Specified compressive strength, the design strength on the drawings, referenced at the specified age and given in psi or MPaIn: Strength cylinders and acceptance
f prime cr
Required average strength, the higher target the mix is proportioned to so the acceptance statistics pass, set from f prime c and the producer's variabilityIn: Strength cylinders and acceptance
F rating / T rating
Hours the firestop holds flame back, and hours before the unexposed side rises about 325°FIn: Pipe penetration firestop guide
Time a firestop holds back flame on the unexposed side, per ASTM E814 / UL 1479; must match the barrier ratingIn: Cabling pathways and firestop
f100
Friction loss in feet per 100 ft of pipe at the design gpm, read from a friction chart for the pipe size and materialIn: Sump and sewage ejector sizing guide
FAA marking / lighting
Obstruction paint and beacons such as the L-864 required above the trigger height per FAA AC 70/7460-1In: Cell tower and antenna install
FAA Part 107
The US federal rule for commercial small drone operation, requiring a remote pilot certificate, a registered aircraft, and compliance with the airspace and operating rules.In: Drone inspection field guide
Fabric validation
Link-by-link confirmation that the high-speed network is up at rated speed with error counters inside thresholdIn: AI cluster commissioning
Face plate
The front of a water closet carrier the bowl seals and bolts to, usually adjustable up and down to set the fixture heightIn: Fixture carriers and supports guide
Face velocity
The inward air speed across the hood opening, in fpm, commonly near 100, the working proxy for captureIn: Lab fume hood exhaust guide
Face weight
The weight of the fiber alone per square yard in ounces, a proxy for density and durabilityIn: Artificial turf installation
Face-frame
Construction with a solid wood frame on the front of the box; stiffens the box and gives material to scribe at the wallIn: Millwork and casework install
Face-lit vs halo
Face-lit glows through a translucent acrylic face; halo (reverse-lit) is solid-faced with rear LEDs that glow on the wallIn: Electric sign installation
Face-shell bedding
Mortar on the outer face shells only; full bedding adds mortar on the webs where the cell is groutedIn: CMU block wall construction
Fail-safe unlocks on power loss; fail-secure stays locked on power loss. The choice is a per-door life-safety and security decisionIn: Access control system field guide
Failover / failback
Switching production to the recovery site, and returning it to the primary after recoveryIn: Data center disaster recovery
Fall clearance
The total room needed below the anchor to arrest a fall before the worker hits a lower levelIn: Roof fall protection
A signal with no real intrusion; enhanced call verification places at least two calls to different numbers before a dispatch is requestedIn: Intrusion alarm field guide
The ratios linking fan or pump speed to airflow, pressure, and powerIn: Fan laws field guide
FAR / FRR
False accept rate and false reject rate, the biometric tradeoff between letting the wrong person in and locking the right one outIn: Data center physical security field guide
Fascia
The vertical board at the roof edge closing the rafter tails and carrying the gutterIn: Fascia, soffit, and eave trim
FAST diagram
Function Analysis System Technique, a how-and-why map of a project's functions used to find high-cost, low-value functionsIn: Value engineering field guide
Fast-track
Overlapping design, permit, procurement, and construction to compress the schedule to the lease dateIn: Tenant improvement fit-out
Fastener upsize
Replacing a wallowed screw with the next larger diameter and a fresh gasketed washer so it bites fresh metalIn: Metal roof restoration
Running a crew at the point of work: the daily planning, make-ready, safety, productivity, schedule, and people decisions that turn an estimate into installed workIn: Field leadership and the foreman role
Field measure
The as-built dimensions taken on site after the walls are up, that the shop builds to instead of the planIn: Millwork and casework install
Field of view (FOV)
The angle and width of the scene the lens captures; set by focal length, and it determines the ppf at a given distanceIn: CCTV system design field guide
Field service management (FSM)
Software built for businesses that dispatch crews to properties, combining CRM with scheduling, jobs, and invoicingIn: Customer database and CRM
A test cylinder cured beside the structure under the same conditions, used to read in-place strength, not for design acceptanceIn: Cold weather concreting
Figure of merit
A score comparing delivered cooling to the ideal for a perfectly stratified tankIn: Thermal energy storage tank
Sum of cable cross-sectional areas divided by the usable tray area, times 100, against the 392.22 limitIn: Cable tray fill and copper takeoff
Fill valve / PRV
The pressure reducing valve that drops building water to loop fill pressure and feeds make-up only when the loop drops below its setpointIn: Hydronic water and glycol field guide
Filled weight
The dead load of the pipe plus its contents plus insulation, in pounds per foot, that the support is sized to carryIn: Pipe hangers and seismic bracing guide
Filling ability
The mix flowing out and filling the form under its own weight, read on the slump flowIn: Self-consolidating concrete
Film-forming coating
A topical sealer or coating that sits on the surface as a layer, giving sheen and a barrier but able to peelIn: Concrete sealers and coatings
Film-tearing bond (FTB)
The weld acceptance where a peeled sample tears the membrane before the seam opensIn: Single-ply seam QA
Filter drier
A desiccant-filled component that catches the trace moisture left after a proper vacuum; a backup, not a substituteIn: Refrigerant evacuation field guide
Filter fabric / geotextile
A non-woven fabric that separates soil from drainage gravel, passing water while holding back the finesIn: Hardscape drainage
Filter integrity test
In-place DOP or PAO aerosol scan of an installed filter for leaks in media, frame, and sealIn: Cleanroom HVAC field guide
Letting water pass across the fabric while holding soil particles in place, balancing flow against retention.In: Geotextile separation fabric
Final completion
The milestone where the punch is closed, all closeout documents are in, and final payment with remaining retention is releasedIn: Punch list and closeout
Final test
The test after fixtures are set, proving the finished DWV system gastight, including the smoke and peppermint methodsIn: Plumbing pressure test guide
An open ring or bowl, versus a masonry firebox with a chimney that drafts smoke upIn: Outdoor fire feature guide
Fire prevention program manager (FPPM)
The boots-on-the-ground person required by NFPA 241 to run the construction fire prevention programIn: Fire watch and impairment
Fire pump
A listed stationary pump built to NFPA 20 that boosts water pressure and flow for fire protection, idle until a fire demand calls itIn: Fire pump and standpipe guide
Fire sprinkler system
A network of pipe and heat-activated sprinklers that delivers water to a fire; heads open individually over the fireIn: Fire sprinkler system design guide
A complete tested system, board type and layers, framing, fasteners, and firestop, that carries a fire-resistance rating only when built exactly as testedIn: Drywall and gypsum board finishing
Fire-rated joint
A tested joint system, commonly to UL 2079, that keeps a fire barrier rated while the joint movesIn: Building movement joint systems
Fire-resistance rating
The hours an assembly was proven to resist a standard fire test, set by the building code by type and memberIn: Structural fireproofing
Fire-retardant treatment / WUI
Pressure-impregnated chemicals that raise the fire class; the wildland-urban interface where wood roofs are often restricted or bannedIn: Wood shake and shingle roofing
Firefighters' emergency operation
Phase I automatically recalls the cars to a designated floor on a fire alarm; Phase II gives a firefighter manual control of a carIn: Elevator modernization and maintenance
A tested, listed assembly of barrier, penetrant, and materials that restores a fire rating, identified by a directory system numberIn: Cabling pathways and firestop
First cost
The initial cost to build the pavement, usually per square yard, before any maintenanceIn: Asphalt vs concrete pavement
First draw
A sample taken after water has sat in the plumbing for hours, showing worst-case lead contactIn: Lead service line guide
First number
Configuration code for voltage, poles, and wires; 5 is 125V, 6 is 250V, 10 is 125/250V ungrounded, 14 is 125/250V groundedIn: Receptacle types and NEMA configs
The table current from NEC 430.250 or 430.248 by horsepower and voltage; sizes the conductor and the branch deviceIn: Motor circuit sizing, NEC 430
Fleet safety program
The written policy and daily practices a company uses to prevent crashes by its drivers and vehicles, distinct from DOT regulatory complianceIn: Fleet and driver safety program
Flex duct
Insulated flexible duct: a wire helix and liner inside insulation and a vapor jacketIn: Ductwork types field guide
Flex tech / flex capacity
A truck or slot held open to absorb same-day and emergency work without breaking the booked boardIn: Service dispatch and scheduling
Flexible connector
A bellows or braided pipe section at the suction and discharge that absorbs movement and keeps pipe strain off the pump flangesIn: Hydronic pump install field guide
Flexible coupling
The element joining the pump and motor shafts; it absorbs a small residual, not a real misalignmentIn: Hydronic pump install field guide
Flexible pavement
Asphalt pavement, which bends and spreads load down through its layers to the subgradeIn: Asphalt vs concrete pavement
Flexure wood (thigmomorphogenesis)
Extra wood a tree grows in response to wind flexing and load, building trunk strength and taper; distinct from reaction wood, which forms in response to a lean.In: Tree staking and guying
Float
Opens and levels the surface, bringing the cream up; magnesium opens, wood pulls pasteIn: Flatwork finishing sequence
Removing drywall a set height above the water line, commonly 12 to 24 inches, so the cavity can dry or be decontaminatedIn: Water damage restoration field guide
Flood level rim
The top edge of a fixture where it would overflow; stack AAV height is referenced to the highest fixture's rimIn: AAV and island vent guide
Flood rim
The level at which a fixture overflows, the reference for which fixtures are at risk in a backupIn: Backwater valve field guide
Liquid returning while running, or liquid in the compression chamber, usually on a flooded startIn: HVAC compressor types
Flooded suction
An arrangement where water sits above the pump and feeds it by gravity, giving positive static head and the most NPSHaIn: Pump cavitation and NPSH field guide
Floor sink
A deep, cleanable receptor set flush with the floor with a removable grate, built to take indirect wasteIn: Indirect waste and air gap guide
Floor surface temperature
The temperature of the finished floor surface, held to about 80 to 85°F for comfort, which caps outputIn: Radiant floor heating design
Flow center
The circulator pump package that moves loop fluid at the design gpm against the loop pressure lossIn: Geothermal heat pump field guide
The multi-point averaging sensor at the box inlet that reads total and static pressure to derive velocity pressureIn: VAV box commissioning field guide
Flow sensor
A mainline meter that lets the controller detect abnormal flow and shut off through the master valve on a breakIn: Smart irrigation field guide
Flow station
A permanent venturi or orifice with a calibrated pressure-drop-to-flow curve, used where a balancing valve is not in the lineIn: Hydronic balancing field guide
Flow-down
A clause making the sub responsible to the GC for the same obligations the GC owes the owner under the prime contractIn: Subcontractor management
Temperature at which flue gas water vapor condenses, roughly 130 to 140 degrees F on natural gas; return must be below it to condenseIn: Boiler startup commissioning
Fluid service category
The B31.3 classification (Category D, Normal, Category M, high pressure) that sets construction and examination rigorIn: Industrial process piping
Fluid trap / knockout
Vessel ahead of the pump that drops liquid out of the airstream before it reaches the machineIn: Lab and process vacuum systems
A valve flushing a closet directly in a short high-flow burst versus a slow-filling tank; the two read different demand lines and need different residual pressureIn: Water supply pipe sizing guide
Flute / rib
The corrugation in a steel deck; you fasten into the top flute, not the open valleyIn: Roof deck substrate types
A light spray of diluted asphalt emulsion on existing pavement to seal the surface, bind raveling, and slow oxidationIn: Fog seal and rejuvenator preservation
Fogging
A fine mist held above the slab to raise local humidity and cool the air, slowing surface evaporationIn: Hot weather concreting
Foot valve
A one-way check and screen at the bottom of a suction line that holds prime and keeps debris outIn: Pump station sizing
T&M work tracked on a daily ticket signed by the owner's representative the day it happens; the signed ticket is the claimIn: Field change order takeoff
The person who leads one crew at the point of work and links the field to the office; closest leader to the toolsIn: Field leadership and the foreman role
Form
A manufacturer designation, such as Form 7 or Form 8, for the body and cover style; bodies and covers must share the form to seatIn: Conduit bodies and fittings
Form face / sheathing
The surface the concrete sets against, which decides the finish: plywood, overlaid plywood (MDO/HDO), steel, plastic, or a lined faceIn: Formwork types and systems
A threaded coupler mounted at the form face so a dowel can be threaded in for the next pourIn: Mechanical splices and couplers
Formicary corrosion
Ant-nest corrosion that bores through copper tube from the inside out, driven by organic acids from off-gassing materialsIn: HVAC coil cleaning and maintenance guide
Formwork
The whole system that supports fresh concrete: the mold plus shores, reshores, bracing, and hardwareIn: Formwork, shoring, and reshoring
Formwork (shuttering)
The temporary mold and framing that shapes fresh concrete and holds it until it sets; shuttering is the same thing in British usageIn: Formwork types and systems
Forward / reverse phase
Leading-edge (TRIAC, incandescent/MLV) and trailing-edge (ELV, LED/electronic) line-voltage dimmingIn: Lighting controls and dimming
Friction rate, the design pressure drop per 100 ft of duct, in inches of water column per 100 ftIn: Manual D duct design field guide
Fractionated RAP
RAP screened into size fractions so the designer can control gradation and binder contributionIn: Asphalt recycling and FDR
Frame
The NEMA dimension code fixing shaft height, shaft, and bolt patternIn: Motor nameplate reading
Frameless (32mm)
European construction with no face frame; hardware mounts to a 32 mm hole grid; more interior room, tighter install tolerancesIn: Millwork and casework install
Free chlorine is the sanitizer still available to kill, in ppm; ORP is the water's oxidizing power in mV, tracking kill speedIn: Pool and spa mechanical systems
Free chlorine residual
The active disinfecting chlorine left in the water, read in mg/L by a test kit; the figure the standards specifyIn: Potable water disinfection guide
Freeze protection keeps the fluid pumpable at the low temperature; burst protection only keeps it from splitting the pipe as slush, and needs far less glycolIn: Hydronic water and glycol field guide
Freeze-drying documents
Vacuum sublimation that turns ice to vapor so wet paper dries without swelling or runningIn: Contents pack-out and inventory
A low-temperature limit control with a capillary across the coil face that trips to protect a water or steam coil from freezingIn: HVAC coil cleaning and maintenance guide
Material that can be crumbled or powdered by hand pressure when dry, releasing fibers easily; the higher-hazard categoryIn: Asbestos abatement procedures
Friction rate
The design pressure drop per 100 ft of duct, ASP times 100 divided by TEL, in in. wg per 100 ftIn: Manual D duct design field guide
Pulverizing the full asphalt section and part of the base in place and stabilizing it into a new base courseIn: Asphalt recycling and FDR
Full-maintenance vs oil-and-grease
Full-maintenance bundles callbacks, repairs, parts, and testing into the monthly price; oil-and-grease covers only basic upkeep and bills repairs separatelyIn: Elevator modernization and maintenance
Full-port / standard-port
Bore equal to pipe inside diameter, versus a bore one size smaller that adds pressure dropIn: Plumbing valve types
Full-pour vs latex porous
Cast impermeable polyurethane that sheds water off, versus permeable latex that drains throughIn: Running track surfacing
Fully adhered
Membrane glued across the whole sheet with adhesive; generally the highest wind-uplift attachmentIn: TPO vs EPDM vs PVC
Fume hood
An enclosure that protects a worker by drawing air in across its opening and exhausting the contaminated air outside, the primary containment for chemical workIn: Lab fume hood exhaust guide
Function
What an element must do, stated as an active verb and a measurable noun, such as support load or resist waterIn: Value engineering field guide
Functional damage fractures the mat or harms the roof's function; cosmetic is surface marking only, often policy-excludedIn: Storm and hail damage restoration
Facility water system, the building primary loop, and technology cooling system, the clean secondary loop, separated by the CDU heat exchangerIn: Liquid cooling concurrent maintainability
fy / fu
Specified yield strength and specified tensile strength of the bar, the figures the splice classes are written againstIn: Mechanical splices and couplers