Roofing
Roof Replacement Cost Calculator
Price a full replacement including tear-off, disposal, deck repair and the accessories a new roof requires.
Result
Deck condition cannot be known until the old roof is off. Ten per cent is a common allowance; older roofs and any history of leaks justify considerably more.
Get a Free Business AuditWhat moves the number
- Tear-off labour and disposal weight, which rise with layer count.
- Deck condition, which is unknown until the covering is off.
- Flashing, vents and penetrations, which should be replaced rather than reused.
Where this one goes wrong
Reusing old flashing to hit a price. Flashing fails before the field material does, and a new roof with old flashing leaks at exactly the points the customer will blame you for.
Questions
About this calculator
Should flashing always be replaced?
On a full replacement, generally yes. It is a small share of the cost and it is where roofs leak. Reusing it to save on the quote is the most common source of a callback on an otherwise good job.
How much deck damage is typical?
It varies enormously with the age and history of the roof, which is exactly why it is quoted as an allowance rather than as a fixed figure. Anyone quoting a precise number has not seen the deck either.
Does ventilation need addressing?
It is worth assessing on any replacement. Inadequate ventilation shortens the life of the new roof and can void the material warranty, and it is far cheaper to correct while the roof is open.
Put this calculator on your site
Free to embed. Paste this where you want it to appear. It stays up to date automatically because it loads from BDEVY.
Please keep the attribution line. It is the only thing we ask in return.
How to use this calculator
- Roof size (squares) (sq). Enter your own figure; the page starts at 24 sq.
- Base installed cost per square ($). Enter your own figure; the page starts at $380.
- Pitch. Enter your own figure; the page starts at 6/12 (common).
- Storeys. Enter your own figure; the page starts at 2.
- Deck expected to need replacing (%). Enter your own figure; the page starts at 10%.
- Deck replacement per square ($). Enter your own figure; the page starts at $120.
The result updates as you type, so you can try a figure, see what it does to total estimated cost, and change it back. Nothing you enter is sent anywhere or saved.
A worked example
These are the figures the calculator opens with. Every number in the results column below is produced by the same calculation the page runs, so you can follow it through before putting your own figures in.
What goes in
| Input | Value |
|---|---|
| Roof size (squares) | 24 sq |
| Base installed cost per square | $380 |
| Pitch | 6/12 (common) |
| Storeys | 2 |
| Deck expected to need replacing | 10% |
| Deck replacement per square | $120 |
What comes out
| Result | Value |
|---|---|
| Total estimated cost main result | $10,046 |
| Base roofing cost | $9,120 |
| Pitch and access surcharge | $638.40 |
| Deck repair allowance | $288.00 |
Replacing this roof comes to about $10,046, $9,120 base, $638.40 for pitch and access, and $288.00 allowed for deck repair.
How sensitive the answer is
Holding everything else steady and changing only base installed cost per square, this is what happens to total estimated cost. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Base installed cost per square ($) | Total estimated cost |
|---|---|
| $190 | $5,167 |
| $285 | $7,607 |
| $380 example above | $10,046 |
| $570 | $14,926 |
| $760 | $19,805 |
Every other input is held at the example value while this one changes, which is not how a real job behaves. Treat it as a guide to which number matters most, not as five separate quotes.
What each figure means
- Roof size (squares) (sq)
- Measured in sq, starting at 24 sq.
- Base installed cost per square ($)
- A money amount, starting at $380.
- Pitch
- Choose from 1/12 (very low), 2/12, 3/12, 4/12, 5/12, 6/12 (common), 7/12, 8/12, 9/12, 10/12, 12/12 (45°), 14/12 (steep).
- Storeys
- A number, between 0 and 6, starting at 2.
- Deck expected to need replacing (%)
- A percentage, between 0 and 100, starting at 10%.
- Deck replacement per square ($)
- A money amount, starting at $120.
What the results tell you
| Result | What it is |
|---|---|
| Total estimated cost | The headline result. A money figure. |
| Base roofing cost | A money figure. |
| Pitch and access surcharge | A money figure. |
| Deck repair allowance | A money figure. |
What this cannot see
Material quantities assume a clean rectangular plane and the waste factor you enter. Valleys, hips, dormers, penetrations and a steep pitch all raise real waste, and a tear-off frequently uncovers decking that was not in the quote.
Keep going
Related calculators
Roofing Cost Calculator
Build a roofing price from squares, material, crew labour and everything a tear-off exposes.
Open calculatorMetal Roof Cost Calculator
Price a metal roof from panel type, trim, fastening system and the substrate it is going over.
Open calculatorRoof Area Calculator
Turn building footprint and pitch into actual roof area, which is what material and labour are priced from.
Open calculatorEstimating is the easy part
The jobs you never hear about cost more than the ones you mis-measure. BDEVY builds the marketing, systems and automation that bring them in.