Coordinate shed openings, header checks and siding

Keep one left-hand reference

Stand outside looking at the selected wall. Its frame-left edge is zero, even when the wall butts inside another wall. Choosing a unit centre or right edge changes the point being located; it does not move zero to the opposite end. Centre on wall uses half the frame length. Snap placement rounds the chosen point to the selected grid.

For example, a 30-inch-wide actual window frame with ¼-inch clearance per side needs a 30½-inch RO. If its centre is 72 inches from frame left, the RO begins at 56¾ inches. Changing from centre to left-edge entry keeps that physical position.

Choose the rough opening from the product

Exact RO mode uses supplied rough dimensions directly. Actual unit + clearances adds the entered fitting allowance to the real outside-frame dimensions. The controls start with zero clearances to avoid inventing a manufacturer requirement; enter the specified allowances before using the result. Door slab dimensions alone do not include the jamb.

The resolved opening drives framing and all area deductions. Raising a window by its top reference updates the sill, header and cripples together. Doors begin at the floor datum; any finish-floor or threshold adjustment must be included in the supplied installation dimensions.

Use a header table only within its stated scope

Manual sizing stays available for any project-specified detail. The optional automatic profile uses the 2024 Ontario Building Code, Table 9.23.12.3.-C, roof-and-ceiling row with a maximum 4.9 m tributary width, from the January 2025 compendium. It is a table candidate, not a permit or engineering approval. Verify the edition, local amendments, occupancy and all applicable conditions before enabling it.

The profile requires SPF No. 1 or No. 2 and a verified specified roof snow load up to 3.0 kPa. It uses the next higher listed snow column and exact metric opening limits. It takes no span or structural-sheathing credits. Every wall uses the conservative loaded-wall row, including the gable walls.

Only roof and ceiling loading is supported. Extra storeys, storage floors, concentrated loads, drift surcharge, unverified heavy roofing, larger supported spans and other conditions outside the table need a separate design. The profile checks the model’s roof/ceiling span and tributary width, but the person selecting it must verify local applicability and the complete load path.

Automatic mode chooses two plies and the table bearing allowance, preserving any larger entered jack pack. King-stud counts, header fillers, fastening, connections and support below remain project details. Changing to manual retains the current candidate as an editable size.

Enter the coverage that will actually be installed

Horizontal wood, vinyl lap and fiber-cement lap use effective course exposure. Board-and-batten uses a board module and separate batten face width. Stock length and end laps come from the selected product. Fiber cement is a category; the controls do not imply that one set of dimensions covers every Hardie product.

The model clips courses or vertical strips to the wall shape. Openings that fully cross a strip can split it; partial cut-outs retain a full blank. Each piece consumes a stock length in the order, with the surface allowance added once. This conservative estimate does not nest offcuts. Joint placement, flashing and fastening must follow the installation detail.

Read the complete finish order

Vinyl lists its starter, opening receiver, outside corner posts and top termination coverage. Other systems use their selected opening and corner trim, with separate battens for board-and-batten. Opening head flashing has its own row. Weather barrier, sill pans, tapes, furring and fasteners require additional specification.

The 3D view uses the same course/module spacing as the takeoff. Review the strip schedule, product-specific trim and missing prices before treating an area allowance as a complete order.