Guide
Hidden costs of modular homes
Factory base is rarely all-in. Use this exclusion checklist before you treat a quote as a budget.
The number most buyers see first is the factory base price. It is often less than half of what they spend. Buyers report a $90,000 to $200,000 module becoming $245,000 to $415,000 all-in once land work, foundation, crane, utilities, tax, and finish are added. This page is the exclusion checklist. For the full cost-versus-timeline comparison, use Costs and timeline. For draw timing, use Financing and affordability.
Competitors such as Modularist and Hammerio say the same thing in 2026: add 30 to 40 percent on a simple suburban lot, and 50 to 100 percent on rural or difficult sites. Treat those percents as a planning band, not a promise.
What almost every factory quote excludes
- Land purchase and closing costs
- Survey, geotech, and percolation test
- Clearing, grading, and drainage
- Driveway, culvert, and crane pad
- Permanent foundation or basement
- Well, septic, or long utility laterals
- Building permits and impact fees
- Delivery beyond a stated radius and the crane itself
- Button-up: seams, roof, siding, interior patch, paint
- Sales tax on the module (often missed)
- Landscaping, decks, garage, and appliances if they were allowances
Abodu is unusually honest for ADUs: it publishes a written list of what sits outside the number (survey package, trench beyond 50 feet, crane beyond 100 feet). Copy that habit on every modular bid. If a line is missing, assume you own it.
Typical 2026 adder ranges
| Line item | Suburban infill | Rural or difficult |
|---|---|---|
| Site prep and grading | $3,000 to $12,000 | $8,000 to $25,000 |
| Foundation (slab / crawl / basement) | $8,000 to $28,000 | $15,000 to $45,000 |
| Delivery | $2,000 to $8,000 | $6,000 to $15,000 |
| Crane and set crew | $4,000 to $12,000 | $8,000 to $20,000 |
| Municipal utilities | $2,500 to $10,000 | n/a |
| Well and septic | n/a | $15,000 to $40,000 |
| Permits and impact fees | $1,500 to $8,000 | $2,000 to $15,000+ |
| Button-up and finish | $8,000 to $25,000 | $12,000 to $35,000 |
| Sales tax (varies by state) | 0 to 8% of taxable base | same |
Two homes with the same factory SKU can differ by $50,000 to $100,000 because of well, septic, basement, and haul distance. That is why a ZIP-priced dealer sticker and a turnkey ADU sticker are not comparable.
Rural versus suburban delta
Suburban lots with sewer, water, and a paved street keep adders toward the low column. Rural raw land adds well drilling, septic design after a perc test, a long driveway that can take a module truck, and sometimes a temporary construction entrance. Electricity billed by the foot from the nearest pole surprises buyers on r/Homebuilding more than the crane.
If the land has not perc'd, walk. Alternative septic exists, but it is not the $7,000 conventional system in a blog table.
Sales tax and impact fees
Modularist flags sales tax as one of the most skipped major costs. Some states tax a percentage of the factory price (California often taxes a materials portion rather than the full contract). Some factories exclude tax from the proposal. Ask: "Is sales tax in this number, and what is the taxable base?" Write the answer on the bid.
Impact fees are the other wild card. School and infrastructure fees can exceed $10,000 in some counties. They do not appear on a factory invoice.
Who pays after set day
Split responsibility is the Reddit failure mode. The factory delivers boxes. A local GC or dealer "set crew" owns connections. If the plumber is late, drywall cannot close the chase. Storage fees start if the site is not ready when the truck arrives. Put finish-work ownership, weather delays, and storage in the contract before the build slot.
Use the site preparation guide for crane-pad and driveway width, and the building process guide for the inspection sequence that releases draws.
A 60/40 planning rule
A useful first-pass budget is 60 percent factory and freight, 40 percent site and finish, then add a 10 to 15 percent contingency. Home Nation and similar dealers often quote the 60. You still own the 40 unless the contract is turnkey. Run both sides through the cost calculator.
Allowances that pretend to be included
Flooring, lighting, appliances, and exterior cladding often sit in an allowance column. An allowance is a budget cap, not a specification. If the bid says $8,000 for flooring and your pick is $14,000, the gap is yours. Ask for a finish schedule with SKUs, not categories.
Decks, garages, and porches are frequently drawn on the rendering and missing from the commercial terms. Same for gutters, driveway base, and final grade. Walk the rendering line by line against the exclusions exhibit.
Contingency that is actually used
Keep 10 to 15 percent of the all-in number in cash or a construction reserve. Soils, rock, and extra trench are the usual draws on that reserve. Buyers who empty the reserve on upgrades in week two have nothing left when the crane needs a second day.
If you cannot fund the reserve, you do not have a project yet. That is a better sentence to hear now than on set week.
How to read a quote in 20 minutes
1. Circle every verb that is not "included." 2. Highlight freight radius and crane language. 3. Find sales tax. 4. Find who owns button-up. 5. Compare the total to the cost calculator median for that model.
If two of those five are blank, the quote is a brochure.
Related pages
Home Nation factory-direct explains ZIP price versus all-in. Top 5 regrets covers buyers who skipped this list. Buyer help if you want a quote packet reviewed before you sign.
FAQ
- What percent over base price should I budget?
- Plan 20 to 40 percent over factory for a simple suburban install, and 50 to 100 percent or more for rural utilities, basements, or premium finishes. Always build a line-item sheet, not a single percent.
- Are crane costs included in the factory price?
- Almost never. Crane rental and the set crew are common delivery-day surprises. Confirm who books the crane and who pays standby time if the site is not ready.
- Is sales tax included in modular quotes?
- Often no. Ask what portion of the contract is taxable in your state and whether the factory collected it. Treat tax as its own line.
- Why do two identical models have different all-in prices?
- Haul distance, foundation type, well versus city water, trench length, impact fees, and how much finish is left after set. The SKU price is the shared part.
- What is the 60/40 rule?
- A planning split: about 60 percent factory and freight, about 40 percent site, foundation, utilities, and finish. It is a starting model, not a quote.