ᐅ OSB boards or tongue-and-groove planking for the floor in a convertible attic?
Created on: 23 Feb 2019 21:39
H
hauspeter- We are building a bungalow with an expandable attic space featuring a 38-degree roof pitch.
- The intermediate ceiling already has a vapor barrier and insulation installed.
- The roof beams are approximately 24cm (9.5 inches) high and spaced 50cm (20 inches) apart, with insulation in between.
- The mineral wool insulation is about 16cm (6.3 inches) thick.
The roof was originally intended to remain unheated (cold roof). However, we are also considering adding insulation next summer. We have read about mold issues with OSB boards and cold roofs because, unlike tongue-and-groove boards, OSB is vapor-tight.
- Are 22mm (7/8 inch) or 25mm (1 inch) OSB boards or 24mm (15/16 inch) tongue-and-groove boards better suited for the subfloor?
- Is a counter batten system useful to allow ventilation between the beams, or should the OSB boards be laid directly on the beams?
- Should the boards be fixed with screws or installed as a floating floor?
A
Appel20005 Apr 2021 23:36Hi!
Basically, I’m facing the same question:
- The ceiling between floors and the sloped roof areas are insulated and have a vapor retarder.
- The attic is a “cold roof,” with an underlay membrane beneath the roof tiles and a 100mm (4 inch) core drill hole on each gable side for air exchange.
My idea was to also insulate between the rafters in the attic to help moderate the extreme temperatures in both summer and winter.
Now I’m wondering the same things:
- Do I need to install a vapor barrier in the attic?
- If yes, it should be as airtight as possible; otherwise, it might not be worth it.
- But installing one in the attic is quite difficult. If anything, it would mainly serve to hold the insulation between the rafters in place, preventing it from falling down (which would be unpleasant).
- What happens if I don’t install it? The insulation might get damp from condensation… but it should also be able to dry out again, right?
Has anyone already been through these considerations or this kind of project and can share their experience?
Thanks and best regards!
Basically, I’m facing the same question:
- The ceiling between floors and the sloped roof areas are insulated and have a vapor retarder.
- The attic is a “cold roof,” with an underlay membrane beneath the roof tiles and a 100mm (4 inch) core drill hole on each gable side for air exchange.
My idea was to also insulate between the rafters in the attic to help moderate the extreme temperatures in both summer and winter.
Now I’m wondering the same things:
- Do I need to install a vapor barrier in the attic?
- If yes, it should be as airtight as possible; otherwise, it might not be worth it.
- But installing one in the attic is quite difficult. If anything, it would mainly serve to hold the insulation between the rafters in place, preventing it from falling down (which would be unpleasant).
- What happens if I don’t install it? The insulation might get damp from condensation… but it should also be able to dry out again, right?
Has anyone already been through these considerations or this kind of project and can share their experience?
Thanks and best regards!
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