Do drywall butt joints between joists need to be reinforced to be flush?

Question

I am in the process of placing drywalls on ceiling and walls. I am placing the sheets perpendicular to the studs and joists. I would like to understand better how to prevent cracking and shrinkage at joints. I am looking at butt joints between two studs or joists without support. If sheets are perpendicular there are spots where the butt will not align with a stud/joist, and the tapered joint will never have a support (because perpendicular). From research, I understand that joints can be reinforced with shims or thin wooden boards behind each joints. What is best practice?

Studs and joists are 16in on center.

1. If butt and tapered joints are not align with studs or joists, do they need to be reinforced to be flush and to prevent cracking?
2. Does the tape or mesh provide enough in plane strength to prevent temperature shrinkage and cracking?

Answer 1

You are asking about supporting joints.

Preventing cracks is primarily accomplished by proper firm framing and proper support at edges/butts, and secondarily by tape to withstand framing movement over time.

Cracking from shrinkage is prevented by using curing/setting compound ("Sheetrock 90") for filling, or by using drying compound ("All Purpose") in thin layers only (max 1/8in). Drying compound on edges must be supplemented by paper tape. The purpose of mesh is to hold setting compound in place over wide gaps while applying.

Plan your sheet edges to align with studs edges, not stud centers. That way, one sheet will be fully supported by the 1.5in stud, and the butting edge will get extra backing: nail/screw an additional stud to the existing stud. The add-on stud does not have to be full length or one piece.

With more experience you might get away with aligning the edges "half-on" the stud, but I always find this inferior.

For floating horizontal tapered butts, the stud spacing of 16in to max 24in plus the deeper fill at the taper taper strengthened by tape will provide full support. No backing needed.

For other floating butts (vertical or horizontal) that are not tapered or that span more than 24in between studs, provide additional backing in the form of a strip of ply wood or piece of 1x / 2x lumber screwed at both edges of the butt. Install one sheet, screw-on backing, install second sheet, and use the location of the existing screws to screw to backing. (The second sheet will conceal the backing but the screws reveal its location)