Walls and Ceilings - help with katrina repairs

finally got new roof 9 months after katrina so now want to attemp ceiling repairs myself. no experience & need help. dimensions of room: length 19.5 feet width 13.5 feet
dimensions of hole: length 13.5 feet width 7.09 feet (85")
do i tear out remaining sheet rock or repair another way? do not have 4 straight edges on existing sheet rock.

I think for peace of mind and because the rest of the ceiling must have gotten wet even if it is still up there that you should take the whole thing down and start over. Patchs can be done but the whole ceiling isn't that much more work. The hardest part is hanging the new rock. Try to have some help for that.

I agree. With the devastation of water, sheetrock will harbor mold and mildew for a long time. I would definitely pull it all down, rent a drywall lifter and install it all new.

Toss your insulation out while you are at it.

It probably has enough moisture it it (1/2 to 2%) to ruin the insulating value even though it may look dry.- It does't take much with fiberglass.

If you got any salt water in the house, make sure you renail everything when you have it open. Most people forget about this. Nails, salt water and wood that holds salt water do not go good together. In a few years, there will be little left to resist anything.

Even good practice for fresh water (cheap and easy insurance).

Dick