Tempered or laminated glass meeting an impact standard, required by code in locations like doors, sidelites, low glass, and wet areasIn: Glass replacement and glazing repair
Safety loop vs exit loop
A safety loop holds or reverses the gate over a vehicle; an exit loop opens the gate for a leaving vehicleIn: Automatic gate operator field guide
Safety relief valve
The ASME valve downstream of the PRV that opens to protect the low side if the PRV fails openIn: Steam PRV station field guide
Safety film retains fragments to protect people; security film delays forced entry, storm, and blast and needs anchoringIn: Commercial window film
Safety wearable
A sensor worn on the worker that detects a hazard and alarms for help; it detects and alerts, it does not prevent the hazardIn: Wearable safety technology field guide
A fall onto the surface the worker is standing on, distinct from a fall to a lower levelIn: Jobsite housekeeping
Sampling hole / capillary
The drilled opening that draws the air sample, or a tube dropped off the pipe to place a sampling point exactly where smoke will beIn: Aspirating smoke detection
Sand, cartridge, DE
The three filter media: sand (coarsest, backwashed), cartridge (mid, rinsed), DE (finest, backwashed and recharged)In: Pool and spa mechanical systems
Sand/oil interceptor
Garage device that settles sand and sediment and separates petroleum oil from floor-drain wastewaterIn: Oil/water separator field guide
Sanitization (Clear / Purge / Destroy)
The NIST 800-88 levels of removing data so it cannot be recovered, from overwrite to physical destructionIn: Data center decommissioning
Weight of the assembly with media at maximum water holding capacity, the number the structural engineer checksIn: Green roof installation
Saturated steam
Steam at the temperature that matches its pressure; raise the pressure and the temperature rises with itIn: Steam trap commissioning field guide
Saturated weight
The fully wet dead load of frame, media, plants, and water that the structure and attachment must carryIn: Living wall and green wall systems
Saturation
The boiling or condensing state; saturation temperature is read from the refrigerant P-T chart at a measured pressureIn: Refrigerant charging field guide
The six-phase study sequence from SAVE International: Information, Function Analysis, Creative, Evaluation, Development, PresentationIn: Value engineering field guide
Saw-and-seal / cutback joint
Sawing a groove on the joint line after paving and sealing it, so the crack forms and stays sealed at a controlled lineIn: Asphalt paving joints and handwork
Sawcut depth
The depth of the joint cut, commonly a quarter of the slab thicknessIn: Control joint layout
A dimple is the shallow set of a correctly driven screw below the paper; a pop is a fastener telegraphing through the finish, usually from a broken-paper or loose screwIn: Drywall and gypsum board finishing
Screw jack
An adjustable base that levels each leg so the scaffold stands plumb on uneven gradeIn: Supported scaffold safety
Scribe rail / filler
The oversized or sacrificial piece left long on the wall side specifically to be cut to fitIn: Millwork and casework install
Scribing
Transferring a wall or floor profile onto the cabinet and cutting to it so the gap closesIn: Millwork and casework install
A non-penetrating bracket that grips a standing seam with set screws, adding no holes to the panelIn: Snow guards and retention
Seam probe
A non-destructive test drawing a blunt tool along a cooled weld to find voids and cold weldsIn: Single-ply seam QA
Seasonal adjust
A controller percentage that scales every zone up or down as plant demand changes through the yearIn: Irrigation audit field guide
Seasonal adjust / water budget
A controller percentage that scales every run time up or down as plant demand changes through the yearIn: Irrigation controller programming
Seasonal color
The planting and rotating of annual flowers in high-visibility beds and containers several times a year for continuous, fresh bloomIn: Seasonal color and annual rotation
Seasonal cutoff
The agency date after which surface paving stops or requires special approval, set by climate and specIn: Cold-weather asphalt paving
Secant / tangent pile wall
A wall of overlapping (secant) or touching (tangent) drilled concrete piles, stiff and low-vibration, and watertight when secant.In: Excavation shoring field guide
The independent backup, inlet set about 2 in above the low point, for a blocked or overwhelmed primaryIn: Roof drainage and drain sizing
Secondary / overflow piping
The independent storm piping for the overflow drains or scuppers, separate from the primary and discharging above gradeIn: Interior storm drainage piping sizing
A second wall around tank and piping, with a monitored interstitial space between the walls that holds a primary leakIn: Fuel storage tank field guide
Secondary FLA
Rated current on the secondary side, off the secondary voltage, sizes the secondary conductors and panelIn: Dry-type transformer guide
Secondary injection
Injecting simulated current into a relay or trip unit's inputs to confirm it picks up and times out at its setting, without energizing the primary systemIn: Coordination study field guide
Secondary overflow
Independent emergency drainage set above the detention depth, sized for the design storm if the restrictor clogsIn: Blue roof controlled-flow drainage
Sediment
Mineral and scale that settles on the tank bottom and insulates the heat sourceIn: Water heater maintenance
Sediment basin
A built pond sized by drainage area that holds runoff and dewaters slowly so dirt settles out before dischargeIn: Erosion control and SWPPP
Sediment control
Measures that capture soil already moving, such as silt fence, inlet protection, and sediment basinsIn: Erosion control and SWPPP
The mix staying uniform while and after it flows, read on the VSI and settlement testsIn: Self-consolidating concrete
Seismic / isolation joint
A wide separation between building sections so they can sway independently in an earthquake without poundingIn: Building movement joint systems
Seismic anchorage / Ip
The restraint tying equipment to the structure; Ip is the component importance factor, commonly 1.5 for essential facilitiesIn: Structural design for AI racks
Seismic bracing / compression post / splay wire
The lateral restraint for a code seismic ceiling: a post resisting upward push and splay wires resisting sideways swayIn: Suspended acoustical ceiling field guide
Seismic hook
A 135-degree hook with a 6db extension, but not less than 3 in, anchoring a tie around a longitudinal barIn: Rebar detailing and the BBS
Seismic joint
An expansion joint sized for the large, multidirectional movement of a seismic event, rated to the structural engineer's designIn: Roof expansion joint installation
Removing specific parts of a building, usually the interior and finishes, while the structure stays standing. Also called interior strip-out.In: Building demolition planning
Self-adhered membrane
Peel-and-stick rubberized asphalt or butyl sheet that is waterproof and seals around fasteners, the ice and water shieldIn: Roofing underlayment types
The thin semiconducting layer over the conductor and over the insulation that smooths the field and sets the equal-stress conditionIn: MV cable termination and testing
Semiconducting shield (semicon)
The conductive-but-not-metallic layers over the conductor and over the insulation that keep the field uniform; the insulation shield must be removed cleanly at an endIn: MV termination and splicing
The heat that changes a fluid's temperature; how single-phase cooling carries its loadIn: Two-phase cooling
Sensible heat ratio
The fraction of a cooling load that is temperature versus moisture, which sets how the DOAS and parallel system split the workIn: DOAS field guide
Sensible heat ratio (SHR)
Sensible cooling divided by total cooling; the slope of the coil process lineIn: Psychrometric chart
Sensible load
The temperature load, the heat that changes air temperature without changing its moisture contentIn: DOAS field guide
Sensible vs latent
Sensible cooling lowers air temperature; latent cooling removes moisture. Beams do sensible; the DOAS does latentIn: Chilled beam commissioning
Sensing cable
Leak detection rope that detects water anywhere along its length and, on addressable systems, reports the distance to the leakIn: Leak detection commissioning
Sensor drift
A sensor slowly reading off true, so the controller holds the wrong condition and the analytics decide on bad dataIn: FDD and building analytics field guide
Sensor grade / calibration / drift
Grade is the accuracy class from consumer to reference; calibration corrects the reading to a known value; drift is the gradual error a sensor develops as it agesIn: IAQ monitoring and sensors field guide
Sentinel flush
An automatic timed flush on a sensor valve that keeps the trap seal from drying out when a fixture sits unused.In: Flushometer flush valve types
A power source with no direct electrical connection, including through the neutral, to another supply; gets its own neutral-ground bond and electrodeIn: Generator grounding and bonding
Separation
Keeping two dissimilar layers, the clean aggregate and the fine subgrade, from mixing under load.In: Geotextile separation fabric
Separator
A device upstream of the PRV that removes entrained water so the valve gets dry steamIn: Steam PRV station field guide
Septic system
Onsite wastewater system that treats sewage on the property where there is no public sewer, using a tank and a soil drainfieldIn: Septic system field guide
Septic tank, scum, sludge
Buried watertight tank that settles solids (sludge, on the bottom) and floats grease (scum, on top), passing clarified effluent to the fieldIn: Septic system field guide
Sequence of operation
The fixed order a furnace fires in, each step proving itself before the next runsIn: Gas furnace field guide
The ongoing maintenance agreement for pruning, plant replacement, irrigation checks, and fertigation that keeps the wall aliveIn: Living wall and green wall systems
The per-course step back (setback) and the resulting lean into the hill (batter) that bias the wall's weight over the soilIn: Segmental retaining wall build
Load-bearing pads under the glass at the quarter points that carry the weight and hold the edge up out of the drainage pocketIn: Glass replacement and glazing repair
Severity (Sev1 to Sev4)
The classification of how bad an incident is, by impact and scope, that drives the size and speed of the response; the scale is the operator's to defineIn: Incident management and outage response
The mix of gases in a drainage system, including hydrogen sulfide, methane, and ammonia, that smells foul and is toxic and flammable at high concentrationIn: Sewer gas odor field guide
A thin, broad film of water moving evenly across a surface, the gentle flow grading tries to keep, versus concentrated flow that erodesIn: Drainage, grading, and slope
Sheet piling
Interlocking steel sheets driven to form a continuous, near-watertight wall for soft or wet soil.In: Excavation shoring field guide
A structure that protects the worker inside it if the wall collapses; it does not hold the soilIn: Trench safety field guide
Shift handoff (pass-down)
The structured transfer at shift change, a written log plus a verbal briefing, that carries open issues and plant state from one crew to the next.In: Data center operations and the NOC
Shipping split
A factory-divided segment of a lineup that ships as one piece and is field-joined on siteIn: Switchgear receiving inspection
A shore carries fresh-slab load to a lower level; a reshore is reset after stripping to spread later construction loads across floorsIn: Formwork, shoring, and reshoring
Shoring
A support system, often hydraulic, that holds the trench walls in placeIn: Trench safety field guide
The fault current MV switchgear withstands and interrupts, in kA symmetrical, per the submittalIn: Switchgear receiving inspection
Shorting block
The terminal block that lets a CT secondary be safely shorted before it is openedIn: EPMS and power metering
Shotcrete / gunite
Pneumatically applied concrete or mortar; gunite is the dry-mix process, mainly in the pool tradeIn: Shotcrete and gunite field guide
Shotcrete / gunite shell
The pneumatically applied, steel-reinforced concrete pool structure. Gunite is the dry-mix process, where water is added at the nozzle; pool shotcrete usually means the wet-mix process, batched with water and pumped.In: Commercial pool construction
Shower pan / pan liner
The waterproof barrier under and around the shower; the sheet liner in the traditional methodIn: Shower pan waterproofing guide
The change in soil volume between bank, loose, and compacted states that throws off cut and fill balanceIn: Site grading and earthwork
Shrink-wrap
Heat-shrink film drawn tight over a roof or structure as a continuous temporary cover with few seams, an alternative to tarps for larger or longer-term securementIn: Emergency board-up and tarping
Shroud
The hood or guard around the wheel or bit that forms the capture zone feeding the dust collector, sized to the toolIn: Silica dust control methods
Shunt trip
The trip coil that opens a breaker on a control signal, which is how an EPO button drops the loadIn: EPO testing field guide
A spark jumping from the LPS to nearby grounded metal at a different potential during a strikeIn: Lightning protection (NFPA 780)
Side-stream filtration
A slipstream off the main flow run through a fine filter that polishes the whole loop volume over timeIn: CDU commissioning
Sidecar power
A separate power rack that rectifies AC to DC and feeds one or more compute racks over a DC bus, freeing rack space for computeIn: Rack DC power distribution (HVDC)
Siding / cladding
The exterior wall covering that sheds the bulk of the rain; the building's raincoat, not a watertight skinIn: Siding installation
Sign disconnect (NEC 600.6)
A disconnecting means within sight of the sign, or lockable open, so a worker can kill and verify the powerIn: Electric sign installation
Sign permit / zoning
The local approval and ordinance controlling sign area, height, setback, illumination, brightness, and countIn: Electric sign installation
An under-floor copper mesh bonded to building ground that ties the floor and gear to a common referenceIn: Raised floor vs slab design
Silane / siloxane
Penetrating, breathable water repellents that bond in the pores; silane penetrates deeper, siloxane suits more porous concreteIn: Concrete sealers and coatings
Silicate densifier
A lithium, sodium, or potassium silicate that reacts with free lime to harden and dust-proof the surface; not a water repellentIn: Concrete sealers and coatings
Silicon photonics
Optical components built directly in silicon by chip fabrication, the basis for dense optical integration and co-packagingIn: Optical circuit switch and photonics
Silicosis
Permanent, incurable scarring of the lungs from inhaled respirable crystalline silica, in acute, accelerated, and chronic formsIn: Silica exposure control program
Silt fence
A trenched-in fabric barrier on the downslope edge that ponds runoff so sediment settles before water leaves the siteIn: Erosion control and SWPPP
SIMOPS
Simultaneous operations, construction work alongside live, energized, or occupied systems in the same buildingIn: Daily huddle field guide
A busway joint clamped by one high-strength bolt and conical spring washers, often with a twist-off or visual torque indicatorIn: Busway receiving and megger QA
Single-mode (SM)
Fiber with a ~9 micron core carrying one mode, low loss, long reach, laser source, graded OS1/OS2In: Data center fiber types
Single-mode / multimode
Single-mode (~9 micron core) carries one path far; multimode (~50 micron core) carries many paths a shorter wayIn: GPU network optics and cabling
Single-phase / two-phase
Coolant stays liquid (single-phase) or boils on the cold plate (two-phase)In: Direct-to-chip cooling
Single-phase cooling
Cooling where the liquid stays liquid and carries heat as a temperature rise (sensible heat), the mature defaultIn: Two-phase cooling
Single-phase immersion
Immersion where the dielectric fluid stays liquid and is pumped or convected past the hardware to a heat exchangerIn: Immersion cooling acceptance
A low-slope membrane in a single sheet, TPO, EPDM, or PVC, seamed welded or taped into a continuous skinIn: Roofing system types
Siphonage
The loss of a trap seal pulled down the drain when a fixture drains without adequate ventingIn: Sewer gas odor field guide
Site datum vs building grid
The real-world coordinate system and elevation datum versus the architect's column-line grid, related by an origin and a rotationIn: Construction layout
Site logistics plan
The layout and rules for moving people, material, and equipment on the site; also called a site utilization plan or construction logistics plan (CLP)In: Jobsite logistics field guide
Site selection
The structured evaluation of candidate sites against power, water, connectivity, land, climate, hazard, and policyIn: Data center site selection
Site WUE
WUE counting only the water used on-site, mostly cooling water, divided by IT energyIn: Data center water use and WUE
Skidmore
Skidmore-Wilhelm tension calibrator that reads actual bolt tension for verificationIn: High-strength bolting (RCSC)
Skimmer
Surface filter at the water line that catches floating debris and houses or pre-filters the pumpIn: Water feature installation
Skin friction (side resistance)
Load shed into the soil along the sides of the shaft through friction and adhesion over its lengthIn: Drilled piers and caissons
How long a mix stays placeable before it stiffens, short on heavy superplasticizer doses and in heatIn: Concrete admixtures
Slurry
The alkaline water-and-concrete mix from wet cutting that must be contained, not drainedIn: Concrete cutting and coring
Slurry (mineral / polymer)
Drilling fluid that holds the wall, either bentonite clay (mineral) or a water-based synthetic (polymer)In: Drilled piers and caissons
Slurry / diaphragm wall
A reinforced concrete wall cast in a slurry-supported trench, the deepest and most watertight system, often permanent.In: Excavation shoring field guide
Slurry seal
A thin cold mix of conventional asphalt emulsion, fine aggregate, mineral filler, and water that seals a sound surface and cures by evaporationIn: Slurry seal and micro-surfacing
Slurry seal vs micro-surfacing
Cold emulsion-aggregate seals; micro-surfacing is always polymer-modified, cures chemically, reopens faster, and can fill minor rutsIn: Pavement preservation treatments
SMA
Stone matrix asphalt, a gap-graded mix with a stone-on-stone skeleton for rut resistanceIn: Asphalt mix types by layer
Smart / ET controller
A controller that sets run time from local weather and evapotranspiration instead of a fixed clockIn: Smart irrigation field guide
Smoke damper (SD)
Closes on a smoke signal to limit smoke through a smoke barrier; listed to UL 555S, leakage-ratedIn: Fire and smoke damper field guide
Smoke test
A diagnostic that pressurizes the DWV system with visible smoke to reveal where the barrier is brokenIn: Sewer gas odor field guide
SMR
Small modular reactor, the long-horizon firm carbon-free option contracted through PPAs and co-locationIn: Data center on-site generation
SN
Structural number: the total structural strength AASHTO 93 says the section needs over the subgradeIn: Asphalt pavement thickness design
Plies brought into firm contact by full effort on a spud wrench or a few impactsIn: High-strength bolting (RCSC)
Snug-tight vs pretensioned / slip-critical
Snug brings plies into firm contact; pretensioned and slip-critical bolts are tightened to a high specified tension, with slip-critical adding a faying-surface requirementIn: Steel erection and connections
A clearance violation where elements are too close, leaving no access, insulation, or service room, even though they do not touchIn: BIM VDC coordination
Soft foot
A machine foot that does not sit flat, so tightening its bolt distorts the frame and ruins the alignment; correct it firstIn: Hydronic pump install field guide
Soft pull / hard pull
A prequalify check that does not affect the score, versus the full application check that doesIn: HVAC customer financing guide
Soft washing
Cleaning delicate surfaces at low pressure with a cleaning solution that kills mold, algae, and mildew at the rootIn: Pressure and soft washing
Soft-close
Hardware with a damper that pulls a door or drawer quietly closed and keeps it from slammingIn: Millwork and casework install
Soil packed dense enough to squeeze out the pore space roots need for air and water, the number one urban tree stressorIn: Plant health care (PHC)
Soil gas
The air in the pore spaces of the soil under and around a building, carrying radon or contaminant vaporsIn: Radon and vapor-intrusion mitigation
Soil nailing
Grouted steel bars drilled into the cut face with a shotcrete facing, built top-down in cohesive soil that stands on a cut.In: Excavation shoring field guide
How particles clump into aggregates and pore space; built by organic matter, wrecked by compaction and wet tillageIn: Soil preparation and amendment
Soil texture
The ratio of sand, silt, and clay, which sets drainage and water holding and does not change with amendmentIn: Soil preparation and amendment
Soil-moisture sensor
A buried sensor reading volumetric water content in the root zone; the controller bypasses a cycle when the soil is above the thresholdIn: Smart irrigation field guide
Soiling
Loss from dust, pollen, droppings, pollutants, or snow on the module glass blocking light, commonly 4 to 7 percent of annual energy and far higher in dusty climatesIn: Solar PV O&M field guide
Solar PV O&M
Operations and maintenance of a photovoltaic plant: monitoring production and doing the preventive and corrective work that keeps it producing over a 25-to-30-year lifeIn: Solar PV O&M field guide
A self-contained unit powered by solar and battery that sends video over cellular, for sites with no power or internetIn: Jobsite camera and video monitoring
Solar-control film / SHGC / VLT
Film that rejects solar heat, UV, and glare; SHGC is the heat-gain fraction, VLT the visible-light percentIn: Commercial window film
Solar-ready / PV-ready
A roof and building designed so a future PV array can be added without a tear-up, with capacity, zone, and pathway reservedIn: Solar-ready roof provisions
Solar-ready zone
The designated, clear, unshaded roof area reserved for the future solar arrayIn: Solar-ready roof provisions
Soldering / sweating
Joining copper by drawing lead-free solder into a clean, fluxed, heated joint by capillary actionIn: Pipe joining methods
Soldier course
A border of pavers stood so the long side runs perpendicular to the edge; a sailor course runs parallelIn: Paver layout and field border
Soldier pile and lagging
Vertical H-piles at intervals with lagging spanning between them, a discrete, non-watertight wall for firm soil above the water table.In: Excavation shoring field guide
Solid-core CT
A closed-ring current transformer the conductor threads through, more accurate, used when the circuit is openIn: Submetering and energy monitoring
Solids-handling vs grinder pump
A solids-handling pump passes whole solids around 3 in through a non-clog impeller; a grinder pump cuts solids to a slurry for a small, high-head force mainIn: Sewage lift station field guide
Standard operating procedure, the standing procedure for routine, repeatable operationsIn: Data center MOP SOP EOP
SOP, MOP, EOP
The three written procedure types: standard operating procedure for routine running, method of procedure for a specific task, emergency operating procedure for failures.In: Data center operations and the NOC
Sound power (Lw) vs sound pressure (Lp)
Lw is the source's emission, what manufacturers rate; Lp is the level measured at a locationIn: Data center noise control
WUE that adds the off-site water used to generate the electricity the facility consumesIn: Data center water use and WUE
SOV (specified overall value)
The F-number required for the whole placement, the composite across all test sectionsIn: Floor flatness and levelness
Spaced sheathing / breathing assembly
Open 1x boards or a ventilated air space that lets the underside of the cedar dry, so the wood does not rotIn: Wood shake and shingle roofing
Spacer
Manufactured base and intermediate pieces that hold the conduit grid at the specified center-to-center spacingIn: Concrete-encased duct bank field guide
Spacing factor
Average distance from any point in the paste to the nearest air void; a small value indicates a durable systemIn: Air entrainment
Spall
A fragment of concrete that has broken or flaked off the surface, usually over corroding steelIn: Concrete spall repair
The surface area of the air voids per unit volume of air; higher means finer, more protective bubblesIn: Air entrainment
Specific volume
Cubic feet occupied per pound of dry air; the inverse of density, used to correct for altitudeIn: Psychrometric chart
Speech intelligibility / STI
How much of a spoken message a listener can understand, reported on the Speech Transmission Index or Common Intelligibility ScaleIn: Intercom and paging design field guide
How fast you respond after a lead arrives; minutes, not hours, and the first credible response usually winsIn: Lead generation and marketing
Speed to lead / first-response time
How fast you respond to a new inquiry; faster usually wins the job because most customers contact several companies and hire whoever answers firstIn: Customer communication and reviews
A catchment basin at the fill for hose drips, plus a shutoff or alarm that stops a delivery before the tank overruns, commonly at 90 to 95 percentIn: Fuel storage tank field guide
A connection joining one conductor to another, as opposed to a terminationIn: Splices and terminations
Splice fill
Conductors plus splices and taps at one point, held to 75 percent of the area, kept accessibleIn: Wireway and gutter field guide
Splice plate
A concealed backer with sealant strips under a coping joint that seals it while allowing thermal movementIn: Roof edge metal and coping
Splice tape
Factory-extruded butyl tape that joins two EPDM surfaces into a seam over a splice primerIn: EPDM rubber roof installation
Split-case pump
A base-mounted pump that splits along the shaft for in-place service, with a double-suction impeller that balances thrustIn: Hydronic pump install field guide
Split-core CT
A hinged current transformer that clamps around a live conductor for retrofit without a shutdownIn: Submetering and energy monitoring
Seal of Testing Assurance, the US Composting Council program certifying compost maturity and qualityIn: Soil preparation and amendment
Stab
The connector that joins a bucket to the section's vertical busIn: MCC commissioning
Stabilization
Putting a temporary or permanent cover back on disturbed soil so it stops eroding, on a permit deadline once work stopsIn: Erosion control and SWPPP
Stabilizer
The agent mixed into an FDR base, chemical (cement, lime) or bituminous (emulsion, foamed asphalt), that gives it strengthIn: Asphalt recycling and FDR
Stabilizer / ladder bracket
A top attachment that holds the ladder off the gutter and widens its contact against the wallIn: Portable ladder safety
The stack vent is the dry top of a soil stack carried to the roof; the vent stack is a separate vent running alongside itIn: DWV venting and pipe sizing guide
Stacking
Two or more trades working in the same physical space at the same time, often one over the otherIn: Daily huddle field guide
Stage-storage
The relationship between water depth in the basin and the volume it holds at that depth, set by the grades you buildIn: Detention and retention ponds
Type 304 or 316 stainless, or hot-dip galvanized nails, the only metals that resist cedar tannin corrosion; never electro-galvanizedIn: Wood shake and shingle roofing
The code-required load a carrier is tested to hold at the fixture, commonly 250 to 500 lb and up to 1000 lb for heavy-duty unitsIn: Fixture carriers and supports guide
Static load test
A direct load applied to the pile with settlement measured, the benchmark capacity test under ASTM D1143In: Driven pile foundations
The field process of picking, setting, connecting, and plumbing steel members into a frame, regulated under OSHA 1926 Subpart RIn: Steel erection and connections
Steep-slope
A roof that sheds water with overlapping materials, commonly above roughly 3:12 to 4:12In: Roofing system types
The voltage difference between your feet in the energized ground around a downed line, which drives current through the bodyIn: Electrical shock first aid
STF
Slips, trips, and falls, the grouped category for same-level loss-of-footing injuriesIn: Jobsite housekeeping
Stick-built vs unitized
Stick is field-assembled mullion by mullion; unitized is factory-glazed panels craned in and interlocked.In: Curtain wall and glazing
STO
Safe torque off, a hardwired function that removes motor torque without removing drive power, not a lockoutIn: VFD install and commissioning
Stone column / aggregate pier
A stiff vertical column of compacted stone that reinforces soft soil; aggregate piers are rammed for higher stiffness, stone columns also drainIn: Ground improvement and grouting
Storefront is the lighter ground-floor system with doors; window wall sits between floors on the slab, while curtain wall hangs past the slab.In: Curtain wall and glazing
Storm collar
An umbrella-shaped counterflashing over a pipe boot's top band that sheds water off the clampIn: Roof penetration flashing
Storm restoration
Assessing and documenting storm damage, helping the homeowner work the claim, and replacing the roof to the approved scopeIn: Storm and hail damage restoration
Stormwater retention
Rainfall the media, drainage layer, and plants hold and release slowly or use, the function many green roofs are credited forIn: Green roof maintenance program
Story pole
A marked stick laid out to the coursing so every lead is built to the same course heightsIn: CMU block wall construction
Straight pull
Conductors enter one wall and exit the opposite wall in line, sized at 8x the largest racewayIn: Pull box sizing, 314.28
Strainer cycle
Direct free cooling routing tower water straight into the chilled-water loop through a filter, most efficient but fouling-proneIn: Waterside economizer free cooling
Strand / lashing
The steel messenger that carries aerial load, and the wire that lashes the fiber cable to itIn: OSP fiber and FTTH construction
The fraction of the tank volume that is usable cooling rather than dead thermocline and end zonesIn: Thermal energy storage tank
Stray-current interference
CP current picked up by a foreign structure that corrodes where the current discharges back to the soil; managed with bondsIn: Cathodic protection field guide
Streaming telemetry
The device pushing structured counters and stats continuously at sub-second rates, commonly over gNMI/gRPC, versus SNMP pollingIn: Network observability for the AI fabric
A worker hit by a moving or falling object: a vehicle, equipment, a swinging load, or a dropped object. One of OSHA's four construction hazard groups, the Focus Four, also called the Fatal Four.In: Proximity warning and struck-by safety tech
The asphalt or concrete pavement under the surface that controls flatness, drainage, and lifeIn: Running track surfacing
Structural fill
Fill placed and compacted to a tested density to carry a structure or pavement without settlingIn: Site grading and earthwork
Structural fireproofing
Insulation applied to structural steel so it stays below its failure temperature in a fire and keeps carrying load for the rated timeIn: Structural fireproofing
Structural number (SN)
The total structural strength AASHTO 93 says the section needs over the subgrade; not a thicknessIn: Asphalt pavement thickness design
Structural silicone glazing (SSG)
Glass bonded to the frame with structural silicone that carries the wind load, with no exterior cap; four-side SSG bonds all edges.In: Curtain wall and glazing
Structural vs architectural
Structural panels span open framing; architectural panels need a solid deck and a steeper slopeIn: Metal roof types compared
Structured cabling / TIA-606
A fixed, tested, labeled patch field, and the administration standard that names every cable, port, and spaceIn: Rack-and-stack deployment field guide
Structured vs unstructured task
A structured task is repetitive and predictable enough for a robot to follow; an unstructured task is custom or unpredictable and needs a personIn: Construction robotics
A fan-driven system that holds the soil under the slab at lower pressure than the building so gas vents outsideIn: Radon and vapor-intrusion mitigation
A two-party insurance policy, often called SubGuard, by which a GC insures against sub default instead of requiring bonds, carrying a deductible and the prequalification dutyIn: Subcontractor prequalification and bid lists
Saturated fines forced up into the aggregate voids under repeated load, contaminating and weakening the base.In: Geotextile separation fabric
Submersible pump
A sealed motor-and-pump unit set down in the water that pushes water up the drop pipe, sized to gpm and total dynamic headIn: Water well drilling and well systems
Submeter
A meter measuring a tenant or load below the utility's revenue meter, owned by the building, not the utilityIn: Submetering and energy monitoring
Submittal
Product data, shop drawing, sample, or mockup sent to prove an item meets the spec before it is ordered or fabricatedIn: RFI and submittal process
Submittal register
The master list of required submittals by spec section, tied to review status and procurement lead timeIn: RFI and submittal process
The installation that ties the site to the grid and steps high voltage down to medium voltageIn: Data center grid and substation
Substrate deflection (L/360)
Allowable bending of the floor framing under load, the clear span divided by 360 for ceramic and porcelain, 720 for natural stone.In: Ceramic and porcelain tile installation
Pressure gauges across the pump that read the head it is making, locating the operating point on the curveIn: Hydronic pump install field guide
Suction diffuser
A pump-inlet fitting combining a flow straightener, a strainer, and a support leg to steady flow and screen debrisIn: Hydronic pump install field guide
The single-conductor fill basis where large conductors lie in one layer and their diameters total no more than the tray widthIn: Cable tray fill and copper takeoff
The protection that keeps an emergency circuit working under the conditions of the emergency, to the level NFPA 72 requiresIn: Intercom and paging design field guide
Survivability / 2-hour pathway
The requirement that the public-safety system keep working in a fire, built from fire-rated cable and listed enclosuresIn: DAS and public-safety radio
Suspended / ACT ceiling
A metal grid hung from the structure on wires with acoustic tiles dropped in, hiding the plenum and keeping it accessibleIn: Suspended acoustical ceiling field guide
A shallow, usually vegetated graded channel that collects sheet flow and carries it to an outlet at a 1 to 2 percent flow lineIn: Drainage, grading, and slope
Stormwater pollution prevention plan, the site-specific written plan and map of the BMPs, inspections, and responsible partyIn: Erosion control and SWPPP
Symmetrical RMS
The fault current measured as a sine wave centered on zero, the base value the study reportsIn: Available fault current study
Synchronization
Matching an incoming set's voltage, frequency, phase angle, and rotation to the bus before its breaker closesIn: Generator paralleling
Synchronized swing
Many GPUs ramping power together on the same training step, so the peaks add instead of scatteringIn: Power capping and oversubscription
Synchronizing
Matching voltage, frequency, phase sequence, and phase angle before closing a breaker to the busIn: Generator paralleling switchgear
Synchronous / asynchronous
Replication that confirms at both sites for zero RPO at short range, versus trailing copy for any distanceIn: Data center disaster recovery
Synchroscope / sync-check (25)
The instrument showing phase relationship and the relay (ANSI 25) that supervises and permits the closeIn: Generator paralleling
System bonding jumper (SBJ)
The neutral-to-ground connection made at a separately derived source such as a 4-pole generator, the counterpart to the service main bonding jumperIn: Generator grounding and bonding