What is a Window Schedule?

Window schedules play a pivotal role in bridging communication gaps between architects, manufacturers, and contractors...
Window Schedule Guide

In this comprehensive article, we are poised to delve deep into the realm of window schedules, illuminating what they are and guiding you through the process of crafting one effectively.

Window schedules play a pivotal role in bridging communication gaps between architects, manufacturers, and contractors. They act as a blueprint of window specifications, essential in conveying detailed information about window requirements. It is critical to understand that a window schedule is just one piece of the larger puzzle of contract documentation. To derive its full potential, it needs to be studied in conjunction with other critical documents such as specification data and general arrangement drawings.

At the core, window schedules are essentially a systematic method of representing intricate data related to the diverse sizes and types of windows prescribed for a project. The goal is to ensure that manufacturers are supplied with a comprehensive set of details that they can use for pricing and fabrication purposes. Similarly, these schedules offer precise installation information, which aids in accurate and efficient window installation.

Despite the term “window schedule” suggesting a focus on windows, its scope actually extends beyond that. It encompasses any external doors and windows which include large quantities of glazing – such as those produced by window suppliers. For instance, it covers a broad spectrum of styles like sliding doors, bi-fold doors, glazed patio doors, and even solid doors which are incorporated into the window frame system.

However, it’s important to note that not all doors fall under the domain of window schedules. Solid doors, like front doors, are typically organized separately or included with the internal door schedule. This segregation helps in maintaining clarity and organization in the planning and execution stages of any architectural project.

In what scenarios is a window schedule necessary?

There might be circumstances when a window schedule is not deemed necessary, particularly for minor residential renovation projects where you’re simply swapping old windows for new ones that match the existing design. In such situations, the common practice is for the contractor, manufacturer, or window supplier to visit the property, take accurate measurements of the windows, and provide you with a manufacturer’s quote and/or manufacturer’s drawings. This helps confirm the design and cost prior to fabrication.

However, for more complex designs, such as when you’re introducing new windows that don’t align with the existing ones, or when designing a new residential building altogether, a written or graphical window schedule can be incredibly useful.

What should a window schedule encompass?

A graphical window schedule offers a way of conveying various pieces of information without having to convert everything into a spreadsheet. This can be achieved by using the projected building elevations, incorporating additional annotations, and removing all non-relevant layers, like the facade. Some of the additional information you can include might pertain to the glazing specifications, the manner in which the windows open, and the window heights from the finished floor level (FFL).

In cases where your building includes multiple identical windows, it can be beneficial to create an extra drawing, such as a window type drawing. This enables you to provide more detailed information about the structural opening dimensions (s/o), frame dimensions, and other specifications. The window type drawing may also include specific building regulation notes related to the window.

Regardless of whether you choose a graphical or written schedule, the following details should typically be included:

  1. Window reference: Construction layout drawings for windows should include a reference code that matches the one in the schedule.
  2. Name: This could be as simple as identifying the window’s location to differentiate it from other similar windows.
  3. Style: This could refer to casement, sash, sliding windows, etc.
  4. Opening type or direction: This includes descriptions like inward opening, outward opening, etc.
  5. Manufacturer: This should also include the product series or the manufacturer’s reference.
  6. Structural opening: This provides the builder with the necessary dimensions for creating the window opening. Each window frame will require a certain installation tolerance between the structure and frame, a detail typically provided by the manufacturer and dependent on several factors including the structural material, window frame material, size, and design.
  7. Window size (width, height, thickness): These are usually the dimensions of the structural opening minus the installation tolerance.
  8. Material: Window frames are generally made from timber, aluminium, or PVC, with many modern windows also combining timber and aluminium.
  9. Colour and finish: This could specify, for example, a painted RAL colour 9003 for timber windows or a powder-coated RAL colour 7016 for aluminium windows.
  10. Hardware style: This relates to features like locks and handles.
  11. Glazing specification: This is particularly crucial for windows with significant areas of glazing.
  12. Weight: If the glazing panels are too heavy to be installed manually and require a crane, this detail becomes necessary.
  13. Acoustic rating: This is often required in urban areas or houses near busy roads as per planning requirements. However, adding this detail can also contribute to enhanced acoustic comfort in the building.

Glazing Types in Detail

Today’s modern windows typically utilize either double or triple glazing as standard. In other words, each window is constructed with either two or three panes of glass, the specifications of which can vary depending on the window’s location or intended use.

S – Standard Float Glass

The most common type of glazing employed is known as standard float glass. This glazing type adheres to Building Regulations part K and is in accordance with all current British Standards. It is usually sufficient for most standard window installations where no special requirements are needed.

L – Laminated Glass

Laminated glass represents another standard in the industry, also conforming to Building Regulations part K and all current British Standards. However, the defining feature of laminated glass lies in its structure; an internal film is sandwiched between two layers of tempered glass. If an impact were to occur, the glass sticks to the film instead of breaking apart and falling through the frame.

This makes laminated glass an excellent choice for increasing security, especially on the external pane of ground floor windows to deter unauthorized entry. It can also be utilized internally for glazing which falls below the 800mm guarding height to eliminate the risk of falling if broken or where the potential for glazing to be struck is high, such as full height doors leading to a terrace.

T – Toughened/Safety Glass

Toughened glass, also known as safety glass, is another type of glazing. Unique in its behavior when broken, it crumbles into small granular chunks instead of splintering into jagged shards. This makes it a safer option in case of accidental breakage.

This glazing is typically used in areas prone to accidental impact such as terrace doors or small areas of glazing on timber doors and shower doors, where there is no risk of falling but the chance of being knocked or hit is higher.

P – Privacy Film/Frosted Glazing

Privacy is a significant concern when designing windows for certain areas, such as on a boundary where planning requires it or in private rooms like bathrooms. Frosted glazing and privacy film are two methods to achieve this.

Frosted glazing incorporates a permanently frosted panel, usually kept internal to the air barrier. This results in a glass surface that is flat and easy to clean on both external sides. On the other hand, privacy film can be applied post-manufacturing to provide a non-permanent frosting which can be removed by the user. However, this option may not be feasible in areas where planning requirements stipulate frosted glazing.

O – Obscured/Back Painted Glazing

Obscured or back painted glazing is generally used in window panel systems where visibility is unwanted, such as window panels located in front of kitchen counters or in bathrooms. This glazing type is often seen in large facades with repetitive windows, though less commonly found in single-family homes.

Important Considerations

In the UK, when creating a drawn window schedule, windows should be drawn as on the external elevations with the arrow pointing towards the location of the handle. Contrarily, in the US, the arrow points towards the hinged side of the window.

Furthermore, it may be beneficial to familiarize oneself with a series of drawings that showcase some of the most common types of window openings, and how to represent them in elevation. This knowledge can be immensely useful in both design and construction stages.