Yes, I have built one, and was very satisfifed with it. Built in a basement area adjacent to a study and a workshop, walls AND CEILING of poured reinforced concrete, used the existing slab basement floor. Mine was not that large, about 7' x 7' inside dimensions plus another 3' x 3' joining that which held very heavy shelving for ammo storage. I bought a Browning brand vault door and it was quite satisfactory, IMO. My vault had commercial carpeting on the floor and on the concrete walls, to help protect barrels against accidental bumps. Fully wired, of course, and I also devised an air circulation system that used a single 100 watt light bulb with a salvaged fan from a computer blowing the somewhat heated air upward and around the room. Worked like a fan forced "goldenrod" device, and worked very well. This unit held about 60 guns in a combination of wall and floor mounts, plus thousands of rounds of ammo. Since a son and I did all the work, my cost was only in the $3,500 range about 7 years ago. Prices are surely up somewhat today, and increasing the size could change that estimate as well. The reinforced concrete ceiling is just as important as the reinforced walls, IMO. If someone did locate your vault while you were away, they couldn't chop down through your upstairs floor and down into your vault. There are numerous makers of vault doors, I was happy with the Browning brand. Shipping the vault door to me from the dealer was not costly at all, but how near you are to a dealer can be a factor if you decide on a D I Y job. I would not hesitate to do something similar again. This vault was certainly not the quality of the one described above, but cost only slightly more than a much smaller gun safe would have cost me, and was very secure and completely satisfactory.
