Door Anatomy | Guide to Parts, Terms and Functions

The anatomy of a door, exterior.

When it comes to historic preservation, the elegance of a door lies not only in its design but also in its anatomy. From grand entryways in landmark buildings to charming brownstone doors in New York City, understanding the parts of a door can help you make more informed decisions. Here’s a breakdown of the essential components that make up a traditional door system.

The Basics

Doorway
The doorway is the opening itself, the passage you walk through to enter a home or room.

Door Frame
Supporting the door panel, the frame includes three key parts: the head (top), jambs (sides), and sill (bottom). Frames are typically constructed from wood, steel, or aluminum, depending on the style and era of the building.

Door Panel
This is the main part of the door that swings open and shut. It can feature solid wood, glass panes, or decorative detailing, depending on the architectural style.

Structural & Functional Elements

Head (or Door Head)
The horizontal top part of the frame.

Jamb
The vertical sides of the frame where the hinges, latch, and strike plate are mounted.

Sill
Located at the bottom of the frame, it sits flush with the floor.

Threshold
Often a sloped piece installed over the sill, the threshold helps keep water and drafts from entering the home.

Weatherstripping & Door Sweep
These components are critical for sealing gaps and improving energy efficiency. Weatherstripping lines the perimeter of the door panel, while the door sweep covers the gap at the bottom.

In-Swing vs. Out-Swing
Depending on your building’s layout or historical context, doors may swing inward or outward. This is typically determined by the positioning of hinges and how the space is used.

Design & Decorative Components

Rails & Stiles
Rails are horizontal segments on the door panel, while stiles run vertically. These structural elements often define the style of the door and house the hardware.

Mullions
A mullion (or “mull”) is the vertical or horizontal element that separates and joins multiple door panels or connects sidelights or transoms to the main door.

Casing & Brickmould
These trim elements add architectural interest and help hide the transition between the door frame and wall—casing on the interior and brickmould on the exterior.

Grilles
Grilles are decorative dividers that mimic the appearance of individual glass panes. They can be surface-applied or installed between panes of insulated glass.

Dentil Shelf
A signature feature of craftsman-style doors, this is a small ledge typically placed below a window pane for decorative effect.

Glazing (Glass)
Historic doors often feature beautiful glasswork. Today, glazing is usually insulated and may include decorative patterns, beveled edges, or leaded details.

Sidelights & Transoms
Sidelights are narrow, vertical windows flanking the door, while transoms sit above it. Both let in natural light and add visual grandeur to an entryway.

Hardware & Security Features

Hinges
These allow the door panel to pivot open and closed. Styles range from exposed barrel hinges to concealed or pivot hinges in modern or minimalist applications.

Knob or Handle
The main mechanism for opening a door. Knobs are round, while handles can vary in design—lever or pull-style depending on preference and accessibility.

Lockset
This includes all elements related to door locking: the handle, latch, strike plate, and interior locking mechanisms.

Deadbolt
An added layer of security, the deadbolt slides a solid metal bolt into the frame and is usually operated by a key or thumb turn.

Latch
The latch retracts when the handle is turned, allowing the door to open. It extends automatically when the door is closed.

Mortise Plate & Strike Plate
These metal reinforcements are located in the jamb and receive the latch or deadbolt. They enhance security and durability by preventing forced entry.

Astragal
If you have double doors, the astragal is the vertical strip that seals the gap between both panels and helps keep the doors secure and aligned.

Planning a full exterior restoration? Don’t miss these window guides.

Understanding window parts is key to choosing, restoring, and preserving historic windows. Learn more in our Window Anatomy Guide, and explore glass types and glazing details in Glass: What a Pane.

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Restoration Tips for Historical Brownstones

Clinton Hill, Brooklyn

Restoring historical brownstones in New York City is a labor of love that requires meticulous attention to detail, particularly when it comes to maintaining the authenticity of windows and doors. For homeowners and preservationists alike, understanding the nuances of window replacement in NYC is crucial to preserving the architectural integrity of these iconic structures.

Assessing the Condition of Existing Windows and Doors

Before diving into any restoration project, it’s important to thoroughly assess the condition of the existing windows and doors. In many brownstones, the original windows and doors have been in place for over a century. While these elements contribute to the building’s historic charm, they may also suffer from wear and tear, necessitating careful restoration or replacement.

Choosing the Right Materials for Window Replacement in NYC

Park Slope, Brooklyn

When replacing windows in historic brownstones, choosing the right materials is key. Wood remains a popular choice for its authenticity and aesthetic appeal. However, modern alternatives that mimic traditional wood while offering enhanced durability and energy efficiency are also available. Ensuring that new windows match the historical profile of the originals is essential to maintaining the building’s character.

Navigating NYC Preservation Regulations

Window replacement in New York City’s historic districts often requires navigating a complex web of preservation regulations. It’s important to work with professionals who understand the local guidelines to ensure that your restoration project meets all necessary approvals. This is especially true when it comes to replacing windows and doors in NYC, where strict guidelines often dictate the materials, styles, and installation methods that can be used.

Balancing Energy Efficiency with Historical Accuracy

One of the biggest challenges is balancing modern energy efficiency with historical accuracy. Upgrading to energy-efficient windows and doors doesn’t mean sacrificing the building’s historical integrity. Many manufacturers offer high-performance windows that are designed to replicate the look of traditional models while providing superior insulation and energy savings.

Working with Experienced Craftsmen

Historical Windows of New York has the expertise to repair your brownstone windows with precision and care. Restoring these windows is a specialized task that demands a deep understanding of historic preservation and the unique challenges of working with brownstone materials. Our skilled professionals ensure that your restoration is both effective and historically appropriate, preserving the character and integrity of your brownstone.

For more information on window replacement in NYC or to consult with our team of experts, contact us today.

Before | St John’s St, Brooklyn

After | St John’s St, Brooklyn

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The Story of 108-110 Franklin Street | Tribeca

Mobilization day is here, marking the beginning of a new chapter in one of our favorite New York neighborhoods, Tribeca. Today, we embark on a journey at 108-110 Franklin Street, a project destined to be a standout in this historic area.

Tribeca, short for Triangle Below Canal Street, is known for its charming streets and rich history. Franklin Street, named after the founding father Benjamin Franklin, was once a quiet residential block lined with Federal-style brick homes. However, by 1860, the landscape began to change as residents either moved away or saw their homes transformed for commercial purposes.

In 1861, Ann Richardson and William Bowne, an unlikely duo, came together to replace two properties with a modern loft and store, completing the project in 1862. This development was among the first of its kind in the neighborhood, designed by an unknown architect to seamlessly blend in. The "shop fronts" at street level were executed in cast iron, with thin piers featuring Corinthian capitals and decorative address plates that still grace the building today. The upper floors were adorned with Italianate elements, including protruding sills, arched lintels, and a stone cornice, all contributing to the building's unique charm.

Over the years, 108-110 Franklin Street has been home to various businesses, reflecting the changing tides of Tribeca's economy. From wholesale dry goods operations to woolen importers and linen companies, the building has witnessed the neighborhood's evolution firsthand. Today, it stands as a testament to Tribeca's rich history, housing high-end artist and residential lofts that retain the building's original facade and storefronts, preserving their integrity after more than a century and a half.

As we embark on this project, we are excited to breathe new life into this historic gem, ensuring that its story continues for generations to come. Stay tuned for updates as we transform 108-110 Franklin Street into a modern masterpiece while honoring its storied past.

Glass: What a pane

When we talk about windows and window design, it is easy to focus on the many types of window styles, sizes, interior and exterior finishes, even hardware. But we’re there’s one item that every single window has: glass.

Glass, in its most basic form, is made by heating sand to an extremely high temperature. In nature, a lightning strike to a sandy beach can form glass from the melted sand. Found near volcanoes, obsidian is a black glass formed by cooling lava.

In manufacturing, glass is made by heating sand, lime, and soda ash together to form an amorphous solid. In amorphous solids, the molecules move very slowly around instead of remaining static, or in one place. Modern glass is called float glass because the molten glass is floated over a layer of molten metal, making the glass very thin, smooth, and uniform. The glass is annealed, or slowly cooled down, to relieve any internal stresses in the material.

The wavy glass you see so often in old homes and buildings was handmade. It’s thicker than modern glass, and includes air bubbles, waves, and other inclusions that give it character. (A definite step up from the first windows, made by the Roman Egyptians around 100 AD—their glass was so thick you couldn’t see through it!) Our team sources salvaged vintage glass to use in projects where it’s important to keep that old-time character.

This vintage glass has inclusions and bubbles.

Stained glass is colored using metallic salts during the manufacturing process. The colored glass pieces are assembled and held together using leading. Historically, stained glass is used in churches and other religious structures. We’ll devote a separate article to this 1,000-year-old window art form soon!

Tempered glass is about four times as strong as conventional glass. Tempering, like annealing, is a thermally controlled process that puts the outer surface of the glass into compression and the inner surface into tension. Tempering not only results in stronger glass, but when the glass breaks you get granular chunks rather than jagged shards. Tempered glass is required by code where there’s possible high impact, there are very large panes of glass, windows are close to the floor, or other safety considerations.

Laminated glass is another kind of safety glass. Instead of treating the glass with heat, layers of glass are fused together with a polyvinyl butyral (PVB), ethylene-vinyl acetate (EVA), or thermoplastic polyurethane (TPU) between the glass. In the event that the glass is broken, the plastic layer holds it together.

This safety glass holds shards together.

Window glass can also be coated to make it more energy efficient. One of the most common coatings results in low-e or low-emissivity glass. Emissivity is the measure of how much a surface emits thermal radiation. Low-e coatings are microscopically thin and minimize the amount of infrared and ultraviolet light transmitted through the glass. The amount of visible light is unchanged. In the summer, low-e coatings keep interiors cooler by reflecting the heat off the exterior of the glass. And because low-e coatings also reflect ultraviolet light, furnishings fade less than with conventional window glass. In the winter, low-e windows reflect the interior radiant heat back into the building rather than transmitting it through the glass. We’ll do an even deeper dive into low-e and other energy-saving components to windows and doors in a later piece on high performance.

Eight over eight divided lite windows.

A window sash may consist of one or more planes of glass called lights or lites. If there’s just a single plane of glass in each sash, the glass pattern is one over one. If there are two lites in each sash, the pattern is two over two. You can have one lite in each sash or twelve or more. The number of lites in each sash can differ as well (eight over one, for instance).

The lites are separated by mutins, sometimes called grilles, which are strips of metal or wood that separate and hold the lites in a grid. A true divided-lite is when the mutins physically hold the panes of glass in place.

A simulated divided-lite is when the mutins are affixed to the surfaces of the window to appear as if the glass is actually divided. When the glass is insulated or there are multiple panes of glass, an optional spacer bar may be used between the panes to make the windows appear to be authentically divided.

Planning a full exterior restoration? Don’t miss these guides.

Understanding window parts is key to choosing, restoring, and preserving historic windows. Learn more in our Window Anatomy Guide, and explore door anatomy and details in Door Anatomy.

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ARE YOU AN AUDIO LISTENER?

Click here to learn about Window Panes

Partnership with Arcadia

Historical Windows Partners with Arcadia

Joining our list of innovating window and door suppliers, Historical Windows partnered with Arcadia. Bringing their ever-expanding range of materials, styles and specialty lines, like Arcadia Custom, and providing the residential luxury market with high-end, high-efficiency options that give clients the design flexibility needed to elevate the possibilities of modern living.

Mahogany Entryways Factory Tour

Mahogany Entryways specializes in manufacturing hand made, Old World style exterior and interiors doors of the highest quality. They personally select only the finest Honduran Mahogany wood and with precision cutting, assembly and hand-matched joinery, their craftsman ensures the doors are as strong as they are beautiful.