If you have bought made to measure blinds then you shouldn't need to shorten your venetian blinds. However, it is sometimes more affordable to opt for the ready made option, and make adjustments yourself. This can be less costly but it does require a certain level of skill, and there are risks of damaging your blind, should you make a mistake. In fact, as not all window sizes are the same and blinds only come in set sizes, it is more than likely that you will need to shorten a venetian blind if it is ready made. So keep this in mind before making a purchase. Now lets cover some of the techniques for adjusting the height of a venetian blind.
Ready made blind size requirements
To start with you will need to buy a venetian blind that is slightly larger than your window frame. By doing this you can ensure that once it has been shortened it fits exactly within the frame. If it is already too short then there is no way to make it longer. Also if it is too large then there might be restrictions on how much it can be shortened. Basically it's the Goldilocks effect, you need a ready made blind that isn't too short, nor too long; it needs to be just right.
Note: Ideally the length of the blind should allow the bottom of the blind to sit ¼ inch above the window sill. Keep this measurement in mind when making the adjustments detailed below.
Removing blind slats to avoid bunching
Although ready made blinds can be pulled tight to ensure the slats don't overhang the window, this can cause a bunching effect at the bottom of the blind. This bunching just isn't a very attractive look, and lets people know you have a window blind that doesn't sit nicely within your window frame. Although this isn't the end of the world, there is a simple set of steps to follows which will avoiding bunching at the bottom of the blind. By simply removing some of the bottom slats you will be able to make your blind fit neatly within the window. Plus doing this will prevent the blind from blocking out more sunlight than they are designed to.
To start with you will need to put the blind in the fully open position, allowing any extra slats to overhang the window frame. Then you will need to remove the bottom rail from the blind by removing the cord plugs beneath the rail. These plugs encase the cord, and are held in place with a knot in the cord. They are secured under the bottom rail within a small hole. There are usually two or three of these, depending on the width of the blind. Once located, unplug these from the bottom rail and you can cut the cord above the plug. The bottom rail should then become loose. At this point you should notice that each slat is sitting on what looks like a ladder, with each slat placed on each step of the ladder. Then each slat also has two or three holes through them, where a single piece of cord is threaded.
To remove slats you will need to start by de-threading the cord from any slat you want to remove. Do this for each hole within the cord, and you should then be able to slide the slat out of the cord ladder. Repeat this process with each slat you want to remove. You should then be left with slats sitting neatly within your window, and pieces of redundant cord dangling below. If you're happy with the remaining slats and the blind sits within your window as required you can then add the bottom rail back to the blind. Thread the cord through the bottom rail and then through the plastic plugs (which you removed earlier).
You will then want to tie a knot in each of the cords at the exact same height. These will sit within the plug and keep the blind cord and bottom rail securely in place. Once the plugs are in place you can then trim the cord below the plug and knot, to remove the excess and make the blind cord look neat.
At this point you should be left with excess ladder cord, as this hasn't been trimmed yet. Identify the last step in the ladder, where the last slat is sitting. You want to cut below this last step, as otherwise the slats will come loose. You should use a sharp pair of scissors to ensure that there is a clean cut through the cord, otherwise the cord may become frayed. Cut 5mm below the last step, cutting through all vertical cords on each of the cord ladders.
Discard excess cord and you are finished. The venetian blind should now sit within your window without any bunching. If done correctly then it will look like a made to measure blind, fitting snuggly within the frame. If all of the steps above seems like too much effort, and you don't have the time to make these adjustments then you might want to opt for the made to measure option instead. This can be a little more expensive, however it can save you time, energy and will ensure that your venetian blind fits perfectly within your window.