Complicated cut!

[darrenh]

Hello. I was hopeful a helpful carpenter might help me with this complicated cut of a dado on top of my diy panelling.

I have tried lots of different options and to no avail! How do I cut this so the dado matches up??

 

[RandomGrinch]

 

[Puzzled13]

Make the sloping piece horizontal before you get to the corner . Then just 45 degree mitre

 

[Puzzled13]

 

[darrenh]

Sorry I am still struggling given it is a slope and then a turn. I can’t visualise what to do. The dado has to sit on top of the mdf panelling.

 

[RandomGrinch]

Sorry I am still struggling given it is a slope and then a turn. I can’t visualise what to do. The dado has to sit on top of the mdf panelling.

Basically, it is impossible to make a single joint in the way you intend.
Cutting the dado at an angle - see my top pic (above) - leaves a diagonal edge that will always be longer than the width of the dado.
To make a neat joint you could cut the dado at an angle and use an infill section as in the lower pic, or as seen in @Puzzled13 's image (which is exactly the same as mine, but upside down).
To do this in your case, you would also need to raise the height of the level dado on the left hand side.

Ideally, the MDF paneling on the stairs side, should have looked something like...

Alternatively, but not as neat, you could try something like this...

 

[darrenh]

Ok I get it! Thank you both for really helping here! I think I need to remove the panelling on the left side and change its height and go for your first picture right hand side option.