This estimator is intended for preliminary planning only. A butt join places two field boards flat and end-to-end. A break board is a full board installed perpendicular to the field boards, with the field boards terminating on opposite sides of it. Break boards occupy deck space and therefore replace a narrow strip of the field decking rather than simply being added over the top. Fascia quantities are calculated from the selected exposed length and width edges. Final quantities can still vary due to set-out, shared edges between multiple areas, offcut reuse, stairs, subframe design and site conditions.