This detail illustrates a modern rebuild strategy for replacing existing architectural terra cotta sill, mullion, and accessory units around window openings. The existing terra cotta is replaced with new hand-pressed terra cotta units. It is installed, not filled, with weep holes at the underside of each overhanging unit, which in turn are each secured with new stainless-steel anchorage. In restoring and rebuilding these types of historic wall systems, moisture mitigation is critical to long-term preservation and performance. Moisture management measures in this detail include horizontal skyward-facing joint treatment of sealant or lead T-caps and an integrated flashing system beneath the sill.

The flashing system includes a self-adhering flashing with ends dams secured by a termination bar with continuous sealant, a stainless-steel drip edge, and weeps in the vertical joints. The existing structural steel supports are also protected by cleaning and coating with a corrosion-inhibiting coating. These terra cotta rebuild details illustrate general best practices. Specific project conditions, configuration, and details will vary and should be determined by the design professional.


This drawing references Sill and Mullion – Original Plate 32.

Pressed terra cotta sill and mullion rebuild

Original Plate 32

This is a modern rendering of an original detail in Plate 32 of Terra Cotta Standard Construction, published by the National Terra Cotta Society in 1914. It provides a general example of appropriate architectural terra cotta design and detailing at the time of publication. Specifically, this detail illustrates an example of an architectural terra cotta sill, mullion, and accessory units around window openings. The units are anchored to a transitional wall system, consisting of a multi-wythe masonry backup wall with structural steel support. The architectural terra cotta is hand pressed and attached with steel anchorage. Though the details in Terra Cotta Standard Construction were intended to illustrate general best practices of terra cotta construction, specific project construction and conditions vary.

Pressed terra cotta sill and mullion rebuild detail

More to Explore

Original Plate

Check out our rendering of Plate 32, originally published in Terra Cotta Standard Construction.

Close-up of original plate 32 pressed terra cotta sill and million

Dynamic 3D Detail

Explore this 3D detail and download the Sketchup model in the 3D Warehouse.

Extruded Detail

You can also take a look at our extruded terra cotta sill and mullion rebuild.

Close-up of extruded terra cotta sill and mullion rebuild

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