Adding block vault to existing basement?

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Old 04-19-16, 12:23 PM
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Adding block vault to existing basement?

I tried posting this in the interior forum but had no success so I will try here. I'm looking for advice and/or ideas on an upcoming project. I'm looking to add a vault to my basement. Maybe 12x8' with a fireproof vault door. The idea is to have this room fully fireproof and able to withstand weight falling from upstairs in the event of a fire. I have a bi-level home built in 1985. The area which I'm going to build is under the master bedroom in a corner of the house where the block walls are fully backfilled. I have no idea how thick my slab is. I also have a single car garage on this level at the other end of the house with a block interior wall dividing it from the living area.

My original idea was to use I beams or 2" square steel, welded into 12"x12" grids for the ceiling, then weld a couple sheets of 1/8" steel sheeting on top, then a layer or 2 of gypsum fireboard. During the build I would have this structure supported from about 1' in from the outer edges since lifting this after the walls are completed isn't an option. Once the walls are completed, cut the supporting structure out from the inside. Now the walls...I was thinking of just using cinderblock again and trying to tie it into the existing walls. Would my slab support that much weight? Would 4" cinders work? Also, bringing in cement to fill the block isn't an option. Masonry isn't a strong point of mine but have done some before so any pointers is also appreciated.

I have been told by neighbors when the foundations were being dug that there was about 3' of red clay then blue limestone beds. Apparently there's some type of underground trench system around the perimeter walls of my foundation??? Hope that helps in some way to better get an idea of how much weight my slab could hold.
 
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Old 04-19-16, 12:40 PM
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You could frame the walls with wood then apply a layer of 5/8" sheetrock to the outside or two layers of 1/2". The ceiling could also be wood framed with the size depending on the amount of weight you expect it to support but you could use lumber span tables to get a good idea. One thing in your favor would be the short spans. Than top the roof with sheetrock fireproofing.

If you've just gotta go with masonry walls the most proper thing would be to cut out your existing concrete and pour proper footings. Baring that you could start with a course of 12" or 8" block to help spread the weight then step down to 4" to help reduce weight.

1/8" sheeting is pretty stout for the ceiling unless you want some armor protection for the room. You can look into corrugated deck sheeting. It's used to support the bottom of concrete pours usually in commercial construction. It's quite heavy duty and able to span long distances without additional support.
 
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Old 04-19-16, 12:49 PM
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I don't know what you plan to store in the vault & you probably don't want to tell us but I don't think that your slab would support it unless you dug footings. If you are storing money, a million dollars in 100s weigh 120 pounds.
 
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Old 04-19-16, 08:12 PM
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Playing the devil's advocate here--what would be wrong with renting a large safe deposit box or two at your local bank, and just paying them a few hundred bucks a year, maximum, for the rental(s)? A lot easier and far cheaper than your vault plan. And if you ever move, you don't have to start another vault project at your next house, either.
 
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Old 04-19-16, 08:19 PM
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what would be wrong with renting a large safe deposit box or two at your local bank,
That goes back to my question as to what's being stored.
 
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Old 04-20-16, 06:20 AM
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I know several people with large gun collections who have walk in vaults. A masonry wall would provide additional theft protection over a wood framed sheetrock wall though a hammer can easily get through un-filled CMU blocks.

I have a safe company near my shop. They also make vault doors and do repairs after burglary attempts. There is the occasional person looking for a quick grab and to get out. A normal safe or vault works well.

Most often a vault robbery happens during the day when everyone is away at work so the thieves have a long time to work. Most often they didn't know the vault was there until they broke in and use tools they find in your home. So, don't keep useful tools at home.

Sometimes there is a break-in intending on attacking the vault. This usually happens when the owner runs their mouth bragging about their vault and what's inside. Then the thieves come prepared with the needed tools to get inside.

At the factory undergoing repairs I've seen vault doors attacked with pry bars, drills, carbide & diamond cutting wheels & saws and plasma cutters. Idiots are stopped and get so involved in the attack that they loose track of time or make so much noise they attract attention. Some give up and leave but there is no residential grade vault door impenetrable. If they come prepared it's less than 10 minutes to get in no matter how thick the steel and how many locking pins/bars and a re-locking mechanism only helps in one type of attack and is easily bypassed.
 
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Old 04-26-16, 12:36 PM
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It would be primarily for a large firearm collection. I cant keep buying more safes as the collection grows.
 
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Old 04-26-16, 12:47 PM
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A lot depends on the security you want. Number one I would work on a way to conceal the vault. If you can make it go to the ceiling to look like another part of the basement wall would be good. Then do something creative to conceal the door.

CMU blocks for the walls are OK. For additional strength I'd consider some rebar and filling the blocks with cement. You don't have to fill the walls after completion. You can fill a row or two at a time as you build the wall up.

For the ceiling you don't really gain much by doing steel framing in a cross pattern though it will help some. If you consider parallel frame members 12" apart the steel sheeting is no more than 6" away from being supported. If you weld in cross pieces forming a 12" x 12" grid the steel sheeting is still only 6" away from suppport and it's a awful lot of work cutting all those cross nibblets and welding them into place. Personally I'd look at concrete deck sheeting. It's available in different profiles and metal thicknesses. It would do everything you want for the ceiling all in one package... quick and easy.

 
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Old 04-26-16, 06:09 PM
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That sounds easier for the ceiling. My concern is more for fireproofing and stability during a fire vs. security. My neighborhood is pretty safe with a lot of retired neighbors so I just want the hassle to get in to be harder than the reward. Any other ideas on if my foundation would hold that much weight? I have read several posts saying dig the footer and others stating they put 15k lbs. of machinery or forklifts on a 4" slab and have no issues. Obviously, not something I want to chance but if someone can provide strong data on how much a 4" slab can support that would put my mind a little more at ease.
 
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Old 04-27-16, 06:23 AM
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Personally I would do the bottom course with 12" block then step back to 8" and finally 4" for the remainder. The wider block at the bottom will provide three times the bearing surface and cut the psi load on your concrete floor by 1/3.

Then if you use the steel decking for your roof you can have a spray on fire proofing applied like they do to protect structural steel in commercial buildings but it would likely be very expensive to do such a small job though. Or, you can lay or attach sheetrock to the top of the steel decking for increased fire protection. Just make sure to seal the ends of the corrugations. And, if you provide fire protection to the outside/top of the steel decking it will retain it's structural strength during a fire and continue to protect the contents of the vault.

Sheetrock is sort of "magic" when it comes to fire protection. Many things don't burn. Hardie Backer for example is mostly cement and does not burn but it transfers the heat of the fire so things on the back side can still be damaged or eventually set on fire. The hydrated gypsum in sheetrock is also fire proof but when it gets hot enough the water in the gypsum cooks off carrying heat away with it which keeps it cool.
 
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