Article No: 265

2009-11-17 11:24:53
A Tilt-Up Home in the Woods
By: Michael Cockram


Photography by Michael Cockram
Natural materials and careful planning integrates the concrete home into the wooded site.
 
Arkansas, known as The Natural State, has millions of acres of forests, 600,000 acres of lakes and almost 10,000 miles of streams and rivers. The people of Arkansas value their natural settings, and it’s not unusual on a drive through the Ozarks to see everything from picturesque log cabins to Victorian and antebellum homes nestled among the trees. What is unusual, if you were to see its walls being tilted into place, is a concrete house. But once it’s finished, you’d never know by looking that the beautiful home in the woods is an engineered concrete house that will stand up to the worst that Mother Nature can offer.

Set among the trees on the edge of a small gorge in the foothills of the Arkansas Ozarks, the Pete and Jeri Cockram home looks like it’s been on the site for years. But the recently completed house is a study in how thoughtful planning can produce concrete structure that is built seamlessly into its surroundings.

Tilt-up concrete construction is typically associated with large-scale utility buildings such as warehouses – often built on flat sites that are clear of obstructions. When concrete contractor Pete Cockram set out to build his dream home in the woods he opted for a tilt-up, a system he knew well and one that had the beauty of finish, insulation and interior wall all in one module.

Cockram’s design places a double-height living area at the center of the house with a sculptural steel and concrete stair leading to a bridge that connects two bedrooms at opposing ends of the house. A spacious colored concrete deck, which wraps around the back of the house and connecting the sun room to the living room, pushes out over the small gorge that tumbles down the back of the lot.
The site presented the first challenge. The owner/builder wanted the house to weave into the many mature trees on the lot. Once he had the basic design of the two-story house, Cockram began organizing how the walls would be poured on the ground.

“It was like a complicated puzzle. The first step was to lay out each wall in AutoCAD,” Cockram says, “then move the pieces around until they fit in the available space. It sometimes meant pouring one wall on the ground then filling the openings with sand and pouring a second wall on top of the first– always keeping in mind the sequence of erection.”

The 10-inch walls are layered into 2-by-12 formwork: a 4-inch exterior wythe allows for the depth of stone; 2 inches of rigid insulation in the middle and a 4-inch concrete interior wythe. The exterior layer of stone is laid into place on a sand bed. All of the stone came from the site – each hand selected by Jeri Cockram, who carefully composed plant fossils and accent elements such as ceramic medallions.

The erection process was not without its challenges. Using a 100-ton crane to set a hefty 33,000-pound wall seemed easy enough. But due to the long extension needed to get the wall in place, the crane shut down automatically when it reached 80 percent of its capacity – just 4 inches shy of its mark. It took a skid loader to relieve enough of the weight so the crane could scoot the wall the remaining distance.
The owner selected a Hambro steel joist system for the upper level concrete floors. The joists are welded to ledgers or weld plates that are cast into the walls. Plywood forms boards are fastened between the joists using special clips and the joists have S-shaped plates that extend into the concrete floor. One advantage of this system is that the plywood forms and clips can be removed and reused after the pour.

“One of the things I’m most pleased with is the stability of the structure – the walls are placed directly on piers that are poured down to bedrock,” he said. “Despite the weight of the walls there’s been no movement, and all of the exposed floor slabs are free of cracks.

A sandwich panel home is not only durable inside and out, it’s also ideal for passive solar applications. Having so much concrete mass in the walls and floors regulates the temperature swings and with good solar exposure in the winter the house warms during the days. The Cockram’s have experienced the most significant difference in their summer utility bills. When fully leafed out, the surrounding trees shade the house well. Utilizing cross ventilation at night cools the concrete and keeps the house comfortable throughout the day.

Cockram’s design places a double-height living area at the center of the three-bedroom house. The living space is focused on a stone fireplace bordered by windows that frame the trees on the wooded backside of the house.

The living area is punctuated by a sculptural steel and concrete stair leading to an upstairs bridge that overlooks the living room and connects the two guest bedrooms at opposing ends of the house. With the master bedroom and bath off the living room, the owners can live comfortably on the ground floor.

A curved glassy stair tower element with a conical roof highlights the entry area and brings architectural interest to both the interior and the exterior.

The house is made for comfortable living both inside and out.

A spacious colored concrete deck wraps around the backside of the house. The deck pushes out over the small gorge that tumbles down the back of the lot and is raised enough to give the experience of being up in the trees.

A sunroom opens to the deck with two curving concrete stairs flowing into the space leading to the kitchen dining area. The warm tones and softer feel of the wood windows, doors and cabinets contrast and balance the concrete and masonry surfaces.

The exterior also achieves a balance of wood and stone. Small areas of wood shingle siding on elements such as dormers give interest and variation to the exterior. The two-car attached garage is pulled to the west end of the house and features slightly arched garage door openings.

Concrete floors also allow for a hydronic radiant heat system, a method that many believe to be the most comfortable way to heat a home. The system is dead silent, and it is efficient because it heats surfaces (like the radiant heat from the sun) so that the air temperature can be kept lower. It also puts the heat where it’s most effective in warming the occupants from the feet up.

The living room slab steps down to allow for hardwood flooring, giving a softer variation to the floor treatment in the house. Although wood isn’t as good a conductor as concrete, it still performs well for radiant systems.

Another feature of the floors is the creative use of concrete stain. In the bedrooms, Cockram masked areas to achieve a variety of geometric patterns in the floors. In the common rooms the subtler color palette was applied so that it has a richly mottled surface.

The Pete and Jeri Cockram Arkansas home serves as a model for combining a commercial building with natural materials and thoughtful composition – and integrating homespun craft into an industrialized building system.

Michael Cockram is a freelance writer based in Fayetteville, Ark. He can be contacted by e-mail at mcckrm11@yahoo.com.