Deck Calculator

A 10x12 deck using 5/4x6 boards (5.5 in actual + 3/16 in gap) laid across the 10 ft direction needs 22 rows. With 12 ft boards (one per row, no joints), that is 22 boards plus 10% waste = 25 boards. Plus about 200 deck screws (2 per joist per board crossing).

At 4.5 inch on-center spacing (the most common to clear the 4-inch sphere code with 3/4 inch balusters), 2.67 balusters per linear foot. A 44 ft railing perimeter = 117 balusters. Always round up - the last bay near each post usually needs a smaller gap to make the math work.

Doug fir #2 2x10 at 16 in OC: 16 ft 5 in maximum span for floor loads (40 psf live + 10 psf dead). For deck loads (wet service), reduce by 10% - so 14 ft 9 in for a deck. SPF #2 spans about 10% less than Doug fir at the same size.

Below the frost line. In northern US states: 42-48 inches. Upper Midwest: 36-42 inches. Mid-Atlantic: 30-36 inches. Southern states: 12-24 inches. Frost line depths are set by local code - your inspector has the final say. Footings above frost line will heave each winter and lift the deck out of level.

Standard semi-transparent stain covers 200 sq ft per gallon. A 10x12 deck (120 sq ft) with small railings (80 sq ft) and 2 coats = 2 gallons. Penetrating oils cover 250-300 sq ft per gallon; solid color stains cover 150. Always buy 10-20% more than calculated for future touch-ups - color match between batches is unreliable.