By: Jim Baty
In the foreground, a section of interior insulation placed in the form permits wiring to be placed in desired locations easily. In the background the concrete wall has furring applied to prepare for bathroom fixtures. Both locations have continuous insulation along the exterior.
Part IV: This article continues the six-part series developing a better understanding of the detailed solutions that are offered in the above-grade concrete home industry delivered by removable concrete forms (RCFs). Since strongly entering the market nearly a decade ago, this method of construction offers an ever-expanding variety of architectural and practical construction solutions for today’s home-owner and designer.
Over the past series of articles, we have investigated the design creativity, the constructability and the energy-efficiency of the above-grade RCF concrete home. These are the processes and the decisions that turn interest into a built reality. The shell components are only part of the equation in turning a concrete house into a concrete home. Deciding on and then producing the finishing touches on a home often determines how livable the spaces are and how much enjoyment is derived from the final product. Let’s take a look at some of these options. You will find that they are not all that different from the finishes you are accustomed to.
The previous two articles presented information on the advantages of the concrete’s thermal mass on the interior of the home with insulation placed within the concrete or on the exterior. Maximizing the energy efficiency in concrete homes involves being able to finish exposed concrete and achieve aesthetic acceptance by the owner. You’ll find this is a relatively simple task.
Exposed concrete walls
A concrete wall is a perfect substrate for one of the most common and original finishes: plaster. Applied to lathe and studs throughout the turn of the 20th century, plaster produced a durable and paintable room finish over the thin slats of wood nailed to the structural studs. In today’s above-grade concrete home, a thin coating of plaster is applied easily and effectively over the solid concrete to impart a textured or smooth finish that is either pigmented when applied to obtain an tone or painted with a myriad of color. The plaster system, a common touch in today’s high-end homes, requires an experienced craftsman to get it right.
Applying a standard texture paint system to the concrete is another option that maintains energy-efficiency while adding cost-effectiveness. This approach is applicable to a broader range of housing markets. Common throughout the country as a finish to “drywall” or gypsum wall board finishes, textured paint or textured paint rollers open up a wide variety of looks and feels from orange-peel to more aggressive sand-aggregate or stucco-like finishes.
There are portions of the home where it just makes sense to place the rigid insulation on the inside of the home. Depending on the design, it is conceivable that some areas will be insulated on the outside while others take advantage of this construction flexibility and place the insulation along the other side of the forms. A finish is needed over the rigid insulation, which often contains electrical or communication runs.
Exposed interior rigid insulation
Finishing an RCF wall with insulation on the interior should be familiar to those who have worked with ICF (Insulating Concrete Form) construction. As with other construction methods which position insulation on the inside of a concrete structure, drywall is the most common finish material. It is attached to the receiving devices. Once drywall is in place, the finishes are no different than any other home built today. Paints, textures, wall paper … all applicable solutions to meet the desires of the home buyer/owner.
It should not be assumed, however, that drywall is the single answer when making the decision to design the insulation for the interior of all or a portion of the above-grade home. These insulation systems are rigidly connected to the concrete wall providing a solid structure to support other finish options. Tile remains today an often higher-end, yet industry-wide finish system. When applying a tile surround or wainscot to a concrete wall with an interior insulation, a cementitious substrate must be attached to the wall prior to installation of the tile. Once again, the system of regular connection points is designed to accommodate the interior finish variety.
Still, there are those times when it is unavoidable or perhaps advantageous to provide an interior system not unlike many of the finished basements that make lower-level living so attractive today.
The stud alternative
When considering what to do with plumbing or other systems that might require a deeper chase than what can be provided for in the thickness of an insulation board, the ability to fur-out the wall with framing is another affordable and effective option. Easily attached to the concrete without concern for tying off at the header or sill, wood or metal furring in the form of shallow or traditional stud depths creates finish-ability and chase depth that is no different than a framed house. The advantage here over the framed cousin is quite similar to the advantage of interior finishes in lower-level living. A constant envelope is maintained behind the studs and the concern for interruption of insulation is eliminated. Between the studs, copper pipes, PVC vacuum systems, in-floor radiant heat manifolds and a variety of other housing items can be fixed. Traditional finish systems of a framed house are placed over the studs.
Some of the most famous architects in the world have chosen to express concrete’s uniqueness within the living space, at least for accents. This is yet another simple, low-maintenance interior finish possibility. Variety can be attained with the use of form liners. Another option is a light sand blasted finish. The sand blasting technique can soften the feel and appearance of the concrete and expose the intricacies of the aggregates used in the concrete.
Individually, these interior finishes provide the flexibility to address the desires and sometimes concerns that homeowners may express when contemplating the all-concrete home. Flexibility is certainly the key here. What is often overlooked, however, is how integrated all three solutions can be to the success of the home. Consider the quality of a textured coating over a concrete wall, adjacent to the same textured coating over an interior framed wall or a transition to that coating over an area of covered interior insulation. It is one that is imperceptible to the eye and reassuring to the touch. Where concrete can be exposed and treated aesthetically, it should be exposed for warmth and maintenance of interior conditions. Where concrete can be insulated while providing the flexibility for wiring systems with construction efficiency, it should be treated as an opportunity for finish variety. Just the same, where deep mechanical and plumbing systems are required along an exterior or interior concrete wall, knowing that the concrete wall can provide the continuity of an envelope without concern for breaks that might cause condensation or mold concerns can be ideal. In the end, what matters most is that the above-grade, all-concrete home is no different than the housing technologies that have been used for the last century and perhaps even longer. The difference is embracing the flexibility rather than ignoring the opportunity.
Established in 1974 for the purpose of improving the quality and acceptance of cast-in-place concrete foundations, the CFA has a variety of resources on this topic including materials available from the Concrete Homes Council established at the CFA to help contractors transition into this market. In addition to providing promotional materials, educational seminars, opportunities for networking and a telephone network that places members in one-on-one contact with an experienced contractor for assistance in resolving a variety of issues, the CFA and CHC represents the interests of its members and the industry on several code and regulatory bodies, such as the American Concrete Institute’s committee responsible for the creation of the “Residential Concrete Standard.” The CFA has several of its members on the ACI committee responsible for this document and will endeavor to ensure that the interests of the foundation contractor are considered. For more information about CFA, see cfawalls.org or call (319) 895-6940. For more information about CHC, see concretehomescouncil.org or call (319) 895-0761.