I have a 32’ 5.5×15 glulam beam supporting the shed style roof on the front of a pavilion building.  Rear is a 2×6 framed wall.   Glulam extends past the columns by 6 or so inches…roof overhangs the columns by 1’ and in hindsight I wish I’d made that 2’ to better protect the beam ends.  The beam is stained (Armstrong Clark stain) and I was planning on getting some copper  beam caps that cover the top of beam from about 4” back to the Simpson column cap the beam sits in and run the copper  over the full end grain  (and an inch or two down the sides of beam) but then worried a bit about water working itself under the beam cap.

Not sure if those caps are supposed to be sized/attached tightly to the beam end or made with a small air gap on sides and on top although not sure how I attach and keep gap on top.   Then I remembered that I have some left over Owns Corning Titanium PSU30 ice and water shield from when we roofed the building.  

I thought maybe running a 5.5” wide strip over the top of the beam end (or maybe a 6.5” wide strip so I can fold down over the sides a bit) and down covering the full end grain of the beam before I cover it with the copper end cap would be a good idea and prevent water from getting under the copper and trapped on the wood.   

Is this a good/bad idea?  Just not sure if there’s something I’m not taking into account.