Safe Question - Too heavy?

Saluki91

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Thanks in advance for any insight you can provide.

Mea culpa - I'm not an engineer, nor do I play one on TV. I'm not even sure I'm asking the right questions.

I'm looking to spend some Santa money on a safe... the safe in question weighs 940lbs empty, and measures 41"x27" (7.69 sq ft). I intend to put the safe on a raised floor (3/4" plywood over a crawl space), and placed against an exterior wall.

My concern is that when it is fully loaded, the safe will be too heavy for the floor. This is based on "Wow! 940lb is a lot!" - nothing more.

So... Am I fine, and worrying about nothing?
Put some post jacks under the floor where the safe will sit and carry on?
Look for a safe that weighs less?
Forget the safe and spend the money on the rifle build I have been daydreaming about?

Thanks!
 
You sure about that?
He’s correct. Look at the small square pegs recliners sit on, and then Jimmy, Bubba, and Jethro (lineman from 1982 state championship) come over and sit, drink bears, eat pizza and reminisce of days gone by while watching the Raiders get beat.

And if the front pegs line up on one floor joist

The above could be 100# per square inch

But the above is just talking a couple of point loads.

With floor systems being a system (floor joists, pony walls, glue, nails, floor sheeting). They are all really strong if current construction. If it’s an older house I would get under there and see what’s supporting the floor joists it’s resting on.

It’s always good to be close to an exterior wall, or above a pony wall underneath. If not, spanning a couple of floor joists is a good idea.

Really the extra 3/4” plywood is doing nothing to help outside of what the bottom of the safe is already doing if it’s the same size as the safe bottom.
 
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If the joist are perpendicular to the outside wall they will carry a lot more weight as you will have at least two under the safe near where they are supported.

If the joist are parallel to the wall you will have only one not supported.

Getting it in place might be a problem also, if you put it on a dolly all the weight is then concentrated on just the wheels ot spread across the bottom of the safe. You might want to lay some sheets of plywood on the floor to roll it across.
 
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He’s correct. Look at the small square pegs recliners sit on, and then Jimmy, Bubba, and Jethro (lineman from 1982 state championship) come over and sit, drink bears, eat pizza and reminisce of days gone by while watching the Raiders get beat.

The above could be 100# per square inch
So your old lady on a 3 legged bar stool is harder on a flooring system than a half ton gun safe?

You shouldn't be using psf to determine if something is too heavy for your floor. You use rated psf to determine the system's (load, not pressure) capacity in that room
 
It'll be fine.
That's less than 130# per square foot.
A 200#+ double recliner couch has a higher per square foot level.

I'd forget the safe and build the gun.

International Residential Codes require live loads for living areas a minimum design of 40 pounds per square foot, sleeping areas at 30 pounds per square foot. Most architects don’t over design for obvious reasons.
A safe weighing as much as the OP suggests would be best to have point load reinforcement.

 
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So your old lady on a 3 legged bar stool is harder on a flooring system than a half ton gun safe?

You shouldn't be using psf to determine if something is too heavy for your floor. You use rated psf to determine the system's (load, not pressure) capacity in that room

Harder on those 3 small points of the barstool on that particular part of the floor.

I was just being snarky. You know like when tile guys get anxious when a full figured woman in stilettos start walking on their work.

Which is why I followed up what I said on those small point loads with looking underneath and how floor systems work together with everything.
 
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Think about the weight that's on each leg of your queen size bed when a couple is laying in bed. I think a flat surface of the safe, especially close to a wall is going to be fine.
 
Removing the door (lift off hinges) and most RSC safes are not that bad to move in two pieces.

The door is most of the time 60-70% of the weight on RSC's.

Good appliance dollies with straps and belt rollers on the back for stairs make it a lot easier as well.
 
Can anybody cite where any safe, anywhere, has ever broken thru a floor just sitting on it

Without a fire or other outside influence affecting it.

Before I built my hardened walk in closet, I had three large safes, no issues with even a sag of the flooring
 
The peak forces recorded in gymnasts' landing ranged from 8.2 to 11.6 times the body weight. Maximum forces in jumping from 0.45 m, which ranged from 5.0 to 7.0 times the body weight

Over a much smaller area. Jump on your floor from 17" above it, if you don't fall through, you are probably good to go. 5 x 200 = 1000
 
I'm looking to spend some Santa money on a safe... the safe in question weighs 940lbs empty, and measures 41"x27" (7.69 sq ft). I intend to put the safe on a raised floor (3/4" plywood over a crawl space), and placed against an exterior wall.

My concern is that when it is fully loaded, the safe will be too heavy for the floor. This is based on "Wow! 940lb is a lot!" - nothing more.
The Specific is far more important here than the General.

And some of the specifics matter. It the safe bottom is perfectly flat, you have 1107 square inches supporting 940#. That's 1.17psi. But if not perfectly flat, then things change, obviously.

Four floor joists at 16" center span 48", so a 41" dimension safe will "catch" either two or three of those joists, if they run perpendicular to the 41" dimension. The 27" dimension might catch the rim joist (you mentioned being on an exterior wall) and either one or possibly two joists. That might be enough, but no guarantees the floor does not deflect a enough to roll a marble to the safe. (I had to move my Liberty Lincoln in my old--1951--wood floored house for being too close to midspan, and had to shim the thing so the door would not swing open to the stop and threaten to tip the thing.)

You mention a raised floor over a crawlspace. I'm presuming you mean a regular wood-framed floor over a crawl space and not a wooden platform raised above a crawlspace floor. Or at least I hope so. All too many crawlspaces have what, in the trade, is known as a "ratslab" which is 1.5 to 2 inches thick of high-slump, low-strength (1600-1800psi) concrete--it may look smooth and strong, but it's not.

What would be good to hear is that you have a couple of clear feet under the wood floor in the crawlspace. A 3/4" plywood subfloor is a touch scant for the application, unless both glued and screwed. I would still be sore tempted to put another sheet of 3/4" over the exiting plywood floor. This would better the span and decrease deflection. I'd probably use that extra sheet to anchor in a base for some built-in shelves for ammo cans, accessories and the like, possibly giving a 4x8 inside closet when finished. Barring the extra sheet, and if having good access underneath, I'd "sister" the existing joists and get some 4x blocking solidly in to set the hold-down lag bolts into.
_______________________________
  • For glue, I like specifying either PL-1 or PL Premium carpentry glue (comes in a caulk-style tube). Screws would be #5 or #6 with 2/3 depth penetration, blocking installed with screws toenailed and not into endgrain if possible.
  • Deflection is tricky. Most lumber is not at the breaking point until passing 1/3 the depth o the material in bending. For a 5.5" deep 2x6 that's around 1.75" well past where most folks would geek seeing it (turned flat, that 1.5" thickness only allow about a half inch of bend.) For tile, you want deflection no greater than l/480, and drywall no more than l/240, that latter being about where marbles will roll on hard floors.
  • Never forget, it's never just the safe, you have the firearms in the safe, the ammo cans next to the safe, and all the accessories--these things add up.
 
The Specific is far more important here than the General.

And some of the specifics matter. It the safe bottom is perfectly flat, you have 1107 square inches supporting 940#. That's 1.17psi. But if not perfectly flat, then things change, obviously.

Four floor joists at 16" center span 48", so a 41" dimension safe will "catch" either two or three of those joists, if they run perpendicular to the 41" dimension. The 27" dimension might catch the rim joist (you mentioned being on an exterior wall) and either one or possibly two joists. That might be enough, but no guarantees the floor does not deflect a enough to roll a marble to the safe. (I had to move my Liberty Lincoln in my old--1951--wood floored house for being too close to midspan, and had to shim the thing so the door would not swing open to the stop and threaten to tip the thing.)

You mention a raised floor over a crawlspace. I'm presuming you mean a regular wood-framed floor over a crawl space and not a wooden platform raised above a crawlspace floor. Or at least I hope so. All too many crawlspaces have what, in the trade, is known as a "ratslab" which is 1.5 to 2 inches thick of high-slump, low-strength (1600-1800psi) concrete--it may look smooth and strong, but it's not.

What would be good to hear is that you have a couple of clear feet under the wood floor in the crawlspace. A 3/4" plywood subfloor is a touch scant for the application, unless both glued and screwed. I would still be sore tempted to put another sheet of 3/4" over the exiting plywood floor. This would better the span and decrease deflection. I'd probably use that extra sheet to anchor in a base for some built-in shelves for ammo cans, accessories and the like, possibly giving a 4x8 inside closet when finished. Barring the extra sheet, and if having good access underneath, I'd "sister" the existing joists and get some 4x blocking solidly in to set the hold-down lag bolts into.
_______________________________
  • For glue, I like specifying either PL-1 or PL Premium carpentry glue (comes in a caulk-style tube). Screws would be #5 or #6 with 2/3 depth penetration, blocking installed with screws toenailed and not into endgrain if possible.
  • Deflection is tricky. Most lumber is not at the breaking point until passing 1/3 the depth o the material in bending. For a 5.5" deep 2x6 that's around 1.75" well past where most folks would geek seeing it (turned flat, that 1.5" thickness only allow about a half inch of bend.) For tile, you want deflection no greater than l/480, and drywall no more than l/240, that latter being about where marbles will roll on hard floors.
  • Never forget, it's never just the safe, you have the firearms in the safe, the ammo cans next to the safe, and all the accessories--these things add up.
Thanks for your detailed response! I'm looking into using some concrete deck blocks and 4x4s to reinforce the joists under the safe.
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Yes - the floor above the crawlspace is just a wood framed floor. I doubt the sub-floor was both glued and screwed. We have learned over the course of ownership that our builder never me a corner he couldn't cut.

The crawlspace is sealed, and the floor of the crawlspace is bare dirt (under the plastic). There is 3 to 4 feet of open space between the dirt and sub-floor. Seems like it might be a good idea to put a thick piece of plywood (cut to the same dimensions as the safe) under the deck blocks to help spread the weight further, and to keep the integrity of the seal.

Thanks again!
 
I'd screw a 2 x 12 at 90 degrees across the joists under the center of the safe, then put down a concrete block. I'd put a screw jack between the block and 2 x12. I'd give it a partial turn every now and then until the dirt quit settling.
 
What does your refrigerator or upright freezer weigh? Or even a full bathtub? Nothing extra under those I bet.
 
Seems like it might be a good idea to put a thick piece of plywood
"Sistering" the joists would get you more "oomph" and less deflection.

To "sister" a joist means to take a similar dimension bit of lumber to the extant joists and fasten it in, face-to-face. Let's say you have 2x8 floor joists now. you'd want around four 2x8x 3' pieces of lumber. These would go in under where the safe is to go. Take and apply glue, then use #6 x 2 1/2" screws zig-zagging across the middle third at about 8" on center. This would want to be "closed off" with solid bridging the same depth as the joist.

The "engineering" of this is in making the wood thicker where you want it to be more stout. You just need a "patch" of this to suit your need.

then put down a concrete block.
The block would want a "footer", ideally a couple of foot square, but an 18 x 18 paver might suffice--if the crawlspace soil is compacted Select Fill.
I'd be inclined, in this back-of-napkin, can't see the actual conditions, situation, to spot two such at the "corners" of where the safe is to go.
I'd likely call for a 4x6x4' or (2) 2x8x4' to make a "girder" to support the front edge of the safe location. Mind, a jack might be "overkill" as a hank of 4x4 would suffice.

What does your refrigerator or upright freezer weigh? Or even a full bathtub? Nothing extra under those I bet.
Fridge is around 500#, and spread over a wider area, typically than an RSC. Full tub, as above can get to 3/4 ton, but that's spread out over five feet (and is only an issue if the plumber has hacked through all the joists to run the drain line--something I've seen in person--eek).
 
Heck, I'd be more worried about when they roll it in. Think of the pounds per square inch exerted by the wheels. Say it's two wheels with about 4" of contact you're talking well over 200 pounds per square inch.
 
Double the joists. Bracing from the ground never stops sinking and is a hillbilly temporary move. Plywood is very flexible. People overestimate it's stiffness. Tough but not stiff. Machinery placement in old wood buildings get fir subfloor.
 
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