How To Build A Concrete Table

  • How To Build A Concrete Table

Stone garden furniture is timeless, but it can be pricey.

This table has a concrete top featuring fern leaf imprints, which is supported on a solid timber base and assembled using dowel joints.

This top costs about $60 to DIY, which includes the formwork and reinforcement, but the total cost will vary with the timber used for the base.

It needs to be exterior grade and the type has to suit the finish. Go for clear treated pine if staining and finger-jointed H3 LOSP pine if painting.

The formwork for the tabletop is made from melamine-coated particleboard so it is easy to remove once the concrete has cured. 

A tabletop slab needs strength, a low shrinkage rate and a long cure time. Use a high-strength concrete mix, add a layer of galvanised light gauge steel mesh and reinforce it with three 8mm galvanised threaded rods.

Shrinkage and cracking is usually caused by excess water, so keep the mix as dry as possible but still workable.

Allow the concrete slab to harden for at least two days, keeping it moist and covered in plastic. To prevent staining, and to give a glossy finish, apply 2-3 coats of an acrylic sealer.   

DESIGN TIP Try inlaying decorative objects like seashells, coloured glass, tiles or even coins in the top.

Build the base 

Cut the legs and rails to length with a mitresaw, then drill dowel holes and assemble the frame using 50 x 10mm dowels and exterior PVA adhesive, pulling it tight with sash clamps.

TIP Use masking tape around the drill bit as a depth guide. 

Step 1. Set out rail centres 

  Set out the rail centres on the ends of all four rails, marking vertical centrelines and hole locations for the dowels 15mm in from each edge along the marked lines.

step 1. set out rail centre, handyman magazine,

Step 2. Drill the dowel holes 

Drill the dowel holes by clamping the rails in a vice and using a dowelling jig with a 10mm diameter brad point bit to drill holes 27mm
deep at each marked position.

drill the dowel holes, handyman magazine,

Step 3. Transfer the hole locations 

  Transfer the locations to the legs using dowel centres so the rails are set 12mm down from the top edge. Drill the holes, then test-fit. Apply adhesive and tap in the dowels.

transfer the hole locations, handyman magazine ,

Building the formwork 

Melamine-coated particleboard is an ideal material for formwork as it’s inexpensive, smooth and water-resistant. It costs about $12 for a 1200 x 600 x 16mm sheet.

Cut the formwork pieces using a tablesaw or circular saw with a straightedge guide. The two sides are cut to extend beyond the ends for easy removal. 

Use a brad nailer or drive screws by hand, drilling pilot holes. Seal the inside corners using silicone to give the cast rounded edges.

TIP To spot smudges during the clean-up, use dark silicone.

formwork cutting diagram, handyman

Make the concrete tabletop 

Step 1. Assemble formwork

Secure the formwork ends to the base then attach the sides using a brad nailer, spacing the fasteners 150mm apart. Rub wax over the surface of the formwork to help release the concrete later. TIP The sides of the formwork extend 170mm beyond each end.

Step 2. Prepare the cast

Create even edges by applying masking tape along the formwork ends and sides 5mm in from the corners and edges. Apply a bead of silicone, smooth it with a wet finger, then remove the tape. Lay the fern leaves on newspaper and spray with adhesive, then press them onto the formwork base.

Step 3. Pour concrete

Use a spirit level to check the formwork is level in both directions, raising one side with shims, if needed. Pour the concrete around the perimeter to 25mm deep, then position the wire mesh with three lengths of reinforcing rod tied on. Pour in the remaining concrete to 40mm deep.

Step 4. Settle the concrete

Wearing plastic gloves, carefully work the concrete mix into the edges and corners of the formwork and around the leaves. To drive out air bubbles, lightly tap the sides of the formwork with a hammer. When the concrete has settled, smooth out the surface using a steel float.

Step 5. Clean the tabletop

Leave the concrete to dry and cure for at least 2-3 days, then carefully turn the slab over and remove the formwork, starting with the overlapping sides. Use a stiff brush and awl, if needed, to work the leaves out of the concrete top, then scrub the whole surface to remove wax and clean up any melamine residue.

Step 6. Finish the table

To give the illusion of natural stone, chip around the edges of the tabletop using a club hammer and cold chisel. Turn the top over and chip from the other side, then hone down any remaining sharp edges using an angle grinder. Build the base, then attach the top using silicone.

Click on the diagram

Click on the diagram to see each element of this concrete table.

Click on the materials list

Click on the materials list to see what materials you will need for this project.

Click on the cutting list

Click on the cutting list to see what sized pieces of melamine and pine you will need to build this table.

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