This can be done with a straight piece of lumber 6 feet to 10 feet long or a long carpenter's level. Trusses or rafters should be shimmed as necessary to provide a level nailing surface.
If top chords of trusses or rafters are warped or bowed, install blocking to straighten. Vent exhaust air from kitchens, baths, and laundry to outdoors with vent pipes that run through the roof cavity or attic to roof ventilators. Do not vent exhaust air directly into roof cavity or attic. For vaulted or cathedral roof construction, provide free ventilation path from eaves to ridge between all rafters. At intermediate supports, fasten panels 12 inches on center.
In high wind areas more fasteners may be required. For pitched roofs, wear skid-resistant shoes. On panels with a screened surface or skid-resistant coating, install panels with the non-skid surface up. Install intermediate fasteners, starting at panel edge. Use chalk line or straight edge to align fasteners on framing. Fasten panels in rows across the width, continuing this sequence along the length of the panel.
This procedure keeps internal stress from accumulating in panels. Stand on panel over framing near the fastener location to insure contact with framing while driving fasteners. Drill pilot holes trough the rafters and insert the screws into the shed rafters, after aligning the overhang at both ends. Continue the woodworking project by fitting the plywood sheeting. Take accurate measurements, if you want to get a professional result. Miter cut the ends of the rafters if you want to create joints with a nice appearance.
Continue installing the trims to the back side of the L-shaped shed. Wok with attention and with great care, if you want to get a professional result. Secure the tar paper to the plywood sheets with roofing staples.
Fit the side drip edges over the roofing felt, while the bottom drip edges should be fit under. Last but not least, we recommend you to take care of the finishing touches. Place a starting course at the bottom of the roof, before installing the asphalt shingles.
Protect the structure during construction. Especially in climates where rain is a common occurrence, it is a good idea to detail the air control layer installed over the existing roof sheathing as a temporary water control layer. Insulation installed to the interior of the roof deck will reduce the ability of the roof deck to dry to the interior.
The exterior water management must be fully implemented and verified before roof cavity insulation is installed. Any roof sheathing or framing that was exposed to water during construction must be allowed to dry thoroughly before installation of insulation e. Unless the manufacturer has obtained appropriate approvals for the product, foam plastic insulations used inside the attic will require a thermal protection or ignition barrier covering. Gypsum wall board can provide appropriate thermal protection.
Intumescent paints may be compatible with some foam plastic products. Typically the combination of specific intumescent paint and foam plastic insulation product will have to have been tested and approved. The thermal control of a high R-value roof retrofit can be bypassed if the assembly is not properly connected to thermal control at the walls. If a gabled attic is to be brought into the thermal enclosure, the gable walls will need to be insulated as well.
The connection between the roof assembly and wall assembly is critical for air control. Mark the location of framing on successive layers so that workers can more easily hit framing with fasteners when needed.
It is especially important to keep track of framing locations in retrofit because the framing may have irregular spacing. The minimum insulation requirements for ceilings, walls, floors, and foundations in new homes, as listed in the , , , and IECC and IRC, can be found in this table.
Additional code requirements are listed on the Compliance tab of this guide. The ratio of insulation above the roof deck or air permeable insulation below the roof deck is a matter of climate and interior conditions. Generally, more insulation is needed for condensation control in colder climates. Also, the higher the indoor humidity, the more insulation is needed to avoid condensation.
The chart below illustrates the amount of insulation relative to total insulation that is needed to control condensation. In regions with greater than 50 pounds per sf ground snow load the roof cladding substrate must be vented to prevent ice damming. The substrate or nailbase is attached to purlins installed over the top of the exterior insulation to create a ventilation cavity. The cavity between purlins is vented by a ventilation opening at the bottom eave and at the top ridge — if the ventilation cavity cannot be connected directly to both a soffit and ridge vent, then the purlins must be made discontinuous to allow crossflow.
With the ventilated over-roof approach, the top of the exterior insulation should be detailed as a drainage plane to allow incident water to be drained from the system.
Compliance The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.
The minimum insulation requirements for ceilings, walls, floors, and foundations in new homes, as listed in the , , , , and IECC and IRC, can be found in this table. This section states that spaces must be brought into full compliance with the new construction requirements if the addition, alteration, renovation or repair changes that space from unconditioned to conditioned space.
Section R Building Thermal Envelope. Section R Note that assemblies achieving high R-value by insulating to the exterior of the sheathing and in the roof framing cavities should not need to use these exceptions. This section indicates the requirement for baffles to be installed next to eave and soffit vents for vented attics using air permeable insulations.
The baffle can be any solid material, must extend to the top of the attic insulation, and must maintain an opening that is at least as large as the vent. Note that baffles should also be used with vented over-roof assemblies that use air permeable insulations.
The IECC notes that the baffle shall be installed to the outer edge of the exterior wall top plate as to provide maximum space for attic insulation coverage over the top plate. Baffles shall be installed continuously where soffit venting is not continuous. This section indicates that the building thermal envelope as it is called in the IECC must be sealed to limit infiltration and that it must be sealed in a manner that is durable allowing for differential expansion and contraction.
Retrofit: , , , , and IECC. Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with this code. See code for additional requirements and exceptions. Chapter 5 in , , The provisions of this chapter shall control the alteration, repair, addition, and change of occupancy of existing buildings and structures. This section of the appendix indicates that any space that is changed to be habitable or occupiable by alteration must be provided with ventilation in accordance with Section R Note that this would not apply where an unvented roof assembly is used as indicated in section R Installation of ventilators in wall systems shall be in accordance with Section R Note that table R Higher R-value assemblies will require a proportionally larger amount of air impermeable insulation below the roof deck or insulation above the roof deck for condensation control.
Refer to specific language of this section for required dimensions of the access. Section N Building Thermal Envelope. Table N Section N The IRC notes that the baffle shall be installed to the outer edge of the exterior wall top plate as to provide maximum space for attic insulation coverage over the top plate.
This section indicates that the building thermal envelope as it is called in the IRC must be sealed to limit infiltration and that it must be sealed in a manner that is durable allowing for differential expansion and contraction. Retrofit: , , , , and IRC. Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with the requirements of this code, unless otherwise stated.
Appendix J regulates the repair, renovation, alteration, and reconstruction of existing buildings and is intended to encourage their continued safe use. More Info. Access to some references may require purchase from the publisher. Using high-efficiency and ultra-efficient insulation along with professional installation e. High-efficiency attic insulation helps provide added thermal protection. What this means to you is less wasted energy along with enhanced comfort and quiet.
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