Glossary
The words that turn up in a foundation quote.
Some of these are geology, some are structural engineering, and several are specific to this county. All of them are worth understanding before you read a quote, because the terms are where the cost lives.
- Bearing capacity
- How much load a given soil can carry per unit area without failing or consolidating excessively. When a foundation problem is described as a soil problem, this is usually the quantity that has been exceeded.
- Bearing strata
- The layer of soil or rock competent enough to carry the building load. Underpinning works by reaching past the failing near-surface soil to this layer. Around Tallahassee its depth varies sharply with which side of the Cody Scarp you are on.
- Carbon fibre stitching
- Strips of high-tensile carbon fabric bonded across a crack in a foundation wall to resist further lateral movement. Used where the wall needs restraint rather than the crack needing structural bonding.
- Catastrophic ground cover collapse
- A defined term in Florida insurance law describing a specific set of conditions involving abrupt ground collapse and structural damage. It is a narrower category than sinkhole loss and the two carry different coverage.
- Cody Scarp
- A relict shoreline escarpment left by Pleistocene sea levels, running east to west and most prominent in Leon County. It separates the Northern Highlands from the Gulf Coastal Lowlands, with a crest around 125 to 190 feet above sea level and a toe at 40 to 50 feet.
- Consolidation
- The gradual reduction in volume of a soil under sustained load as water is squeezed out of the pore spaces. It is a normal process, and it is why new houses settle uniformly in their first few years.
- Crawl space encapsulation
- Sealing a crawl space from outside air and ground moisture with a heavy sealed liner over the soil, sealed vents, and usually controlled humidity. In a humid climate this is preventive structural work, because the alternative eventually costs you joist ends.
- DBPR
- The Florida Department of Business and Professional Regulation, which licenses construction contractors under Chapter 489 of the Florida Statutes and maintains the public licence lookup.
- Desiccation
- Drying of soil, and the shrinkage that comes with it. In clay-bearing soil, desiccation under a tree root zone or during a dry autumn reduces soil volume and can allow a foundation above it to drop.
- Differential settlement
- Settlement that varies across a structure, so one part goes down relative to another. This is the mechanism that causes damage. Uniform settlement, where the whole house goes down together, is largely harmless.
- Elevation survey
- A set of floor height measurements taken across the whole floor plate, usually with a laser or manometer, producing a contour map of the floor. It is the single most useful diagnostic step and it is the thing a serious assessment starts with.
- Epoxy injection
- Low-pressure injection of structural epoxy into a crack in poured concrete, restoring the section to monolithic strength. Appropriate only where the movement has stopped; injecting an active crack relocates it.
- Floridan aquifer
- The major regional aquifer underlying Florida and parts of neighbouring states. The Red Hills north of Tallahassee are a recharge zone for it, and Lake Jackson has periodically drained straight into it through sinkholes.
- French drain
- A gravel-filled trench containing a perforated pipe, used to intercept subsurface or surface water and carry it away from a structure. Named after Henry French, who wrote about the technique in the nineteenth century, not after France.
- Frost line
- The depth to which soil freezes in a given climate, which sets minimum footing depth in cold regions. It is essentially not a design factor in North Florida, which is why footings here are shallow compared with northern states.
- Grade
- The level and slope of the ground surface. Positive grade falls away from a building, negative grade falls toward it. Common guidance is around six inches of fall over the first ten feet, and a great many older lots have lost it under decades of added landscaping.
- Heave
- Upward movement of a foundation, the opposite of settlement. Caused by soil taking on moisture and expanding, or by a long-dried root zone rebounding after a large tree is removed. Frequently misread as settlement of the areas around it.
- Helical pier
- A steel shaft with helical bearing plates welded to it, screwed into the ground to a target installation torque that correlates with load capacity. Suits lighter structures, additions, and porches where a push pier would have insufficient reaction mass.
- Karst
- Landscape formed by the dissolution of soluble rock, typically limestone, producing sinkholes, springs, swallets, and cave systems. The Woodville Karst Plain south of Tallahassee is a textbook example.
- Monolithic slab
- A concrete slab poured in one operation with its thickened perimeter footing integral to it. The dominant residential foundation type in Tallahassee from the 1960s onward.
- Mudjacking
- Lifting a settled slab by pumping a cement-based slurry beneath it through drilled holes. Cheaper per volume than polyurethane foam, heavier, slower to cure, and it leaves larger visible patches.
- Pier and beam
- A raised foundation type where the floor structure spans on wood girders between masonry or concrete piers, with a crawl space beneath. Standard construction in Tallahassee before slab-on-grade took over, and still common in the older neighbourhoods.
- Polyurethane foam injection
- Lifting a settled slab by injecting expanding structural polymer through small ports. Light, cures in minutes, unaffected by water, and the current default method for residential concrete leveling.
- Push pier
- A steel tube hydraulically driven to refusal beneath a footing, using the weight of the structure as the reaction mass. Well suited to heavier buildings; less so to light structures that would simply lift.
- Refusal
- The point at which a pier will advance no further under the available driving force, taken to indicate it has reached competent bearing. In karst ground, refusal depths can vary sharply between piers only a few feet apart because the rock surface is irregular.
- Shrink-swell potential
- A soil's tendency to change volume as its moisture content changes, driven mainly by clay mineralogy and clay content. Red Hills soils carry enough clay to move measurably over years; they are not comparable to the true expansive clays of Texas or Oklahoma.
- Sill plate
- The horizontal timber sitting on top of a foundation wall or pier, which the floor structure bears on. Because it sits directly on masonry that stays damp, it is one of the first components to decay in a wet crawl space.
- Sistering
- Fastening a new structural member alongside an existing damaged or undersized one so the pair share the load. The standard repair for a sagging or split floor joist in a raised foundation.
- Stair-step crack
- Diagonal cracking that follows the mortar joints of a block or brick wall, because mortar is the weakest path through the assembly. It indicates that one end of the wall has moved relative to the other, and the width taper shows which end.
- Underpinning
- Extending a foundation down to a deeper, more competent bearing layer, usually with steel piers. This is what most people mean when they say foundation repair, though it is only one of several possible answers.
- Vapour barrier
- A sealed sheet, typically reinforced polyethylene, laid over crawl space soil to stop ground moisture evaporating into the space above. The cheapest structural intervention available on a raised house.
- Woodville Karst Plain
- The geomorphic province running from the Cody Scarp south to the Gulf across parts of Leon, Wakulla, Jefferson, and Franklin counties. Thin sandy soil over Suwannee limestone, averaging around twenty feet elevation, with sinkholes, swallets, and springs throughout.
Where these come up
Most of them appear in the main guide, the pier systems guide, and the Red Hills clay guide, each in context.
Find out what is moving under your house
Someone comes out, takes the elevations, walks the drainage, and writes you a price. Ring (850) 391-4290 or send the details through the form.