using 1/2″ maple veneer plywood glued on interior walls of home can that serve as vapour barrier requirements as well to satisfy NBC?
Builder24
| Posted in Building Code Questions on
I want use 1/2″ maple veneer plywood on interior of home. Panels will be glued to studs and have laquer finish. Can this also serve as vapour barrier requirement.
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Replies
I hope no one ever has to renovate.
Our building department likes drywall to retard fires. I think you might have a code problem.
piperspace,
Can you be more specific about the code reference.
When we remodeled in San Franciso two layers of drywall were required on walls adjacent to our neighbors house. But I don’t know the codes. Sorry.
When you're close to property lines, the rules about how walls are constructed get a lot more strict.
Climate zone 7 NO! Climate zone 3 or lower YES in between?
What is the plan for making all the seams air tight?
Walta
Just do a layer of Membrain or similar underneath.
No glue then
Put furring strips over the membrane.if you use 1x3 you get twice the gluing area. Plus you can shim them perfectly flat and plumb.
I don't know how your going to assemble it but that's not the question you asked.
I was not suggesting glue was a good idea (on contrary it seems like a bad idea), was just pointing out you could not assemble as they described. Furring strips would certainly work and be much easier to remodel.
Also I didn’t ask a question.
Sorry, the second paragraph was directed at the OP.
Builder24,
If you can do this you are a much better builder than I am. I've done plywood as a finished surface in a few rooms. Even with good framing the process was complex and painstaking - and that's when using shims and brads to hold the pieces. I can't imagine how, even with a high initial grab adhesive, you would do it.
We're currently building a home and using pre-finished maple plywood for interior walls. No glue, though, instead we're using trim head screws and brad nails.
Using 1/2″ maple veneer plywood glued on interior walls of a home as a vapor barrier may not satisfy the vapor barrier requirements of the National Building Code (NBC) of Canada. Vapor barriers are specifically designed to prevent moisture from passing through walls, ceilings, and floors. Here are some key points to consider:
Vapor Barrier Requirements and Plywood
Vapor Permeability:
Plywood: While plywood can provide some level of resistance to moisture movement, it is not typically classified as a vapor barrier. Plywood's permeability varies depending on the type and thickness, but it generally does not meet the low permeability levels required for a vapor barrier as defined by building codes.
NBC Requirements: The NBC requires materials used as vapor barriers to have a permeability rating of 1 perm or less. This is to ensure that the vapor barrier effectively limits the passage of water vapor through the building envelope.
Material Specifications:
Plywood Properties: The permeability of plywood can be higher than what is required for a vapor barrier. For instance, 1/2″ plywood has a higher perm rating compared to dedicated vapor barrier materials like polyethylene sheeting.
Code Compliance: To meet the NBC requirements, it's essential to use materials specifically designed and tested as vapor barriers. Common materials include polyethylene sheets, foil-faced kraft paper, and specialized vapor barrier paints.
Installation Considerations:
Sealing and Joints: Even if plywood were to be used as part of a vapor barrier system, all joints, seams, and penetrations would need to be meticulously sealed to prevent moisture ingress. This level of sealing is typically more complex and less reliable compared to using designated vapor barrier materials.
Vapor Barrier Placement: According to the NBC, the vapor barrier should be placed on the warm side of the insulation to prevent condensation within the wall assembly. This placement is crucial to the effectiveness of the vapor barrier.
Conclusion
While 1/2″ maple veneer plywood offers aesthetic and structural benefits, it does not fulfill the stringent requirements of a vapor barrier as per the NBC. For proper moisture control and to comply with building codes, it is recommended to use materials specifically certified as vapor barriers.
For more detailed information and guidance on selecting appropriate building materials, visit our blog at (https://plywooders.com/blogs/).
WanPin,
"Sealing and Joints: Even if plywood were to be used as part of a vapor barrier system, all joints, seams, and penetrations would need to be meticulously sealed to prevent moisture ingress."
Unless the plywood was also being used as an air-barrier, no sealing would be necessary.
Vapor permeance of plywood varies a lot depending on humidity. For an interior use that factor will probably remain relatively constant, around 50%. Assuming that you can expect about 1 perm for a 1/2" unfinished panel. Your lacquer finish will reduce that but I haven't looked into how much. I expect finishes will vary a lot and so it depends on which one you choose.
That said, plywood permeance also varies with the glue type. Panels made with exterior glues have a lower perm, closer to 0.5. If you're after higher permeance use panels made with an interior glue. I can't find hard numbers for lacquer permeance on manufacturers' websites but if you're after a higher perm interior then a spray applied water-borne finish will probably work.
The American Plywood Association cites the 1 perm figure at 50% humidity. Building Science Corporation gives a much higher permeance of 10, but I expect that is for exterior situations with higher humidity.
Frank Lloyd Wright made great use of exposed plywood panels in some of his Usonian homes, especially on the ceilings, where he would cut an 8' panel into 2 4' squares and the rotate each panel. Glue alone may be challenging to assemble. But an 18 ga brad nail applied 1/2" in from each corner would help a lot to hold the panel tight to the framing while the glue dries, and be relatively inconspicuous. Wright used flat slotted screws and then made sure the slot was aligned with the panel edge.
Plywood panels won't provide the fire protection of a 1/2" gypsum panel. But if you're building a single family detached house that may not be a code issue. Do check with your local building department though. I'm not familiar with the Canadian code.
Best of luck with your project.
https://www.performancepanels.com/permeability
https://buildingscience.com/documents/information-sheets/info-312-vapor-permeance-some-materials