Roof Weight and Tear-Off Calculator
Last reviewed How we calculate
Roofing materials differ enormously in weight. A square of steel panels can weigh a tenth of a square of clay tile, and the structure has to carry whichever is on it. This works out the weight of a new roof covering, the load it puts on the roof, and how much debris comes off when the old roof is torn off.
Roof covering weight and tear-off debris
The weight of a new roof covering, the load per square foot, and how much old roofing a tear-off produces.
This calculator needs JavaScript to work. The measurements below are the ones you would need to do the sum by hand.
Weight of the new roof covering
- Load per square foot
- Load per square meter
- Tear-off debris
- Tear-off debris, US tons
- Tear-off debris, metric tonnes
This is a heavy roof covering. If the roof now carries asphalt shingles or metal, have the rafters or trusses checked by an engineer before switching: the structure was sized for the load it was built with, not for this one.
These weights are for the covering only. They leave out the deck, underlayment, battens and snow, all of which the structure also carries. When hiring a dumpster, give the company the tonnage: most price by a weight allowance as well as by size.
How the calculation works
Materials are weighed per square, so the weight of the covering is the number of squares multiplied by the weight per square. Divide the weight per square by 100 and you have the load in pounds per square foot, which is how structural loads are usually expressed. Tear-off debris is the number of squares, times the layers coming off, times the weight of one layer.
A worked example
A 1,250 sq ft roof in architectural shingles at about 350 lb a square weighs about 4,375 lb. The same roof in concrete tile at about 950 lb a square weighs 11,875 lb, a load of 9.5 lb per square foot. Tearing off one layer of old shingles at around 300 lb a square produces about 3,750 lb, or 1.9 US tons, of debris.
About the typical weights
The weights in the list are round figures near the middle of each material range, and real products vary on either side of them. Shingle lines differ by a hundred pounds a square or more, and tile and slate vary with thickness and profile. For anything that matters, use the weight per square from the manufacturer data sheet with the Other option.
Changing to a heavier material
A roof structure is designed for the loads it was built to carry. Moving from asphalt shingles to concrete tile, clay tile or slate can more than double the weight on the rafters, and that change needs an engineer to confirm the structure can take it, or to specify how to strengthen it. Adding a second layer of shingles over the first also adds load, and building codes limit how many layers a roof may have, so check before planning a re-cover.
Frequently asked questions
How much does a square of shingles weigh?
Three-tab asphalt shingles typically weigh around 200 to 250 pounds a square, and architectural shingles roughly 250 to 430 pounds, depending on the product line.
Can I put a new layer of shingles over the old ones?
Building codes allow a re-cover over one existing layer under certain conditions, but not where two or more layers are already on the roof. Your local building department has the final say.
How do I choose a dumpster for a tear-off?
Give the hire company the tonnage from the calculator. Most dumpsters come with a weight allowance as well as a size, and roofing debris usually reaches the weight limit before the container is full.