Mobile home piers, footings and tie-downs in Tennessee: what the rules require
Short answer: Tennessee requires a licensed installer to set up a manufactured home, following the home's own installation manual (or an engineer's sealed plan, or the federal standards in 24 CFR 3285). Most homes sag because the soil or the piers under them moved, so knowing what a correct pier, shim and anchor setup looks like helps you judge a relevel quote.
Last checked 2026-11-03. This page summarizes public rules with links to the text. It isn't engineering or legal advice. Your home's installation manual and your installer's license come first.
Which rules apply to your home
Tennessee's Manufactured Home Installation Act sets the order (T.C.A. § 68-126-403):
- New homes are installed to the manufacturer's installation instructions approved by its DAPIA (the third-party agency that approves the design). If the maker doesn't provide suitable instructions, the installer uses instructions sealed by a Tennessee-registered engineer that meet at least the federal installation standards in 24 CFR 3285.
- Used homes installed after July 1, 2003 follow the manufacturer's manual from when the home was built, or a Tennessee engineer's sealed instructions, or the national standard named in the law (ANSI A225.1, now replaced by the federal standards).
- Both must also meet FEMA rules if the site is in a flood zone.
- It's unlawful to occupy a manufactured home in Tennessee unless a state-licensed installer installed it, and unlawful to locate or relocate one without a licensed installer, apart from homes the law exempts or that were already installed and inspected under the rules in effect at the time.
If you still have your home's installation manual, it is the most specific rulebook for your home. The checklist below uses the federal Model Installation Standards because they are the floor every manual and engineer's plan has to meet.
Wind and roof-load zones in Tennessee
HUD's rules list, by county, the coastal areas in Wind Zones II and III. No Tennessee county is on those lists, so Tennessee homes fall in Wind Zone I, the base zone (24 CFR 3280.305). Your home's data plate, which HUD requires to be posted near the main electrical panel or another easy-to-reach spot (24 CFR 3280.5), shows the wind and roof-load zones it was built for, and the anchoring plan has to meet the loads on that plate (§ 3285.401).
Checklist: what a correct setup looks like
These are the federal minimums from 24 CFR 3285, the standard Tennessee law points back to. Your manual can be stricter, and an engineer can approve a different design.
| What to look at | What the standard says | Source |
|---|---|---|
| Clearance under the frame | At least 12 inches between the lowest part of the main frame (I-beam) and the ground, under the whole home. | § 3285.305 |
| Pier spacing under the main frame | Piers no more than 24 inches from each end of the frame and no more than 120 inches (10 ft) apart, center to center, unless an engineer's design or the manufacturer's manual says otherwise. | § 3285.310(c) |
| Concrete block piers | Load-bearing blocks at least 8 x 8 x 16 inches nominal, hollow cells vertical. Under 36 inches tall: single stack, long side across the I-beam. 36 to 67 inches tall (and corner piers over three blocks): double, interlocked blocks. Over 67 inches: must be engineer-designed. Mortar isn't required unless the manual or an engineer calls for it. | §§ 3285.304, 3285.306 |
| Pier caps | Solid concrete or masonry at least 4 inches thick, hardwood at least 2 inches nominal, or corrosion-protected steel at least 1/2 inch, the same length and width as the pier. | § 3285.304(b) |
| Shims | Nominal 4 x 6 x 1 inch shims, used in pairs and driven tight, taking up no more than 1 inch of height. Fill bigger gaps with hardwood plates no thicker than 2 inches nominal or 2- or 4-inch solid block, not a taller stack of shims. | § 3285.304(c) |
| Adjustable steel piers | Must be listed and labeled, installed to the pier maker's instructions, and sized so the adjustable riser sticks out no more than 2 inches. Metal piers need corrosion protection. | §§ 3285.304(d), 3285.308 |
| Footings | Every pier sits on a footing placed on undisturbed soil or compacted fill: 4-inch precast concrete pads, 6-inch poured concrete, layered pressure-treated wood, or listed ABS pads. Footings must be below the frost line unless an engineer designs a frost-protected alternative. | § 3285.312 |
| Perimeter and door supports | Piers on both sides of exterior doors and other side-wall openings 48 inches or wider, and under load-bearing porch posts and factory fireplaces. On double-wides, piers along the marriage line as the manual shows, including both sides of mate-line openings 48 inches or wider. | §§ 3285.310, 3285.311 |
| Drainage | Ground graded to slope away from the home at least 1/2 inch per foot for the first 10 feet, or drains or swales to carry water away. | § 3285.203 |
| Vapor retarder | The whole area under the home covered with a vapor retarder (except under open porches, decks and recessed entries), joints overlapped at least 12 inches. | § 3285.204 |
| Tie-down straps | Steel strapping at least 1-1/4 x 0.035 inch (ASTM D3953), rated at least 4,725 lb ultimate and 3,150 lb working capacity, with corrosion protection. | § 3285.402(c)(2) |
| Ground anchors | Listed or certified for the soil class at your site and installed to their full depth. In frost-susceptible soil, augers go below the frost line. Any sidewall, over-the-roof or mate-line straps on the home must be connected to an anchor. | §§ 3285.402(c)(1), 3285.403, 3285.404 |
| Anchoring products sold in Tennessee | Tennessee's rule requires anchoring systems used under the Installation Act to be approved by the Commissioner, with test data showing each ground anchor withstands at least 4,725 lb. | Rule 0780-02-05-.03 |
What usually goes wrong, and what to ask for in a relevel
- Too many shims. The standard caps paired shims at 1 inch of height. A stack of loose shims or wood scraps on top of a pier is a sign the pier should have been rebuilt or capped properly (§ 3285.304(c)).
- Piers on bare dirt or broken pads. Every pier needs a footing on undisturbed or compacted soil. Piers sitting on topsoil, grass or a cracked pad tend to sink again (§ 3285.312, § 3285.201).
- Water under the home. The site must drain away from the home at 1/2 inch per foot for the first 10 feet, or have drains or swales. If water pools under the home, a relevel alone won't last (§ 3285.203).
- Gaps in pier spacing. Main-frame piers can be no more than 10 feet apart and within 2 feet of each end, plus piers at wide doors and openings (§§ 3285.310–311).
- Loose or disconnected straps. After leveling, straps should be re-tensioned and every strap on the home connected to a listed anchor (§§ 3285.402–403).
When you get quotes, ask each company to put in writing whether it will check every pier, replace cracked blocks and failed shims, add missing piers, and re-tension or replace anchors and straps. Ask for its Tennessee installer license number too; see how to check a license and the cost guide. Then find a company in your area in the directory.
Own a tiny home, park model RV, modular or shipping container home instead? See tiny home foundations and tie-downs in Tennessee.
Frost depth
Footings and ground anchor augers have to sit below the frost line unless an engineer designs a frost-protected foundation. When the local building department (the "LAHJ") doesn't publish a frost depth, the federal rule says to get one from a registered engineer, architect or geologist (§ 3285.312(b), § 3285.404). Frost depth varies across Tennessee, so ask your county building office or your installer what they use.
Sources
- T.C.A. § 68-126-403 (installation criteria and standards)
- Tenn. Comp. R. & Regs. 0780-02-05 (installation of manufactured homes; approval of anchoring systems)
- 24 CFR 3285 Subpart C: site preparation (soil, drainage, vapor retarder)
- 24 CFR 3285 Subpart D: foundations (piers, caps, shims, footings)
- 24 CFR 3285 Subpart E: anchorage against wind
- 24 CFR 3280.305: wind zone and roof load zone maps and county lists