Can I build up a low spot with fill dirt before setting the home?

Yes, but fill must be compacted properly or the home can settle. HUD's manufactured home installation standards allow footings on fill only when it is compacted to at least 90 percent of its maximum relative density; otherwise footings belong on firm, undisturbed soil. Massachusetts' IRC-based code similarly limits footings on compacted fill and requires clean, free-draining backfill without organics or debris. Loose dirt dumped from a truck is not compacted fill. It should be placed in layers and compacted with a roller or plate compactor, and a soils engineer or testing lab can verify density with field tests. If HUD's standards find the soil is uncompacted fill, peat or organic clay, a registered professional must determine its bearing capacity instead of using default values.

Check your local rule. This varies by state, county or city. Your permitting office has the final word; the official lookup pages below show you who that is.

Sources

• 24 CFR Part 3285, Model Manufactured Home Installation Standards (2020 edition)U.S. Government Publishing Office (HUD regulation)
• 780 CMR Residential Chapter 4 Foundations Amendments (IRC-based)Commonwealth of Massachusetts