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.
Not really. All joists will be the same whether you are working on a 1st or second floor, so your floor does not have a bunch of different levels. Usually we use 2 x 12 lumber, doubling joists which have walls above them or decreasing the spacing if you are at the limits of the span. example you have a 22' span in a garage with living area above it, you would use 2 x 12 with 12" on center spacing.
For ceiling joists, the minimum dimension per the IBC is a 2 x 12 inch, with spacing dependent on the load. Ideally, these would be screwed to blocking between the joists.
You would either have to remove the ceiling in the kitchen or the floor in the bath, and add additional joists to strengthen them, or possibly add steel in combination with the joists.
It could be the floor spacing because it is like the spacing between the cell membrane and the nucleus.
answerYou would lay timber floor joists acroos the the size would depend upon how high you need to raise the floor. Then you'd lay floor boards over the joists. the joists would be layed every 400mm and would require noggings to reduce movevement and 'creaking'. The floor boards should be of a tongue and groove type for the same reasons. The cheapest floor bords are made of chipboard and are 8' by 2' and they should be glued.If you wanted to raise it a matter of a few inches then you could just screed over the top of it. If you wanted just a few mm then a self leveling liquid can be applied.
The existing ceiling would have to have a framed roof above it, not roof trusses or second floor joists. The ceiling joists would have to be temporarily supported and walls may have to be temporarily braced from lateral movement. Ceiling joists would then need to be cut and headered off with properly sized headers with the ends properly supported with appropriate weight transfer methods. New ceiling joists would then be added above the raised area. Not a job for a do-it-your-selfer usually.
A joist note on a first floor plan would refer to the Joist below that floor, a joist note on the third floor plan woud be for that floor.
If you have access to the underside you can screw another 2 x 6 along side of each existing 2 x 6 to add strength. If you do not have access, you would have to remove the flooring and sub-floor to do this.
I don't understand your question completely, but I think what you are asking is how far apart support can be for a subfloor or floor decking. It will vary with the type of construction, but for residential housing it's almost always 16 inches between the floor joists. That would be measured from the center of the joist to the center of the next joist.
That depends on the sise and the type of timber the floor boards are made of, However standard practice with flooring is 450mm centers or 600mm centers if the boards are thicker to allow for the extra 150 millimeter's
Typically you would not put hardwood flooring directly over the joists. You should first put down a subfloor.