The cost is very vary depend on your location and how complicate the job will be. It would be best if you ask your local contractor or the building material store ( Home Depot, Lows ). Many contractors do a free estimate so use them to your advantage. Get several estimates and compare the price and service. Also you will save half of the total cost if you do it yourself.
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.
Put them in the opposite direction of the ceiling joists
It is usually 16 inch.
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.
Try a foaming machine. It sprays an dense foam between the walls
The size of ceiling joists is primarily influenced by the span they need to cover and the load they must support. Other factors include the type of wood used for the joists, the spacing between joists, and any additional load considerations like heavy fixtures or storage. Local building codes and regulations also play a role in determining the size of ceiling joists.
Suggest you try http://hardware.hardwarestore.com/27-110-insulation-supports/16-insulation-support--646131.aspx
A false ceiling is a ceiling which is lower than the real ceiling attached to the joists. False ceilings are often used in kitchens and on the first floors of houses with different tenants living on the second floor.
Joists are supported by the walls underneath them. The tops of your walls all need to be on the same plane, level. That will make your ceiling lines straight after drywall.
These are used to secure the ends of ceiling joist etc. used to form hatches /stairwells.
The tiles sit on a grid either 2x2 or 2x4 foot sections. The grid is held up on wires fastened to the ceiling joists.
It sounds like who ever built the structure never intended to hang anything from the joists. You are not adding allot of weight, but I would still add a joist 2 x 4 so you have 24" centers to work with. that way all of your outside edges and the center will be supported when using 4' x 8' sheets.