I've never seen smooth barnwood siding
So, what have you got? Most barnwood I've seen is really aged, dried, showing that the soft grain has been eroded away by sunlight and weather. Got any photos you can post...
use (Manage Attachments) button, (browse) your computer for the pictures, (select), click the (Upload) button in full screen .... and wait! Pictures will upload shortly.Close the attachment window and they will show in your post.
As far as how to make it, that depends. Several layers of barnwood would not be my choice. I would use a 3/4" plywood base, glue one layer of barnwood to it, trim out the edges in a 2" or so strip all around for the thicker look. The barnwood will probably be dry, but let it stand in the shop for a while, exposed on all sides to air movement to make certain.
The top usually be allowed to move across the width, but by attaching it to a plywood substrate minimizes or eliminates that issue.
The next issue, is how to achieve the smooth/tight look you mentioned. A glass top is one method. Any sanding or planing you do to make it smooth will remove all the character of the barnwood, you can't get there from here. An epoxy bar top finish could be floated over the entire table and you would still have the character, grain and color with an impervious finish. JMO
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
Last edited by woodnthings; 03-30-2014 at 12:28 PM.