How can I make a wall keep the measure without the wall itself?

[kajus24]

So, I measure a wall of the room (from the inside of the apartment) and write it down... but when I'm actually trying to make it, the measure is somehow wrong, because it does count the walls.

When I create a dimension later to measure the wall, it's always shorter, as if the measure of the wall was taken from the middle of inside my walls. d oh
Like, one wall is 96 inches, but then the dimension from inside says 93.5 (my walls are 5 inches thick).
Any way to fix it?

It's not a big problem, but in an apartment like mine with many walls, inches after inches it won't square up at the end. Kinda hard to explain the whole situation, and maybe there's a setting somewhere... Thank you.

[Puybaret]

Please have a look to the video How to design rooms from their inner dimensions.