A surround for glass block is essential for connection and restraint. This can be formed from any material, including timber or brickwork. A four-sided opening is the most stable. The aperture opening size should modulate with glass blocks and additional framing is optional (see calculating opening sizes).
Framing is used for different reasons, whether aesthetic, performance-related or due to an incorrect opening size.
Framing may be considered in conjunction with other building finishes, such as cladding. It may serve a design purpose. If a building is rendered framing offers a solution as render can be applied up to the frame, creating a watertight seal whilst ensuring an expansion joint between frame and blocks is maintained (render must not bridge the expansion joint).
Frames may be required to divide or support glass block panels, vertically or horizontally. For example, if the panel is quite large it has to be supported at a high level or for a 360o curved rotunda. It is possible to design these frames or intermediate supports to be integral and hidden within the glass block construction or revealed to aesthetically enhance the feature.
When designing frames*, it is important to calculate the opening size required for the glass blocks (incorporating frame dimensions and tolerances). The opening is the number of glass blocks, plus the number of joints, including perimeter expansion. The following formula and example demonstrate this:
*Structural engineers need to advise on wind posts and shelf-angle calculations. These designs and specifications cannot be underwritten by Glass Block Technology Ltd as they are usually uniquely fabricated. U-channel and box sections are sometimes fabricated to specification but also standard sections are available off the shelf. It is advisable to seek assistance from steel specialists.