Home DIY

Good chance the hinge is goosed, you'll need to open it to work out the size to order a new one. Whilst you're at it, replace the other side too.

Don't know about where you live, but around here houses can settle causing windows to stick and not work properly.

The friction hinge is broken, but should be repairable. The top fixed section on the frame has a top cap receptacle to receive the location lug atop the opening sash... The two parts mating together should pull the top of the sash against the frame. But metal type top caps often open up when the lug hits it and doesn't slide into its closed position. Some cheaper plastic top caps just snap off.

I prefer to fit Avocet Phocas hinges, as they have a sprung top cap and a good guarantee. However you need to pay attention to positioning a replacement hinge so the sash sits at the correct height in the frame.

It may be easier to do a like for like replacement if there's a name on them.

1. Your window is top hung (hinges at the top and handle at the bottom).
   
2. Measure the length of the hinge on the frame. They are normal expressed as 8,10, 12, 16, 18, 24 inches.
   
3. Measure the width of the track on the frame 17-18 mm is standard, whilst 15-16mm is less common slim line
   
4. They come in 13 and 17mm variations, of stack height. Which if the thickness of the hinge stack when it's closed together in the gap between sash and frame.
   
   
   

You don't want to drop the window, so I'd suggest taking the glass out of larger windows, then you can hold onto the frame easily. But for a smaller window that's not going to be too heavy and awkward, wrap one of these around it a couple of times to use as a handle. Don't use suckers on patterned glass or rely on them to stay in place with holding a sash whilst your changing hinges!
https://www.screwfix.com/p/cambuckle-tie-down-straps-2-5m-x-25mm-2-pack/87355

Reusing screw holes often needs larger diameter screws to get a good bite as the thread comes away when you remove the screws. So grab a pack of 19 and 25mn of these.
https://www.screwfix.com/p/easydrive-self-drilling-pan-head-screws-4-2-x-25-x-100-pack/2929h

1. Open window and wrap your straps around the sash. Take note whether the hinge top cap is hard up against the top of the frame, or a gap. Remove all but one screw from either side of the frame.

2. Remove the remaining screws then push the window outwards to free the sash complete with hinges from the frame.

3. Collapse the hinges to make it easier to bring the sash indoors.

4. With the hinges closed. Measure how much the top cap is sticking up, because you'll want the new hinges at the same height.

5. Offer your new hinges up to the frame to see if there's screw holes through the slotted holes in the hinge. Mark and pilot drill if needed, as doing this whilst holding the sash in place is fun.

6. Make sure your new hinges are opening the correct way. Some can be opened backwards and won't close correctly when fitted.

7. Fit new hinges to the sash, using the slotted holes. Close hinge and check the height of the top cap from part 4. Fix remaining screws.

8. Pass sash back through the window opening and extend the hinges and get them to sit into the frame. Get a screw in one side to take the weight, so you can sort the other side.

9. Position the hinge at the required height and fix with a couple of screws.
   Set the height of the second hinge and fix with a couple of screws.

10. Close the window and ensure it closes and locks correctly

11. Fit remaining screws to frame.