How To Install Outside Mount Window Blinds
Outside mount window blinds mount on the wall above the window opening and span wider than the window. They provide more complete light and environmental control than inside mount blinds, which fit inside the window opening. They can also camouflage worn or otherwise unsightly window frames and sills. Outside mounts can be a cost saver for non-standard window shapes, avoiding the need for costly custom blinds, and may even be a necessity if your window is flush with the wall.
You will need a metal tape measure, a pad and pencil, a drill with the appropriate bits, and screws and screw accessories for whatever material your window casing is made of (concrete, wood, drywall, etc). A level can be helpful to help make sure that your installation is even.
When taking your measurements, measure the window cavity itself first. Measure at a few different points across for the width, and down for the length, as your window might not be perfectly symmetric. For outside mounts, take note of the widest and longest dimensions of your window to make sure you have full coverage. You may wish to have a couple of extra inches on each side and on the bottom, as well as the necessary extra inches on the top to allow space for the mount. When choosing how much wider to order your blinds, remember that when they are raised you will be exposing the wall beneath, so two or three inches on each side is probably sufficient. Follow the manufacturer's instructions and communicate with the vendor before finalizing your purchase, because you will be ultimately responsible for providing accurate width and length measurements.
Once you have received your blinds, hold them above the window frame at the desired height. They should be level, and centered across the opening. Make pencil marks at each of the lower corners of the headrail. If you have somebody working with you, now would be a good time to ask them to hold the blinds in the chosen location while you test to make sure that they will work freely and provide the desired coverage when extended. Make an additional mark 1/8 in out from the left and right of the outermost pencil marks. This will help allow for the additional thickness of the support brackets. Hold the brackets in the location. The first marks for the width of the headrail should be just visible on the inner side of the bracket. Use your pencil to make marks for where the screws will go. Set aside the brackets, and pre-drill holes as necessary. Secure the brackets with the appropriate screws and install the blinds according to the manufacturers instructions. If any additional support brackets are required, space them evenly or as recommended by the manufacturer, remembering to allow for the proper movement of the blinds. When installation is complete, test the blinds a few times to see if they move freely and are stable.