Adding 8 foot to current lean to. Full length is 18 foot . Space between corner posts is about 16. Using standard tin for roof. Is this too far to use a single 2x12 as header with only the two posts? Or is not two will3 posts work. This is current configuration.

Edited April 16Apr 16 by Gerald

You don’t get much snow down there. In southern PA we would use two 2x12’s

Current configuration your single 2X12 works fine.

I sure like your style Gerald, cool looking woodworking!

Use four just four consistency if for no other reason.

19 minutes ago, HandyDan said:

Use four just four consistency if for no other reason.

Would look good that way.

3 posts would work IMO, but would definitely go with double 2x12's for the header. Honestly, I'd go double 2x12s header even with 4 posts. Doing so will help keep the posts from twisting besides lessening the chance for sag. Like Lew noted, snow load is not much of a factor in your location but it will help stiffen the structure from winds. I'm not a real carpenter nor ever played one on TV but have built a few garages and a couple of houses that are still standing.

My projects are always over-built. An extra board or two doesn't cost that much.

29 minutes ago, JimM said:

My projects are always over-built.

Yes...me too! The "better safe than sorry" approach.

Speaking of lean-tos, I read an article once of a guy who was checking out a ship wrecked on a beach. He fell into the toilet on board and couldn't get out. He was up to his neck for a week. Finally a couple walking along the beach heard him and rescued him.

Edited April 26Apr 26 by MrRick