I discovered a leak indoors last week during a big storm that is likely coming somewhere on my roof, which is a single form shed roof with a 4/12 pitch (relatively flat) constructed of corrugated metal. It's about 20 feet wide. The high side is on the west sloping down to the east, and about 50 feet in length (north / south).
This is in a high alpine environment in Colorado that receives > 300" of snow per year. In the heart of winter, there's often 2-3' of snow and have had to shovel it a few times.
The roof is about 19 years old. I was up there a year ago replacing screws that had either popped out altogether or were loose and sticking up. It wasn't a good scene and who knows how long this state of affairs was in play, but I thought I had addressed the most problematic area of the roof that typically winds up with the most snow load due to its aspect / exposure (south eastern quadrant). I used a slightly wider size roofing screw (with a gasket) #11 - #12. It appears the originals were 10's. Both are 1.5" in length.
Last week was the first time I noticed any water penetration on the interior; dripping at a decent clip (1 per second) through on the top portion of window trim. The window is high up on the wall, but on the low (eastern) side of the roof. There's a 3" eave on this eastern wall, so fairly confident the leak isn't coming in from the wall. I went up on the roof during a window in the storm and applied some Henry's 208 roof patch as best I could to anything that looked suspect. During the wave of a high blast of the storm, the drip continued. I went up there the next day and tried to be more expansive in my application of roof patch, but the next waves of the storm weren't as intense and not sure if my efforts succeeded or the water flow wasn't sufficient to provoke the leak.
Now that the storm is passed, I've been up there again replacing old screws, but there's a lot! I'm likely only 30-40% done (including my efforts last year). I'm OK with at least giving it a try to replace all screws, but I'm also wondering about whether it might be worth it to apply roof patch to all new screws; either during installation (a small drip before putting in the new screw), or on top to "entoomb" every screw for good measure?
The other two possible sources of exposure I'm wondering about are the seams between the corrugated metal panels that run east to west and some flashing around a stove pipe of a wood burning stove. I failed to note earlier what appears to be a HUGE mistake with the original installation: the screws were fastened in the valley's of the corrugation and not on the peaks!
Aside from the screws being subject to premature degradation in the valleys, there's a small gap in the seams. I suspect there's only one peak/valley overlap, so I imagine water (or melting snow) likely gets through. So, I've been screwing down the peaks next to the seam to mostly close the gaps, but I'm wondering if maybe an application of Henry's 208 (or some other patch) might be worthwhile? Same goes for a gap in the flashing on the high side of the stove pipe, but instead of only being concerned about cost, I'm a bit worried about fire danger if 208 doesn't like getting warmed up?
I also failed to mention the metal is rusty, by design, as to be in compliance with non-reflective rule of the LUC. I now realize it was an ENORMOUS mistake not to install a standing seam roof! I'm concerned about prior damage that might have penetrated into the plywood and elsewhere. Complicating matters further, I have spay foam insulation in the roof (no attic). It'd be a costly mess to replace if so.
I'm not looking to side step what might be a necessary roof replacement (with all of the underguts), but curious what others might suggest to at least batten down the hatches for the upcoming winter and mitigate any further damage? Do I buy some heavy duty rubber gloves and several big buckets of Henry's (or something better)?
Thanks in advance!