Estimates the material cost, labour cost and total price of a residential re-roof from footprint area, roof pitch, material choice and whether the old roof is torn off.
Which cell does what, and which worksheets the model reads. These are the assignments you recreate when you import the file.
| Cell | Role | Note |
|---|---|---|
| B1 | Input | Ground footprint of the house under the roof, in square feet. Not the sloped roof area and not the interior floor area — measure the outside walls including any eave overhang. |
| B2 | Input | Roof pitch, stored as the pitch factor sqrt(rise^2 + 144) / 12. Multiplying the footprint by this gives the real sloped surface. |
| B3 | Input | Material choice, stored as the all-in delivered material cost per square. Also the lookup key into the Rates sheet for the matching labour rate. |
| B4 | Input | 1 when the old roof is torn off and hauled away, 0 when the new roof goes over the existing layer. Used as a multiplier so the tear-off line collapses to zero. |
| B6 | Result | Actual roof surface area: footprint multiplied by the pitch factor, rounded to the nearest square foot. |
| B7 | Result | Surface area plus a 10 percent waste allowance for cuts, starter course and offcuts. |
| B8 | Result | Squares of material to order. One square is 100 sq ft. Always rounded up, because material is bought in whole squares. |
| B9 | Lookup | Labour rate per square for the chosen material, read from the Rates sheet using the material price in B3 as the key. |
| B10 | Result | Steep-roof labour factor. 1.2 for pitches of 8/12 and steeper, otherwise 1. |
| B11 | Result | Install labour: squares times the labour rate times the steep-roof factor. |
| B12 | Result | Tear-off and disposal at $95 per square, zeroed out by B4 when the old roof stays. |
| B13 | Result | Material cost: squares times the material price per square. |
| B14 | Result | Labour cost: install labour plus tear-off and disposal. |
| B15 | Result | Total estimate: material cost plus labour cost. |
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Start from this model rather than a blank sheet. The inputs, the results and any lookup worksheets come with it.
The prices here are examples. Change them in the Formula view and the calculator follows — no rewiring.
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A square is 100 square feet of roof surface. Roofers buy and price material by the square rather than the square foot, and shingles are bundled so that three bundles cover one square. A 2,200 square foot roof is 22 squares.
The footprint is the part a homeowner can measure from the ground with a tape, using the outside walls. The pitch factor converts it to the sloped surface, which is always larger. A 1,800 sq ft footprint at a 6/12 pitch is about 2,012 sq ft of roof.
Pitch is the rise in inches over 12 inches of horizontal run. Hold a level against the roof, mark 12 inches along it, and measure straight down to the roof surface at that mark. Six inches of drop is a 6/12 pitch, the most common on modern homes.
Most building codes allow a second layer of asphalt shingles over one existing layer if the decking is sound and there is no trapped moisture. Going over an existing roof saves roughly $95 per square here, but it hides deck damage, shortens the new roof's life and rules out any warranty that requires a clean deck.
Standing seam panels are cut and formed to length on site, fastened with concealed clips, and need custom flashing at every penetration and edge. The work is slower, needs more skill, and a mistake wastes a full panel rather than one shingle.
No. It is a ballpark that covers material, install labour and tear-off on a straightforward roof. It does not include permits, decking replacement, rotten fascia, chimney or skylight flashing, gutter work, or the extra waste a cut-up roof with many valleys and dormers generates. Those come out of a site visit.