Formula version: 1.1.0. This methodology describes a planning estimator. It does not design or inspect framing, select a decking system, or approve structural, drainage, fire, permit, or code compliance.
Surface geometry and board rows
Included deck regions and openings are axis-aligned rectangles in one shared coordinate system. The usable surface is the geometric union of included rectangles minus the union of exclusion rectangles. Overlapping included regions therefore contribute area once, and overlapping exclusions are not subtracted twice.
Board direction establishes two axes: length along each board and coverage across the rows. With installed board face width W, clear gap G, and perpendicular field width C, the row pitch is P = W + G. Whole rows are advanced at that pitch. The final row is reported at its remaining visible width rather than silently treated as a full board. A final rip is allowed only when the user explicitly permits it.
Picture-frame borders and breaker boards are modelled as explicitly entered strips. Their occupied surface is removed from the field-board region before field rows are solved. Border and breaker quantities remain separate so their lengths are not also counted as ordinary field-board coverage.
Cut segments and supported seams
Each field-row line is intersected with the usable surface to create one or more disjoint board segments. Exclusions may split a row. Collinear segment lengths are not pooled into one fictional board: each segment retains its location and identity.
A required segment longer than available stock may be divided only at an explicitly supported seam location supplied by the user. A seam must lie on a recorded existing joist intersection and inside the segment. The calculator does not invent a butt joint, assume that every joist accepts one, or validate blocking, clips, staggering, minimum end distances, or product-specific joint rules.
Existing joist lines are intersected with each surviving board segment. Duplicate geometric intersections are counted once even when rectangle boundaries or entered regions meet at the same point. These unique intersections form the basis for fastening quantities; they do not prove the framing or attachment is suitable.
Stock allocation
Every field, border, and breaker requirement becomes an identified cut. Stock allocation accounts for the entered saw kerf between cuts and distinguishes discarded remainder from remainder at or above the user-entered reusable-offcut threshold.
The deterministic allocation objective is fewest stock pieces, then least purchased length, least discarded remainder, most reusable remainder, and stable IDs. A small exact search that reaches its work limit retains its best valid plan and labels it heuristic. Larger-list placement and the separate conservative fallback are described under Bounded stock optimization below. A heuristic result is not guaranteed to be globally optimal.
Board contingency is applied to the selected purchase basis and shown separately from geometric cut loss, reusable remainder, and package surplus. These categories are not interchangeable.
Fastening methods
Face fastening and hidden fastening are isolated calculation methods. A face-fastener estimate multiplies unique board-to-joist intersections by the user-entered fasteners per intersection. A hidden-fastener estimate uses only the user-entered clip or fastener rule for that selected system. The calculator does not combine the two methods or add an undocumented default.
Starter and ending components remain separate from the selected face or hidden-fastener package. User-entered extra fasteners are either included transparently in that selected package calculation or, for manufacturer-coverage mode, shown as a separate package line. This release does not estimate breaker, border, butt-joint, plug, or other product-specific fastening categories unless the user includes them in the explicit extra quantity. Contingency is applied before division by the user-entered package quantity or labeled coverage; packages round up. Package surplus is reported after rounding and is not labelled as installation waste.
Limitations
This axis-aligned model supports level included rectangles, rectangular exclusions, one board direction per calculation, explicitly entered picture-frame or breaker strips, recorded existing joist lines, and explicitly supported seams. It excludes curved, diagonal, herringbone, chevron, radial, stair, fascia, ramp, heat-bent, and automatically optimized decorative layouts. The calculator page has a separate 45-degree supported-layout worksheet with its own method and limits; fascia quantities use a separate tool.
The estimator does not determine span ratings, joist size or spacing, blocking, ventilation, drainage, board expansion, acclimation, attachment suitability, fire classification, load capacity, ledger or beam design, permits, or code compliance. Product instructions and local requirements control. If the real layout cannot be represented without approximation, calculate supported regions separately or obtain a project-specific takeoff.
Corrections can be reported to feedback@materialnest.com.
Bounded stock optimization
Field-board cuts and border/breaker cuts are allocated separately to the selected stock lengths; offcuts are not pooled between those categories. Kerf and the entered reusable-offcut threshold remain visible. Small bounded searches retain the best valid plan at the work limit and label it heuristic. Larger lists use deterministic placement, with a labelled one-cut-per-stock conservative fallback when placement exceeds its work limit or is unavailable. This stock plan does not create unsupported seams or decide fastening requirements. Saved quantities remain unchanged until recalculation.
Source context and internal method
Trex’s spacing and fastening explanation provides product-specific context for separate gap, face-fastener, and hidden-fastener inputs. It does not validate MaterialNest’s rectangle unions, row intersections, supported-cut generation, or stock-search objective; those are internal calculation methods described above. Source and implementation explanation checked September 27, 2026. Product instructions and project review still determine acceptable installation details.