Interior Walls - Why do some rooms become blue and some don't?

Hi, I am currently working on a floor plan. As Im creating interior walls, some rooms become “blue” like a surface, although non of the interior walls close in on each other. Only with the exterior walls does all geometry meet. If that makes sense. Some rooms are blue and others are not… And I ideally I don’t want them to be have surface as it creates a problem when I load in flooring from 3d warehouse… Is there any way to avoid it becoming a surface? Thank you!!

The blue indicates you are seeing the backs of the faces, not the fronts. This is common when you draw a floor plan on a rectangle and extrude the walls with Push/Pull. If you orbit around to the bottom you will likely see you can look up inside those walls and you’ll see the white front faces. You can right click on those blue faces and then choose Reverse Faces to correct them. If you want to avoid them altogether, you can do one of several things. Give the floor thickness before you draw the edges for the walls, you can leave the floor 2D but delete the floor faces leaving only the wall faces for extrusion, or you can use the modifier key with Push/Pull to create a new face. The modifier key is different depending on your operating system.

FWIW, although it isn’t what you want to see, Push/Pull is working correctly when it shows those reversed faces.

Which version of SketchUp are you using? Your profile says you are using the free web version but youposted in the SketchUp Pro category.