Ceiling - dimension?

[johan_byggare]

Hi

I am planning to redo the roof on the house and I'm wondering a bit about what dimension is needed for it to be okay. I plan to use construction plywood as the underlay and have gotten a good price on 18 mm, is that enough? I initially thought about 20 mm, but I wonder how big the difference could be. On top of the plywood sheets, it will be covered with felt and then tiles will be laid.

Thankful for tips.

//Johan

 

[imported_Byggaren]

18 mm ply is more than sufficient. Normally, it's 12 mm K-ply. The roof tiles should not rest directly on the plywood but on horizontal battens, nailed to counter battens that should run from the ridge to the eaves to allow any water/moisture that might enter under the roof tiles to flow down to the drip edge/gutter. The battens mainly support between the rafters.
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Byggaren