Excavation
Compaction, Shrink, and Swell: Why Your Yardage Changes (Oregon)
Cojo
June 19, 2026
6 min read
Soil compaction, shrink, and swell in Oregon is the reason the yardage you order, the yardage you haul, and the size of the hole never quite match. Soil sitting undisturbed in the ground is at "bank" volume. Dig it out and it loosens and expands, called swell, so it takes up more space in the truck than it did in the ground. Place fill or rock and compact it and it shrinks, taking up less space than the loose pile you bought. That is why you over-order fill and under-estimate haul-off if you ignore these factors. This page explains bank, loose, and compacted volume, why they differ by material, and how that changes your load counts and cost.
The core idea is that the same soil occupies different amounts of space depending on its state:
A cubic yard measured one way is not a cubic yard measured another. Once you know which volume a number refers to, the math finally makes sense. For the broader materials picture, see the excavation materials and hauling guide.
When you excavate, the bucket breaks the soil apart and introduces air between the particles. That loosened material takes up more room than it did packed in the ground. So a hole that measures a certain bank volume produces more loose volume to haul away. This is swell, and it is why haul-off truck counts run higher than the in-ground hole size suggests.
Different materials swell by different amounts. Loose, granular soils swell less; dense clay and rock swell more once broken up. Wet Oregon clay is heavy and bulks up noticeably when dug, which matters for both volume and the weight the truck carries.
The flip side happens when you place material and compact it. Loose fill or rock delivered to your site is full of voids. Compact it in lifts and those voids close, so the compacted result occupies less space than the loose pile you bought. This is shrink, or compaction loss, and it is why the gravel you ordered does not fill as much space as the loose yardage implied.
The practical consequence: to end up with a needed compacted volume, you order more loose material than the compacted number, because some of it disappears into compaction.
| State change | What happens | Effect on you |
|---|---|---|
| Bank to loose (digging) | Soil expands, gains air | More loose volume to haul off |
| Loose to compacted (placing) | Voids close, soil densifies | Need more loose fill than final volume |
| Clay, wet | Swells more, weighs more | Higher truck counts and weight |
| Rock | Compacts less than soil | Less shrink, plan accordingly |
Materials behave differently, so crews think in approximate swell and shrink tendencies rather than one universal number:
The exact factors come from the material and the job, which is why an experienced contractor's estimate accounts for them rather than treating every yard as identical.
Ignoring shrink and swell leads to two classic mistakes: ordering too little fill and renting too few haul trucks. Both cost you. If you order fill at the compacted volume, you come up short and pay for a second delivery. If you size haul-off at the in-ground volume, you run out of truck capacity and the job stalls.
For estimating the truck side, our how many truckloads is my project guide walks through load counts, and for sizing fill orders, how much fill dirt do I need accounts for compaction.
Shrink and swell are exactly why takeoff math should be done by someone who plans for it. A homeowner who orders gravel at the compacted volume runs short; one who estimates haul-off at the hole's bank volume underbooks trucks. The extra delivery or extra trips are real costs that good estimating avoids by building in the right factors.
Here is how shrink and swell shift load counts using baseline ranges.
| Sample situation | Volume effect | Material at baseline |
|---|---|---|
| Haul-off, dug clay (swells) | More loose yards than the hole | $250 - $750+ per truck load |
| Fill order to compact (shrinks) | Order more than final volume | $20 - $75+ per cu yd fill |
| Gravel base to compact | Order extra for compaction loss | $45 - $110+ per cu yd |
The same dirt has three volumes: bank in the ground, loose in the truck, and compacted in place. Dug soil swells, so haul-off runs higher than the hole; placed fill shrinks, so you order more than the final volume. Account for it and your load counts and orders come out right; ignore it and you pay for a second delivery or stalled trucks. Cojo is CCB licensed and insured and does takeoffs that build in shrink and swell across Oregon. See our excavation services or request a free estimate. For more, read how many truckloads is my project and the Oregon excavation contractor guide.
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