Video: How To Build A Fire Resistant ICF House
Here’s a video on fire-resistant construction in wildfire-prone areas!
In this video, we’ll take you through a construction model of an ICF home that meets fire code standards. We’ll pay special attention to high-risk areas and give you practical suggestions on how to design and build. We’ll be using the framework of a simple, cost-effective home, that has a vented roof, but we’ll look at unvented roofs and concrete roofs that provide added protection and higher performance. We’ll start by going over how the walls are formed using our example model.
Starting with the basement, we poured the concrete footing, stacked our basement wall blocks, and put in the horizontal rebar. After the first two courses, take time to level and square the project. It’s important to complete this step at this point because it will greatly affect the end result of the project. Once satisfied with their location, we’ll spot glue the blocks in place and continue stacking. More information on the specifics of the ICF construction process can be found on our YouTube page and website, which you can find a link to in the description below. We also cut out window and door openings, erected our bracing to support and align the walls, and put in place Simpson ICF-VL’s for our ledger system.
During the pour, we inserted our vertical dowels into the top of the wall, making sure to place two by each opening. It’s very important this step is completed before the concrete sets to save a tremendous amount of time and labor. It’s also important to straighten and align the walls at this time. Do these steps before you walk off the job after the pour. Next, we poured our basement floor and put in the beam for carrying the joists. After that, we put the hangers on for the I-joists, put the I-joists in place, and sheet the floor. Next, we apply waterproofing. The gray bar is the foot that’s exposed above ground, which is also called the parge coat. The main floor is braced as well to align the walls. Once it’s poured, make sure the walls are straight and plumb. As they’re straightened, place the anchor bolt for the top plate. After the sill plate is placed, we can start to form the interior walls. The outside walls in themselves provide a 3-4 hour fire rating, so now we just need to focus on sealing up the joints between the walls, and the rest of the house to create a sealed envelope.
In this example, we used Burmon hangers. The model shown here attaches to the top plate and then connects to the trusses. They provide 150mph wind speed protection. Next, the trusses are put in and their wind bracing is added. In this project, there are both normal and scissor trusses for a vaulted ceiling. Here, an optional spacer has also been added that can be used to properly space out the trusses. The gables are added next, which can be constructed out of wood, but ICFs are an option for those as well. Also, add ceiling nailers to give your drywall a place to attach to. From here, plywood the gables and put a sub fascia on. Add roof sheeting and a drip edge. These pieces are all metal to act as a seal for our roofline. Next, we’ll put our ace guard on the roof and shingle it, making sure to leave a cut out for our ridge vents.
The two types of roof options we’ll be looking at are vented and unvented. In this project, we used approved ridge vents that keep the fire out but still allow the building to breathe. This is because one of the main dangers during wildfires is wind-borne embers that fly in front of the fire and land on combustible materials in and around the house. These embers are commonly sucked up into the eaves. The model shown here protects against this.
Next, set your F-channel, which acts as a guide for your soffit. Here are our gable soffits. These are usually solid and not vented. On the sides, we put in a vented soffit that’s approved for fire construction. It acts in a similar way to the ridge vent, allowing the building to breathe without letting embers in. The vents are spaced out every other covering to limit possible ember access. A 16th-inch screen can also be added to the backside of it for added protection.
While vented rooves are a more traditional, and cost-effective option, unvented rooves are an option as well. Unvented rooves fully seal the building envelope, offering more protection and efficiency than a vented roof. By fully sealing the building envelope, and using noncombustible finishes, the only way for flames to enter is if the exterior envelope is compromised. There are no spaces for wind-borne embers to be sucked inside the structure, or combustible finishes for embers to ignite on. Examples of an unvented roof would be BuildDeck, our ICF decking product, or using a layer of spray foam insulation from the top plate, entirely throughout the ceiling of the structure. Using spray foam, you create a controlled attic, completely sealing the building envelope. Unvented roofs pair well with air filtration systems, such as an ERV, to keep fresh air venting through the structure.
Moving back to the model, we’ll now add our finishes. Stucco is used for the gables. Hard stucco usually consists of type s mortar and sand over galvanized diamond lathe. It’s a great finish for gables and siding. It’s an easy way to gain a 1-hour fire rating and roof eaves are a huge fire hazard and need to be encased. A surrounding stucco finish is a helpful and easy way to finish boxing in your eaves. Next, windows and doors are set. Window compliance with fire code requires a dual-pane with tempered glass or glass blocks or a fire rating of over 20 minutes. Door compliance requires approved noncombustible construction, solid-core wood no less than 1-and three-quarter inches thick, or a fire protection rating of at least 20 minutes. A concrete slab is poured at the entry because it’s an area where leaves and other combustible materials can accumulate and become a landing spot for embers. In this instance, we used a cultured stone siding to further prevent fire in this area. For other areas, cement board siding was used.
And what we have now is a simply built, cost-effective home that meets and exceeds fire code standards. Using these methods and systems will give your house the best chance of surviving a wildfire. Thanks for watching, and good luck building.
A version of this video was a part of a larger training presentation on this topic. The entire presentation can be viewed here for free: https://buildblock.com/event/webinar-fire-resistant-icf-construction/
More info on ICFs and Fire Resistance: https://buildblock.com/insulating-concrete-forms-icfs/icf-disaster-resistant/fire-resistant/
More info on BuildDeck: https://buildblock.com/products/builddeck-floor-roofing/
Free Training Courses: https://training.buildblock.com/