Man with blue hard on standing in front right foreground smiling in front of stacks of cut wood.

Builder’s merchants and tradesmen have been creating their own language for centuries, and while some jargon has reached the mainstream, other terms can sound confusing if it’s not a term that’s part of your daily use.

Prepare yourself for your next visit to the builder's merchant with this alphabetical quick guide to builder’s merchant jargon — both simple and complicated!


Construction aggregate is a broad term used to refer to small, coarse materials used in the creation of concrete. Aggregate is also used in other areas of construction, such as drainage, and plugging voids.

Bulk bags

Bulk bags are those big woven bags that you often see packed full of materials at a builder's merchant. A bulk bag is typically around 90 cm high by 80 cm wide -the right size to fit on a pallet - and can hold upwards of 500 kg. Bulk bags tend to come filled with sand, gravel, and other forms of aggregate.


Shavings or chips of wood are pressed together and reconstituted to form chipboard, a building material that’s often used to make floors and furniture.


Designing plans or blueprints before getting to work is often referred to as drafting. These drawings are generally more complex than what you might consider a “draft” to be.

“Finished” Dimensions

The finished dimensions are the final dimensions of the wood, once it’s been planed or machined down to size. The original sizing is the rough-sawn sizing before the timber is ready for use.


The frog refers to the slight indent you find in most bricks. The frog both reduces the weight of the brick and saves on clay.


A lath is a small piece of material, typically wood, that supports the plaster.


Another name for cement. Sometimes called “Gobbo”.

Poured concrete on ground.

Oversite Concrete

Oversite concrete is a concrete underlayer that can often be found beneath timber flooring or slab flooring. It serves as a protective barrier against damp.

Party Wall

When you and a neighbour share a wall between properties, this communal boundary is known as a party wall. When it comes to construction, it’s helpful to know which walls are party walls, and which are your own.


A coating applied to external walls, rendering is typically a wet mixture made with either a sand or cement base. Rendering is partly done to protect the wall, but it can also be used to give a less-than-attractive wall a smooth finish.


Screed is a thin layer of sand and cement that’s applied between the concrete slab and the timber flooring.


A sleeper is a big, rectangular piece of wood, once used to lay railway tracks. They’re now popular materials for both landscaping professionals and DIY enthusiasts.

Stack of red blonde coloured wooden sleepers.


The long and labour-intensive process of underpinning replaces a weak existing foundation of a house with a stronger material, typically concrete. Underpinning is hard work but often done by necessity.

Ask an expert

Still unsure of terminology? Find expert advice at Alsford Timber, and get your project underway today.