Built-Up Wall & Roof Systems
Here at Trillium Dell we have utilized many enclosure systems for our projects since the mid 1990’s. While we often use Structural Insulated Panels (SIPS) for our homes and commercial projects, as an alternative we also offer built up wall and roof systems for all of our projects. A built up system is generally made of dimensional lumber of any species, most often material found at your local lumber yard. In some cases we create this system out of reclaimed material or new material sawn from our clients own materials, such as trees from their woodlot.
A major advantage of a built up wall or roof system is cost, built up systems are more economical. A major disadvantage is timing as these systems take longer to install in the field than SIPS, thus subjecting the timber frame to more exposure to the weather. Timing can be critical, especially during winter months and rainy seasons. SIP systems generally create a tighter whole house system, but also require more types of HVAC equipment.
A built up wall involves installing a perimeter wall around the timber frame. Typically these walls are built using 2 x 6 lumber on 19” or 24” centers and a layer of rigid foam board is installed over the framing to aid in reducing thermal breaks in the wall. This rigid foam can be anywhere from ¾” to 2” in thickness, or in some cases foil backed “roll out” bubble insulation is used. Over the years we have used many types of insulation including sheep’s wool, mineral wool (spun basalt fiber), various types of spray on insulation (including those containing high amounts of soybeans), fiberglass, EPS, rigid foam, and cellulose. All of these insulations have various advantages that range anywhere from life cycle benefit analysis’s, ease of installation, durability, and performance. The framing in the wall is non-structural and only needs to be strong enough to support the windows, doors, provide a cavity for the insulation and accept exterior sheathing. Generally Trillium Dell uses ½” or 5/8” plwood (not OSB) over the framing as the final layer before sleepers and siding. The constructed wall is at this point plumbed and screwed to the frame using 8”-10” long structural screws, the end result is a wall that is very strong, provides shear benefits for the timber frame, is very durable and insulated.
Built up roof systems are not much different though the lumber used may be of greater width due the need for greater insulation. Typical roof cavities are built using 2 x 8 or 2 x 10 lumber screwed into the timber frame principle purlins, or timber rafters below with long structural screws. Once the timber frame is completed tongue and groove sheathing is installed directly to the frame with stainless steel nails (to prevent staining), and 30lb felt paper installed onto the T& G with cap nails. At this point the building is “dryed” in and the balance of the built up roof system can be completed at any time. Over the felt paper we generally install a layer of ¾” rigid insulation, fastened with cap nails. The actual structure of the built up roof framing may be made with 2 x 8’s or 2 x 10’s, the cavities filled with a variety of insulation types, though spray in is the most common for the timber frames we enclose with built up systems. Once the insulation is complete we close the roof cavity with plywood or solid wood sheathing, and in some cases use only skip sheathing.
Built up walls and roof systems can allow any type of roofing product, siding material, or veneer to finish the project. There are myriad walls to create built up systems such as; woven walls wherein the wall is built using offset studs so that insulation may be woven between them or various methods of stick framing infill where we cut a dado in the posts and plates of the timber frame to receive either the exterior sheathing and or the siding. In an infill wall it’s important to prevent air infiltration which may occur due to shrinkage so extra care is take to create grooving in the timbers that captures the framing material. Infill systems are very similar to how timber frame structures were insulated and finished in Europe. Trillium Dell offers this type of method for new construction (using rigid foam and spray foam) and historic buildings. Infill walls are often built using clay as a finish or in rare cases as the insulation of the wall when mixed with straw.
Whatever your framing and enclosure needs are with built up systems Trillium Dell has the training, experience, and knowledge for your project.