Built in Safe Room

[Dale Moser]

I still havn't settled on how I'm going to do mine, but for the sake of discussion I have a couple questions. Mine will be inside an insulated (but not air conditioned) shop, and I want to make it a "Hunting Room", with safes, cabinets, shelves, some taxidermy, and also double as a tornado bunker, spare room. I'm thinking 12X14 or close to that.

1. What type of span can you expect from 4", or 6" concrete on the ceiling?
2. What type of re-enforcing steel is best?
3. Is there a particular cement mix that is better/lighter/etc?
4. I was going to put a window unit in mine, for moisture removal as much as anything, but what type of extra ventilation would be required if several people were to sleep in there?
5. What R value does a grout filled 8" CMU block wall have? 6"?

[175gr7.62]

I still havn't settled on how I'm going to do mine, but for the sake of discussion I have a couple questions. Mine will be inside an insulated (but not air conditioned) shop, and I want to make it a "Hunting Room", with safes, cabinets, shelves, some taxidermy, and also double as a tornado bunker, spare room. I'm thinking 12X14 or close to that.

1. What type of span can you expect from 4", or 6" concrete on the ceiling?
2. What type of re-enforcing steel is best?
3. Is there a particular cement mix that is better/lighter/etc?
4. I was going to put a window unit in mine, for moisture removal as much as anything, but what type of extra ventilation would be required if several people were to sleep in there?
5. What R value does a grout filled 8" CMU block wall have? 6"?

Dale,
I'm a mechanical engineer, not a structural engineer but I dabble a bit on some of the stuff we do. Here are some general rules of thumb we use.

1. Ratio of span to depth if the slab is supported all around. 30:1
2. Slab reinforment shall be at least 0.15 percent of the cross sectional area.
3. Pitch of the bars should be no more than 3 times the depth of the slab.
4. Pitch of the opposing distribution bars should not exceed 5 times the depth of the slab.

[junkmanhunter]

It appears there are many different variants to the CMU rooms.

I just had one built for my new house. Mine is 12'x12'x9'tall. I poured the house slab with reinforced footing where my room was going to go. We framed the exterior walls and had them insulated and sheet rocked. then we epoxied #4 bars to go in every cell of CMU. We filled every cell with concrete. We put #4 bars that were bent 90% in every other cell for the roof to tie to. We used a 6" steel roof decking. I tied the ceiling steel at #4 bars 16" OCEW. In the roof I put 2 - 4" sleeves (should have put 2 more). those were put in for the data and control wires for the smart home wiring. I set it up to have my control brain in there so I can see tv, cameras and anything else to control my house with. I also put in block outs for AC vents.
After all that we framed the inside walls and ceiling with 2x4's. that allows for electric, data and fire insulation to be installed. Sheetrocked and painted walls. Had cabinets built.

My door is a safe vault door.

This room will be used as a control room for all audio, security and home systems, Storm shelter and a safe room for personal and legal papers and maybe a firearm or two if I can find any....

[SmTx]

This thread always deserves a mention on this topic

https://discussions.texasbowhunter.com/forums/showthread.php?t=410116&highlight=safe+room

[7sdad]

If you haven't poured your slab yet I'd look at these.

https://nwastormshelters.com/storm-shelters/under-garage

[gandergitter]

Ours was blocked in the way Dale talks about. 4" roof. The door is a heavy duty industrial door with additional 3/16 plate skinned onto it. We built an oversized master closet, 12x18 so it houses everything with extra space for us. I didnt think it would be used, but we had 2 tornadoes within 5 miles of the house the first year.

[Sticks&Strings]

I still havn't settled on how I'm going to do mine, but for the sake of discussion I have a couple questions. Mine will be inside an insulated (but not air conditioned) shop, and I want to make it a "Hunting Room", with safes, cabinets, shelves, some taxidermy, and also double as a tornado bunker, spare room. I'm thinking 12X14 or close to that.

1. What type of span can you expect from 4", or 6" concrete on the ceiling?
2. What type of re-enforcing steel is best?
3. Is there a particular cement mix that is better/lighter/etc?
4. I was going to put a window unit in mine, for moisture removal as much as anything, but what type of extra ventilation would be required if several people were to sleep in there?
5. What R value does a grout filled 8" CMU block wall have? 6"?

Dale,

I wish I still had the engineering plans on the one we built. It was similar in size. The ceiling was I think 3/4" rebar mat. Then another 3/4" rebar mat on top. Formed up and Poured 6" thick I believe. I feel it would have held a mack truck on top of it. As for the rest of your questions, I think the r value is pretty decent. The one we built was inside a house. No ac in the room only the aforementioned elbows for future wires or ducts.

You could probably use smaller cmu block and line the outside of it with fire brick.

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[MIHunter]

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[Take Dead Aim]

I still havn't settled on how I'm going to do mine, but for the sake of discussion I have a couple questions. Mine will be inside an insulated (but not air conditioned) shop, and I want to make it a "Hunting Room", with safes, cabinets, shelves, some taxidermy, and also double as a tornado bunker, spare room. I'm thinking 12X14 or close to that.

1. What type of span can you expect from 4", or 6" concrete on the ceiling?
2. What type of re-enforcing steel is best?
3. Is there a particular cement mix that is better/lighter/etc?
4. I was going to put a window unit in mine, for moisture removal as much as anything, but what type of extra ventilation would be required if several people were to sleep in there?
5. What R value does a grout filled 8" CMU block wall have? 6"?

I would use 3.50-24 Formlok 18 guage GR40 Deckpan with #3 on 12" centers concrete should be 5 1/2" to 6" thick. 3500 psi concrete should suffice. I would skip the window unit. Just an avenue for a person animal and moisture to get in. Since its in a shop I would definitely plumb it for a dehumidifier and not a dinky one. You could also put a small 4" round vent along with a fart fan. That can cycle fresh air if someone is inside.

[Briar Friar]

7.62…cinder blocks crack under fire pressure. You might not want the safe room walls to potentially crumble after or during a house fire.

Good luck Sir.

[muzzlebrake]

1" of 40 lb ft3 calcium silicate board will withstand 1700 F
It's what I line my forge with. 2 layers and i get 2600 F inside and still can touch the outside. The stuff ain't cheap.

[Kong]

Build a 10x10 room underground with a staircase and a vault door, if this is your forever home splurge and build it right and you will be glad you did. You can get creative and hide the entry way as well, it takes some hunting to find ours. I went with a 15X15 and have zero regrets and my only worry is a tsunami coming in, other then that it would take dynamite or a bulldozer to get it in after you find it.

[StrayDog]

I still havn't settled on how I'm going to do mine, but for the sake of discussion I have a couple questions. Mine will be inside an insulated (but not air conditioned) shop, and I want to make it a "Hunting Room", with safes, cabinets, shelves, some taxidermy, and also double as a tornado bunker, spare room. I'm thinking 12X14 or close to that.

1. What type of span can you expect from 4", or 6" concrete on the ceiling?
2. What type of re-enforcing steel is best?
3. Is there a particular cement mix that is better/lighter/etc?
4. I was going to put a window unit in mine, for moisture removal as much as anything, but what type of extra ventilation would be required if several people were to sleep in there?
5. What R value does a grout filled 8" CMU block wall have? 6"?

I’m not a structural guy but I’ll chime in on your mechanical questions.
3. In general, heavy weight concrete has a lower R-value than light weight concrete as there is less “air voids” in heavy duty concrete. Encapsulated air is actually a great insulator. However, there is obviously a trade off in strength with lightweight concrete.
4. Ditch that window unit idea and put you a mini-split. There are options with mini-splits now that you can cool and heat. The problem with a small space is you really won’t need much tonnage of AC even with mediocre insulation. This means when it gets hot, the AC will kick on and shutoff quickly. The AC really needs to run for more than just a minute or two to dehumidify. If you are going to store guns in there and the room is out in an unconditioned shop, strongly consider putting in a dehumidifier - cheap insurance. I’d get one that I could plumb to a drain so you don’t have to jack with emptying the water. They also make humidifier/ dehumidifier combo units now but honestly, I’ve never messed with them. In general, for residential occupied spaces you need the greater of either 15 cubic feet per minute air flow or 0.35 air changes per hour of the space(i.e. a 20 foot x 20 foot room with 10 foot ceiling = 4,000 cubic foot * .35 air changes per hour = 1,400 cubic foot per hour or a little over 23 cfm.) The drawback of a mini-split is you don’t get fresh air into the space. I’d still go mini split though and add a small fan /vent to bring in outside air and just close off the vent/turn off the fan when not using it as a sleeping quarters - get a CO2 alarm (very cheap insurance) and sleep away.
5. R value depends on the block and what it’s filled with but it’s not great. Here’s a decent chart - scroll way down��

https://ncma.org/resource/rvalues-ufactors-of-single-wythe-concrete-masonry-walls/

[3ChordTruth]

Following, good ideas and information here, thanks to those who posted.

[Landrover]

Following....we did multiple escape routes in our build 11 years ago. This could be a good project and addition.

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