Roofing / Layout planning
Roof Sheet Layout and Overlap Planner
Work out sheet columns, rows, and cut sizes for one rectangular roof slope. See how side laps, end laps, and stock lengths affect your material estimate.
Plan one roof slope
Compare available sheet sizes and entered laps against your roof geometry.
Roof dimensions
One rectangular slope. Include any required side coverage allowances.
Eave reference to ridge reference, measured horizontally.
Rise between the same references; enter 0 for a flat plane.
Extra coverage beyond the eave reference; avoid counting it twice.
Coverage deducted below the ridge reference.
Sheets and overlaps
Full sheet width before the side-lap allowance.
Use the project or manufacturer detail. Effective width is overall width minus this allowance.
Each installed piece uses one stock sheet; offcuts are not reused.
Measured along the slope. Applied only when more than one row is needed.
Sheet schedule
- Stock sheets · one per installed piece
- 20
- Columns across the eave
- 10
- Rows along the slope
- 2
- Effective cover width per column
- 1 m
- Required coverage along slope
- 4.522136 m
Cut schedule
- Cut length · every sheet
- 2.361068 m
- Final column cut width · includes lap reserve
- 1.1 m
- Width trimmed from each final-column sheet
- 0 m
- Length trimmed from every stock sheet
- 0.638932 m
- Sheets requiring a width or length cut
- 20
Material and offcuts
- Net roof coverage area
- 45.22136 m²
- Stock sheet area to purchase
- 66 m²
- Material retained for laps and edge reserve
- 6.722136 m²
- Offcut area · no reuse assumed
- 14.0565 m²
- Offcuts as a share of stock area
- 21.298 %
Eave · 10 columns
Ridge · 2 rows along slope
Start with the roof you need to cover
Enter the width across the eave, then the horizontal run and vertical rise for one slope. The planner calculates the sloping length, adds the eave extension, and deducts the ridge setback. Those last two allowances are measured along the slope.
For a gable roof, calculate each slope separately. Double a result only when the two slopes have identical dimensions and details. Hips, valleys, openings, and irregular boundaries need a separate layout.
How the sheet layout is calculated
The planner uses the same engines as the effective-width calculator and panel cut-length calculator.
- Effective cover width = overall sheet width − side lap.
- Columns = roof width ÷ effective cover width, rounded up.
- Coverage length = √(run² + rise²) + eave extension − ridge setback.
- Rows = (coverage length − end lap) ÷ (stock length − end lap), rounded up, with a minimum of one row.
- Equal panel cut length = [coverage length + (rows − 1) × end lap] ÷ rows.
- Stock sheets = columns × rows, with one stock sheet for each installed piece.
Every column uses effective width, including the first. This reserves one side-lap width at the outer edge as well as material at internal joints. It is deliberately conservative and may differ from a supplier’s full-first-sheet convention.
The final column’s cut width is its remaining effective coverage plus the side-lap reserve. All other columns retain the full profile width. These are geometric widths: check that the proposed trim is compatible with the actual ribs and edge details.
A simple worked layout
Take a roof 5.5 m wide with a 4 m horizontal run and zero rise or allowances. Use 1.1 m wide sheets, a 0.1 m side lap, 3 m stock lengths, and a 0.2 m end lap.
Effective cover is 1 m, so the roof needs 6 columns. Two rows cover the slope, with each piece cut to (4 + 0.2) ÷ 2 = 2.1 m. That makes 12 stock sheets. The last column covers 0.5 m and retains 0.1 m for the lap reserve, giving a 0.6 m cut width.
The stock area is 39.6 m². Retained pieces total 25.62 m², of which 22 m² covers the roof and 3.62 m² is lap and edge allowance. The remaining 13.98 m² is offcut material, about 35.3% of the purchased area. No offcut reuse is assumed.
Overlap material is not the same as waste
Side and end laps consume material that remains on the roof. Offcuts are the pieces removed when stock sheets are shortened or the last column is narrowed. The planner reports them separately, without double-counting the corner where a length trim and width trim meet.
Changing stock length can reduce offcuts, but adding joints also changes support and installation requirements. The lowest offcut percentage alone does not establish a suitable roofing layout. There is no allowance for cutting kerf, damage, or spare sheets in these results.
Roof sheet layout FAQ
Does the planner choose a safe overlap?
No. Enter the lap dimensions specified for your product and project. The example values are calculation inputs, not installation recommendations.
Why are all rows cut to the same length?
Equal lengths provide a simple schedule using the existing cut-length engine. Actual joints may need to align with supports, which can require unequal lengths and a revised schedule.
What if one sheet reaches the ridge?
The planner uses one row and applies no end-lap material. It still checks that your entered end-lap value is non-negative and smaller than the stock length.
Are the diagram cells the full sheets?
No. They show each piece’s effective coverage. The overlapping material is excluded, and the roof is shown unfolded with schematic proportions. Large layouts compress repeated cells to keep the diagram readable.
Can I reuse the offcuts?
Possibly, depending on the profile, orientation, and required dimensions. This planner does not match offcuts to other pieces and assumes one stock sheet per installed piece.