.
Of course, all flat roofs on the dwelling, porches, etc require certifications.
Also, while viewing the roof, a check of the condition of the masonry chimney is in order, if applicable. Those old, leaning brick chimneys could be a safety issue. Also, I'm looking for attic ventilation via roof ridge vents or gable end vents to make HUD happy......
Anybody care to add to this list????
How do you guys up north handle ice dam problems? Do you check for proper soffit ventilation and require it if not present?
Ben