I am about to begin a project to install a plywood ceiling in an outdoor BBQ area. The ceiling slopes from the outer walls to a flat area in the center. I plan to install the ply with 10mm gaps between each sheet and there will be strips of thin ply painted black attached to the ceiling battens where the gaps are between sheets. I also plan to paint the edges of each sheet black.
The building frame is not very square and I was wondering if anyone has any advice on methods to help keep the gaps between each sheet consistent, especially at the points where the corners of 4 sheets meet.