Balancing drop-ceiling border tiles — the Armstrong worksheet method
Center the grid, don’t start at a wall. Add one full tile to the leftover on each axis and halve it — B = (r + M) ÷ 2 — so borders match on opposite walls and stay larger than half a tile (here 21″ across and 13″ along).
What this diagram shows
A scale plan view of an 11-foot-6-inch by 14-foot-2-inch room laid out in 2-by-2 tiles, showing how to balance the border tiles. Instead of starting full tiles against one wall and leaving a skinny sliver at the other, the border ring is shaded and sized so the borders match on opposite walls: across the 11-foot-6-inch width there are 4 full tiles with a 21-inch border on each side, and along the 14-foot-2-inch length there are 6 full tiles with a 13-inch border on each end. A callout gives the arithmetic: the border width equals the leftover plus one full tile, divided by two — (18 inches + 24 inches) ÷ 2 = 21 inches across, and (2 inches + 24 inches) ÷ 2 = 13 inches along — which keeps every border wider than half a tile.
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