When concrete should not imitate stone or timber

Concrete is already a material. It does not need a second identity to justify its presence on an Australian house. That should be too obvious to write, and yet a large part of the decorative trade of the last thirty years has asked a slab to look like something it is not: slate from a country the house has never visited, sandstone from a quarry the budget could not reach, hardwood boards that would not have survived the same western sun.

The results are not always ugly on handover day. They are often worse later, when the fiction thins. A stamp cannot keep pretending once the antique release has gone and the saw cuts have declared themselves. A printed timber overlay cannot keep pretending once the film has worn in the chair legs. What remains is concrete prevented from being good concrete — grey or oxide or exposed stone — that has also failed at being the other thing. This is an aesthetic argument with technical consequences. The two cannot be separated in a climate that fades prints and moves clay.

The lineage we already have

Australian modernism, at its least theatrical, understood concrete as a surface that could carry light. The better university courts, the quieter civic buildings, the houses that treated the slab as a continuation of the wall did not apologise for grey. They specified it. They let formwork leave a mark, or they honed it, or they left a wood float that caught the afternoon. Colour, when it appeared, was oxide in the mass or the honest colour of local aggregate, not a picture of a material from elsewhere.

That lineage is a permission, not a style to copy. A house in Fitzroy or Fremantle or nipaluna / Hobart does not become cold because the terrace is grey. It becomes cold when the terrace is a confused quotation — Tuscan slate against cream weatherboards, or timber boards stamped onto a box that has already used real timber in the eaves.

Clients are shown photographs in which a patterned drive looks finished and a grey drive looks like a building site. What the photograph cannot show is year eight: the grey, if it was specified and cured, still reading as a material; the pattern reading as a date. Walk any estate built between 1998 and 2012 and the chronology is written in mats.

When faux slate becomes kitsch

Kitsch, in this narrow trade sense, is not “popular” and it is not “cheap”. It is a sign that has come unstuck from what it claims to mean. A slate stamp on a house that would never have been paved in slate, in a street that has no slate, in a climate that would have delaminated real slate anyway, is such a sign. The mat quotes a paving culture the house does not belong to. The antique brown quotes age the slab has not earned. The fake grout quotes units that were never laid.

The same holds for sandstone-effect shakes in suburbs that sit on clay, not on Hawkesbury rock, and for cobblestone stamps at the entrance to a double garage. Real cobbles were not designed for a family SUV turning on a six-metre apron. The stamp knows this and does it anyway.

Stamped and patterned concrete can be a texture rather than a quotation. A broken-stone skin that does not insist on units, a fine crease that takes light, a pattern whose module is the bay — these are concrete being concrete with a more interesting face. The line is crossed when the drawing asks you to believe in laid pieces that the saw cut then contradicts. Once the eye has seen the contradiction, the court looks like a printout.

Timber is the more recent temptation. Board-form walls are not the issue: that is concrete recording the timber that made it. Board-stamped floors and driveways ask the foot to read grain that is a millimetre deep and a sealer film thick. In Australian UV the grain is the first thing to lose its antique, and the long ridges can be a slip problem under AS 4586 once a film has filled the microtexture. A wet timber-board stamp on a south-coast winter morning is a quotation that does not love you back.

Honest grey and oxide versus a print

The alternative is not austerity. It is specification.

Grey, as the colour essay argues, is not the absence of a decision. Cement shade, finish and cure will move it from cool to warm. A magnesium-float grey beside bagged brick is a pairing with history in this country. A light broom, run across the fall, gives grip without quoting a material. A honed interior slab is one of the few decorative finishes that becomes more itself with use.

Oxide is colour in the mass. A muted red in a South Australian court, a dusty charcoal in a Melbourne warehouse conversion, a warm taupe sampled in the actual sun — these are concrete accepting pigment, not wearing a costume. They fade as minerals fade, which is slowly, and they can be repaired as concrete is repaired, which is in bays.

Exposed local aggregate is the third honest path. Basalt, granite, a river pebble that already exists on the street: the journal’s piece on exposed aggregate in Australian sun is the method. You are looking at stone that is really there. The sun will bleach a film and not the geology. That is a different contract with the client than a photograph of slate.

Prints — stamps, stencils, some overlays that carry a timber graphic — invert the contract. They look most like the thing on day one, which is when the invoice is paid, and least like it when the household has finished paying attention. Colour, texture and exposure are available without that inversion.

If the house is telling the truth in its walls — brick as brick, timber as timber, a bagged surface as a coating — the ground should not start lying.

Exceptions that still earn their keep

Absolutes make poor specifications. There are briefs in which a fiction is the least dishonest option.

Imitation still earns its keep in a short list of briefs:

• Access, where a house must take a wheelchair or a frame and real stone would make a lip or a joint pattern that fails a smooth crossing. A quiet stamp or tinted overlay can keep the ground traversable. The fiction is then in service of a body, not a brochure. Specify the slip class under AS 4586 as a requirement, not an afterthought.
• Heritage streetscape — parts of Adelaide, inner Hobart, the older Victorian grids — where a raw grey apron would be the rude object. If you cannot relay the stone, a carefully matched exposure or a restrained stencil may be the civic compromise. The test is whether a person at the gate reads a pavement in the street’s dialect, or a product.
• The tired slab that cannot be replaced — a court over a basement, a driveway whose removal would take a tree — and that must be made safer underfoot. An overlay with a modest texture can be a kindness. The overlay essay sets the technical conditions. Do the least pattern that achieves the grip.

In all three exceptions the joints should still be joints. Imitation that also denies movement is two fictions for the price of one.

Designing the real material

The constructive half of this argument is not “do less decoration”. It is “decorate the material you are actually pouring”.

Choose a finish for the way Australian light will hit it at 3 pm in February, not for the way a display slab looked under a marquee. Sample oxide and aggregate on the site. Draw the bays so the slab’s structure is the pattern: a grid of joints can be as handsome as a grid of pavers, and it will still be true when the clay moves. Put real timber where timber wants to be — a bench, a screen, a soffit that can be oiled — and not under the ute. Put real stone, if the budget and the geology allow, in a threshold or a garden wall, and not as a print on the drive.

Accept that concrete will look like concrete at the edges, at the saw cut, at the chip that will happen when the skip arrives. If that prospect is unbearable, the wrong material has been chosen, and no mat will save it. Australian houses, at their best, have always been good at this kind of plainness: a slab, a wall, a roof, a tree. Decorative concrete belongs in that company when it is a refinement of the slab, not a rumour of another building culture. The sun will have the last word. It is kinder to give it a mineral to work on, rather than a picture.