Trade Jargon Explained: A Homeowner's Glossary

Tradespeople and builders use a shorthand that can leave homeowners nodding along while having no idea what is being discussed. Understanding the most common terms puts you in control of conversations about your home, helps you understand quotes, and prevents expensive misunderstandings.

First fix refers to all the work that goes inside the walls and floors before they are closed up — running cables, laying pipework, positioning junction boxes, setting soil pipes. Second fix is everything that happens after plastering and drylining is complete — fitting sockets, switches, radiators, taps, sanitaryware, and light fittings. If a tradesperson says they do first fix only, they will not return to connect up the visible elements after plastering.

DPC (damp-proof course) is a horizontal barrier built into the wall — typically a layer of impermeable material — that prevents ground moisture rising up through the masonry. It should be visible as a thin line in the mortar courses, usually 150mm above external ground level. DPM (damp-proof membrane) is a similar barrier installed horizontally in floors — a polythene sheet beneath screeds and floor slabs that stops moisture rising from below. Both are legal requirements under Building Regulations for new construction and renovation work.

An RSJ (rolled steel joist) is a steel beam used to carry loads when walls are removed — typically when creating an open-plan space or widening a door opening. They are also referred to as universal beams (UBs) or I-beams. The size of RSJ required is calculated by a structural engineer based on the span and load. Padstones are the blocks of dense concrete or stone that sit beneath each end of the beam, spreading its load onto the masonry below.

In timber frame construction, studs are the vertical timbers that form the frame of a partition wall. Noggins (or noggings) are the short horizontal timbers fixed between studs, either to stiffen the frame or to provide a fixing point for heavy items like radiators or cabinets. Joists are the horizontal structural timbers that support a floor or ceiling — either timber or engineered timber (I-joists) in modern construction. Knowing which direction joists run helps you understand where you can and cannot take fixings from above.

Understanding basic trade terminology is not about becoming an expert — it is about being able to ask the right questions and recognise when an answer does not make sense.

— Federation of Master Builders

Pointing refers to the mortar between bricks or stonework. Repointing is the process of removing old, failing mortar and replacing it with fresh mortar — essential maintenance for older properties where the mortar has eroded or cracked. Rendering is the application of a sand-cement or lime-based coat to the external face of a wall, providing weather protection and a smooth or textured finish. Silicon render refers to modern silicone-modified renders with high flexibility and water resistance.

Lintel: a structural beam above a door or window opening. Reveal: the sides of a window or door opening, from the face of the wall to the frame. Chase: a groove cut into a wall to conceal cables or pipes. Soffit: the underside of a roof overhang, staircase, or floor. Fascia: the board along the bottom edge of a roof at the eaves, to which gutters are fixed. Barge board: the equivalent board running up the gable of a roof. Valley: the internal angle where two roof planes meet.

• First fix = inside the walls; second fix = after plastering
• DPC = damp-proof course in walls; DPM = membrane in floors
• RSJ = steel beam for carrying loads over openings
• Studs = vertical frame timbers; noggins = horizontal braces
• Lintel = beam over door or window; soffit = underside of structure