When preparing the roof base, it is recommended that barrier layers (moisture and vapor barrier) be installed as underlayment. The vapor-permeable protective underlayment protects the attic space from dust, soot, rain and snow, and protects the thermal insulation. It is installed starting from the ledge going up to the ridge with 4” overlap. The water barrier is extended upward to 1 ½” on vent pipes and 4 – 6 “ on chimneys, and its top must be sealed against the vertical surface.
Warm air rises from the interior of the building and moisture condenses on cold surfaces. To prevent this, it is necessary to insulate the attic spaces, install proper moisture barriers under the strapping, and provide sufficient ventilation.
To assure proper ventilation, air circulation must be permitted long the entire roof perimeter. Our strapping assures free air movement from the roof ledge to its ridge, thereby cooling the warm air inside to complement the outside temperatures without any condensation.
The strapping is constructed of 2” x 2” or 2” x 3” planks, 1” x 3” cross-brace rails are installed first, at right angles to the roof ledge, starting at 3 1/2” from the ledge all the way to the ridge. The distance between the rails equals the distance between the principal trusses, i.e. the rails are installed over the principal trusses every 16 – 24 “.
The first plank is then nailed 3 ½” away from the eave, parallel to the ledge. The spacing between the first and the second plank is 12” measuring from the center of the plank. The other planks are nailed with 13 3/4” between centers or between the top edges. The strapping is constructed of 2” x 2” or 2” x 3” planks. The first plank should be ¼ - ½” thicker than the rest and must be installed very precisely because it will be used as the guide during installation.
We use the following checklist to ensure that your roofing job is completed to your satisfaction.