Is there a way to select a material like 2x4 and draw a wall using the line tool without using the offset tool?
??? Say that again? 2x4 is not a material, the offset tool generally would not be used on a wall, and SketchUp is a 3D program so everything is 3D. Try describing in more detail what you want to accomplish.
According to the tutorials, creating a 2D floor plan is the best way to start as a beginner I just want a top down view of the floor plan. I am trying to create walls with the appropriate dimensions based on differ types of lumber (example - 2X4) but to do that I need to know that actual dimensions of the lumber which are not 2x4, to use the offset tool. I would think for ease of use, I should be able to select some kind of tool and tell it that I want a 2x4 wall without having to calculate the actual dimensions myself by drawing two separate lines. Does this makes sense? I am new to Sketchup and it seems like it should be easier.
Although SketchUp is wonderful at 3D, you can make 2D drawings. I would set the view type to parallel and set the camera angle to Top. Then be careful to not rotate the view. Use the rectangle tool (r on the keyboard) and drag out a rectangle. You can type the dimensions after the first click. 2x4 are actual 1.5 x 3.5, so type 1.5,3.5 enter. If you want the wall it would most likely be 3.5 by the length of the wall. Be sure to group each shape as you make it (right click choose make group) or over lapping geometry can cause undesired results
As a follow-on to the above: SketchUp doesn’t ‘know’ about construction materials. The ‘outside’ information you may be looking for is called “actual vs nominal size lumber”.
You can use the Line Tool, with or without Guides (Tape Measure Tool), if you want a very simple way to draw walls.