Making It Right

Measuring and Installation

Pity the poor artist! Having consulted the clients, designed a window that suits the architecture while capturing the desired thematic elements, and built it to the highest technical standards, he brings his masterpiece to the site and...well, it fits at the top, but unfortunately, the opening isn’t square, and while the left side will go in with a little shaving, the right side will still be an inch too wide at the bottom. Moreover, the sun is now shining through a nearby window that he had barely noticed before, and its red background seems to be in battle with the blue he has used. It’s at this point that he begins to think that a little better planning might have been in order...

For the routine - but essential - task of measuring up for a window, a “Glazier’s Draft” is invaluable. The one I use is a compilation of measuring-up information from Swansea College of Art, Glass Master Lawrence Lee, and my own experience. Along with the Glazier’s Draft, measuring up requires a reliable tape measure (you’d be surprised how many are inaccurate) and a steady ladder. A camera may be useful; and an assistant can be very helpful in recording and verifying the measurements, especially for large, complex windows.

Glazier’s Draft

1. Name and location of the building.

2. Position of the windows in the building and direction of light source (north, east, south-east, etc.). If more than one window in the building is being designed for, draw a quick floor plan and indicate each with an assigned number. Tracery and head templates should all be numbered with the corresponding window, indicating left and right where necessary.

3. Indicate any exterior environmental features that affect the window and the amount of light it receives (i.e. trees, buildings, fences, etc.). Note the color it brings to the window and whether this is seasonal (i.e. maple trees). A photographic record is valuable for this.

4. Indicate "style" of architecture, materials, textures, color patterns - include any environmental information or impressions you consider important.

5. Indicate extraneous and reflected light - both natural and artificial; its amount and direction.

6. Measuring Height:

   1. Total height Sill to Point of Arch

   2. Sill to Transom

   3. Springing Line to Point of Arch

   4. Springing Line to Top of Head

   5. Sill to Divisions

   6. Sill to Floor

   Check all lights in a window for differences in measurement—more often than not they are different. Also note whether measurements were taken from the outside or inside. If you have taken measurements from the inside check the outside for "surprises" and vice versa.

   Note: The Springing Line is usually taken from the masonry but can be taken from the center line of an existing bar - check to make sure the bar is not above or below this line.

7. Measuring Width:

   1. Total width of window

   2. Width of each light (bottom, middle & top)

   3. Width of mullions

   4. Width of transom

   Check all lights for differences.

   Note: Be aware that out-of-square windows can pose special challenges when you are trying to align lead lines between panels. Also, if it’s out by too much, the whole window can appear to be askew. A good design can compensate for some framing errors, but only if you first know what you are dealing with.

8. Indicate sight size (S/S) and full size (F/S) for all measurements of individual lights.

9. Indicate existing divisions, saddle bars and stanchion (vertical) bars, with their width and position and whether bars are on outside or inside of window. Note their condition. The decision of whether or not to use the existing structure can be made while designing.

10. Indicate depth and width of rebate. Note any oddities (i.e. a deep rebate on the outside but not inside, which will obscure some of the glass). Indicate depth of sill on the inside.

11. Examine stonework/woodwork both internally and externally to determine if any repair work is required before plans for an installation are made.

12. Tracery and Templates:

    Templates are usually made for all tracery lights and shaped heads above the Springing Line. To make templates:

    1. Using good quality kraft paper (large enough to cover the entire tracery area plus) snip out a small hole in the center and tape the paper firmly to the glass so that it stays in place.

    2. Press the paper into the window opening, following the window shape.

    3. With a sharp "Exacto" blade cut out the shape while the paper is still in place until the exact window shape is attained.

    4. Transfer to thin card and note the following:

       • Template taken from inside or outside

       • Tracery position (left, center, etc.)

       • Indicate divisions in large traceries

       • Indicate F/S (full-size) — depth of rebate

       • Indicate Top, show vertical and center line

    Make a quick sketch to indicate tracery position and all necessary measurements between the tracery lights. Note the relationship of the tracery vertical line to the center line of light or mullion.

13. In a building which is partially glazed, a photographic record of the existing windows will be helpful to note their style, color, scale, and level of light intensity.

14. Decide whether ladders or scaffolding will be required. Check to see if any removable furniture is being planned for underneath or in front of your windows, as this may hinder your scaffold arrangements. Make sure that you will have the required amenities (i.e. lighting, water supply, electrical outlets, etc.). Check about access times during the installation. For a new building, you will want to know what other work is planned (There’s nothing like showing up for your installation and finding out that that is the day the floor is being finished!), as well as make sure that such jobs as the window frame painting will be complete. For existing buildings, especially busy ones, try to get a schedule of events, so you will know what you will be working around.

15. Make notes, and if necessary a sketch, to show how the window will be installed and held into the frame.

The last point is a crucial one, and one that can make an important difference in the design and fabrication of the piece. After all of the measurements are recorded and the architectural details noted, take some time to look around and get a “feel” for how the windows will work in their frames. Although every installation is different, and framing systems vary, some points should be kept in mind:

Installations of stained glass into double-glazed window sash should always be ventilated - to prevent condensation and the build-up of heat between the two layers. A common method is to add a back stop one inch in front of the existing clear glass, then the stained glass, followed by the front stop. Ventilation can be achieved in a number of ways, including drilled holes, breathing slots (in different positions on the front and back stops so that light won’t leak through) or metal vents in the window stops or elsewhere in the frame. We never seal the perimeter of the window in these installations, as this allows it more room to “breathe”. The stops used should be metal, and coloured to match the existing frame; however, painted wood stop is an acceptable alternative. For this type of installation, the depth of the frame must be at least three inches deep to accommodate the glass and stops.

An alternate method is to install the window in a separate metal or wood frame, which is then secured in front of the existing windows. Hinges on the stained glass frame will make it easier to clean and maintain both the stained and clear glass.

On interior doors, there is usually not enough rebate room to add stained glass, and a separate metal frame attached to the door in front of the clear glass is the best solution. Alternatively, the clear glass can be removed and the art glass installed directly into the clear glass framing device.

Installation plans will also consider the support needs of the window. The means of support will depend on the size and the design of the window, and the nature of the stresses. Basic support can be provided by soldering flat bars to the window. Bars are usually added every eighteen inches, depending on the width of the panel. Alternatively, the window can be strengthened by the use of zinc channels and framing in place of some of the leads. If the window will be exposed to extremes of heat and cold, more flexible support will allow the glass to expand and contract. For this, round bars can be installed, and the panel fastened to it with copper ties. Windows that open, or that are installed into doors, are subject to additional stresses from movement. They need extra support.

An article such as this cannot possibly cover all of the situations and requirements of every commission. Time, thought and common sense are essential. Even then, every artist will make the occasional mistake. If that happens, all you can do is to put it down to learning, and know (if there’s any comfort in it) that you aren’t the first!