Roofs: from the layout to the estimate

This house is made for the tutorial (no client, no real site): a 7.28 × 6.37 m two-storey block, a 3.64 × 4.55 m study wing on the east and a 2.73 m wide porch at the front door. It gets three roofs: a gable 切妻 on the 2F, a lean-to 片流れ over the wing against the 2F wall, and a hipped porch roof that meets the front wall.

The region (北海道 札幌市) comes from the address, so the snow load (190 cm) is already set for the structure check later.

Type sets the shape: Mono 片流れ, Gable 切妻, Hip 寄棟, Butterfly, Flat (and Custom, edge by edge, once a roof exists). Low eave FL+ is the height of the eave line above this floor. Every value here is kept for the next roof you draw.

Pitch fields understand 寸 (4寸 = 4/10 = 40 %), % and °; they always show % and 寸 side by side. A 4寸 galvalume roof is common in Hokkaido; for a standing-seam roof on a lean-to, 1–2.5寸 is enough.

The sides are true compass sides (the project north), so you set them once for the house: here 600 for the eaves 軒の出 and 450 for the gable verges けらばの出. A roof drawn later can still get its own value per edge.

The magic wand (Space+click) is the quick way for a roof that follows the walls. You can also click the corners of any outline (a polygon, double-click or click the first corner to close): SumiCAD measures each edge from the wall centre behind it, so the overhangs stay editable.

The dashed line is the roof edge; the arrows show the fall with the pitch.

Every field changes the selected roof at once (one undo step each). Low eave FL+ moves the whole roof up or down; Thickness is the roof build-up drawn in sections. The grips on the plan move corners and edges; dragging an edge midpoint adds a corner.

For a gable the low edge is the eave the roof rises from; the ridge runs parallel to it. A mono roof uses the same idea for its low side (Reference).

Eave on every edge is a hip roof 寄棟; two opposite gables is a gable 切妻; one hipped end gives a half-hip. Changing an edge makes the roof a Custom multi-plane roof: hips 隅棟 and valleys 谷 are worked out for you and go into the 3D, the framing and the quantities. Ctrl+Z puts the gable back.

Side A is the low edge side, side B the far side. Type an offset or a distance from eave A; Same eave height changes the pitch of side B, Same pitch moves eave B up or down. You can also drag the middle of the ridge on the plan or in 3D.

The gable end walls of the 2F rise to the roof by themselves (their top is "Up to roof"). Orbit with the left mouse button, pan with the right, wheel to zoom.

Each roof belongs to a story: this one is drawn on the 1F, so its heights are from the 1F floor. A lean-to against the upper wall has its high edge on that wall and falls away from it.

A drawn outline is fitted to the walls under it: each edge gets the overhang it really has (here 455 on three sides, 0 along the 2F wall), so you can change them later in Overhang… like a Space+click roof. The arrow shows which way the roof falls; the next step sets it to the east.

Low edge (the default) keeps the eave at Low eave FL+ and the roof rises with the pitch. High edge keeps the top edge level at a height — the natural choice when the lean-to must meet the 2F wall under a window sill: type the height of the high edge and the eave follows. Pick chooses the edge on the plan.

Three roofs now sit at three heights: the 2F gable (eave 2F+2,800), the lean-to (1F+2,600 rising to the 2F wall) and the porch (1F+2,300). Each is its own element with its own pitch, framing and finish.

With the wall edge a gable, the porch becomes a three-sided hip that rises to the front wall — the usual entrance canopy. The same trick gives a lean-to with hipped ends, or a gable that turns into a hip at one end.

The wing walls were drawn a full story high (up to the 2F floor), so they stood through the lean-to. Trim elements below sets them to "Up to roof": their tops follow the roof underside, piece by piece, and keep following when you change the pitch. One element stays listed: the 2F wall the lean-to leans against — it stands on its own floor, as it should. Do the same on the porch roof for its two posts. One undo step each.

Where a lower roof meets an upper wall, the roof stops at the wall face. The quantities count each roof separately (part 5).

和小屋 puts roof beams 小屋梁 across the walls, struts 小屋束 on them, purlins 母屋 and the ridge beam 棟木 on the struts, rafters 垂木 on top. 登り梁 runs sloped beams from the eave plate to the ridge beam (often exposed 現し). 垂木構造 is rafters only, for short spans. 母屋下がり carries the purlins from gable wall to gable wall — this house's default.

Under the system: rafter, purlin, ridge-beam and strut sizes (0 = sized by the beam check), purlin layout, what happens past the gable (purlins out, outrigger ladder or verge beam), species, the roof plane stiffness and the rafter-to-plate hardware (告示1460).

The popover now shows the sloped-beam rows: their size and spacing and Past the wall (cantilever beam) for beams that carry the eave overhang themselves. Each roof can have its own system; Save as project standard makes it the default for every roof without its own.

The rafters run square to the eave from the plate to the ridge, cut at the hips and valleys. They are drawn in plan, sections and 3D, sized in the beam check with the snow load, and counted in the quantities.

The roof framing plan is a view of the story with the framing layers: each member with its code (K plate 桁, KB roof beam 小屋梁, MN ridge beam 棟木, M purlin 母屋, KZ roof strut 小屋束, R rafter 垂木) and the schedule of sizes. Members drawn orange are close to their limit in the beam check. It is placed in the structural sheets of the permit set.

The list is grouped by kind — purlins side A and B, ridge beam, plate ends, roof struts, rafters — with each member's size and its ratio from the beam check (1.00 = at the limit). Click one to select it, Shift+click for several; changes are one undo step each and the check follows. Show the 3D Structure view opens the same members in 3D, where a double-click on the roof opens this editor too.

Purlins, ridge beams, plates and the sloped beams of the lean-to are in the frame with the 45 × 105 rafters; Rafters turns the rafters on and off, Ply the structural panels, Hardware the N値 hardware. Cutaway opens a section box to look inside.

Plumb cuts the rafter tails and fascia vertical, Square perpendicular to the slope. The soffit 軒天 is sloped (on the rafter underside), level (boxed), Exposed (no board: the rafter tails show — this also turns on 化粧垂木) or none; its area is shown. Fascia 鼻隠し and barge 破風 boards have a material and t × h. Everything goes into the 3D, the sections and the quantities.

New roofs in a snow region start with no gutter: on a steep metal roof the snow slides off and would tear gutters away (common in Niseko) — plan a gravel drip strip instead. Where you do want them (over an entrance, on a low pitch), pick the type: the gutter runs along every eave of the roof, the downpipes are placed for you, and the last line gives the lengths for the estimate (fascia, barge, gutter, downpipes).

The finish is the outer layer; Thickness is the whole roof build-up shown in sections (roofing, underlay ルーフィング, sheathing 野地板, the ventilation gap 通気層 and the insulation when it sits in the roof). The roof weight class for the structure check (light / slate / heavy roof) is in the structure settings (part 5).

Without snow stoppers a steep roof may reduce the snow load by its slope (勾配低減, μb); over a door, a parking space or a neighbour's land you usually want the snow to stay up. The rows are drawn on the roof and counted in the quantities.

The ceiling is a property of the room, so the roof stays one element. Open to structure raises the ceiling to the roof underside; the Ceiling type then says how it is finished: sloped and boarded 勾配天井 (with the room's Ceiling build-up, e.g. plasterboard on battens or sugi panelling), exposed (no ceiling: rafters, sloped beams and the deck underside show), or flat at the ceiling height and sloped only where the roof comes lower. Sections, 3D, interior elevations and the finish quantities follow.

SumiCAD adds the cross section B-B by itself. The section is drawn from the model every time: roof thickness and finish, rafters and sloped beams in cut, the plates, the soffits and the fascia, the eave and maximum heights on the level chain. Click a roof in the section to select it; drag its eave or its pitch grip to change it there.

The four elevations are made for you and follow every edit; they are already placed on the layout sheets. A roof plan as a drawing of its own (屋根伏図) is not a separate view yet: the 2F plan and the site plan show the roof outlines from above.

The region comes from Permit data (or the address); the snow depth, the snow sub-area (多雪区域 区分) and the roof weight class can be set here. The snow load reaches every roof member through the beam check (snow stoppers: no slope reduction), and the 2025 wall-quantity rules use the real roof weight.

In 3D, Snow covers every roof with snow, and the Snow depth slider sets how deep — the client sees what a Sapporo winter does to the eaves and the porch.

Roofing is measured on the slope including the overhang, with a waste factor; the edges give the fascia, barge, gutter and flashing lengths; the timber rows (ridge beam, purlins, plates, rafters, sloped beams, struts) come from the same members as the framing plan. Export CSV… sends them to a spreadsheet.

Set your unit prices once in Price list… (roofing per m², fascia per m, rafters per m…) and every project's roofs are priced from the model. Change the pitch or the overhang and the area, the lengths and the price follow.