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Build a concrete bench

Build a concrete bench

A secluded spot, out of direct sunlight, is the perfect place for a garden bench. A well-placed bench invites you to sit and admire your garden and it also acts as a focal point. This concrete bench is made in three separate sections, a seat and two sturdy legs, by moulding the concrete in boxes made of shutterboard. Placing quadrants in the moulds gives the edges of the concrete and attractive shape.

What you need:
Shutterboard* (22 mm thick) to build the moulds, as follows:
Seat (5 pieces)
Base: 1220 x 400 mm (x 1),
Long sides: 1220 x 90 mm (x 2)
Short sides: 440 x 90 mm (x 2)
Legs (8 pieces)
Wide sides: 200 x 400 mm (x 4),
Narrow sides: 300 x 400 mm (x 4)
wood screws (+- 60)
3 x 3-m quadrants**
35 mm flat head wire nails (+- 50)
1 bag PPC cement
3 bags river sand
2 bags 19 mm crushed stone
1 m BRC mesh
80 grit sandpaper

*Shutterboard is board made from very thinly cut pine sheets that are bonded together.
**Quadrants are thin lengths of wood with two flat sides and one curved side, often used to finish off skirting.

mitre box
float, wood or plastic

Step 1: Build the boxes that will form the moulds. Start with the seat, joining the sides and the base by first drilling holes and then screwing them together. Next do the legs, making two identical boxes by using two wide pieces and two narrow pieces for each. The boxes for the legs don’t have a base; you should place them on a flat board to fill them.
Step 2: The lengths of quadrant must be sawn to size so that they can be used to ‘line’ all the inside corners of the three boxes. Cut the ends of the quadrant for the seat at a 45° angle, using the mitre box. Now fit these pieces into the corners of the boxes (curved side outwards) and nail them in place. This completes the moulds. Now cut the BRC mesh to size – you need a layer for the seat and a piece for each of the legs.
Step 3: Mix the cement, using 1 part cement, 1 part stone and 1 part river sand (this 1:1:1 ratio ensures strength). Add enough water to get the mix to a ‘yoghurt-like’ consistency. You need the mixture to be fairly sloppy because you will be pouring the concrete into the moulds.
Step 4: For the seat: fill the box to half way with concrete, put down the layer of BRC mesh, then fill the remainder of the box with concrete. Use the float to agitate the mixture so that there are no air pockets left in the concrete. For the legs: make sure the boxes are standing on a level piece of board then place the BRC mesh inside them and fill them with concrete.
Step 5: Wait! The concrete must cure for at least 21 days. Thereafter unscrew the boxes to reveal your handiwork. Any sharp bits and rough places can be gently sanded smooth with sandpaper. Brush off the resulting powder with a dry paintbrush. (Keeps the moulds – they can be reused.)
Step 6: Place the legs in position and lower the seat onto them, and your bench is ready to use.

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