Our property to be renovated has a 1.26x1.26 window to the garage. I would like to replace it with a side entry door about 1.00x2.00. I don't see a problem in increasing the window cut up and down. But the window should also become narrower. The house was built in 1980 and is clinker. I am already trying to arrange the right bricks at the same time.
Is this action in principle relatively trouble free or will I get myself in trouble?
Could the door be too wide? I wouldn't make the doorway narrower, I wouldn't use a side panel either, that would be too narrow. A wide frame would be better. Zooming up is not as trivial. Going down is usually not a problem.
If this were my house, I would probably use a double-wing balcony door, which would also look good in terms of width.
You may be able to remove the clinker bricks set under and over the window so they can be reused. You will only need 26 cm width by 1.26 m height. If you need to widen the space upward, you will also need to raise the lintel. Are there any pipes (heating pipes) under the window? If not, it shouldn't be a problem for a specialized construction company, or do you want to do it yourself?
Why not just order the right door? If it's going to be done by a specialized company anyway, they can supply any size door.
They can then fabricate the right door for you. There are several options. Either add a side panel or a wider frame. Or you can just get a door that is wider.
It will look better than patching brickwork or clinker. This is something you will always see.