Warming up to concrete floors

Hey there, time traveller!
This article was published 09/10/2005 (7329 days ago), so information in it may no longer be current.

OTTAWA — David Larcher is a magician with concrete and acid. He is also the supremely confident contractor who took the floors of our new Ottawa home and embedded plastic tubing in wet helpings of grey, runny concrete.

Within days, we were walking barefoot over warm, glorious floors. It’s a story of technology, artistry and trust.

“Wait until you see the finished product,” the concrete contractor said at the start of this summer project to install acid-washed concrete floors warmed by radiant heat. “You won’t believe the transformation.”

Our concrete specialist oozed confidence. The floor, on the other hand, seemed to ooze all manner of discouraging hues, including rust, black foam and curious greenish bubbles. It looked nothing like the brochures or the beautiful room in an architect’s house Larcher had done last year. Ours looked like the oil-streaked floor of a garage. Lucky for us, he was right.

First, a few words about concrete. Anyone who has walked across a basement floor in bare feet knows it’s hard, cold and often damp. Why would anyone want concrete floors? The answer lies under the surface.

In recent years, radiant floor heating has grown in popularity; the system works by applying heat underneath or inside the floor.

This is hardly a new idea. The Romans heated the floors of their bathhouses. Korean palaces did the same for hundreds of years. European homes and businesses have used radiant floor heating for decades.

In recent years, radiant technology has improved and prices have fallen to the point it’s no longer necessary to be a Korean princess or Bavarian auto magnate to enjoy it.

There are three radiant heating types: hydronic, electrical and air. We chose hydronic heating because of its practicality. It’s a system of durable plastic tubes that circulates hot water through the floor. These tubes can be embedded in a concrete slab or a gypsum cement overlay, or laid between narrow strips of wood on a subfloor.

It can also be hung below the subfloor. The amount of heat depends on how far apart the pipes are spaced, the temperature and flow rate of the circulating water, and the floor covering … which brings us back to concrete.

Not all flooring surfaces are good heat conductors. For example, thick carpets absorb radiant heat, so it takes more energy to warm a room. The same is true of wood and even vinyl. Radiant heat flows most efficiently through ceramics, such as tile, or bare concrete. This is why many homeowners put radiant tubes in the basement during construction when the concrete slabs are poured.

Knowing we wanted efficient radiant heat throughout the house, our builder, Peter Markhauser, offered a solution. “Why not pour a concrete slab on the upper floors?”

“Won’t that be too heavy?”

“Not really,” said Markhauser, who is also an engineer. “You add a few more floor joists to support the load.”

There are a lot of perks to concrete. It doesn’t squeak. It’s easy to clean. It doesn’t shrink or expand according to humidity like hardwood. And unlike hardwood or wall-to-wall carpet, concrete will stand up to hordes of stomping, muddy, roughneck children without a problem. After all, they park cars on the stuff.

But who wants a living room that looks like a parking space? Fortunately, new interior concrete floors can be finished in a bewildering but beautiful array of colours and styles. A good website for an introduction to the subject is www.concretenetwork.com. Some companies, such as Colormaker, offer toppings and coverings. Others will polish the floor to a smooth, Teflon-like finish.

One of the most interesting techniques is acid-etch staining. Unless you’re a chemistry buff, the explanation is superfluous. But here goes. Acid stains are acidic, water-based solutions containing metallic salts. The acid opens the surface of the concrete, allowing the salts to reach free lime deposits in the hardened concrete. Water from the stain then fuels the reaction, which can last up to 30 days. The result is a mottled, swirling finish looking something like marble.

“There are a lot of things that can cause variation,” warned Larcher. The properties of the cement used may vary. Humidity, finishing methods and the type of aggregate (rocks) used can influence the colour. In the end, acid staining is a chemical reaction, fascinating but unpredictable.

None of this is made easier by stain companies, which supply colour samples the size of fingernails, making any selection feel like a gamble. Websites show dazzling pictures of the floors created by artisans with inlaid sundials and extravagant patterns.

But unless you’re hosting the Cirque du Soleil in your living room, you’ll likely want a simpler pattern.

Fortunately, Larcher had a previous client with similar sensibilities, who chose a rich, dark brown colour for his bedroom. After a brief visit, we agreed it was perfect.

In the end, the colours weren’t what we expected. The living room, now a rich gold with mottled brown, needed a second application of stain to achieve the right effect. And the second floor, which was supposed to be a pale wheat colour, instead has Tuscan gold highlights. It’s growing on me.

After several layers of wax sealer, the floors gleam, smooth and warm. They’ll need a fresh coat of sealer every few years. There’s also a compound near the doors to prevent entrants with wet feet from slipping.

Acid staining is not for the faint of heart, but the results can be extremely satisfying.

Anne Trueman is a deputy managing editor at the Ottawa Citizen.

–CanWest News Service