So this is one of the topics, how do I say it properly? I'm never going to have one of the nicest rifles or optics or setups on this forum. (Well, if I hit the lottery, then definitely. Short of that, probably not.)
I definitely have a pretty sweet, extremely strong "Safe Room".
We built our house with Fox Blocks ICF - 8" of double-double rebar, matrix-reinforced premium concrete - I guess you can choose different sizes , but really you only save in the actual concrete costs. The Blocks themselves are pretty close in price, so if you think "Well, I'll buy 4" instead of 8" blocks, and save Half!" - it doesn't work like that. Unlike the rest of the house, the 'Safe Room' (which really is more of the house Office- it has two separate Office rooms (including mine, which is my Gun Room), a pantry, a small bathroom, a half-aced lounge, etc. - the Safe Room has a 4" fiber-matrix reinforced concrete roof (on top of the 8" double-double-reinforced walls.) - The Architect basically was told, "Spec it out to be a fortress, whatever amount of Rebar you think should be used, then Double it..." - and he did, no problem - then the Concrete Wall contractor (as opposed to the concrete pad / foundation contractor, who was a *real* professional) was all enthusiastic at first, "This is going to be like a Castle! We could even DOUBLE the amount of reinforcing Rebar your Architect spec'ed out (and doubled) ... if you wanted, if you pay for it , we'll put it in, it will be awesome to do!" - It wasn't much of a cost in the long-run, so sure, we'll pay for that extra steel and it will be that much more strong. (And I should be clear here, I'm talking also about the entire house walls, not just the Safe Room. We wanted to make sure the entire exterior construction was as solid as possible.) When the Rebar was delivered, you could see the guy looking like, "What am I going to do with all those rods?" - and sure as sugar, a few days later (and the rods need to be hand-laid into the plastic pieces that are molded into the ICFs, so when the concrete is poured, they're aligned properly both up and down & side-to-side etc...) - he starts complaining, "You know... you don't really NEED this much reinforcing ... it's really just a lot of work for nothing... I don't think you should even worry about it, we'll just use it for a different job..." === yeah, no, you not only agreed to do it, you *suggested* it, put all the rebar in.
The roof (of the Safe Room I mean now) was a little odd ... it has a 4" fiber-matrix reinforced concrete composition, whereas the walls are all the 8" Fox Blocks ICF rebar/matrix reinforced concrete. (As is the rest of the house)
The door was something we wanted quality but not necessarily Fort Knox because we're not exactly expecting to have Delta Force breach us, we're just regular people. We went with Smith Security Safes "Magnum Vault Door" - the owner of the company specifically recommended that and told us that for our purposes (mostly trying to provide security from hurricanes, while retaining the ability to serve as a secure room in an unlikely-yet-extreme scenario or emergency etc.) - Very nice, it's got a 1/2" solid steel plate along with very solid channel-iron frame and extremely thick and strong solid stainless steel plungers etc. The next step up would have been a 1" steel plate (and they have an extremely expensive 1 1/4" model) - but they were very nice and honest - unless you're *specifically* planning on blocking someone from concerted breaching, even the 1/2" is overkill, and that's why they sell more of that one than any other. (they go as low as 3/16" for Light Vault Door applications etc.)
One thing I highly recommend, whomever you go with - take the installation and make sure you have some help. Strong help. They told us they highly recommend that they do the installation, and it's only a hundred or so extra (since they're delivering it anyway.) - We thought, great! I'm not a big dude, only 5'8" , my Dad was getting close to 70 so it's not like I want him manhandling this thing, and they assured us they can take care of it. When the day was approaching, we got an email from the delivery & install gentleman, who basically said, "I just need a few extra sets of hands, 1 or 2 people" - we made sure, "Ok, do we need to do the work or do we need big strong guys or is it hard?" .... "Nono, I have a fully-auto lift truck, I have tools and do this all the time, I just need a few extra sets of hands, it's easy, no problems.." I had arranged for 4 extra people to come, 2 couples. One couple cancelled because of some family issue that morning, the other husband cancelled, only his wife. (Smaller than me.) Let me tell you, "I do this all the time, just need some extra hands" was BS. He expected to have 2 sets of Offensive Lineman hands. It took several hours to get it up into place. We actually resorted to maneuvering my JD Gator as close to the house as possible, hooking up the winch, and winching it up - and *right before* it got up, the cable snapped, dropping the thing on the ground, which nearly killed us and I'm literally lucky to be alive, I moved at the split second before it would have crushed me. The cable similarly almost killed the woman operating the winch on the Gator. I was getting pretty PO'd - you pay for "professional installation" and one college-age kid shows up and having been told he just needed a few extra hands to 'steady it' , what he meant was, lift it up off the ground and manhandle it into place. (it weighs over half a ton.) He's getting upset because he's supposed to be done and on to the next job in the next State by now, I'm getting increasingly upset because *if they TOLD US* they really expected a team of guys to lift the thing up, I could have made that happen. But that's not what they said - and I think we were all about to just give up when my Dad used his Kubota tractor and straps to lift it up, THEN the installer got it into place. Once he got it roughly into the frame area, it was gravy, he did a pretty quick and easy job from that part. Tough part is getting it maneuvered around.
And it's been absolutely perfect, with multiple daily uses, for coming up on 4 years now.