Our expert guide on measuring a window for roller, roman, vertical and venetian blinds
When measuring for window blinds, you should adopt the carpenters’ motto – measure twice, cut once. You shouldn’t be afraid of getting it wrong the first time since you can re-measure the windows again to determine the accuracy of your first numbers. Your best tools in this task are a tape measure, pen and paper, perhaps your common sense in following instructions.
You must decide whether you want an inside or outside mount for your blinds. Your choice will affect not just the appearance of the blinds when mounted, but also the steps in measuring them prior to installation.
Inside MountFor an inside mount, experts recommend that the window’s depth should be a minimum of 60mm so that the blinds will neatly fit inside the recess. Otherwise, the blinds will likely protrude out of the recess when the window’s depth is less than 60mm.
- On a piece of paper, draw either a rectangle or square to represent the window frame. Give each window a label, such as “kitchen window, left side”, to avoid confusion.
- Place a tape measure inside the window recess. Be sure to measure from one end of the frame to the next, a process that must be done at the top and bottom to get accurate measurements for the blinds. Write down this down as the width.
- Measure the vertical drop from the inside recess’ top to the window sill’s base. Write it down as the length of the window frame.
- Measure the width and length again to ensure accuracy.
Outside MountThere are two ways that measuring an outside mount should be done depending on the type of window. First, in a window with architraves, such as a metal or timber frame, just follow the instructions below. Second, in window without architraves, add at least 100mm to the width and length of the original measurements. Also, you have to locate the stud embedded into a plaster or gyprock wall when installing roller or Roman blinds. The stud will be used to secure the blinds and, therefore provide it with the required strong support to hold the weight.
- Draw a rectangle or square on a piece of paper to represent the window frame.
- Place the edge of the tape measure on the outer edge of the architrave and pull the rest of the tape to the opposite edge. Write the number down as the width.
- Measure the vertical length from the architrave’s top to the edge where the blind will likely end. You can choose to let the blinds end at the window’s edge or at the floor.
- Double-check both of these measurements.
Roller and cheap Roman blinds are well suited to be fitted on the outside recess, as this allows the header rails to be fitted slightly above the window itself so that natural light is least obscured. Likewise, if your windows have protruding sills it is a good idea to follow the same width as these to achieve a neater finished look. All style of blinds can be fitted either inside or outside the frame of the window, as mentioned above Venetian and cheap vertical blinds are best suited to an inside fitting so that they can sit close the glass, whereas made to measure roller blinds and Roman blinds fitted to the outside can give the illusion of larger windows which allow plenty of natural light to flood into the room.
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