Gap Between Roof Sheathing And Insulation

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.

Gap between roof sheathing and insulation.

By leaving an air space between the insulation and the sheathing we can have air flow over the framing. For vaulted or cathedral roof construction provide a free ventilation path from eaves to ridge between all rafters. So you re talking about you re going to reroof and you have a gap between the wall sheathing and the roof sheathing. Without a proper air space to allow the insulation and roof to dry out this water will collect potentially leading to rot and mildew.

The solution is not to ignore the insulation but to add one component. Synthetic stucco photograph 8. This ventilation offers another benefit. 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.

Fasten roof sheathing panels properly. 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. With the air gap we get drainage and the control of hydrostatic pressure. The one bit of advice is to leave a little air barrier between the top of the insulation and the bottom of the roof sheathing just in case you get some condensation it will have a chance to burn off better from sun on the roof if you don t firmly pack insulation against the sheathing.

However it is considered good practice to leave a 1 8 gap between sheets and that is also recommended by apa but it is not required. 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. And i was advised that that gap should be protected by a home inspector. In cold climates snow can enter the soffit and ridge vents melt and potentially cause rot.

But where the wall sheathing meets the roof sheathing there is a gap of approximately 1 8 of an inch. Beyond the decreased capacity for insulation when venting the roof deck venting the roof deck or the attic has some other drawbacks worth considering. 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.