Hi Todd,
Thank you for your inquiry. A good manufacturer to look at for this type of exterior door is TruStile www.trustile.com doors. Look at their VG1000 Select Alder Plank Doors, these can be used in an exterior application.
Also Sun Mountain http://www.sunmountaindoor.com Doors has a vertical plank door option in their custom door selection.
Hope this helps!
Tim Homburg | NSPJ
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