What Is a Terra Cotta Top Plate?

A Storm Collar

• The near-seamless construction of the terra cotta top plate keeps water off of the surface of the chimney crown and from entering the mortared lines that connect the terra cotta flue to the brick of the chimney, much like a flashing barrier. This is important as a guard that shields the mortar from the elements that slowly break it down over time: the sun, water and wind.

Support

• In conjunction with its weather-barrier function, a terra cotta top plate lends additional support to the chimney's liner system inside by holding it in place against the wind, and to the chimney's crown. Once the unit is tightened in place, it gives the top of the terra cotta flue additional support with its metal composition that can take a longer beating over the inflexible clay of the terra cotta. It then becomes a small investment that can save costly chimney repairs later on.

Mounting Options

• The condition of the chimney's crown will determine the best way to install the terra cotta top plate. With the terra cotta flue intact and with the top plate fitted over it, secure the unit to the chimney with a built-in clamp on the inside -- through the opening on top -- and with screws around its base on the outside of the unit. The other type of top-plate installation adds the option of installing the terra cotta top plate flush with the chimney's crown. This means knocking off the part of the terra cotta flue that extends above the chimney until it is level with the chimney's top, and then fitting the top plate over that. This type of installation is called a flush mount.

Further Protection

• Although the terra cotta top plate covers the chimney's opening with a neat and finished cap appearance, the central collar -- or opening to the inside of the chimney -- still remains exposed to the elements. Prevent this from happening with the addition of a hinged cap designed to cover the opening with a well-vented net for its sides and a solid, run-off cap on top. Rain, snow, flying debris, leaves and even small animals will not find their way into the chimney with this extra guard attachment.