Mobile Home Piers and Anchors Explained

Piers hold a manufactured home up. Anchors hold it down. Piers are the columns that carry the home's weight from the steel frame to the ground, and anchors are steel devices driven into the soil and connected to the frame with straps to resist wind uplift and sideways movement. They are separate systems solving opposite problems, and a home needs both working.

The pier system: carrying weight

How the load travels

Start at the roof and work down. Roof, walls, floor, contents, and people all load into the floor system, which loads into the two steel I beams that run the length of the chassis. Those beams do not rest on a continuous foundation. They rest on individual piers spaced along their length, and each pier passes its share of the load into a footing pad that bears on soil.

Everything about how manufactured homes behave follows from that. The load is concentrated at points rather than spread out, so the ground under each pad works much harder than the ground under a slab. When one pad gives, one part of the frame goes down, and the rigid box above it distorts.

Types of piers

The most common configuration is dry stacked concrete block on a poured or precast pad, capped and shimmed with wood to make final contact with the beam. Dry stacked means no mortar, which is intentional: it lets the column be dismantled and reset during future leveling. Taller columns are typically double stacked and interlocked for stability.

Adjustable steel piers are also used, especially on newer or heavier installations and on sites with grade changes. Their advantage is that height can be fine tuned later with a screw adjustment rather than by dismantling block. Poured concrete piers appear on permanent foundation installations, which are less common in this area's rental and owner placed housing but do exist.

Where the pads matter more than the piers

A footing pad's job is to spread a concentrated column load over enough soil area that the soil can carry it. Pad size should be matched to both the load and the soil's bearing capacity. On the heavy clays common through Liberty County, and especially on recently placed fill, undersized pads are a frequent root cause of early settlement. Increasing pad area is one of the most effective corrections a contractor can make during a repair.

The anchor system: holding down

What wind actually does

People imagine wind pushing a home over. What mostly happens is uplift. Air moving fast over a roof surface reduces pressure above it while pressure inside the home stays higher, and the net effect pulls the structure up. Combine that with lateral pressure on the long side of a home, which presents a very large flat surface, and you get forces that piers cannot resist. Piers are excellent in straight compression and nearly useless against uplift or sliding, because the home is simply sitting on them.

How an anchor works

An anchor is a steel shaft with a helix or plate at the bottom, augered or driven into the ground next to or under the home. A strap runs from the anchor head to the steel frame, tensioned with a buckle or turnbuckle. When wind loads the home, the strap goes into tension and the anchor tries to pull out. It resists because pulling it out would require lifting the mass of soil engaged above the helix.

That last point is the key to understanding anchors: their strength lives in the soil, not in the steel. The same anchor performs differently in dense clay, in loose fill, and in saturated ground. It is why anchor requirements vary by soil class, and why anchors set into freshly placed fill can lose capacity as that fill consolidates.

Frame ties and over the top ties

Frame ties connect the strap directly to the chassis and are standard on modern homes. Over the top ties pass across the roof and down the other side, and are found on older homes, typically single wides. Some installations use both. Over the top straps need attention at the roof edge, where they abrade the roofing and where corrosion tends to start.

What fails first, and why

Shims and pier caps

The most common failure in the whole support system is the smallest component: the wood shim pack at the top of the pier. It sits in a humid crawlspace, absorbs moisture, compresses, and eventually rots. Once contact is lost, that pier carries nothing and its neighbors take the load. Shims fail long before block does.

Footing pads

Next is the pad, and specifically the ground under it. Clay softens when saturated, shrinks when dry, and fill continues to consolidate. Pads sink and tip. This is the failure driving most of the releveling work in this region.

Block columns

Block usually fails as a consequence rather than a cause. Once a pad tips, the column is out of plumb and the load runs down one edge instead of through the center. Concrete block is strong loaded straight down and weak loaded off center, so it cracks, spalls, and in bad cases crushes at a corner.

Straps and anchor hardware

On the anchoring side, the usual first failure is tension. Straps go slack, either because the home settled and changed the geometry or because the soil around the anchor consolidated and the anchor rose slightly. Corrosion at the buckle and fraying at the frame contact point come next. Actual anchor pullout is rare outside of a major wind event or very poor soil.

Why the two systems interact

Leveling a home changes anchor tension, because raising the frame changes the distance and angle between the anchor head and the frame connection. That is why anchors should always be inspected as part of a leveling job. Working the other direction, a home that shifts during a wind event puts new load paths into the piers and can loosen shims. Neither system should be evaluated in isolation.

What a homeowner can reasonably check

From the crawlspace access opening, with a flashlight and without crawling into a wet or tight space, you can usually see whether columns are leaning, whether block is cracked, whether there is a visible gap under any beam, whether pads have tipped, and whether water is standing. From outside, you can look at anchor heads for any that have risen out of the ground, and press on visible straps to feel whether they are firm or slack.

Anything beyond that observation belongs with a contractor who works on manufactured homes. Jacking a home is not a homeowner task: lifting too fast or at the wrong points puts the load into drywall and glass instead of into the steel frame, and the damage from a bad lift costs more than the repair that was needed in the first place.