As foundation contractors your focus in this recession is certainly obtaining work…any work and as much of it as you can. One way to secure more work in this down economy (and into the future) is to do more on the jobs you do get. Your crews are on the job, your equipment is there, the concrete pump is there – but you only cast the foundation walls and footings. Some of you have made the jump to above grade housing and most of you have at least contemplated it. If you aren’t quite ready to jump in with both feet why not go part way—cast the deck (main floor of the house) in concrete. You might not be able to increase the number of your projects this year but you can increase your gross sale. One contractor, who has built several decks, said the concrete decks cost around 30% more than a traditional wood deck.

Why would an owner spend more to get a deck; and, what is in it for you?

WHY AN OWNER SHOULD INCLUDE A DECK

There are many good reasons for owners to consider concrete decks. Here are some of them:

• Clients get the ultimate Safe Room. A basement with six to eight inches of concrete on 3 or 4 sides and 6” to 8” above. A room with those specifi cations can resist just about anything Mother Nature can throw at it.
• Concrete floors are quiet. Six inches of concrete has tremendous sound absorptive qualities at all spectrums on the audible scale.
• Fire protection. A fire that starts in the basement (say, the furnace room) is going to take much longer to spread and will be much more easily contained if there is a horizontal concrete layer separating the fire from the balance of the habitable space.
• The elimination of mold and varmint damage. Mold needs three things to grow: mold spores (they are everywhere), moisture, and a food source. Concrete is not a food source for mold growth like wood or drywall, so this is not a concern. As to wood eaters such as termites, mice, and carpenter ants – if you find one that eats concrete then we’ve got a lot bigger problems to worry about.
• Thinner floors. A six inch concrete deck can span up to 20’ without intermediate support. It would take at least a premium grade (Douglas Fir-Larch #1) 2×10 spaced 12” o.c. to span that distance – and the wood won’t provide any of the other qualities discussed. The continuous connection between a concrete deck and a standard 8” foundation wall produces a strong structural detail at the wall/floor juncture, which will further improve the structural efficiency and performance of the floor system and wall.
• Radiant floor heating. In-floor heating is the ultimate in comfort and efficiency. Concrete floor systems are the best material to use with radiant heating systems.
• Decorative concrete floors. This craft has come a long way since its introduction. Stains, stamps, and a host of other concrete finishes will add durability, beauty, and functionality to your home.
• Energy efficiency. The most efficient method of casting the walls and decks is in a single placement operation. The resulting monolithic cast will provide the most airtight, structurally integral basement wall/deck available on the market with little, if any, material waste.

HOW DECKS BENEFIT CONTRACTORS

What’s in it for you, the contractor, in addition to more work and money from the same project?

• Top restraint. You will get the best support possible for the top of the wall so there won’t be any more call-backs because the excavator pushed a wall in during the backfilling operation.
• Anchorage to deck. You won’t have to be concerned about anchor bolts giving way during backfilling.
• End wall bracing. There won’t be any more issues about the possible lack of “required” bracing for the joists parallel to the end walls.
• Performance. There are fewer problems with cracks because the top of the wall is not only fixed, it gives greater load capacity to the wall itself.
• Floor Diaphragm. If you are building walk-out basements, there is always concern since there is no soil opposite the backfilled wall to resist the force of the soil. With a concrete deck, you have the ultimate diaphragm which can transfer load to the transverse or perpendicular walls.

The ACI 332 Committee is contemplating the inclusion of decks in future versions of the ACI 332 Standard. Empirical tables will likely be part of the output of the committee reducing or eliminating the need for an engineer on many decks, or if an engineer’s approval is required, the cost can be substantially reduced.

EQUIPMENT NEEDS

What do you need to begin pouring decks as well as walls? Fortunately, the form manufacturers have anticipated this need and have all of the accessories and tools required to form, brace, and support the decks. Decks are typically cast at the same time as the walls, which makes casting a one-step operation. The two major needs are a ledge or support to form the transition from the wall to the deck and to support the deck form. The second is the temporary intermediate beam and shoring system to support deck form panels.

How does it change your operation? You will spend more time on the job (for which you will be compensated) and as you do more of them, you will develop crews who can be as efficient with wall/deck combinations as they are with wall/footings (relative to the cost or man/hour).

PREPLANNING – OPENINGS AND SERVICES

One aspect of building concrete decks that becomes more important when compared to building with wood is planning. With wood, you simply drill and cut openings where required for plumbing chases and vents. Wiring is installed after the wood deck is already in place.

While it is possible to drill and saw concrete after placement, it makes more sense to use block-outs and simply eliminate the concrete from locations where stairs, ducts, and chases are required. The location and size of these elements should be included in the plans. Why not save time and concrete? Both equate to cost savings. The also needs to know where the openings will be placed as additional reinforcement may be required at the openings.

Wiring can be installed in surface mounted “Wiremold” or similar products, but it is more efficient and aesthetically pleasing to have conduit in the slab instead of surface mounted. The location of lights, outlets, and switches can be easily predetermined. When in doubt, install an extra conduit. Depending on your local codes, the concrete contractor may be able to install the conduit with a licensed electrician making all of the connections.

REINFORCEMENT

Steel reinforcement in a structural slab is a critical component to its performance. Depending on whether or not there is an intermediate beam, the reinforcement may be near the bottom or top of the slab. Drawings and specifications prepared by an engineer will inform you as to the proper size, location, spacing, and cover for the reinforcement.

LARGER SPANS

When spans are longer than twenty feet, there are several options. First, you can thicken the slab. An additional 2” of concrete with the appropriate amount of reinforcement will allow you to increase the span by several feet.

A second option is an intermediate, integral concrete beam. You could also use a steel beam but a concrete beam can be cast integral with the floor and wall pour.

The beam can be supported with steel columns spaced appropriately to the beam depth and loading conditions. Another option is an intermediate bearing concrete wall, cast monolithically with the exterior walls and deck. Post-tensioning is yet another option if the expertise is available in your area. A down economy is an excellent time to entice specialty contractors who otherwise might not consider residential construction.

OTHER SYSTEMS

The fl at slab system is not the only option available for doing concrete decks. Another innovation for residential construction is the oneway or ribbed slab, which consists of a concrete beam spanning one direction cast integrally with the floor. The advantage of this type of system is that you can span much greater distances. The total depth of the floor system will be greater but the amount of concrete used will be less for greater spans. One system uses sliding pans that can be varied depending on the span length.

HEATING AND COOLING

Another advantage in making more of your home of concrete will be less dynamic temperature gradients. The thermal mass inherent in the concrete will absorb heat and once at a given level, it takes much longer for concrete to change temperature. While it takes less heating and cooling energy to maintain temperature, space conditioning is still required.

Radiant heating is considered the ultimate heating system by many and with an in-floor radiant heating system you attain this goal without the cumbersome radiators typical in traditional hot water or steam systems. In-floor heating systems are simple with concrete decks. They are cast into the deck in conjunction with the reinforcement and electrical conduit.

Preplanning is again important as you cannot attach plates or cut openings where the piping has been placed. A warmed slab can be a real comfort on cold winter days.

Air conditioning can be accomplished using a traditional duct distribution system or with a high velocity duct system which uses much smaller ducts. Dehumidification is typically the number one need for cooling in a home with concrete decks or walls.

FLOOR FINISHES

You have several options when it comes to finishing concrete floors. You can carpet the floor, but you will greatly reduce its ability to improve energy performance by isolating the thermal mass of the floor from the habitable space. Carpet also increases the possibility of mold, mildew, and other undesirable things that reside in the piling. If you must use carpet, consider using area rugs, which can be removed, cleaned, and varied as your tastes change.

Placing wood over concrete will also reduce thermal performance but not to the same degree as carpet. Tile of any kind, applied directly over the concrete is the best way to introduce more variety in appearance for entries, kitchens, and baths while maintaining the mass storage potential.

Decorative concrete is one area of that has made great strides over the past decade. It has evolved from a curiosity to an art form with contractors specializing in the craft. There are dozens of systems producing an unlimited number of patterns, colors, and textures. They result in a low maintenance, durable, and unique finish that will serve you well for years to come.

The case for considering concrete decks is compelling. Yes, it will cost a little more but as the saying goes, you get what you pay for. In the case of concrete decks, you get a lot more than what you pay for.

BUT HOW DO YOU GET STARTED?

What are the tools you need, the information and support and more importantly, how do you get your mind around how it might make a difference?

This is where the CFA comes in. At Summer Convention this year in Amelia Island, we’ve brought back our resident concrete expert, Brent Anderson. A significant amount of his work over the last half-decade has come from the transition internationally to concrete shells, including concrete decks.

If you want to get started in this transition, what better way to meet with your peers and discover the reality behind this opportunity? There is much more here than adding to your potential work. Concrete decks have the ability to significantly strengthen the wall, reducing the required concrete thickness and/or the amount of steel reinforcement.

Here it all as you take in Summer Convention 2009 with the CFA. See the Summer Meeting information packet in this magazine, contact a CFA staff member today or visit our website at www.cfawalls.org to get more information.