Demolition debris and dumpster calculator

How demolition debris is actually taken off

Debris is not measured. It is derived from the removal quantities you already took off, and it is taken off in the same units the scope is written in. Interior work comes off the floor plans as square feet of finish at an assumed in-place thickness, because that is how the demolition notes are written: remove all flooring, remove ceilings, remove partitions on this level. Structural work comes off the sections and details as cubic yards in place, because a footing or a wall is a solid with dimensions on the sheet.

So a real debris takeoff is a list of removal lines in mixed units, and each line has to be pushed through two conversions before it means anything to a hauler. First to a common volume unit, then to loose volume, because broken material occupies more space than the same material did in place. Only then can you divide by a container.

The output that gets priced is not cubic yards. It is pulls. A hauler quotes a delivery, a haul, and a disposal charge per container, so the bid line is a whole number of containers times a rate. Getting the cubic yards close and the pull count wrong is a common way to lose money on a demolition bid, because the error is quantised: one extra pull is a full pull, not a rounding difference.

The formulas

Area lines: cubic feet = area in sf x (thickness in inches / 12) Volume lines: cubic feet = cubic yards in place x 27 In-place volume: cy = cubic feet / 27 Loose volume: loose cy = in-place cy x (1 + swell percent / 100) Weight: pounds = cubic feet x in-place unit weight in lb per cf, and tons = pounds / 2,000 Effective container capacity: cy = nominal container size x fill efficiency Pulls by volume = roundup(total loose cy / effective capacity) Pulls by weight = roundup(total tons / payload limit per pull) Pulls required = the larger of the two

Two points about that last pair. Swell changes volume but not weight, so the tonnage is computed off the in-place volume and is unaffected by whatever swell figure you use. And the pull count has two independent ceilings, one volumetric and one by weight, so you have to compute both and take whichever binds. On light interior work volume binds. On concrete and masonry, weight binds well before the box is full.

The constants, and where they come from

The calculator holds in-place unit weights fixed per material, because those are published values, and keeps swell and fill efficiency as inputs, because those are not.

In-place unit weights (lb per cf)

• Reinforced concrete, 150: ASCE 7 Table C3.1-1a lists reinforced stone concrete at 150 pcf. One in-place cubic yard is 150 x 27 = 4,050 lb.
• Plain concrete flatwork, 144: the same ASCE 7 table lists plain stone concrete at 144 pcf.
• Asphalt paving, 145: compacted hot mix asphalt. Check it against the figure paving crews use: 145 x 9 sf x (1 in / 12) = 109 lb per square yard per inch, which lands on the familiar 110 lb per sy per inch.
• Hollow CMU wall, 61 (gross wall volume): an 8 in normal weight hollow CMU wall, ungrouted, runs roughly 36 to 42 psf in the NCMA TEK 14-13B wall weight tables. Taking 39 psf over a 7.625 in gross thickness gives 39 / 0.635 = 61 pcf. Use the gross wall envelope as your volume, not solid volume, because the cores are already accounted for in that number. If the wall is grouted or reinforced, the figure climbs toward solid concrete.
• Brick masonry, solid, 125: clay brick masonry is commonly published in the 120 to 130 pcf range.
• Interior finishes, 40: derived from gypsum board, which is the mass in most interior demolition. One half inch regular board is about 1.6 lb per sf at the ASTM C1396 nominal weights, so 1.6 / (0.5 / 12) = 38 pcf. Round to 40. A mix heavy in acoustic ceiling tile and carpet sits lower, near 25. A mix with plaster, tile, and thinset sits higher, near 55. If your scope is one of those, adjust the thickness input to compensate or split it into two lines.
• Lumber and timber, 30: softwood framing lumber. The NDS specific gravity range for common species is about 0.42 for SPF to 0.55 for southern pine, and 0.48 x 62.4 lb per cf = 30 pcf. Enter solid wood volume from the framing schedule, not the wall envelope.

Swell (percent volume increase from in-place to loose)

Swell is an input, not a constant, because the same material swells differently depending on how finely you break it and how the operator loads. The published starting points come from the swell and load factor tables in the Caterpillar Performance Handbook, which lists well blasted rock in the 50 to 60 percent range and soil around 25 percent. Broken concrete behaves like blasted rock, so the defaults here are 50 percent for concrete and 55 percent for masonry rubble, 40 percent for asphalt, and 60 to 70 percent for sheet goods, framing, and mixed light debris, which bridge and void far more than rubble does. Those ranges are wide on purpose. If you have container history on similar work, back the number out of it: divide the loose cubic yards you actually hauled by the in-place cubic yards you took off, subtract one, and that is your shop's swell.

Fill efficiency

A roll off is never loaded to its nominal rating. Debris does not nest, the load has to sit level with the rails to be tarped and hauled legally, and a 40 cy box collects awkward long pieces that hold voids open. A practical range is 70 to 90 percent, with the low end on unbroken sheet goods and structural steel and the high end on rubble that a machine can push down. The calculator defaults to 80 percent. That is a starting rule of thumb, not a measured figure, so replace it with your own history.

Payload limit per pull

There are two separate ceilings that both look like a tonnage number, and they are not the same thing. The first is what the truck can legally carry. A tandem axle roll off truck against a legal gross weight around 54,000 lb, less the tare of the truck and the container, commonly nets about 10 tons of payload. Tri axle and quad units carry more. The second is the tonnage allowance included in your hauler's flat rate before overage billing starts, which varies by market and by container size. Set the input to whichever one binds for you, and confirm both with your hauler and your local axle weight limits before you bid.

What the volume math misses, and it is most of the risk

The volume is the easy half. It is arithmetic on dimensions that are printed on the sheet, and once you have the swell and fill figures from your own history it is repeatable. What decides whether a demolition bid holds is what is concealed behind and above what you are removing, and none of it is on the plan.

Behind is the first problem. A partition shown as one line on a demolition plan can turn out to carry a live sprinkler branch, a plumbing riser serving the floor above, or three data drops nobody documented. Older buildings hide a second layer of finish under the first, so the flooring you priced as one layer is vinyl over vinyl over adhesive on a topping slab. Fire rated assemblies have to come out and go back to a rated detail, which is a different scope from removal. Above is the second problem. What you are cutting out may be carrying something, so the removal turns into shoring and needs an engineer, and the ceiling above the wall you are removing is full of live services that stay live while you work around them.

Then there is the one that stops the job. Hazardous material abatement is a separate licensed scope, and it must be excluded explicitly and in writing. Asbestos and lead are federally regulated work, governed by the EPA asbestos NESHAP in 40 CFR Part 61 Subpart M and by OSHA 29 CFR 1926.1101 for asbestos and 1926.62 for lead in construction, and most jurisdictions require a licensed abatement contractor plus a pre demolition survey before anything comes out. If suspect material turns up mid job that the survey did not cover, your work stops entirely until an abatement contractor clears the area, and the debris you already have on site may be reclassified and priced as regulated waste rather than C and D. Exclude abatement by name, cite the survey you priced from, and state that suspect material found outside that survey is a change. Do not carry an allowance for it hoping to cover yourself, because you cannot legally perform the work anyway.

Tipping fees are billed by weight, containers are billed by volume

This is the mismatch that puts demolition bids underwater. The hauler prices the container by volume, because that is what fits on the truck. The disposal facility prices by weight, because that is what the scale says. Most landfills and C and D recycling facilities bill per ton at the gate. So the box you selected on volume gets charged on a number the box has nothing to do with.

On light debris the two rarely fight. On concrete and masonry they always do. A 30 cy box loaded with concrete rubble at roughly 1.3 tons per loose cubic yard would weigh about 39 tons full, which is several times what any roll off truck can legally leave the site with. That is why heavy debris goes in 10 cy boxes, often called concrete or lowboy boxes, which exist for exactly this reason: they are sized so a full box is a legal load. When you see a demolition contractor ordering small containers for a big scope, that is not inefficiency, that is the weight ceiling.

Two practical consequences. First, separate your heavy lines from your light lines and haul them in different container sizes, then price each stream on its own. Clean concrete usually has a lower per ton gate rate than mixed C and D, and some markets take it for free or near free at a crushing facility, so mixing rubble into a mixed debris box converts cheap tonnage into expensive tonnage. Second, when you check the calculator's container comparison table, notice that once weight governs, a bigger box buys nothing. The pull count stops falling. Paying for 40 cy boxes you can only fill to 25 percent is a straight loss.

Worked example

Take the calculator's own defaults: a floor gut plus some structural removal.

Line 1 is 5,000 sf of interior finishes at 3 in in place. That is 5,000 x 0.25 = 1,250 cf, which is 1,250 / 27 = 46.3 cy in place. At 70 percent swell that is 46.3 x 1.7 = 78.7 loose cy, and at 40 lb per cf it weighs 1,250 x 40 = 50,000 lb, or 25 tons.

Line 2 is 1,200 sf of 6 in slab on grade. That is 1,200 x 0.5 = 600 cf, which is 22.22 cy in place. At 50 percent swell that is 33.33 loose cy, and at 144 lb per cf it weighs 600 x 144 = 86,400 lb, or 43.2 tons.

Line 3 is 8 cy of reinforced concrete taken off the sections. That is 8 x 27 = 216 cf. At 50 percent swell it becomes 12 loose cy, and at 150 lb per cf it weighs 216 x 150 = 32,400 lb, or 16.2 tons.

Totals: 76.52 cy in place, 124.04 loose cy, and 84.4 tons.

Now size the containers. A 30 cy roll off at 80 percent fill efficiency has an effective capacity of 24 cy, so pulls by volume = roundup(124.04 / 24) = roundup(5.17) = 6 pulls. Pulls by weight at a 10 ton payload limit = roundup(84.4 / 10) = roundup(8.44) = 9 pulls. The larger of the two governs, so the answer is 9 pulls, and weight is what sets it.

Look at what that means. At 9 pulls each box carries 9.38 tons and only 13.78 loose cy, which is 46 percent of the 30 cy nominal rating. You are paying for nine hauls of half empty boxes because the concrete hit the scale first. Run the comparison table and the 20 cy box also comes to 9 pulls, and so does the 40 cy, because above 20 cy the weight ceiling is the only thing that matters here.

The move on this scope is to split the two streams and run the calculator twice. Put the concrete lines, 45.33 loose cy and 59.4 tons, in 10 cy boxes: 6 pulls, and the box is close to full both by volume and by weight. Put the 78.7 loose cy and 25 tons of interior finishes in 30 cy boxes: 4 pulls. That is 10 pulls against 9, so the split costs you one extra haul. It is still usually the cheaper answer, because 59.4 tons of clean concrete moves off the mixed C and D gate rate onto the concrete rate, and in many markets a crushing facility takes clean rubble at a fraction of the landfill rate. Price both versions on your own gate rates rather than assuming, because the answer flips depending on the spread between the two rates in your market.

From debris quantity to a priced line

The pull count is one line of a demolition bid. The rest is labour and equipment hours to break and load, the gate fees on each waste stream, and the exclusions that keep the scope honest. That last part is not arithmetic, and no calculator produces it.

Ruh works on the quantity half. It reads the drawing set, measures the scope, and prices the measured quantities against your own price book, with every line traceable back to the sheet it came from. Your estimator still owns the swell and fill figures, the concealed conditions allowance, and the abatement exclusion. For the trade workflow around this see demolition estimating software, and for how the whole bid gets assembled and qualified see the guide on how to bid demolition as a subcontractor.