Why Are My Aluminium Venetian Blinds Uneven or Crooked

Aluminium venetian blinds go crooked for a handful of reasons, and most of them come down to cord tension or a headrail that isn’t sitting quite right.

It’s fixable at home in most cases. You don’t need specialist tools, just a steady hand and about 20 minutes.

What You’ll Need

Tools

• Step ladder or sturdy chair
• Small flathead screwdriver
• Spirit level (useful, not essential)
• Scissors

Materials / Replacement Parts

• Replacement ladder string (if yours is broken or badly frayed)
• Replacement lift cord (if the existing cord is kinked or snapped)
• Cord condenser or equaliser clip (optional, for cord tension issues)

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How to Fix It: Step-by-Step

Step 1: Check the Headrail is Sitting Level

Before touching anything else, the headrail needs to be properly seated in its brackets. A twisted or tilted headrail is the most common cause of crooked slats, and it’s easy to miss.

1. Take the blind down from its brackets by pushing up the front of each bracket cover and tilting the blind forward
2. Hold the headrail up to the window and check both ends sit at the same height
3. Place a spirit level on top of the headrail if you have one
4. Look at the brackets themselves: if one is slightly higher than the other, loosen the screws and adjust before rehanging
5. Rehang and check whether the slats now hang straight

If the headrail was out of level, this is likely your fix. If the slats are still uneven, move to step two.

Step 2: Check the Ladder Strings

The ladder strings are the two fabric or cord strips that run the full height of the blind, holding each slat in its own horizontal rung. If one string is twisted, tangled, or has slipped, the slats it supports will hang at an angle.

1. Lower the blind fully and tilt the slats to the flat/open position so you can see the ladder clearly
2. Run your eye down both ladder strings from top to bottom
3. Look for any rung where the slat is visibly tilting more than the others
4. Check whether the ladder string has wrapped around itself or is threaded behind a slat instead of in front
5. Gently work any twisted sections back into position with your fingers
6. If a ladder string is broken, it’ll need replacing entirely. Replacement ladder string is inexpensive and available by the metre

Step 3: Check the Lift Cords

The lift cords run through holes in each slat from top to bottom, and they’re what raises and lowers the blind. If one cord is tighter than the other, the blind will bunch unevenly on one side when raised, or hang at a slight diagonal when down.

1. Pull the blind down to its lowest position and hold both lift cords between your fingers near the bottom
2. Check whether one cord has noticeably more slack or resistance than the other
3. If the tension is uneven, the cord may have jumped its routing track inside the headrail, or may be knotted somewhere inside the slat stack
4. Open the headrail end caps (they usually unclip or unscrew) and check how the lift cord is routed through the cord lock mechanism
5. Re-route any cord that’s come off its intended path, making sure it feeds through the centre of each slat hole cleanly and evenly

Lift cords stretch over time. If yours have stretched so much that one side is noticeably longer than the other at the bottom equaliser, the easiest fix is replacing both cords at the same time.

Step 4: Test the Tilt Mechanism

Once the ladder strings and cords look right, give the tilt mechanism a proper test. The tilt rod (the wand or cord that rotates the slats) connects to a tilter inside the headrail, which turns all the slats together. If this tilter is worn or the rod has slipped from its socket, the slats won’t rotate evenly.

1. Open the blind fully and tilt the slats to horizontal using the wand or cord
2. Watch the slats as you tilt: they should all move together in one smooth motion with no stragglers
3. If a group of slats in the middle or at one end aren’t rotating with the rest, that section of ladder string has likely lost connection to the tilt rod
4. Check where the ladder strings attach to the tilt rod inside the headrail and reattach any that have slipped free
5. If the tilter mechanism itself feels gritty or has seized, a small amount of silicone spray lubricant on the mechanism will usually sort it