>From the "Dictionary of Building Preservation" Edited by Ward Bucher
1996

wythe, wyth, withe

1. (pre-20c) A brick wall separating shimney flues that is the width of
a lingle stretcher brick.

2. A single layer of wall thickness of masonry material; typically the
depth of a brick stretcher; generally used to indicate the number of
brick thicknesses of a solid wall, or one part of a cavity wall. Also
know as 'tier'.

=========
Ken Follett wrote:
>
> In a message dated 98-06-08 01:09:13 EDT, you write:
>
> << Amazingly, the OED has no entry for wythe, except as an obsolete  spelling
>  for white and with (wythe a brief stopover at withe). >>
>
> We've been going at this a wythetime.
>
> OK, _Construcution Glossary_, J. Stewart Stein, Wiley, 1980
>
> Wythe (leaf)
> 1. Each continuous vertical section of a wall, 1 masonry unit in thickness and
> tied to its adjacent vertical section or sections (front or back) by bonders
> (headers), metal ties, or grout.
> 2. Thickness of masonry separating flues in a chimney.
> 3. Four-inch partition or tie between two walls, such as two walls of a
> chimney.
>
> ][<en