One of the items that tops the Eichler owners' to-do list is exterior beam repair/maintenance... and with the recent rains a few weeks ago, I was reminded that it was time to get busy in the atrium.
I was worried that our exterior beam was dry-rotten on the top from exposure and lack of maintenance, but we got lucky and it wasn't too bad -- perhaps the old-growth redwood is indeed a good thing (thanks to Casie's brother Matt for the sanding). That said, there were still a good number of cracks on the sunny side and the top needed some TLC as there was a small bit of dry rot, so the products we ordered from "The Rot Doctor" were put to good use. In the time since we ordered them, I've also seen it in several local (smaller) hardware stores, so check around locally — there are also a few brands: Smith's, Restore-it and others... all the same stuff, really (a 2-part epoxy wood sealer).
Matt sanded the top of the beam with a random-orbital sander and the paint pretty much blew right off. On the sunny-side of the beam, however, the paint was a bit more adhered so I took out the the big guns -- the angle grinder with a sanding wheel. On a friend's house, I've also used the Wagner "Paint Eater" and on another a belt sander... both also worked well. The entire beam took about 20 minutes or so to sand to bare wood. It certainly takes a steady hand and it makes an epic mess... it's necessary, though. For a proper sealing and repair, all the paint needs to be gone.
After sanding came the sealing. We used the 2-part CEPS (clear epoxy penetrating sealer) to help seal the beam and it definitely seemed to do the trick -- the beam soaked up a quart of the mixture easily (CPES is a 2-part potion). I found that mixing it in small batches in small plastic cups was successful — you don't want to mix up too much at one time as it cures quickly. The top was a pretty easy paint-on/soak-in application, but the side took a bit of trickery. Using a brush loaded with the mix, I let it dribble into the cracks -- presumably the same way water would (so sealing was indeed a good thing). After the sealer dried, some auto-shop Bondo did well to fill in most of the larger cracks and holes. A special wood-epoxy-putty is sold, but it's pretty much the same as Bondo and is unnecessarily expensive. After a final sanding and priming (Zinzer 1-2-3 is my favorite exterior primer), it was ready to cap.
We had called several folks about a beam-cap, but no one returned our calls, so I ended up heading to Big Orange for some stock sheet metal. 3 pieces of 1inX2in roof-edge flashing did the trick (2 long pieces + 2 cut pieces) along with a generous bead of PL-brand flashing sealant. While not as ideal as a one-piece cap, the metal was less that $10 for the 3 pieces and the sealant was $5, so for $15 plus a few screws, we have a beam-cap that looks very non-obtrusive and will protect way better than the non-existent coat of paint that was up there. For extra protection, prior to the beam cap, you could run a strip of Vycor or other self-adhering flashing to prevent any future water issues. I didn't do this, but in hindsight, it'd have been a very simple and effective fix — these self-adhesive flashings were invented after the house was built and could be useful in many places where water might be a concern (I used a lot on the deck, for instance, but it would also be useful on the framing under the window sills, around framing for through-the-wall ACs, etc.).
[Edited Fall 2014 with updated information]