Protecting Guns in Basement Vault from Moisture

[wacki]

I hope to build a basement vault to store my long guns in the future. The purpose of putting it in the basement is that it will serve a dual purpose as a storm shelter as I happen to live on the edge of a high risk tornado area in Indiana:

http://www.tornadochaser.net/images/frequency.jpg

My only question is how to protect the basement from moisture?

Right now I'm aware of the following countermeasures for preventing water from touching the basement:

*french drains around the foundation and under the basement slab (apparently you can't drain below the foundation otherwise the dirt might settle too much)
*Spraying tar on the outside of foundations
*having drainage ditches around the perimeter of the property
*Xypex waterproofing concrete: http://www.xypex.com/aboutus/media.php
*Drainage boards, membranes and bentonite on the outside of the concrete walls:

Can you use membranes under the basement slab?

On the inside of the the basement:
There are membranes that you tack on the inside of concrete to drain water to a sump. Industrial epoxy (which you put on concrete floors) might help as well. Those are the technologies that I'm aware of but I don't know which ones are worth pursuing and which ones aren't. The goal is to make the basement as dry as possible and the gun vault bone dry even during a torrential downpour without electricity. Not sure what else is out there.

 

[cracked butt]

Can you use membranes under the basement slab?

Yes. We built a house in Upper Michigan where we put 2" of styrofoam and a layer of visqueen under the basement slab.

There's also a product called "drylock" which is a latex based paint that you slop and slather on the interior of the basement wall. I used this stuff on my own home as the Block foundation was a little damp- not wet, but had visible phosphoresence in a few places. The Poured wall in our place in Michigan are very dry.

 

[Cosmoline]

In addition to guarding against intrusion of outside water, remember to have a good air flow to minimize water buildup from inside and to keep the temp. constant. Many basements, esp. older ones, have very little airflow and this creates the same kind of temp. variations and moisture buildup you find in cabins. In the midwest I would suspect humidity is as big a threat as leaks.

You can also take precautions to store the firearms properly. As a secondary level of defense you can store them within a nice wicking material like a fleece. The cotton faux sheepskin lined rifle cases, on top of the silicone treated rifle bags, turned out to be some of the best anti-rust storage devices when I lived out in the sticks. And I've heard horror stories about guys opening up a gun safe in the basement after a few months only to find millions of tiny red speckles all over their iron from ambient humidity.

 

[never_retreat]

If your building this from scratch use higher psi concrete to start with. Typical home construction is 3,000 psi if i remember correctly. I heard that if you use 5,000 psi concrete water cannot get through like the lighter stuff.
Any masons here want to chime in on this?

 

[a1abdj]

Basements and moisture go hand in hand.

When we build residential vaults we have the plumbers install a drain against the outside wall near a corner, and run electric in from above. We'll core a hole large enough for a plastic tube to run from inside the vault to the drain, and hang a dehumidifier on the inside wall. The humidifier will drain through the wall and into the drain.

Since the electric is already run into the vault, lighting and other power consuming toys are easy to install.

 

[Aguila Blanca]

If your building this from scratch use higher psi concrete to start with. Typical home construction is 3,000 psi if i remember correctly. I heard that if you use 5,000 psi concrete water cannot get through like the lighter stuff.
Any masons here want to chime in on this?

NOT true.

5,000 psi concrete is more dense than 3,000 psi concrete, but it is NOT waterproof by itself. There are additives you can have put into concrete to make it more water-resistant (notice that I didn't say water-proof), but they're expensive -- and if the concrete cracks, they're useless.

The best approach is the drains around the footings, combined with waterstops where the slab meets the walls and good waterproofing on the outside of the foundation. Forget about drains beneath the slab -- you don't want to water to get to the slab, and if it gets there, then you have to have a way to carry it away. "Footing" drains are so-called because that's where they go -- at the level of the bottom of the footing, below the level of the floor slab. Footing drains are required by building code to carry water to "daylight," meaning the water has to drain off somewhere. If you can't get the drain pipe to an outlet, all you're doing is trapping water in the drainage system.

Water-stops between the wall and the slab should be flexible rubber, and cast in. They are NOT standard for residential construction, so be prepared to pay for them if you want them. The alternative is to pour the slab with about a 1/2" gap to the foundation wall, let the concrete cure for a couple or more months, and then seal ("caulk") the joint with a high-quality polyurethane construction sealant.

On the outside, do NOT coat the foundation with "tar." At best, that's what the codes refer to as "dampproofong." "Waterproofing" is another animal. Again, if you want the real deal, it's going to cost more than "dampproofing," which is what 99% of houses get -- if they get anything.

I don't like Bentonite. It can work, but it's ancient technology. Bentonite is expanding clay, ground into a powder and molded into a "board" between two layers of kraft paper. Once the foundation has been backfilled so these boards are held in place by the dirt, the theory is that when the clay gets wet, it expands and doesn't allow water to get through to the foundation. Sounds great, right? And the stuff is VERY effective. So ... what happens when the water gets between the foundation and the Bentonite? This is what happens in very heavy rains -- the water just flows right over the top of the Bentonite boards. Now you have a water sandwich. The water can't get out through the Bentonite, so it goes in through the concrete.

There are fluid-applied "waterproofing" compounds that can be painted onto foundations and are very effective. The ones most preferred seem to vary by location, so check with local subcontractors. Just be sure they are talking "waterproofing" and not "dampproofing." Personally, I like a physical membrane. There's a product called Bituthene that's sort of like the Ice & Water shield used on roofs, but thicker. It sticks to the concrete, and to itself at lap joints. Then you install a protection board, so that rocks in the backfill won't puncture it, and backfill the foundation. IMHO that's the best product -- but it ain't cheap.

If you decide to also paint the inside of the foundation walls to reduce moisture -- wait at least a year. Concrete cures by giving off moisture. If you seal the outside with waterproofing and then seal the inside with a vapor-retarder paint, you're trapping moisture inside the wall, as well as interfering with the long-term hardening of the concrete.

Confused yet?

 

[U.S.SFC_RET]

That's good stuff as posted but most of us can't afford it. Take em out and clean em. Break free rub down and don't forget the chamber. Dessicant, Dessicant,Dessicant,Dessicant.

 

[TAB]

You actually don't want to build a house that is air/ water tight. Air must be able to move or you will have moisture probs. the idea is to make it move very slowly.

 

[wacki]

*deleted*

 

[wacki]

Aguila Blanca,

Thanks for the very informative response. If Bentonite is "VERY effective" as you say then I wonder if rock solid choice is:

Concrete--drainboard--bentonite--drainage overkill on the perimeter
That would prevent the water sandwiches.

or
Concrete ---membrane---drainboard

???

Right now I'm not particularly worried about costs. I'm just trying to figure out what my options are. I'd like to make the basement as dry as possible without turning the home into the titanic and having a steel hull for a basement. If I have to I will limit the expensive waterproofing techniques to just the vault room.

 

[atomchaser]

Perimeter drain tile and proper backfilling around the foundation would probably be a 90% solution. I'd just be sure to be on site when they were doing the backfilling to make sure they are doing it to your design spec.

 

[Aguila Blanca]

Thanks for the very informative response. If Bentonite is "VERY effective" as you say then I wonder if rock solid choice is:

Concrete--drainboard--bentonite--drainage overkill on the perimeter
That would prevent the water sandwiches.

or
Concrete ---membrane---drainboard

???

I do NOT recommend Bentonite. It's okay if the problem is a rising ground water table, but if you have effective footing drains the water would then never reach the Bentonite anyway. If it rains, or if you have an irrigation system (as a huge underground parking garage found out the hard way!) you have to face the fact that water can enter at the top of the Bentonite "boards" -- there is no effective way to positively seal the interface along the top. That's when you get the water sandwich.

If I were doing it I would use Bituthene. If I were doing it and cost wasn't an issue, I would do a double layer of Bituthene.

 

[brickeyee]

No matter what you do there will still be residual humidity in the air in the vault.
Use a low level heat source to keep the guns warmer than the surrounding air and condensation will be prevented.
Goldenrod heaters, or just some plain old light bulbs in an enclosed space will do the job.