Gun Room Build Question - Concrete Foundation Related

patsfan1986

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Hello,


Thank you in advance for your time/assistance. Always found this forum to be a wealth of info.

Per the attached picture, I plan on building something quite similar (15W x 15L x 10H (ft)) . The walls will be full of concrete and rebar. The safe door will weigh over 500lbs. The contents inside the room will be over 5,000lbs.

Should I reinforce my concrete foundation? House was built in the early 1990's and we have an insanely high water table. We live at the bottom of a very large.. very wet hill in a valley that just gets an absurd amount of water.

My thought was to cut out the foundation for just the wall atleast ; pour new concrete that is 2x deeper and use rebar to connect the old foundation to the new slot I just poured.

But then during the winter... will I damage or alter the original foundation if a part of it is heavier/deeper than the rest?

Thoughts?

Thanks, friends.
 

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I would not be at all worried about the weight. Re-enforced concrete can handle an insane amount of weight. My biggest concern would be the moisture you described.
I would recommend you make allowances for water. I am sure you have a sump pump if the house experiences that much water, but I would suggest you plan storage to be well off the floor and back ups to electrical power.
Imagine going away for a few days, losing power, and having everything ruined. A de-humidifier sounds like a must, and unfortunately, are expensive to run.
As the old saying goes, the two biggest threats to your guns are rust and politicians.
 
I’m a lot more concerned about the environmental issues with water and moisture than the rating of the floor. We have hundreds of feet of block wall inside laid directly on the slab. Not a single issue.
What’s your plan for the ceiling?
 
I think what you're calling the "foundation" is really just the floated concrete basement floor. The question then becomes: How thick and well-supported (underneath) is that basement floor and can I add a lot of weight to it without cracking, settling, sinking, etc.).

The real fly in the ointment is the very high water table. Lord knows I have the same problem. It's awful. Is your basement floor often wet? And if so, is the water coming up through the basement floor? Or just around the edges?

I fear that if you dig down to try to strengthen or replace that basement floor, you will end up with a swimming pool in your basement. That's what would happen if I tried to do the same.
 
Significant modifications to a structure generally require approved plans from an engineer or architect and submitted to your Town building official.

That said, I would not cut out a portion of the foundation slab because you will never be able to seal/waterproof the cold joints as effectively as the existing slab.

keeping @fencer recommendations in mind pertaining to moisture, you are better off using lumber to keep metal off the concrete to prevent oxidation. Additionally, you can reinforce the framing to distribute the load as @Mesatchornug suggested.

personally, I would leave the framing open on the ends so that moisture through the foundation slab does not result in mold. You’ll have to decide if you want pressure treated for the additional moisture resistance off-gassing in your house, or just use framing lumber.

take pictures and post them so we can see the progress! Good luck!
 
If your foundation does not have a French Drain, I would consider that, and have your sump as a back up. Think of placing a de humidifier in the room with a drain hose so you do not have to empty a bucket. Nice room!
 
Hello,


Thank you in advance for your time/assistance. Always found this forum to be a wealth of info.

Per the attached picture, I plan on building something quite similar (15W x 15L x 10H (ft)) . The walls will be full of concrete and rebar. The safe door will weigh over 500lbs. The contents inside the room will be over 5,000lbs.

Should I reinforce my concrete foundation? House was built in the early 1990's and we have an insanely high water table. We live at the bottom of a very large.. very wet hill in a valley that just gets an absurd amount of water.

My thought was to cut out the foundation for just the wall atleast ; pour new concrete that is 2x deeper and use rebar to connect the old foundation to the new slot I just poured.

But then during the winter... will I damage or alter the original foundation if a part of it is heavier/deeper than the rest?

Thoughts?

Thanks, friends.

My biggest concern would be moisture infiltration as well. It is always something that you have to balance when storing firearms, ammo, and powders in the basemen. I run a dehumidifier that drains into existing p to remove excess moistur. The dehumidifier combined with the residual heat from my steam boiler do the trick for me.

As an aside, with the work that you are doing it wouldn’t take much to set that room up as a safe room as well.

Bob
 
I would not be at all worried about the weight. Re-enforced concrete can handle an insane amount of weight. My biggest concern would be the moisture you described.
I would recommend you make allowances for water. I am sure you have a sump pump if the house experiences that much water, but I would suggest you plan storage to be well off the floor and back ups to electrical power.
Imagine going away for a few days, losing power, and having everything ruined. A de-humidifier sounds like a must, and unfortunately, are expensive to run.
As the old saying goes, the two biggest threats to your guns are rust and politicians.
yeah, OP did NOT say the floor was reinforced concrete.

so, some questions:
Have you ever seen water weeping thru the walls after a big rainstorm?
Have you ever seen water coming up thru the floor cracks after a big rainstorm?
Is the humidity high in that basement.
Is there a sump pump, and how close to that corner.

If you make a vault, there will be no air circulation. and obviously you do not want to be storing gunz in100% humidity

if you do not have all sorts of water/humidity, i would coat the floor and walls with some sort of good moisture barrier, and have at it.
Xypex comes to mind. Caulk the joint floor to wall very well too.
 
Significant modifications to a structure generally require approved plans from an engineer or architect and submitted to your Town building official.

That said, I would not cut out a portion of the foundation slab because you will never be able to seal/waterproof the cold joints as effectively as the existing slab.

keeping @fencer recommendations in mind pertaining to moisture, you are better off using lumber to keep metal off the concrete to prevent oxidation. Additionally, you can reinforce the framing to distribute the load as @Mesatchornug suggested.

personally, I would leave the framing open on the ends so that moisture through the foundation slab does not result in mold. You’ll have to decide if you want pressure treated for the additional moisture resistance off-gassing in your house, or just use framing lumber.

take pictures and post them so we can see the progress! Good luck!
I have had good luck with concrete blocks on basement. All good points here. Reinforcing the ceiling is still an open concern. Venelation. Second. As without it, you will have mold mode on. Third is water. Venelation design vital during temp swings.

I would suggest filling the walls with sand. The silica does a surprisingly good job of breathing, and does a great deal to settle the structure.

The lab facility I worked in for a decade had mostly sand filled concrete block walls between offices. 40+ years later, never an issue.

I might **might consider doing the whole build on top of a membrane. There are some systems which work for that. Build the room as if it would be a shower?

Also. Reloading bench ! Air filtration system!
 
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