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Furring Rafts – Vaulted Ceiling – Top Plate Detail

Konphy89 | Posted in General Questions on

Hi all,
I am sure this is a silly/dumb question but I cannot figure it out. 

We are renovating a summer kitchen to be a conditioned office / ADU. The original 100+ year old building had 3×4 rafter falling on a single true 2×4 plate. 

My plan to insulate was to fur down the rafter with rips of of 2x6s we have leftover (see true 2×4 walls). What is really throwing me for a loop is that as I fur down the rafters with a few of these 1.75 inch depth boards they will quickly start falling below the top plate. 

Am I making this much too difficult? Do I simply cut them to have a plumb cut at the wall/studs and then sheetrock down to that?

Further does anyone have any thoughts on the best way to vent this whole assembly (It currently has/will have a metal roof of some sort over ancient sheathing)? I probably should replace the sheathing but haven’t gotten that far yet and its 12/12.

My plan is to use rockwool. Current plan was just to use owens corning vents in between each rafter but venting kind of intimidates me and I do not have a good handle on it. 

Thanks in advance!

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  1. Expert Member
    DCcontrarian | | #1

    I'm assuming your drywall is the air barrier? You just need the drywall to be continuous then.

    Use a piece of 3/4" plywood as a spacer and leave a 3/4" gap between your furring strip and the top plate. Run the wall drywall to the top of the top plate, behind the furring strip. Run the ceiling drywall into the wall drywall and tape and mud.

  2. Konphy89 | | #2

    Gotcha! That makes sense. Yes the plan is to use the drywall as the air barrier. Thank you!

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