Building a Vault/Concrete Weather room in basement, moisture considerations?

[SilentStalker]

Guys, I am building a new house in the next few months and am building a vault room/storm shelter into the basement. I am not sure if i will be running ac into the vault room or not as I expect the basement to be a pretty consistent temp. Thoughts on this and moisture considerations? The room right outside the vault will be temp controlled though.

 

[desidog]

Siting the house is important. Where are you geographically? What sort of terrain, soils, and climate are you in?

I design houses based on their geography as much as a client's wishes and whims...homes in neighborhoods are generally sited facing the street, without thought to light and other natural conditions. These can affect the building's heating and cooling abilities based on sunshine and energy conservation. People who experience living in a well lit environment are much happier overall than those living in a dark box ..and they have lower heating and cooling bills too. But i digress...

Make sure there's no slope, ledge or hillside that will direct water runoff towards your house. Then footing drains that are properly sized, with storm water retention ability, so as not to get overwhelmed by a downpour. Proper waterproofing of the foundation is next before you backfill....

Depending on a lot of stuff you haven't elaborated on, i presume you'll finish the basement (at least partially for the gun room!), in which case you'll have heating/AC, which helps to keep air moving and expel humidity (and mold). If you're in a swampy area, you probably want to install a dehumidifier from the get-go. Of course, if you're in AZ, moisture isn't the concern it is in AL.

Anyways, I'm rambling to procrastinate checking over a steel order...

 

[SilentStalker]

Thanks for the response Desidog. To answer your question, the house will be built outside of Birmingham, AL. The lot is at the top of a small hill/mountain if you want to call it that. Its at the top of the neighborhood. Plenty of trees around if I want to keep them. The house will be facing the street and the sun will rise behind the house and set in the front. It will see light most of the day. The reason I chose this lot is because it is oriented in such a way that water run off will certainly be going away from the house. The basement where the safe room will be will be finished and right outside the finished area will be the downstairs garage. So, in a way, yes it will be temp controlled but not directly. Any other hints/thoughts?

 

[buckhorn_cortez]

Soils in Alabama may contain a high percentage of clay. Clay does not drain well, and holds a lot of water. Also, some types of clay expand when it is wet.

You need to get a soil report including the percolation rate. This will tell you about the general soil condition and drainage.

If it was my house, I would make sure that the basement floor was poured on compacted, engineered fill and not native soil. I would also want a waterproofing membrane between the fill and concrete.

After the walls are constructed, I would waterproof the outside walls of the basement with a membrane waterproofing system made for that purpose. This would probably include gravel between the walls and surrounding soil, and you might want to consider a French drain system around the basement perimeter.

The waterproofing, gravel and French drain should keep the interior of the basement dry.

 

[JSH1]

Is this going to be a storm shelter, a gun vault, or both? I lived in Birmingham for 7 years including during the 2011 tornado outbreak. I can see why you would want a storm shelter. I would not put a gun vault in the basement unless you are willing to keep your guns well oiled and use a dehumidifier or A/C at all times. I had a similar arrangement to yours when we lived in East Tennessee (similar climate and soil) and fought moisture the entire time. (Not water leaks but high humidity and rust on tools)

I would also highly recommend you give desidog's comments on house orientation. For good natural light you will want the long axis of the house to run east / west and have most of your windows facing south. It is much easy to work with nature than fight it. We just bought a house less than a month ago and house orientation was a key consideration. That was reinforced by living for 15 months in a rental that had almost no natural light due to horrible orientation. It only had 1 window on the south side of the house!

 

[oneounceload]

With humidity being what it is, you'll want to run HVAC in their for humidity control. If it will really be used for storm/panic issues, then a generator and vents/air supply will also help. You'll want to add a way to open the door from the inside

 

[suemarkp]

You'll need air of some sort if this room is well sealed, so an HVAC duct would be wise. Also think about floor drains -- it is nicer for air conditioners and dehumidifiers to gravity drain their condensate and not rely on a pump, so if you want provisions for a dehumidifier in that room, give it a floor drain. If it is outside that room, or your air conditioner fan unit/evaporator is in that basement, give it a floor drain.

 

[Jolly Rogers]

After two days spent addressing a condensation pump issue, this is good advice!
Joe

 

[Cowhide Cliff]

Modern basements should be fairly dry regardless of soil if built properly and proper drainage is around and under the foundation. Besides making sure of all that I also recommend having a drain in the floor so you can run a dehumidifier in the room.

I also recommend keeping that room climate controlled. Unfortunately you have to penetrate the concrete for duct work so how you do that should be taken in consideration in order to keep the room as fireproof as possible.

Have the heating and air man use steel duct work and install dampers at the openings of the vault. I don't know what you call them but they are the dampers with a lead link that melts and lets the damper slam shut should there be a fire.

 

[hso]

Installing a dehumidifier high on the wall that gravity drains through the wall is an effective way to avoid hvac openings in your walls. The drain can go to a rust proof metal line through the concrete wall and the hole sealed with fire seal. This makes for a much smaller hole than ductwork and easier to make fire resistant and waterproof (no drain to back up and flood). This requires electrical to be run in, but you need lights anyway so it seems silly to not surface mount conduit and outlets for a bench.

 

[Bobson]

Thanks for re-opening this; seems to be some great info here.

 

[hso]

Remember that basement vaults have to withstand not just an hour and a half long fire, but the accumulated water the fire department is pouring on the fire to knock it out. That water in the basement may sit for days infiltrating your vault if you don't plan to keep the water and heat and bad guys out. Plan so your basement passively drains without power AND raise the floor of the vault enough to keep water out. Talk to the FD about how many inches/feet of water they see collect in basements and plan accordingly.

 

[CapnMac]

The other thing that client, designer both have to remember is that both vaults and storm shelters need a roof. That's a proper roof, and not merely the floor structure above.

hso's comment is germane here. Keeping the fire fighting water out is as important as ground moisture; it's also the only way to stay safe in an F-4 or F-5 tornadoe (which will strip floors from foundations, as was seen in Jarret).

This need not be complicated, a 1.5" "W" deck with 1.5" of concrete over that will suffice nicely--if the deck is tied to the walls.

As a storm shelter, you probably do not want to install a safe (or RSC) door. These would be too slow to get into, and be something of a hassle to exit through. Not a bad idea to have a second exit from a storm shelter, in case the first is blocked by debris.

To keep this on topic, let us now address guns and ammo. Resist any idea of placing either guns or ammo directly on the floor. Concrete passes moisture, slowly, but surely. Also, the issue of water, rain, storm, firefighting remains . You probably will want locking cabinets (of the Stak-On variety or the like) too, as a goldenrod or similar dehumidifier works better in confined spaces.

Alternately, since this is a "protected" space, one could keep the arms in glass fronted cases, if that suits the fit and finish of the space.

As to design, a tornado warning sledom lasts more than an hour, so you'll want seating for everyone you expect to shelter. Now, the time spent in a shelter is laregely one of listening to the weather radio, unless you care to make other entertainment options available.

This is important as, if you are finishing this space as a "gun room" with leather chairs and the like, that will warrant a different sort of fit and finish than a painted block wall with wooden benches for ammo and people sheltering for a time.

That's my 2¢, any much more and I'd have to bill you (and bet an AL license, too).

 

[Cowhide Cliff]

I have worked on and around several houses over the years with vaults built into them and have seen mistakes made that makes them unsuitable for gun storage. Usually the biggest mistake is not addressing dampness so I have learned you really do need a dehumidifier at the least and preferable also heat and air circulation to keep it climate controlled.

The ideal situation is for the house to be positioned on a hill and have a gravity floor drain so if there was a fire and the metal duck work lets in water it can drain out.

I prefer to see the guns and ammo positioned in the room and elevated off of the floor so that water will hopefully not fall on them and pour onto the floor should there be a fire or disaster that lets water come in through the duct openings.

Install minimal electrical, a light and a plug in steel conduit fastened to the concrete ceiling away from any wood or shelving that could cause a fire inside the vault itself. I like to see the switch on the outside that way their is minimal usually just one conduit on the concrete ceiling.

 

[oneounceload]

A quality safe, installed on a platform above the floor, makes the guns at a nice eye level and keeps water damage away.

 

[Upstater]

I would recommend using a separate ductless a/c system within the vault so only a small penetration will be made. If you insist on using a ducted system have your contractor price out insulated steel ducts for all of your basement to eliminate the possibility of condensation on the ducts and mold growth in the ducts, this is a very common problem especially in the new construction homes were this is very little to no excess air.do not rule out the possibility of installing a fresh air intake from the outside that is conditioned and filtered when it enters the space as well.

 

[cdk8]

About how many cubic feet is the vault room?
How often do you plan to have the doors of the vault open? (i.e., when not in use will it be open or closed for extended periods?)
What is the approximate humidity of the rest of the basement?
What is the approximate humidity level you are looking for?
Do you prefer a passive or active humidity control system?

 

[Chuck R.]

I sort of have what you're asking about, but we built our "safe-room" during the construction process under the 3 car garage. The roof is a reinforced 10" slab that sits on I beams (it's also our garage floor).

Mine's about 700 sq' and we ran the HVAC (Geothermal) in and it's in it's own zone on the system. We also had a drain installed for a dehumidifier for those times when the room's temperature is above/below the HVAC temp (spring/fall). We also "finished" it with drywall and insulation, which did cut down on the humidity issue with one part of a wall that was above grade.

We've been in the house going on 3 years now with zero issues.

Our door is fire resistant, swings inward and has a "panic" lock. It does have a mechanical S&G lock, but when we get the storm warnings, I simply open it and go to "key mode".

Chuck

 

[hso]

Keep in mind that there are some conflicts inherent in vault, storm shelter, and safe room designs, first of which had been mentioned, the door. Vaults have one door and the door is slow to access. Escape routes are a must in storm shelters in addition to the primary door. Both have to withstand the force of a tornado. Yet, you don't want a second door for a vault. Water is important to protect from in all 3 regardless of conditions, but moisture has to be kept out of a vault and the humidity kept low enough to prevent corrosion and high enough to keep wood "happy".

 

[JimPGov]

I had a poured concrete vault put in my retirement home when i had it built. I have radiant heat in the floor and a 6" ac duct. I do run a dehumidifier during the summer months. I keep the room at 45% humidity year round.

A couple of suggestions.
1st. Build it twice as big as you think you need it!
2nd. If you have any inclination to also use it as a storm shelter. Spend the extra money for a vault door that opens to the inside.