Subfloor and window installation The vast majority of our work has been from customers requesting that their entire house be constructed of ICF's. The benefits of ICF's are even greater in above grade applications, particularly their tornado and fire resistance and also the near zero air-infiltration qualities. We at R-Value believe that a full ICF home is the absolute best quality home available, at any price. And based on the amount of business we have seen in the last 5 years, this seems to be the general consensus of the public. Building the entire house from ICF's is a little different than most people are used to. This article looks at both the subfloor connections and window/door installations.
Options for subfloor installations. There are several different ways to install the subfloor in an all-ICF home. Since the exterior walls are insulated concrete, they are quite heavy and must bear on concrete, not a subfloor. This means that after the basement wall is poured, the framer will not be building the box and setting the subfloor on top of the wall as usual. Your typical ICF basement wall is 6" of concrete with 2.5" of foam on either side, leaving an 11" overall wall thickness. The wall continues at this thickness all the way up to the trusses, where a top plate is bolted down and trusses conventionally installed, or individual anchors embedded in the concrete fasten each truss to the ICF wall. This type of wall has two methods of subfloor installation: top chord bearing floor trusses or ledger board with joist hangers. (There are other methods that are not cost or quality effective). Top chord bearing floor trusses are installed by hanging the top chord from an interior brickledge on the ICF wall. The brickledge protrudes out from the surface of the wall an additional 4", and is completely hidden within the open space of the floor truss. Installation is simply bolting down a treated 2x4 and then attaching the individual trusses to it. This is a fairly expensive option unless floor trusses are going to be used anyway. If that is the case, the cost to the framer is less than normal, since a rim joist isn't used; although it costs slightly more to install the brickledge.
Ledger boards with joist hangers are used when 2x or I-joist floor systems are installed. A galvanized steel bracket made by Simpson© is installed in the wall prior to the pour at 48" o.c. in the area the floor will attach. After the pour, the framer will snap a line around the interior perimeter of the home for the top of joist height. Then he will use the other half of the bracket and the self-tapping screws supplied by us to hang a ledger board. This will be either a 2x12 or an LVL depending on the loading of the floor. From this ledger board, all of the joists are hung with joist hangers. This is also a fairly expensive option because installation of the ledger board and hanging all the joists takes a bit more time than normal. In addition, you have the cost of the ledger board and all the hangers. This option is probably slightly less overall cost than the floor truss, due to no charge for brickledge and a more inexpensive joist.
Change wall thickness to create a ledge. Another innovative way to install the subfloor that is quick, low cost, and easy is to use a 6" or 8" taper top form for the basement, with the taper to the inside, and then a smaller form for the above grade level(s). This creates a 2" to 4" ledge on the inside to bolt a treated 2x4 and set on the floor joists. This is likely the most inexpensive option, but there are certain limitations which we can discuss with you when the project is bid.
These are the typical ways we connect a wood subfloor, there are others that may make more sense depending on the specifics of the project. We discuss them thoroughly when we meet with our clients to determine which will be best for their home. Some produce less waste than others, some use less materials; but one is right for your project! Lite-Deck floor systems An option gaining popularity for many reasons is the use of concrete floor systems. An ICF for floors is an excellent way to construct your subfloor, as it is hands-down the quietest, most energy efficient, and healthiest option.
When a Lite-Deck floor system is installed, there is no need for a framer to come in between ICF pours. All of the work is done by R-Value. The Lite-Deck floors bear directly on top of the ICF wall pour, and then the ICF walls continue up from there.
Options for window installations. Cutting out ICF's, building bucks, and forming around them consume a significant amount of time. The cost of the buck material is offset by the savings of not using blocks, concrete, and rod in the opening, but you are still left paying for time. So we are always looking for ideas on forming and installing window bucks. There are no limitations in window placement and design, any shape opening can be formed.
There are several ways of forming out and then installing the windows and trim. All of them will have similiar R-Values. Each builder will likely have his or her own preference. Treated wood bucks can be built several ways, and have an advantage over V-Buck in that there is a more solid attachment surface throughout the width of the buck and that they do not bow as much under pressure. Disadvantages include difficulty handling the heavy window bucks, lots of waste generated, warping lumber, messy appearance, gaps that form between the lumber and concrete as both shrink with time, and the ability to rot. The cost of wood bucks is equal to V-Buck without the wood inserts, as the materials are less expensive, but the labor is higher.
Pre-Buck is a wood buck that is delivered to our jobsites, pre-built to the sizes we specify. Pre-Buck is made from rim joist material, which is essentially extra thick OSB. The bucks feature v-grooves on the back side to interlock with the concrete, and a full waterproof coating, as well as metal flanges to align the buck with the wall. Advantages include: they are made from waste materials, there is no jobsite waste generated, the bucks will not shrink, warp, and split like treated does as it dries, solid attachment surface with a material familiar to builders, and little movement under pressure. Disadvantages include: hard to find any.
Since Pre-Buck comes pre-built and half of the bracing is already in, the labor cost is very low on these windows; low enough to almost always be less expensive than treated wood or V-Buck. V-Buck is a vinyl buck material made specifically for framing openings in ICF's. It is lightweight, straight, will not rot, is easy to use, produces absolutely no waste, and makes clean and neat appearing installations. V-Buck is 1 1/2" thick and has several channels. As it comes from the factory, it has an r-value of around 3; which is similiar to most low-e argon filled windows, and about the same as a wood buck. Spray foam can be inserted into these channels to increase the buck's insulating value. The caveat is that everything must be screwed or glued to the V-Buck. You would use 1 3/4" pan head screws to grip two of the channels. Using this method, V-Buck claims a 250lb. pullout strength. This is our most common method for framing out windows and doors.
V-Buck with wood inserts is perhaps the best, but also a more costly method. It has all the benefits of V-Buck while also letting the contractor nail in the windows and trim. Scrap wood from the jobsite is ripped down and installed in the outside channels of the V-Buck, giving it a more solid grip than V-Buck alone. This give V-Buck a 400lb. pullout strength with screws, but most people just nail the windows and trim in as normal. For LEED-H or Green Built certification, this is likely the highest scoring option, as it uses scrap lumber, generates no waste, and will not rot (long life cycle).
Internal wood bucks might be an option for some builders. Instead of leaving a finished rough opening which spans across the entire width of the form, R-Value will only block off the (typically 6") core of concrete with treated 5/4". This will leave the thickness of the foam on either side, and thus, nothing to attach the window to. The windows are screwed into the 5/4 through the foam with 3 1/2" screws, and are held in place by pressure against the foam, and hanging on the screws.
Since ICF walls are thicker even than a 2x6 wall, no extension jambs are made to finish out the inside. Most builders opt to use a piece of 1x to extend the jambs, but a less costly option is to return the drywall on the top and sides, using 1x only on the bottom. Several window manufactures can manufacture the windows with a receiving channel on the inside of the window to accept either 1x or 1/2" drywall. Insulbuck is a combination PVC/EPS buck that provides high r-values and no wood to rot. Stala is a steel buck which is also the finished opening for windows and doors. It is most appropriate for commercial buildings. The initial cost of the buck is higher than other buck types, but the cost is more than recovered by the time the building is complete. Jamb-It-All is another steel buck especially suited to commercial structures, this is not a finished opening, but commercial type doors and windows fasten directly to it in a secure manner. As with Stala, the initial cost is greater than vinyl or wood bucks.
Conclusion Given the various methods shown here, we are sure one will be just right for your next project. As demand continues to grow; architects, installers, and builders will become more familiar with ICF construction, and will continue to innovate more ways to attach floors and walls, as well as buck out and install windows; which should contibute to lower overall costs in the future. The switch is easy to make to begin using ICF's for your next basement and above grade project! Contact us today for further information, or a free estimate! More information "I highly recommend R-Value Concrete Structures. Jake is a professional from start to finish, the quality of his work was superior."--Mike Golden, R-Value customer |
