The two walls you have drawn in 3D don’t meet because they don’t start at the bottom from the same corner.
All your faces are reversed (showing blue). That’s natural for the floor since SU assumes you will be pushpulling up walls.
But make your walls into components as soon you draw them.
I made the longer wall into a component, cleaned up a few extra lines I’d included by mistake in my window selection, and moved it to one side.
You can see in this image that the floor plan has three lines at that corner. So they wouldn’t meet when you pushpulled up.
More or less right. But a couple of things will help.
First, I converted your image to a texture rather than an image and applied it to a rectangle exactly the size of your image. I found (I hadn’t known before) that you can’t Lock an image in SU. Slightly tricky, and I can describe in detail if you need to repeat it.
By convention, not a rule, the long axis of a building runs along the red, not the green, axis, and the lettering on the floor plan image is the right way up when you do that - easier to read.
So I next rotated everything 90° clockwise.
Then locked the Floor image component.
And I made a component out of the floor plan you have drawn, and placed it back on top of the floor plan. And reversed faces so it’s right side up.
Then work in Xray mode (View/Face style/X-ray). It’s worth making a shortcut key for that, so you can toggle in on or off with a tap on a key (I use x).
And probably you will find it easier to erase the floors inside the rooms, at least while you are drawing the interior walls.
I’d suggest making just the exterior walls first. Draw a rectangle round the outside, then oFfset it inwards by the wall thickness - looks like 300mm in your case. (I typed oFfset oddly to remind you that the built in default shortcut key for offset is F.)
Pushpull the exterior walls to height, then make that into a component immediately. Height seems to be 2760 mm - is that right?
Some of the longer dimensions are a lot of digits in mm. You might want to change the units to metres, perhaps with 2 decimal places - so the last digit is 1cm; or alternatively work in cm. That’s about as precise as most buildings can be made, and if all your dimensions are multiples of a cm you’ll find it easier to get clean corners.
Then clean up your floor plan drawing. This image highlights some problem areas. Look where the lines aren’t clean and thin-looking.
Turn off Length snapping in Model info/Units.
Once you’ve cleaned up the floor plan, exit the component, and lock it.
Then draw your interior walls on top, and make each one a component as soon as you’ve drawn it. Always make sure that your default tag is Untagged in SU 2020 onwards as you are using. or Layer0 in versions 2019 and earlier.
Assign Tags ONLY to components, groups, or (later) dimensions or text.
That way you can control the visibility of selected parts of your model.
isberne blueprintsJWM.skp (4.5 MB)
The blueprint image is slightly distorted. I notice as a result (I only checked a few dimensions) that the few handwritten dimensions don’t always match you floor plan - for example at the left edge.
Anyway, all I’ve time for at the moment.
Hope it helps.
Post later how you are getting on, or ask for help again.
Have you watches the learn.sketchup.com videos? If not, highly recommended. You MUST understand components, groups, and tags (formerly layers) to use SU effectively.
PS. I noticed that your walls aren’t all the same thickness. Use the Tape measure tool to draw a guide for the thickness and adjust the floor plan lines there with the Move tool to snap to the guides.