select "Home tab" -"opening" cut by "vertical"command, select roof then use pick line tool or draw line tools to create shape to cut. Using plick line lets you pick valleys etc.

I'm guessing there is something wrong with the forum or the inline-attachments are turned off. Can't seem to be able to open it, clicking the attachement logs me out. Would you repost it, not using the "attach inline" option (simply click Done after uploading)

[/ATTACH]I re-posted like you said.

Thanks

[ATTACH]727

If you also draw the walls under the gable roof you can use the Dormer opening. Home tab > Dormer opening. Go to the roof plan view, select the edges on the gable roof where they attach to the main roof, and select the end line of the main roof. go to the plan view below, select the walls underneath the gable roofs, trim those together and finish.

Thanks for the replies. I will give it a try.

What do mean when you say trim these together and finish. I am just trying to learn how to do roofs, and I am having a tough time. I have attached a file to show what I have done so far.

Thanks

Ok, so that was a bit too fast. The thing is: dormer openings are a great tool, once you get the hang of it. But they require a different approach then all other kinds of openings. You can't sketch them, you have to pick edges. You can either pick edges from roofs and or walls attached to the roof that you want to cut, or an edge of the roof that you want to cut. Here it goes, step by step:

Home > Dormer opening.
Select the main roof, this is the one you need an opening in.
Now you need to select edges along you wish to cut. First select the roof attached to the main roof. You will get both edges at once as a purple sketch line (if you do it correctly)
The third part of the dormer opening is defined by the lower edge of the main roof, meaning you want to cut all the way down. So select the lower edge of the roof (where you would attach the gutter).
By doing this you get a sketch line over the full length of the lower edge. Use trim to connect all lines and make a triangular shaped dormer opening.
Click finish and you're done. Doing this for all three gable roofs will create a roof as in the attachment.

Now, in this case the gable roofs and main roof share about the same gutter height. But sometimes the gutter height for the gable roof is higher. I demonstrated this by lifting the gable roof on the back of the building. This will result in interior walls sticking through the main roof to connect to the gable roof.
In order to create this kind of dormer opening you follow the same steps:

I'm going to assume you attached your interior walls to the main roof already. If not, do this first.
Home > Dormer opening and select the main roof.
Now you need to select edges along you wish to cut. First select the gable roof attached to the main roof. Again, you will get both lines at once.
After this select the interior side of both walls (that being the face on the side you wish to cut out of the main roof)
After this, select the lower edge of the main roof.
Use trim to connect all 5 lines.
Click finish and you're done. Doing this will create a roof as in the attachment.

Before trying this yourself I recommend you select the dormer openings in the file I created and choose Edit. Now you can determine where the sketch lines are located. You might need to turn on wireframe to get a decent view.Let me know how it works out.

great explaination Martijin.
You have more patients than me when it comes to typing.
Max if you are just starting out with revit and roofs there is heaps of tutorials around,just google.
Here is a selection.

http://wn.com/Dormers_In_Revit_Architecture

Thanks for the replies. I will search out some tutorials