A post and pier foundation carries the house on points instead of a wall: concrete piers at intervals, posts rising to beams, floor framing bearing on the beams, with the crawl space open below. The design is legitimate, adaptable, and everywhere, older homes, slopes, coastal stilts, porches and additions, and its failure modes are correspondingly point-by-point: each pier, post, and connection is its own small foundation with its own inspection. This reference covers the anatomy and the circuit.
The anatomy, and where the trouble concentrates
Load flows down a chain, joists to beams to posts to piers to soil, and every link has a characteristic weakness. Piers: precast pads, poured columns, or masonry stacks, sized for bearing and, in cold climates, founded below frost, with the shallow versions subject to the frost-jacking heave that walks and tilts them seasonally; individual settlement, one pier easing into soft or washed soil while its neighbors hold, is the design’s signature movement, reading upstairs as a localized floor dip rather than the wall-wide patterns of continuous foundations. Posts: wood’s base is the wet zone, end grain on concrete wicking moisture, soil or debris piled against it, per the same fungal rules as the sill-rot reference, with untreated posts of older practice and posts buried in soil as the aggravated cases; steel posts trade rot for base-plate rust and the adjustable-column caveat that temporary jack posts are not permanent columns unless rated so. Connections: the era before hardware relied on toenails and gravity, and uplift, lateral, and seismic demands find those joints first, which is why modern practice ties post to pier and post to beam with steel connectors, and why an inspection counts hardware as carefully as rot.
The inspection circuit
Underneath with flashlight, probe, and a level, pier by pier: each pier, plumb or tilting, cracked or spalling, undermined by erosion or animal digging, soil washed or ponding around it (the drainage rules apply under the house too, and a downspout discharging toward the crawl space writes its signature in one pier’s settlement); each post, probed at the base for rot’s soft acceptance, sighted for plumb (a tilting post is redistributing load it was not asked to), checked for full bearing top and bottom, and its shims read honestly, tight steel or hardwood full-width shims being ordinary adjustment, stacked scraps and loose wedges being settlement’s improvised confession; each connection, actual hardware present versus toenails and hope; the beams, sighted along their length for sag between supports, crushing at bearings, and splices landing off-post; and the floor above, the localized dips, bouncy zones, and doors racking near one point that map which link moved. Coastal, flood-zone, and seismic contexts raise the connection stakes formally, bracing and tie-downs being engineered items there rather than upgrades.
Repairs, and the escalation line
The routine tiers: re-shimming at minor settlement, proper shims replacing improvisations after the cause (drainage, usually) is addressed; post replacement, the rotted base’s cure, temporary support carrying the beam while a treated or steel post with a real base connection takes over, with the post-on-pedestal detail, wood held above concrete and splash, correcting the original sin; pier re-support, re-founding or replacing settled and frost-jacked piers at proper depth and bearing, and adding piers where beam spans sag between too-few points; and hardware retrofits, connectors added through the chain, cheap insurance everywhere and required work in wind and seismic country. The escalation line is the category’s standard one: movement that continues after drainage correction, multiple links failing together, beams undersized for their spans, or any leveling project beyond shims buys an engineer’s assessment before a contractor’s jacks, since lifting a point-supported house redistributes loads in ways judgment should precede.
The bottom line
Point support means point failures: walk the circuit yearly, probe every post base, sight every pier and beam, count the hardware, and read stacked shims and floor dips as the settlement reports they are. Fix the water first, replace what rot has taken, tie the chain together with steel, and buy the engineer’s judgment before anyone starts lifting.