Jerafter

What would be the best way to tackle this project? I want to keep the front of both buildings facing the bottom of my screen and at 90° angles. If I draw the house and garage as separate plans, is there a way to combine afterward to reference the separate garage plan in the specific location and angle on the image? I want to show what the perspective view would be for the client, but I don't like drawing the detached garage at this off-angle.

All roof planes have the same settings in my plan. The valley issue only shows up on two valley situations on the left side elevation view. It doesn't show up on the rear and right side elevations though. I do have the roof planes on different layers in those areas. (One is existing and one is new construction.) I was able to make it appear correctly on my layout plot line elevation views by spraying the problematic valleys with an air gap material.

In X18 I am getting a wide valley "flashing" showing in my perspectives and elevations. I never had this problem before in previous versions. I tried turning off the ridge caps for both of the selected edges and tried the join roof plane tool, but I still can't get it to not show up. In my elevations that are sent to layout, it shows as a blank area. Am I missing a setting or is this a glitch that needs to be reported? I drew these roof planes manually.