Jet Sitter....I will ask my brother about the measurements.
The paint on the inside walls isn't really necessary because no-one
will ever see it, but he is a perfectionist and likes to do stuff like that.
The paint is some kind of special concrete paint and sealer. I will get
the name for you....he bought it at Lowes. They are going to install
coping along the top on Monday and I will post the pics for you to
check out. When you design your vault be sure and leave some
access area so if repairs are needed they can get to it. Also a drain
in the vault is helpful in case rain or a leak would ever cause water
to accumulate. And of course have them leave a pvc pipe in the vault to
bring in the electric. When you get ready to start let me know and if you
want you could e-mail or even call my brother to discuss. This is his 2nd
hot tub vault. Below is a picture of the one he built in Colorado...notice
the access hatch....he also likes putting in the removeable pool ladders
on his in-ground tubs....once you use the ladder in an inground...you love it.
I also have tons of pictures of in-ground spas if you need to get some ideas.