Gluing letters onto a sidewalk sign but having problems.

[knight_toolworks]

I built a wooden sidewalk sign with wood letters. sealed it well with a waterborne finish. the first time I used a latex calk and screwed the letters from behind (I had finished the letters on all sides and the sign first) well the company complained because I made it look like their sample (long story) they did not like seeing the screws from the back so this time I just glued on the letters with a 50 year silicone caulk. well after a month or so the letters are coming off. I think I put the last coat of finish on that night and then stuck the letters on first thing. or I could have put the last coat on first thing and the letters at the end of the day. that worked fine with the latex as I could hardly remove the letters. but I am thinking the finish had not cured enough for the silicone. I like using the e6000 glue but I find letters move as it flattens out so I used silicone.

[bleeth]

For exterior silicone adhesion I would use 5200. Typical big box 2-5 dollar caulk just isn't as strong/weatherproof.

Bummer that this little job is still haunting you.

[knight_toolworks]

I bought the good stuff but I bet the finish hand not cured fully so the 5200 may have given away too. I wish my pin nailer worked have not used it for years. But I had the letters fully finished before I glued them so it would have been a pain to cover the holes.
Last time I used the e600 I had to go back several times to fix the letters. a simple method is to drive in a bad nail that is not flush to the surface then cut it off and the sharp stub works to hold the part in place. plus it is not seen.

Yes this is the sign from hell.

[tuck]

Silicone, in my experience, is a sealant, not an adhesive. You should try some 'Power Grab' by Loctite. Use with a caulk gun, needs to set up overnight, goes on white, dries clear. They make a heavy duty exterior version that should work well for this sign from hell. Available at most home stores.