How to Make Concrete House Numbers (DIY Address Sign)

Pick a font and print your house number at the size you want. Spray-mount the printout onto 12mm plywood so it sits flat, then take it to the band saw. Tilt the table to about 10 degrees so each digit is cut with sloped sides - that taper is what lets the wooden number pull cleanly out of the set concrete later.

Sand right up to your line on a disc sander for crisp edges. For closed numbers like 6, 8 or 0, drill a hole in the middle and thread a fret saw blade through to cut the centre out.

Your mould is a shallow open box the size of the finished plaque. Cut the base and sides from glossy melamine board, because the shiny face barely sticks to concrete and strips away clean. Screw the sides down into the base from underneath so no fixings show on the casting face.

Want a rounded top like a traditional marker? Drop in a curved hardboard former. Run a thin silicone fillet along each inside corner, or tape in a 45-degree bevel strip, to give the front edge a chamfer instead of a sharp arris.

Lay the wooden numbers face-down on the base of the mould and shuffle them around until the spacing looks right against your printed guide. Remember the layout reads back-to-front in the mould, so check it in a mirror if that helps.

Stick each digit down with a thin smear of silicone. You want them anchored so they do not float when the concrete goes in, but not so glued that they will not release when you demould. They sit proud now and leave the recess later.

Brush mineral or butcher-block oil over the whole mould and the numbers. This release agent is what stops the concrete bonding to the melamine and tearing when you strip it.

Mix a 4-to-1 sand-and-cement batch. Stir the dry ingredients first, add a pigment if you want a colour, then drop in a handful of reinforcing fibres to cut down cracking. Add water slowly until it is thick and spreadable, like stiff porridge, not soupy.

Trowel the concrete into the mould and push it firmly down into every number so it fills each impression. Build it up to the top of the box and screed the back flat.

Now get the trapped air out. Hold a vibrating sander against the mould walls, or dip a concrete poker into the mix for a few seconds at a time. Bubbles left around the numbers show up as ugly pits, so work all the way round until the surface settles.

Leave the cast flat, out of direct sun, and give it a few days to cure hard. A slow cure is stronger than a fast one, so do not rush it.

When it has set, back the screws out and gently prise the melamine sides away, then lift the slab off the base. Work slowly around the wooden numbers so the edges of each recess stay crisp. The digits usually stay locked in the concrete and leave clean sunken figures.

Rub the faces down with a sanding block to knock off any sharp arrises, and vacuum the grit out of the number recesses. If the surface has a few small voids, fill them with a slurry of the same mix and wipe it back.

For hanging, set two screws into a steel plate cast or fixed into the back, or drill fixing holes now while the plaque is flat on the bench. Doing it here is far easier than drilling it once it is up on the wall.

If you want the digits to stand out, paint or stain the recesses and wipe the excess off the flat face. Then brush a coat of exterior concrete sealer over the whole plaque so rain and frost cannot get into it.

Screw it to the wall or a gatepost, or sink a taller garden marker a few inches into the ground. Sealed and mounted, a concrete number will happily outlast the house it is nailed to.