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Basement windows are useful for letting light into otherwise dark spaces, but not every basement requires windows that can be opened. In many cases glass block basement windows, which tend to be both cheaper and more durable than ordinary windows, can be installed instead, subject to the approval of local building codes. The process of installing glass block basement windows begins with careful measuring and planning, followed by the selection of materials. The old window is then removed, and a new glass block window is mortared securely into place.
The first step in installing glass block basement windows is careful measurement. The size of the window opening should be measured from cement to cement and cement to sill board. If a window opening is irregularly shaped, all dimensions should be measured carefully, as such windows will likely require either special order panels or hand assembly.
Glass block basement windows can be purchased in prefabricated panels or assembled on site from individual blocks. Panels are generally easier to install, but may need to be custom ordered for windows in non-standard sizes. Assembling a window out of individual blocks requires more patience but allows for special effects such as curved windows.
Once materials, including mortar, have been obtained, the old window must be removed. Care should be taken to avoid damage from broken glass. All the wooden framing around the window must be removed up to the base of the sill plate. The top framing should be removed carefully to avoid damage to the structure of the home.
After the window has been cleared, the block panel or individual blocks can be installed. Wood blocks should be mounted around the edges of the window, to serve as guides for the glass blocks. A flat piece of plywood can be temporarily mounted to provide a regular surface, which is particularly helpful if the window is being assembled from individual blocks.
The installation process itself is straightforward. A panel of blocks can simply be placed into the window opening and then mortared into place. Individual blocks must be installed one at a time, and care should be taken to ensure regular spacing. A grid on the plywood sheet can be useful in this process. Mortar should be applied from both sides of a window, to ensure that there are no voids that could cause the window to fail. The mortar should be smoothed around the base and sides of the window both for cosmetic reasons and also to enhance the durability of glass block basement windows.