Gap Between Roof Sheathing And Insulation

Fasten roof sheathing panels properly.

Gap between roof sheathing and insulation.

With the air gap we get drainage and the control of hydrostatic pressure. Beyond the decreased capacity for insulation when venting the roof deck venting the roof deck or the attic has some other drawbacks worth considering. Providing an air gap between the stucco cladding and the exterior face of the foam sheathing prevents the debacle we got with face sealed exterior insulated finish systems a k a. By leaving an air space between the insulation and the sheathing we can have air flow over the framing.

Install baffles providing a minimum of 1 inch of clear space between framing and or under roof decking at eaves to ensure that ceiling or roof insulation does not block ventilation paths. In cold climates snow can enter the soffit and ridge vents melt and potentially cause rot. Shingles roofing felt stackups are on the boundary between class i class ii vapor retardency when dry at about 0 1 perms and when the roof is wet there is. This ventilation offers another benefit.

Now wait a minute. If there is a leak the air flow ventilation will help dry out the moisture. An air space between the insulation and the bottom of the roof sheathing is desirable. In the winter humidity from the house s interior will get past the insulation and come in contact with the cold roof sheathing where it will condense into water.

And i was advised that that gap should be protected by a home inspector. Actually panels marked sized for spacing simply mean that they are slightly smaller to allow for the recommended 1 8 gap see attached apa tt 055. Without a proper air space to allow the insulation and roof to dry out this water will collect potentially leading to rot and mildew. Synthetic stucco photograph 8.

The solution is not to ignore the insulation but to add one component. But where the wall sheathing meets the roof sheathing there is a gap of approximately 1 8 of an inch. So you re talking about you re going to reroof and you have a gap between the wall sheathing and the roof sheathing. Unless you have at least a 1 gap between the roof deck and roxul with both ridge soffit venting putting putting foil facers on the interior side is going to create a moisture trap.

For vaulted or cathedral roof construction provide a free ventilation path from eaves to ridge between all rafters.