A note on basements & safes

[Ole Humpback]

I've been researching gun safes here and elsewhere and I've seen several comments that have given me pause. Quite a few people have made a statement along the lines of "I don't need to worry about how heavy the safe is, I'm going to put it in the garage/basement. The problem is, the concrete basement or garage isn't much better than a wood framed floor when it comes to supporting weight.

A typical wood framed floor in a bedroom or closet is rated for a 20psf deadload and a total load of 30psf. A concrete basement/garage is rated for a 50psf deadload/total load or a 2000lb point load over a 20"sq area. This is from the 2003 IRC and the codes have changed since then, but the load ratings haven't changed in the 2011 IRC as far as I can tell.

http://www.aacounty.org/IP/PAC/CodeRequire.cfm

The typical 20 gun fire rated RSC with a full load is running just under 1000lbs with a foot print of 644sq" (4.47SF). A wood framed floor is only capable of safely carrying 30psf total load which for a 4.47SF area is 134.4lbs. A concrete garage or basement slab would be able to carry only 223.5lbs over the same foot print. This means that for the typical home, a 20-gun fire safe is overloading the floor 7.5 times its designed loading and 4.5 times the design loading for a concrete slab. This is for something the size of a Liberty Centurion safe that most consider as safe to keep on a wood floor. An empty Centurion weighs just under 500lbs, which is already over loading even a concrete floor.

Now, I grant you all that the slab won't fail or the safe fall through to China the moment a Centurion sized safe is placed on them, but bear in mind that even a small fire safe for even 10 guns is 5 to 10 times in excess of the designed floor loading. And most of the safes I've seen mentioned as garage or basement items weigh several thousand pounds empty and weigh more than the two cars they have in the garage.

Garage slabs are thickened under the tire tracks, basement slabs are thickened where they turn down to intercept the footer. None are designed with a several ton permanent deadload in mind. A garage slab will be about 6"-8" thick Type III 3000psi concrete and have either #4 bar mats or sheets of 1.4 WWF steel reinforcing. A basement slab will be 4"-6" of the same concrete and have a wide web of #4 bar or a single layer of WWF reinforcing it.

When buying a safe, give serious consideration to the loading it will apply to your structure. Structural repairs to wood floors aren't cheap, but can be limited in cost if the engineer & contractor know what they are doing. Structural repairs to concrete slabs on the other hand aren't cheap. It starts out with mud jacking and can end up with foundation excavation & undercutting so that the damaged concrete & soils can be cut out & replaced with extra reinforcing to support the safe.

An ounce of prevention now is worth a pound of cure later.

 

[cbuttre835]

Just a wild guess, here, but my right foot is approx. 12" long and 5" wide. So is my left foot.

Add them together, they're 0.83 SF.

I'm 270 LB.

That means I apply 324 psf of load whenever I stand somewhere. Or 1.44 times the unit loading of a loaded safe. Or 10.8 times the IRC design loading required.

 

[a1abdj]

I can tell you that what building code says, and what a structure will really do, are two totally different things.

As I type, I have whole row of 5,000 pound safes (about 50,000 pounds total) lining one wall of my pole barn that has the same floor in it that a normal residential garage would. Each one of these safes is on two 4x4 pieces of wood, about 30" long. That's 1.7 square feet of contact with 5,000 pounds, or 2,941 pounds per square foot. None of them have fallen through yet.

 

[Ole Humpback]

Not exactly. If you could somehow put your feet together with 100% contact area and stand straight up, then that would be true. However, your feet can't do that and your shoe, even though its slightly larger than your foot (say 13" by 6"), results in a 1.083SF contact area. That results in a 249PSF loading, but since you're moving around, that really isn't of much concern.

People are called a live load. The reason for a 20psf dead load and 30psf total load is that people won't be in the same place for long, they move around. Hence, the reason for a difference between the dead load & total load. That difference is the live load that accounts for people moving about.

Safes are a dead load. They sit in place for years on end. Residential floors aren't designed with 1000lb+ deadloads in mind.

 

[a1abdj]

Residential floors aren't designed with 1000lb+ deadloads in mind

Homes have had extreme weights placed in them for years without issue. Waterbeds can weigh 1,500 pounds. A baby grand piano can weigh around 500 pounds (focused on those little legs), with a grand piano weighing in at 1,300 pounds. A 150 gallon aquarium will run 1,800 pounds if it has water only. Put in coral or any other rocks, and that can get much heavier.

I had this conversation with my insurance company when they wanted to cancel our policy upon the discovery that we were placing gun safes into homes. Since then, we have used 1,500 pounds as a general rule. So long as you are 1,500 pounds or less, chances are good that you won't have any problems.

 

[Ole Humpback]

I can tell you that what building code says, and what a structure will really do, are two totally different things.

As I type, I have whole row of 5,000 pound safes (about 50,000 pounds total) lining one wall of my pole barn that has the same floor in it that a normal residential garage would. Each one of these safes is on two 4x4 pieces of wood, about 30" long. That's 1.7 square feet of contact with 5,000 pounds, or 2,941 pounds per square foot. None of them have fallen through yet.

I understand this completely. I've been building buildings the last 10yrs and have seen some very lightly built structures carry extremely heavy loads that aren't code legal. I know that a safe on a concrete slab isn't going to sink through the floor and into the dirt underneath it.

However; how long do all your safes stay put along that specific wall? I've seen several times where a large heavy objects (safe, tool chest, machining center, ect.) have all been left on the same spot on a slab for the last 20+yrs and the slab was fractured all the way around, through & out several feet from the object. In a residential situation, that kind of damage has to be fixed before the house can be sold.

I'm not trying to be an alarmist, but I'm rather making a very valid point. Just because a structure can carry a heavy safe doesn't mean that you should put your safe there.

Homes have had extreme weights placed in them for years without issue. Waterbeds can weigh 1,500 pounds. A baby grand piano can weigh around 500 pounds (focused on those little legs), with a grand piano weighing in at 1,300 pounds. A 150 gallon aquarium will run 1,800 pounds if it has water only. Put in coral or any other rocks, and that can get much heavier.

I had this conversation with my insurance company when they wanted to cancel our policy upon the discovery that we were placing gun safes into homes. Since then, we have used 1,500 pounds as a general rule. So long as you are 1,500 pounds or less, chances are good that you won't have any problems.

There is a monster difference between live loads & dead loads. Yes, you CAN put a 1500lb water bed on a wood framed floor. I'm not disputing that at all. Have you ever walked through a house that had that water bed set in the same place for the last 20yrs? The last house I was in that had a water bed in the bedroom, me & several of my friends spent a good amount of time cutting, jacking, shoring, and splicing in new joists to fix the nearly 4" of sag that had occured in that single bedroom. Every door in the house wouldn't shut, after we fixed the floor, the doors all shut nicely.

My point is, a 1000lb+ permanent deadload is going to do you no favors in the long run. Take the time to look into how well your house was built and see about some cast-in-place footings. A common cost saving feature I've seen often over the last several years is a typical slab, but where a heavy permanent load will be, there is a thickened pad cast on the slab for the extra point load. An engineer would have to design it & stamp, but I'd be willing to bet that a little time with a hammer drill and some dowels & sackcrete and you'd have a pad for the safe that would result in no headaches ever.

 

[Ohio Gun Guy]

Concrete is typically a minimum (Footers) of 2000psi. Most typically 3,000 or 3,500 psi. slabs are often 4,000psi (Thats Pounds per square inch.) the wood floor rating you referenced is pounds per square foot. A factor of 144..... Also, buildings have dead and live loads factored. dead loads = furniture / stuff and live loads = people. 150lbs per sqft is typical for a live load. Shear strength is what keeps things from falling through the floor. Design loads are given a safety factor. Often 50% of the rated capacity. Not that you should count on that, but that is common. also, where in the span of the floor makes a big difference. Putting a 5,000 lb safe mid span is more troublesome than at one end or the other. Typically wood joists are sized to reduce / eliminate bounce and therefore over-sized. I personally would reinforce or carefully place a very large safe on a wood framed deck/floor. I have never seen a garage floor thickened at the tire tracks. Thickened slabs are often used at the edges and where a bearing wall may stand on a slab on grade.

I personally do not think anyone putting a safe on a concrete floor in a garage or a basement has anything to worry about, unless it took a crane to put it there, even then..... Yes, if you have an extra large safe on the 2nd floor of your wood framed house, you should place it carefully...

 

[a1abdj]

I personally do not think anyone putting a safe on a concrete floor in a garage or a basement has anything to worry about, unless it took a crane to put it there

Uh oh!

 

[Ohio Gun Guy]

You can bet that it's being placed on a thickened slab / house keeping pad.

That's how you do it, install during construction.

 

[Ole Humpback]

Concrete is typically a minimum (Footers) of 2000psi. Most typically 3,000 or 3,500 psi. slabs are often 4,000psi (Thats Pounds per square inch.) the wood floor rating you referenced is pounds per square foot. A factor of 144..... Also, buildings have dead and live loads factored. dead loads = furniture / stuff and live loads = people. 150lbs per sqft is typical for a live load. Shear strength is what keeps things from falling through the floor. Design loads are given a safety factor. Often 50% of the rated capacity. Not that you should count on that, but that is common. also, where in the span of the floor makes a big difference. Putting a 5,000 lb safe mid span is more troublesome than at one end or the other. Typically wood joists are sized to reduce / eliminate bounce and therefore over-sized. I personally would reinforce or carefully place a very large safe on a wood framed deck/floor. I have never seen a garage floor thickened at the tire tracks. Thickened slabs are often used at the edges and where a bearing wall may stand on a slab on grade.

I personally do not think anyone putting a safe on a concrete floor in a garage or a basement has anything to worry about, unless it took a crane to put it there, even then..... Yes, if you have an extra large safe on the 2nd floor of your wood framed house, you should place it carefully...

I have. The garage slab of two houses I've built have had 2' wide haunches placed under where the tires would track. I also understand how floors are designed. Span deflection is L/360 or 1/270 depending on where you live, dead loads are furniture, live loads are people, soil bearing capacities and so on. Two degrees in Architecture and Construction Management taught me a ton about design and engineering as well as the legal ramifications of the code. They go nicely with my 10 years of field work.

Also, 150PSF is not a typical live load for residential or for that matter any project I've ever done. I've been doing construction for large public projects (schools, colleges, etc.) for the last couple years and the heaviest total I've ever seen was a 130psf total load (30psf dead load, 100psf live load) and that was for a slab on grab floor in the gym of a co-rec facility. Heck, even if you used engineered trusses for the floor, they'd need to be spaced 6" apart and have an 18"+ web so that you could have a wooden floor support a 170psf total load (20psf dead load, 150psf live load). A typical 2x8 joist & 16" OC with 3/4" floor decking is good for a 50psf total load, which is well in excess of what most homeowners can come up with.

I'm not trying to argue that the safe will go flying to China. Rather, I'm trying to point out that a typical home isn't meant for a heavy point load such as a safe unless, like Franks picture shows, the house is built with a safe in mind. Some thought and/or modification of the structure will be required if you don't want to have problems later.

BTW Frank, that is an awesome picture. How big was the critter?

 

[a1abdj]

BTW Frank, that is an awesome picture. How big was the critter?

Not as heavy as it looks. I think it was around 1,100 pounds. It was going into an elevated river home that was being renovated along with some addition work. Since they knew the safe was coming, they were able to take that into consideration ahead of time.

Speaking of concrete. The fab shop where we do a lot of our vault work has a 6" slab with no expansion joints. It's a solid slab from wall to wall. They have tractor trailers, forklifts, and all other sorts of heavy equipment driving across it every day, and it's been there since the 1940's. There's not a crack in that concrete anywhere. If that isn't impressive enough, the walls of the building are cinder block, also no cracks. The building is probably 100' x 60' give or take.

I'm not trying to be an alarmist, but I'm rather making a very valid point. Just because a structure can carry a heavy safe doesn't mean that you should put your safe there.

We have that disclaimer in our liability waiver. There's not an engineer out there that would tell you that it's OK to put a safe into a house. Almost every gun safe would exceed the design.

 

[Ohio Gun Guy]

I on the other hand, slept at a holliday in last night.....

 

[rondog]

Aw jeeze, math nerds.....

 

[CapnMac]

Basements can be problematic, as there are a number of those with only 2-3" "rat slabs". These can carry larger loads near the walls, as the slab is poured to overlap the footer.

Really, it's only a problem when your 6" expansion anchor bolts are merely pulling on the bottom of the slab when you bolt the safe down.

Also, it's a bit tough to be declarative about residential construction. First off, 3/4 of it is existing and built (presumably) to earlier standards. Secondly, all, I'll say that again, ALL construction is regional.
In seismic areas, foundation construction is very different than in the midwest, is different than in New England is different than the construction in Florida and the Gulf South.

I've seen 2x4 (only 3.5" actually) used to screed "four inch thick" concrete. I've also seen beautiful rebar covered up in concrete reduced to 10" slump; I've seen full-rusts #6 WWM used in 4000psi 2" slump mix, too.

It's like that "perfect" .22lr ammo; what shoots best in mine, might not in yours.

Same thing with houses and safes, you can get all sorts of opinions; you probably need someone locally to assess what's there.

 

[Ole Humpback]

Speaking of concrete. The fab shop where we do a lot of our vault work has a 6" slab with no expansion joints. It's a solid slab from wall to wall. They have tractor trailers, forklifts, and all other sorts of heavy equipment driving across it every day, and it's been there since the 1940's. There's not a crack in that concrete anywhere. If that isn't impressive enough, the walls of the building are cinder block, also no cracks. The building is probably 100' x 60' give or take.

That is very impressive. That would had to have been a monolithic pour and whoever did the rebar for that slab got it perfect. Nice find.