Shuttering Plywood 18 mm

What it is

Kitovu keeps 18 mm shuttering plywood in its stock in Zanzibar and sells it by the sheet at TZS 54,000. Shuttering plywood is the panel that faces the wet concrete in formwork: the deck under a slab, the sides of a beam or a wall, the box around a column. Once the concrete has hardened, the panels are stripped, cleaned and used again.

The sheet size, the face film and the wood of the core are not in Kitovu’s records yet. Plywood on sale in Zanzibar usually comes in sheets of 1220 × 2440 mm, the size Zanzibaba Timber lists for every thickness from 3 to 18 mm; one sheet of that size covers 2.98 m² (our calculation). Ask on WhatsApp for the size and whether the faces are film-coated.

Why 18 mm

Thickness sets how far a panel can span between the timbers under it before it sags under wet concrete. Formwork data sheets give the stiffness of each thickness: the Doka sheet for Dokaplex, a film-faced birch panel, quotes a bending stiffness of 4.56 kNm²/m along the grain for 18 mm. That is the figure an engineer uses to set the spacing of the joists under a slab deck. For the thinner sheet in stock, see Shuttering Plywood 12 mm.

How it is used

On a slab, the sheets lie on timber joists, which rest on bearers and props; the joints between sheets fall over a joist so that no edge hangs free. On walls and columns, the sheets are held by timber studs and ties. Sawn Timber 50 × 100 mm (2 × 4) from Kitovu’s stock is the usual size for the joists and studs behind the panels.

Before each pour, the face gets a coat of release agent suited to the panel, so that the concrete lets go cleanly. After stripping, concrete residue comes off straight away, before it hardens on the face.

How many sheets

For a slab deck, divide the area by the area of one sheet and add some for cuts. With 1220 × 2440 mm sheets (our calculations):

How many sheets

Slab deck	Area	Sheets, before cutting waste
Room 4 × 5 m	20 m²	7
Floor 10 × 12 m	120 m²	41

How many pours

The number of times a panel can be used depends on its film and on handling. For its film-faced birch panels, Metsä Wood puts the figure at 30 to 100 uses in the FormPLUS data sheet, depending on site practice, release agent and storage. That figure is for a premium birch panel, not confirmed for the sheets in Kitovu’s stock. Panels last longer when they are stored flat, off the ground and out of the sun, and when cut edges are sealed.

The formwork and shuttering page compares plywood with steel and other formwork.