Home maintenance glossary

Plain-language definitions of the terms that come up when you're dealing with home maintenance in the UAE — so you can talk to a technician with confidence and spot when something doesn't add up.

AC Service

· 45 terms

Air changes per hour (ACH)

How many times the whole air volume of a room is replaced with fresh air each hour — the number behind stuffy rooms, lingering smells and humidity.

AMC (Annual Maintenance Contract)

A yearly service agreement — common in the UAE for scheduled AC upkeep.

C-wire (thermostat common wire)

The 'common' wire that gives a thermostat continuous 24V power — why smart thermostats need it and what misbehaves without one.

Capacitor

A cheap part whose failure often mimics a dead compressor.

Check code (fault / error code)

The code an AC shows — on its display, the wired remote, or as a pattern of LED blinks — to tell you WHICH part of the system has faulted.

Closed-cell vs open-cell insulation

Two foam types that behave oppositely around cold pipes: closed-cell resists water and stays insulating; open-cell soaks it up. On a Dubai chilled pipe, only one is right.

Compressor

The pump at the heart of the system — and the costliest part to replace.

Condensate drain

The line that carries away the water your AC pulls from the air — and the usual cause of ceiling leaks.

Condensate drain pan

The tray under the AC's indoor coil that catches condensation and sends it to the drain — the No.1 source of AC water leaks when it or its drain line clogs.

Condensate pump (& float switch)

The small pump that lifts AC condensate up and out when a unit can't drain by gravity — plus the float switch that cuts the AC off to stop an overflow.

Condenser (outdoor unit)

The outdoor box that releases your home's heat to the outside air.

Condenser coil fins

The thin metal fins on the outdoor unit that dump the AC's heat — when they clog with dust or get bent flat, the AC works harder, cools less, and can trip on high pressure.

Contactor (AC electrical switch)

The heavy-duty electromagnetic switch that powers the AC compressor and outdoor fan when the thermostat calls — a cheap, common wear part.

Cooling capacity (BTU & tons)

How much heat a unit can move — sized in BTU/h or 'tons'.

Cooling load (heat load)

The total heat an AC must remove to keep a space cool — the basis for correctly sizing a unit. Get it wrong and the AC is either undersized or short-cycles.

Delta-T (temperature split)

The temperature difference between the air (or water) going in and coming out of a cooling coil — the number that proves cooling is actually working.

Demand-controlled ventilation (DCV)

Ventilation that ramps fresh air up and down with actual occupancy instead of running flat-out — a big energy saver in Dubai's heat.

Dew point

The temperature at which humid air starts to condense into water. In coastal Dubai it's why cold pipes, vents and windows 'sweat' — and why AC has to dry the air, not just chill it.

DEWA

Dubai's electricity & water utility — your AC is the biggest line on its bill.

Ducted AC

A concealed central system that pushes cooled air through ceiling ducts to each room.

Economizer (free cooling)

A control mode that cools with cool outside air or water instead of running the compressor — a big energy saver in temperate climates, and useful on Dubai's cooler nights and for 24/7 loads.

EER / SEER (AC efficiency ratings)

The numbers that tell you how much cooling an AC gives per unit of electricity — higher = cheaper to run. SEER is the seasonal average; EER a single fixed rating point.

Evaporator coil

The cold indoor coil that actually absorbs heat and dries the air.

Expansion valve (TXV)

The metering device that controls how much liquid refrigerant sprays into the evaporator — the throttle of the cooling cycle, and a common cause of poor cooling when it sticks.

Fan coil unit (FCU)

The in-room unit on a chilled-water or district-cooling system that blows cool air. The apartment equivalent of a split AC's indoor unit.

Gas top-up (regas)

Refilling refrigerant — only a real fix once the leak is sealed.

Hard-start kit

An add-on that gives a compressor a stronger starting kick — helps a reluctant compressor start, but can also mask one that's dying.

High-pressure switch (AC safety cut-out)

The safety switch that shuts an AC compressor off when the refrigerant pressure climbs too high — often why a unit cuts out in peak heat.

Inverter (variable-speed AC)

An AC that varies its compressor speed to match the cooling load, instead of a fixed-speed unit that only cycles full-on then off — steadier, more efficient, gentler on start-up.

MERV rating (air-filter efficiency)

The 1–16 scale of how much fine dust and particles an AC filter actually captures — and why higher isn't always better for your system.

Pipe lagging (AC pipe insulation)

The foam insulation wrapped around AC refrigerant and chilled-water pipes — stops them sweating and dripping, and saves energy. It perishes over time and needs replacing.

Plenum (AC air distribution box)

The air-distribution box on a ducted AC where conditioned air collects before the ducts — and why its size and sealing affect airflow and running cost.

R-value

The number that says how well insulation resists heat — the higher the R-value, the better it insulates. It's why the right AC pipe and duct lagging stays dry and keeps cooling in.

Refrigerant (AC gas)

The 'gas' that carries heat around the system — R410A and older R22.

Relative humidity (RH)

How damp the air is compared with the most it could hold at that temperature. In coastal Dubai it's the reason an AC has to dry the air, not just chill it.

Reversing valve (heat-pump 4-way valve)

The valve that flips a heat-pump AC between cooling and heating by reversing the refrigerant flow — why most UAE units don't have one, and what a stuck one does.

SEER / EER (AC efficiency ratings)

The two numbers that tell you how efficient an AC is — EER at one hot-day condition, SEER across a whole season — and why a higher figure means a lower running cost.

Split AC

The quiet indoor-unit-plus-outdoor-condenser system found in most UAE apartments.

Static pressure (AC airflow resistance)

The resistance an AC's blower has to push air against — and why too much (a too-fine filter, choked ducts) starves cooling and freezes coils.

Superheat & subcooling (refrigerant charge check)

The two temperature measurements a technician uses to verify an AC's refrigerant charge and diagnose a leak or overcharge — the real 'is the gas right?' test.

T3 rating (tropical climate class)

The 'tropical' climate class that says an AC is built and rated to keep cooling in extreme Gulf heat — the rating that actually matters when Dubai hits the high 40s.

Ton of refrigeration (TR)

The unit AC and chillers are sized in — one 'ton' is about 12,000 BTU/hr of cooling. The number behind whether your AC is the right size for the room.

TXV / expansion valve

The metering valve that controls how much refrigerant flows into the evaporator — the 'throttle' that sets an AC or fridge's cooling.

Vapour barrier

The sealed layer that stops humid air reaching a cold pipe or duct. Without it, insulation just hides the sweating — and the pipe drips and corrodes inside the lagging.

VRF / VRV (variable refrigerant flow)

A system that runs many indoor AC units off one outdoor unit and varies refrigerant to each — common in larger UAE villas and offices.

Water Chiller Service

· 10 terms

AHU (Air Handling Unit)

A larger central air unit that conditions and distributes air for a whole zone or building — the big brother of the FCU.

Approach temperature (chillers)

The small temperature gap across a chiller's heat exchangers — when it grows, it's the early warning that the plant is fouling and wasting energy.

Balancing valve

The valve that sets HOW MUCH chilled water flows through an FCU or a branch — throttled too far and that unit under-cools even when everything else is working.

BTU meter

The meter that measures the cooling energy you use on district cooling — the basis of the consumption part of your bill.

Chilled-water loop

The closed water circuit that carries cooling from the plant to every FCU in a chilled-water or district-cooled building.

Cooling tower

The rooftop unit that rejects a chiller plant's heat to the air — the district-cooling equivalent of an outdoor condenser.

FCU (Fan Coil Unit)

The in-room unit of a chilled-water/district-cooling system — the part you actually own and maintain.

Two-port valve (motorised)

The motorised on/off valve that lets chilled water through an FCU's coil when the room thermostat calls for cooling — no call, valve shut, no cooling.

VAV box (variable air volume)

The duct damper that varies how much cool air each zone gets on a central system — why one office room can be freezing while the next is warm.

Y-strainer

A Y-shaped in-line filter with a mesh screen that catches grit and debris in a pipe — on a chilled-water FCU it protects the coil and control valve from the muck in the system water.

Plumbing Service

· 20 terms

Backflow preventer (non-return valve)

The valve or air gap that stops used or contaminated water being drawn back into your clean supply — the fitting that quietly protects what comes out of the tap.

Biofilm

The slimy microbial layer that builds up inside a neglected water tank or pipe. It's why tank cleaning is a water-quality issue, not just a taste one.

Check valve

A one-way (non-return) valve that lets water flow in a single direction and shuts to stop it flowing back — common on booster pumps and water-heater feeds.

Cleanout (drainage access)

The capped access point that lets a plumber rod or jet a blocked drain without cutting into the pipe or smashing the floor.

Expansion vessel

A small pressure tank on a sealed hot-water or heating system that absorbs the expansion of heated water. When it fails, pressure spikes and the relief valve drips.

Gate valve

A full-bore on/off water valve that lifts a gate out of the flow — great for isolating a supply, but prone to seizing in older buildings if left untouched for years.

Grey water

The lightly-used wastewater from showers, basins and washing machines — reusable for irrigation with the right setup, unlike toilet (black) water.

Gully trap (yard / floor gully)

The outdoor floor drain with a built-in water seal that collects wastewater and yard run-off while stopping drain smells from rising back up.

P-trap

The U-bend under every sink and drain that blocks sewer smells from rising into your home.

PEX piping

Flexible cross-linked plastic pipe used for hot and cold water in many modern UAE homes.

Potable vs non-potable water

Potable water is treated to drink; non-potable (like recycled TSE or greywater) is for irrigation and flushing only and must never cross-connect to the drinking supply.

Pressure-reducing valve (PRV)

The valve that caps incoming mains water pressure to a safe level for the house. When it drifts, you get pressure that's too high, too low, or uneven.

Sacrificial anode (anode rod)

The 'sacrificial' metal rod inside a water heater that corrodes instead of the tank — quietly extending the heater's life.

Sacrificial anode (water heater)

The replaceable metal rod inside a water heater that corrodes instead of the tank — check and replace it and the heater lasts years longer.

Stopcock (main water shut-off) & isolation valves

The main valve that shuts off your home's water supply — plus the smaller isolation valves under fixtures. Know where yours is before a leak forces you to find it.

TDS (total dissolved solids)

A quick number for how much dissolved mineral and salt is in your water — the reading behind hard-water scale, taste, and whether an RO filter is doing its job.

Thermostatic mixing valve (TMV / anti-scald)

A valve that blends hot and cold to a safe, steady preset temperature at the tap or shower, and shuts off fast if the cold supply fails — the everyday anti-scald guard.

Vacuum breaker (anti-siphon)

A simple valve that lets air in when pressure drops, so used or dirty water can't be siphoned back into your clean supply — the everyday guard on hose taps and irrigation.

Water hammer

The loud bang in the pipes when a tap or valve shuts suddenly — and why it damages plumbing over time.

Water-hammer arrestor

The small shock-absorber that stops the bang in your pipes when a washing machine or quick-closing tap shuts off suddenly.

Electrical Service

· 16 terms

Busbar

The metal bar inside a distribution board that distributes power to all the breakers — a loose breaker-to-busbar joint is a classic cause of overheating.

Conduit (electrical)

The protective tube — PVC or metal — that cables run inside, shielding them from damage, heat and moisture and letting them be rewired later without opening walls.

Distribution board (DB)

The panel of breakers that splits your home's power into separate circuits — the first place to look when something trips.

Earthing (grounding)

The safety connection that gives fault current a path to ground — why it protects you from shock and how the RCD relies on it.

IP rating (Ingress Protection)

The two-digit code (like IP65) that says how well an electrical fitting keeps out dust and water. It's what makes an outdoor socket, pool light or bathroom fitting safe in Dubai.

Isolator (isolating switch)

A manual switch that fully disconnects an appliance — an AC, water heater or oven — from the supply so it can be worked on safely. It isolates; it doesn't protect.

Junction box

An enclosure where electrical cables are joined or branched. It must stay accessible — a buried or hidden junction is a fire risk and a code fault.

KNX (smart-home standard)

The open, wired smart-home standard — a control bus that reliably links lighting, blinds, AC and more across a whole villa.

MCB (miniature circuit breaker)

The switch in your board that trips to cut power when a circuit is overloaded or short-circuits.

RCBO (Residual Current Breaker with Overload)

A single protective device that combines an MCB and an RCD — it trips on both overload/short-circuit AND earth leakage, protecting one circuit on its own.

RCD / ELCB (residual current device)

The safety device that trips in milliseconds if current leaks to earth — the one that protects you from a fatal shock.

Surge protection device (SPD)

A device in the distribution board that clamps a voltage spike and diverts it to earth, protecting your electronics — different from an MCB or RCD.

Surge protector / SPD

A device that clamps damaging voltage spikes before they reach your electronics — at the board (whole-home) or the socket (point-of-use).

SWA cable (steel wire armoured)

Steel-wire-armoured cable — a tough, protected cable used for sub-mains, outdoor runs and heavy loads like AC and pumps, where a normal cable would be too exposed.

Three-phase power

A supply that delivers power on three 'phases' instead of one — used where a home or building's total electrical load is large.

Voltage drop

The loss of voltage along a cable under load — why lights dim on a big motor start and why long runs need thicker cable.

Kitchen Equipment Maintenance

· 7 terms

Combi oven (combination oven)

A commercial oven that combines convection heat and steam in one cabinet — versatile but reliant on water quality, so it needs descaling, gasket and calibration upkeep.

Descaling

Clearing the hard, chalky limescale that Dubai's hard water leaves inside anything that heats or holds water — water heaters, boilers, dishwashers, ovens and coffee machines.

Door gasket (appliance seal)

The flexible seal around a fridge, freezer or oven door — a cheap part whose failure quietly wastes energy and temperature.

Extraction hood (kitchen canopy)

The canopy, filters and duct that pull grease, smoke and heat out of a kitchen — and a real fire risk if the grease isn't cleaned out.

Grease interceptor (grease trap)

A large external or below-ground separator that catches fats, oils and grease from a commercial kitchen's wastewater before they reach the public drain. Needs regular pumping.

Grease trap (grease interceptor)

The chamber that catches fats, oils and grease from a commercial kitchen's wastewater before the sewer — a Dubai Municipality requirement.

Make-up air

The replacement air fed back into a space to balance what an extraction system pulls out. Get it wrong and a commercial kitchen hood 'won't pull' — the real fault is starved air, not the hood.

Aluminium & Glass Work

· 30 terms

Aluminium extrusion

How the aluminium frames of windows, doors and facades are made — a heated billet pushed through a shaped die into precise profiles. It's why aluminium work is systems, not just metal.

Annealed glass (ordinary float glass)

Standard, untoughened glass — cheaper, but it breaks into large sharp shards, so it isn't safety glass and shouldn't be used for doors, big panes or wet areas.

Anodising (anodised aluminium)

An electrochemical finish that grows a hard, corrosion-resistant oxide layer into the aluminium itself — durable and colour-fast in the sun.

Back-painted glass

Glass with its rear face painted in any colour — the seamless, wipe-clean choice for splashbacks and feature walls.

Curtain wall (glass facade)

The aluminium-and-glass outer skin of a tower — it keeps weather out but carries no building load, and it's shared facade responsibility, not a single flat's.

Curved (bent) glass

Flat glass heated and slumped/bent over a mould to a permanent curve — available toughened or laminated, so it keeps its safety rating for curved showers, balustrades and shopfronts.

Door seal (weatherstrip)

The compressible strip or gasket around a door or window that closes the gap to the frame — keeps dust, draughts and cooled air where they belong.

Double glazing

Two glass panes with a sealed gap between them — cuts heat and noise, and the whole sealed unit is replaceable if it fogs.

Espagnolette (multipoint lock)

The rod-and-cam locking mechanism inside an aluminium, uPVC or timber window or door — one handle throws several locking points around the frame at once.

G-value (solar factor / SHGC)

The share of the sun's heat that comes through glazing — in Dubai you want it LOW. The partner figure to the U-value.

Galvanic corrosion

The accelerated rust you get when two different metals touch in damp, salty air — a common reason cheap fixings streak rust down aluminium and glass work near the coast.

Glazing gasket (seal)

The rubber seal that holds glass in an aluminium frame weathertight. When it perishes in the sun, you get draughts, whistling and water ingress.

Insulated glass unit (IGU / sealed double-glazing)

The sealed sandwich of two glass panes with a spacer and dry-air gap that IS double glazing — and when its edge seal fails, it fogs permanently between the panes.

Louvre & damper

Louvres are the angled slats that let plant and AC 'breathe' while keeping rain and sun out; dampers control airflow inside ducts. Both keep Dubai equipment from overheating or going unbalanced.

Low-E coating (low-emissivity glass)

A microscopically-thin, transparent metal coating on glass that reflects heat while passing light — the main reason modern Dubai glazing keeps rooms cooler.

Low-E glass

Glass with an invisible metallic coating that reflects radiant heat — cutting solar heat gain in the Gulf sun.

Low-E glass (low-emissivity)

Glass with an invisible heat-reflecting coating — the single biggest glazing upgrade for cutting AC load in the UAE.

Low-iron glass (extra-clear glass)

Ultra-clear glass with the green tint removed — used where true colour and clarity matter, like pale splashbacks, shower screens and glass balustrades.

Mashrabiya (decorative screen)

The traditional Arabic latticed screen — now often laser-cut aluminium — that shades, gives privacy and adds pattern to facades, balconies and partitions.

Movement joint (expansion joint)

The deliberate gap that lets a facade, tiled floor or long wall expand and contract without cracking — essential in Dubai's big temperature swings.

Mullion (and transom)

The vertical bar that divides a window, door or facade into sections — a transom is the horizontal one. In aluminium systems they carry loads and hold the glass.

Patch fitting

A small metal corner clamp that grips frameless glass — the fitting that holds a frameless glass door, screen or balustrade with minimal framing.

Powder coating

A tough, baked-on dry finish for aluminium windows, railings and gates that resists the UAE sun and salt.

Spacer & desiccant (sealed-unit edge)

The edge bar that holds a double-glazed unit's panes apart and the drying agent inside it — the parts whose failure fogs your glass.

Spacer bar (warm-edge / desiccant)

The perimeter bar that holds a sealed glass unit's two panes apart, holds the desiccant that keeps the gap dry, and — if warm-edge — cuts edge condensation and heat loss.

Tempered vs laminated glass

Two kinds of safety glass — tempered is heat-strengthened and shatters into blunt pebbles; laminated is bonded and holds together when broken.

Thermal break

An insulating barrier inside an aluminium frame that stops heat conducting straight through the metal.

Tilt-and-turn window

A window that does two things on one handle — tilts inward at the top for secure ventilation, or turns fully inward like a door for full opening and easy cleaning.

U-value (thermal transmittance)

How much heat a window, glazed unit or wall lets through — lower is better. In Dubai it's the number that decides how hard your AC has to fight the sun.

Weep hole

The small drainage slots at the bottom of an aluminium window or sliding-door frame. When they clog with dust, water backs up and leaks inside.

Painting & Gypsum Work

· 8 terms

Chalking (paint)

The powdery, faded residue on tired exterior paint — rub a finger on it and it comes away chalky. In Dubai's sun it's the number-one sign the paint is finished.

Cornice (gypsum cornice / coving)

The decorative moulding that runs along the wall-to-ceiling junction — hides the joint, finishes the edge and can conceal indirect lighting.

Elastomeric paint (flexible weatherproof coating)

A thick, flexible rubber-like exterior coating that bridges hairline cracks and resists UV, heat and chalking — for exteriors that last in the UAE sun.

Gypsum board (plasterboard / drywall)

The plaster-cored board used for partition walls and false ceilings — with moisture-resistant and fire-rated grades for specific rooms.

Mist coat

A watered-down first coat of emulsion that seals fresh plaster so the proper paint can bond — skip it and new-plaster paint peels.

Moisture-resistant (green) gypsum board

Plasterboard with water-repellent additives (conventionally green-faced) that resists humidity and splashes in bathrooms/kitchens — moisture-RESISTANT, not waterproof.

Primer / sealer

The prep coat that seals a surface and helps the topcoat stick, cover evenly and last — the step that makes or breaks a paint job.

Skim coat (skimming)

A thin final layer of plaster/filler that smooths a wall or ceiling to a flat, paint-ready finish.

Tile & Ceramic Service

· 11 terms

Cementitious waterproofing

A cement-based waterproof coating brushed onto bathroom and balcony substrates — the default wet-area method in the UAE.

Efflorescence (salt bloom)

The white powdery salt bloom that surfaces on tile grout, natural stone, concrete and plaster — a moisture signal, not just a stain.

Epoxy grout

A waterproof, stain- and mould-resistant resin grout for wet areas — far tougher than cement grout, but harder to apply.

Grout float

A flat rubber-faced hand tool used to press grout fully into tile joints and scrape off the excess — the tool that decides whether joints look sharp or patchy.

Honing (stone finish)

Grinding a stone surface to a smooth, matte/satin finish that stops short of a full gloss — grippier and lower-maintenance than a polish.

Lippage (tiling)

When one tile's edge sits higher than its neighbour, leaving a lip you can feel underfoot. The classic sign of large-format tiling laid on an uneven bed.

Movement (control) joint — tiling

A deliberate flexible gap left in a tiled area — filled with sealant, not rigid grout — that absorbs thermal and structural movement so tiles don't tent or crack.

Screed (floor screed)

The mortar layer over the slab that levels the floor and, in wet areas, forms the slope to the drain.

Tile levelling system

Clips and wedges that hold adjacent tiles flush while the adhesive sets — preventing lippage (uneven edges) on large-format tiles.

Tile trim (edge trim / profile)

The metal or PVC profile that finishes an exposed tile edge or external corner — protects the vulnerable edge and gives a neat line instead of a raw or mitred edge.

Waterproofing membrane

The hidden waterproof layer under the tiles and screed that actually keeps water out — not the grout or silicone.

Wood Work Service

· 3 terms

MR-MDF (moisture-resistant MDF)

Moisture-resistant MDF — a treated board (usually green-tinted) that resists humidity and damp far better than standard MDF, common for UAE kitchens and wardrobes.

Plywood (incl. marine / BWP grade)

An engineered board of thin wood layers cross-bonded for strength and stability — with water-resistant grades for wet, humid areas.

Veneer (wood veneer)

A thin layer of real wood bonded to a stable engineered core — the look of solid timber with far less warping.

Apartment & Office Renovation

· 6 terms

Defects-liability period (DLP)

The warranty window after handover when the contractor must fix defects in their own work, free of charge.

Fit-Out NOC

The developer or building 'no objection' letter you must get before any renovation work can start in a Dubai property.

MEP (Mechanical, Electrical, Plumbing)

The mechanical, electrical and plumbing systems of a home — the behind-the-walls work that goes in first and usually needs approval.

Provisional sum (and prime cost / PC sum)

A budgeted allowance in a renovation quote for work or items not yet fully defined — a placeholder that's reconciled to the actual cost once specified, so a quote full of them isn't really a fixed price.

Snagging

The final defect inspection of a renovation or a new handover — the punch-list of everything to fix before you sign off.

Spalling (concrete)

When concrete flakes, cracks or breaks away — often from rusting reinforcement inside. Common on Dubai balconies, car parks and coastal facades.