Edge banding and grain direction on 18 mm board

Which edges get banded

Edge banding is the thin strip glued to the raw edge of a board so the core never shows. Ours is 1 mm thick in the same decor as the board, applied on the visible edges only. Doors, drawer fronts, fillers and any loose panel are banded all round, because every edge of them is seen at some point. Carcass parts, the sides, tops, bottoms and shelves, are banded on the front edge only. The other three edges meet another part or the wall.

That rule is why sizes on our cut lists are finished sizes with banding included. A shelf written 524 by 500 is cut to 523 by 500 and banded on one long edge, and the saw operator knows which edge from the drawing, not from a calculation.

How much banding a job uses

More than you think, and it is a line on the quote. Our rule of thumb for a wardrobe is about 16 metres per bay. The engine's count for a four bay wardrobe of 2400 by 2600 mm, with three drawers, a jewellery drawer, shoe shelves and top boxes, is about 64 metres. For a kitchen, every door and drawer front is banded all round, so a run of handleless fronts uses more than the carcasses behind them.

On a damp site or in a bathroom, the banding is also what keeps water out of the core. A raw bottom edge on a board drinks, swells and lifts its face. A banded one does not.

Grain: when a part may turn, and when it may not

A plain board, melamine or MDF to be lacquered, looks the same in every direction. So when the cutting plan lays the parts on the board, a part may be turned 90 degrees to fill the end of a strip, and the board is used harder. Our wardrobe boards run 85 to 95 percent used that way, with the worst board as the spare.

A veneered board has real wood on its face, and the grain runs along the length of the board. A part's length must lie along it and may never turn, or a door's grain runs across when every other door runs up. The engine has a switch for this. With grain on, the layouts are longer and the yield lower, and a bookcase side 2100 mm long waits for a full length strip even when a turned part would have fitted. Our workshop boards are 2800 by 2070 mm. Retail boards here are usually 2440 by 1220 mm, with the grain along the 2440 mm length, and the same rule applies.

Two boards make a shelf

A single 18 mm shelf sags under books. The panel association's shelving bulletin puts the single span of 19 mm particleboard and MDF at roughly 510 to 580 mm under its heaviest listed load, about 2.4 kilopascals, at a sag of span over 240. A bookcase bay wider than that in 18 mm bows within a year.

So every open shelf, worktop and short upright in our wall units is doubled to 36 mm: two 18 mm layers glued face to face, each its own part on the cut list with the same code and a quantity of two. The front edge is banded after the glue up and trimmed flush, so the shelf reads as one thick board. A long shelf also carries two steel flat bars, 30 by 10 mm on edge, bedded in grooves between the layers. Where two boxes meet, the 36 mm line is simply their two 18 mm sides.

Source: Composite Panel Association: Particleboard and MDF for shelving, technical bulletin

Kerf, trim and the parts you cut late

A saw blade takes 4 mm out of the board with every cut, so a strip of parts has one kerf between each pair. Our cutting plans count it. Factory edges are used as they come, with no trim allowance, and the sheet says to rerun the layout if your saw or your trim needs more.

Some parts depend on a measurement nobody has yet. Top box sides and backs, fillers, the top panel to the ceiling and the end panel scribed to the wall are marked cut late. Their strips are ripped now and crosscut after the site check, so the boards are ordered once and nothing waits.

Board moisture and the UAE

Our carcasses are moisture resistant MDF, class E1 or better for formaldehyde, one decor on both faces. The kitchen under a sink and the wardrobe against an outside wall in August are the test. A moisture resistant core swells less when it does get wet, and the banding keeps most of the water out in the first place. For a bathroom vanity we go further: every edge banded, including the ones nobody sees, and a finish on all six faces.

If you are building yourself, buy the board for the room, not the price. Then read how we draw a box and what to order for a bookcase, where the board count comes out of the engine.