About 5metres(16') but would have to be stress graded timber.
14'
too many variables here, mostly the size of the roof above it (steepness, weight of shingles, tile or slate? etc. You're best to overengineer it. A double thickness (3.5" X 12" or 16" wide) glulam will support a reasonably large roof above it, otherwise a simple double 2x12 would work for a 3/12 -6/12 pitch roof with light grade 30 year shingles.
If I am reading the question correctly, a load bearing wall was removed and replaced with a beam? Clear span, no post in the middle? If cracks are appearing, the beam that was used was not big enough. For any space of 8 feet or more, 2x12 and plywood should be used for the beam or an engineered truss used.
Triple? That sounds an awful lot like gluelam... Which requires engineer approval to meet code. The inspecting engineer will be able to tell you.
Not sure why you need a beam that bears no load. You can go 22'. Beyond that it needs to be broken down to shorter lengths.
It depends on its moister content.
Depends on the area above the ceiling joists. Is it a live load (living space) or dead load (just the joists with maybe an attic above)? Also, the length of the ceiling joists from the last bearing point is a factor. How much weight is bearing on the beam is the critical issue.
Even using a 2x12 the spacing for 20 feet will be less than 12 inches on center. I would recommend splitting the distance with a double beam perpendicular to the joist run. This will allow you to go up to 24 inches on center. Your span will only be ten feet aproximately this way. I would double the beam. (2-2x12 joined together) Good luck. when building your beam make sure the laps on the beam are at least 6 foot apart and put a good wood glue on the 2x12s plus for added strength put 1/2 inch O.S.B. in between the 2x12 and I would also lag or bolt them together, at about 16 to 24 inches O.S.B. = Oscilating Strand Board.
1x24, 2x12, 3x8, 4x6 are all the natural number combinations.
96
Two boards nailed together for strength. Over a door or window opening, two 2x12 with a piece of 1/2 inch plywood in between for a header.
The width is 2 in this case.
1x24, 2x12, 3x8, 4x6
How much slope and how long of a run? For short distance, up to 12 feet, and 12 inches of drop, you cut a 2x12 at the right slope and use them for the floor joist. For longer runs or greater slope, Use 2x6 level and use 2x4 legs under them.
1dozen=12 so 2x12 24