Prefab Home Foundation and Site Prep Costs: The Line Items
If you are pricing the ground under a prefab home, 3 makers put a figure on it. Next Modular estimates a poured crawl space at $25,082 under its 1,600-square-foot Walnut Forest Ranch. Abodu prices installation, with the foundation and site work in it, at $64,000 to $105,000. Deltec builds a $35,000 site-preparation allowance into its estimated total. The other makers here state which foundation they require and leave the price to you.
This guide covers the ground layer only. For the unit, delivery, and permit layers, see the cost of prefab homes. Every figure below comes from the maker’s or the agency’s own page. Where nobody publishes a figure, the cell says “Not published”.
The Foundation Each Maker Specifies
Next Modular says its turnkey figures are averages under ideal building conditions, and the price is not a quote. Boxabl says the promotion is subject to terms and may end at any time.
Slab
Deltec’s shell price assumes a slab, and its estimate assumes a slab unless you select a floor system. A crawl space or piling foundation adds a floor system to the shell, and the estimate rises to reflect it. Deltec’s Backyard Cottages accept a slab, a crawl space, or piers, and cannot go on a basement.
Avrame does not accept a slab. Its FAQ says a slab is “not feasible” with its system, because Avrame is a traditional stick build and not a prefabricated home.
Crawl Space
Avrame includes a standard crawl space design in its plan sets, designed for a flat lot. For the Trio, it specifies an 8-inch foundation wall with #4 rebar on 12-inch vertical centers. Footings are 36 inches wide and 12 inches deep on the sidewalls, and 24 inches wide on the gable walls. Avrame no longer offers a strip-footing design, partly because most building departments do not allow an open foundation.
Next Modular’s $25,082 crawl space is 1 line of a turnkey estimate. For an Avrame crawl space, ask a local foundation contractor to price the same line before you compare the two.
Piers and Pilings
Avrame says piers or post and beam are feasible but not offered. You hire a third-party engineer to design and stamp them, and Avrame says they can be necessary in flood zones. Deltec accepts pilings, and its estimate rises for them. Zook says not to put a park model on pier and beam, a crawl space, or a pit foundation.
Full Basement
Avrame’s Trio basement option can work on a sloped lot. Its $1,500 (Trio) and $2,500 (Duo) figures are for the plan option, and the concrete is a separate cost. The higher end of Deltec’s Design Studio range covers a basement. Next Modular lists a basement as something that changes the price and asks you to call for a quote.
Gravel Pad and Park-Model Setup
A Zook park model stays attached to its wheels, blocked up on wooden or masonry blocks so it does not rest on them. Zook requires at least 4 to 5 inches of crushed stone or a concrete pad, and recommends a pad 4 to 6 inches thick that extends past the edge of the unit. For gravel, it recommends Âľ-inch clean stone, tamped level. For concrete, it specifies at least 4 inches on 4 to 6 inches of gravel, cured for up to 4 weeks. Parking on bare ground voids the warranty.
Zook does not offer site preparation or setup. Leveling, skirting, and decks are the buyer’s work, and delivery needs at least 18 feet of width on a straight drive-through.
Other Ground Costs and Who Publishes Them
Warrenton’s taps run from the city main to your property line or the edge of the right-of-way, and the city requires a separate tap for each structure. Ask the city who pays for the line from there to the house. Zook says to lay underground lines before or during foundation preparation.
As an example only, Next Modular’s Walnut Forest Ranch estimate puts $58,782 into the ground and the connections: $25,082 for the crawl space, $8,500 for water, $12,000 for septic, $7,000 for drain lines under the home, and $6,200 for electric service. That is 44% of the $132,460 home-only price.
What the Line Items Say
Most makers publish the foundation type and leave out its price. Only Next Modular prices the foundation itself. Abodu and Deltec fold it into a larger figure, and the other 4 makers in the table publish no price.
Avrame and Deltec accept different foundations. Avrame cannot use a slab, and a slab is the base assumption in Deltec’s price.
The soil test decides the septic fee. The county site evaluation decides which system you can build, and the system sets the fee. Grand Traverse County charges $545 for a standard new septic permit and $1,625 for a new alternative treatment system.
Installed prices include a fixed amount of trenching. Abodu’s price covers 50 feet of trenching and 100 feet of crane reach, and charges for anything beyond.
Before You Order
3 checks before you pay a deposit.
- Price the ground. Run the lot through the site-prep cost estimator, and read the raw land guide if the parcel has no utilities yet.
- Get a soil test before you choose the foundation. The county septic site evaluation decides which system you can build, and its fee is published.
- Confirm the loan. Start with the lender locator. Ask whether the lender finances the foundation and site work with the unit.
For finished units, see the 8 best prefab cabins, rated, and for a resort built from small units, the tiny home resort playbook. For related comparisons, see the cost of prefab homes and turnkey prefab vs kit.
Host Camp is not a licensed tax, legal, or financial adviser. Confirm figures for your situation with a professional.
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