My mentor taught me better. "No pieces less than a half tile - anywhere." I found that you can almost always do that. It might mean that you have to center the grid intersection in the room, or center a tile in the room, or start with a slightly offset grid. But there is always a solution. If you try.
There are special challenges - non-parallel walls, skewed walls, floating items like a section of wall or columns. CAD really simplifies things since you can move a grid around until you are happy with the edge conditions. Include fixtures in that exercise and kill two birds with one stone. Some times there might not be a great solution unless you can change the layout, which seems a bit excessive. Light fixtures complicate things. Occasionally you find that you can't place fixtures where you want and locate the grid ideally.
One way to minimize the issues is to use a planning grid of 2'x2' or 4'x4' when laying out the walls in the first place. If you stay on the grid, which is hard to do, you get a great ceiling tile layout automatically.
At some point we decided to write a recipe and move on to worrying about bigger issues. We called that recipe:
Rules of Ceiling Grid Placement
- Generally, 2x4 tiles have long dimensions parallel with narrow dimension of the room.
- Avoid pieces less than one foot in the smallest dimension.
- Hold lights more than 2’ from a wall – same for grilles.
- Center sprinklers in tiles wherever possible.
- Lights “2” ends can touch.
- Check that light placement will work well before committing to the grid layout.
- Where possible, center grid in room both ways.
- If grids are not centered in room, then show where grid starts.
Rules 2 and 6 are key.
Rules 1 and 7 can be violated for good cause.
Rules 3, 4, and 5 can almost always be met.