Pouring a 30"×40" concrete pad on top of concrete floor?

[ClangClang]

Let me preface this - I dont know shit about concrete. The most I've ever done is mix up some quickcrete in a bucket and poured it into a hole in the ground to repair a fence post.

I would like to pour a 30"×40" pad, 6" tall, in my basement utility room to elevate a gun safe to protect it from any possible future water on the ground. The floor is a 1960's era poured concrete slab. It has a very smooth, almost polished finish. The floor has a gentle slope towards the center of the room so I need to have a flat pad.

My plan is to drill the current slab and hammer in maybe 6 pieces of rebar vertically so they stand 4" proud from the existing slab (and therefore will be 2" below the top of the new pad). Then pour the slab. Then finish with a sheet of heavy duty plastic on top, followed by a bit of carpet. Once the safe is dropped on the pad, I'll drill the 4 anchor holes and secure with Titen HD anchors from Simpson.

I've watched a couple YT videos and have a pretty good idea about the general process but I have some specific questions:

- Whats a good, self leveling concrete mix to buy that will withstand ~1500 lbs of static weight?

- I presume i will want to roughen up the surface to promote adherence. Whats a good DIY tool option for that? Then I'll apply a bonding agent before pouring.

- What else should I be thinking about or doing to make my life easier and ensure this pad stays intact and doesn't fall apart in 5 years?

 

[Maggot]

High strength ready mix should do just fine, dont get it too wet, like a moderate porridge. I never hurts to roughen up the existing slab and or use a bonding agent, but with the rebar inserts and weight of a 30"x40" slab its not going anywhere. If you just have to, use a grinder and cut 1/2" grooves but not too close to the edges. Tap the edges of your form so te mud will settle and not leave voids on the edges.

Let it cure for at least a week as it takes 30 days to dry about 80%. IIRC Be sure to have a steel or magnesium trowel for finishing the surface.

 

[babyguppy]

High strength ready mix should do just fine, dont get it too wet, like a moderate porridge. I never hurts to roughen up the existing slab and or use a bonding agent, but with the rebar inserts and weight of a 30"x40" slab its not going anywhere. If you just have to, use a grinder and cut 1/2" grooves but not too close to the edges. Tap the edges of your form so te mud will settle and not leave voids on the edges.

Let it cure for at least a week as it takes 30 days to dry about 80%. IIRC Be sure to have a steel or magnesium trowel for finishing the surface.

hey now...
How much can you bench? LOL

 

[John?]

In addition to your vertical tie rebar connecting to the existing slab you’re going to want some horizontal mesh to prevent tension fracture. 2”x4” welded wire will work fine for your application. Tie it to your verticals about half way between bottom and finished top.

Rough up the existing slab with sidewinder. If you have a slab saw available cut grooves about 1/4” deep spaced a foot apart. That will help adhesion.

You should calculate you load per square inch to determine the strength cement you need. My rough guess based on my safe is 1.5 psi. So any readi mix is plenty strong. Hell, most quickcrete is plenty strong if you mix it thick for low slump.

You’d be smart to rent a magnesium float to make sure there are no voids in your new slab. Trowel around the edges of forms to make it pretty.

Curing takes a while, depending on what mix you use. I would plan on at least a week to set up. It won’t be fully cured but strong enough to work on. Be careful around edges while it is still green because it is super easy to crack a corner loose.

Also, don’t skimp on your forms.

Hope this helps.

 

[Maggot]

In addition to your vertical tie rebar connecting to the existing slab you’re going to want some horizontal mesh to prevent tension fracture. 2”x4” welded wire will work fine for your application. Tie it to your verticals about half way between bottom and finished top.

Rough up the existing slab with sidewinder. If you have a slab saw available cut grooves about 1/4” deep spaced a foot apart. That will help adhesion.

You should calculate you load per square inch to determine the strength cement you need. My rough guess based on my safe is 1.5 psi. So any readi mix is plenty strong. Hell, most quickcrete is plenty strong if you mix it thick for low slump.

You’d be smart to rent a magnesium float to make sure there are no voids in your new slab. Trowel around the edges of forms to make it pretty.

Curing takes a while, depending on what mix you use. I would plan on at least a week to set up. It won’t be fully cured but strong enough to work on. Be careful around edges while it is still green because it is super easy to crack a corner loose.

Also, don’t skimp on your forms.

Hope this helps.

Agree iwth the wire mesh. Probably not necessary but it cant hurt and is cheap insurance.

 

[camotoe]

How many bow kills you got.

 

[Alphatreedog]

How many Bow kills ?

 

[Alphatreedog]

How many bow kills you got.

This must have posted while I was typing ..

 

[ClangClang]

In addition to your vertical tie rebar connecting to the existing slab you’re going to want some horizontal mesh to prevent tension fracture. 2”x4” welded wire will work fine for your application. Tie it to your verticals about half way between bottom and finished top.

Rough up the existing slab with sidewinder. If you have a slab saw available cut grooves about 1/4” deep spaced a foot apart. That will help adhesion.

You should calculate you load per square inch to determine the strength cement you need. My rough guess based on my safe is 1.5 psi. So any readi mix is plenty strong. Hell, most quickcrete is plenty strong if you mix it thick for low slump.

You’d be smart to rent a magnesium float to make sure there are no voids in your new slab. Trowel around the edges of forms to make it pretty.

Curing takes a while, depending on what mix you use. I would plan on at least a week to set up. It won’t be fully cured but strong enough to work on. Be careful around edges while it is still green because it is super easy to crack a corner loose.

Also, don’t skimp on your forms.

Hope this helps.

Thanks, these are really helpful.

I'm estimating around 1.75-2PSI (it's a very heavy custom safe). But since all the mixes I look at are 3000-6000 PSI rated, I'm sure it will be fine (assuming proper mix and pour). I'll rent a magnesium float.

What's a sidewinder? Google wasn't helpful. I just see a bunch of concrete screws. I don't have a slab saw. My plan is just to score up the surface in a hatch pattern with my angle grinder. I'll keep it wet to keep the dust down and run my shop vac right next to the grind wheel. That's my best plan so far.

I should be able to give it 10-12 days cure time before the safe gets delivered. I can probably delay delivery by a couple extra days if necessary.

 

[Maggot]

Thanks, these are really helpful.

I'm estimating around 1.75-2PSI (it's a very heavy custom safe). But since all the mixes I look at are 3000-6000 PSI rated, I'm sure it will be fine (assuming proper mix and pour). I'll rent a magnesium float.

What's a sidewinder? Google wasn't helpful. I just see a bunch of concrete screws. I don't have a slab saw. My plan is just to score up the surface in a hatch pattern with my angle grinder. I'll keep it wet to keep the dust down and run my shop vac right next to the grind wheel. That's my best plan so far.

I should be able to give it 10-12 days cure time before the safe gets delivered. I can probably delay delivery by a couple extra days if necessary.

Your grinder will be fine. Even after 12 days, as noted above, be careful of the edges. If its only 30x40 just a good steel hand trowel will do it, You'll never see the top so it doesnt have to be perfect.

 

[rjacobs]

Get some expanding anchors and use those with long bolts or all thread instead of just rebar stuck in holes... Secure those bolts/all thread to your wire or a simple square loop of rebar in your form with a tack weld or 3... that small pad will never be able to be pulled up without also destroying the original floor.

You will NEVER get new concrete to bond with old, especially really old concrete. Dont waste your time IMO. Mechanically secure it and be done.

Get you a couple 80 lbs bags of quick-crete, mix em up, pour em in and rough finish it with a cheap ass trowel.

 

[redneckbmxer24]

Get some expanding anchors and use those with long bolts or all thread instead of just rebar stuck in holes... Secure those bolts/all thread to your wire or a simple square loop of rebar in your form with a tack weld or 3... that small pad will never be able to be pulled up without also destroying the original floor.

You will NEVER get new concrete to bond with old, especially really old concrete. Dont waste your time IMO. Mechanically secure it and be done.

Get you a couple 80 lbs bags of quick-crete, mix em up, pour em in and rough finish it with a cheap ass trowel.

All of this, rebar in drilled holes won’t hold shit. You don’t need to tack it though, the concrete will bond to the anchors holding it down and the rebar/mesh is just to give the slab strength. If you want added strength get the stud kind of anchors and after you run the nut down to expand it take two more nuts and thread on and tighten them together a few inches up.

I don’t know why you want to put plastic down but it isn’t going to do shit other than cause a moisture barrier that works both ways. You’re also just going to tear it up and drill holes through it to anchor the safe. Same with carpet, there’s no point as it will just hold moisture against the safe. If you want added protection then paint the bottom of the safe with a few thick coats of POR-15 and set it right on top of your slab.

 

[Inline6]

Lot of good advice.

Not much to add, I would do this if it were mine.

1. make sure the top of the concrete form work is level. You don't want to fight the door one way or the other. (I'm sure you know this, it is something people overlook).

2. Know where the anchor points are in the safe, I'm hoping they are closer to the inside vs outside. Personally would run rebar along the of the vertical dowels, you intend on installing. You would want that to be outside the bolts to anchor the safe. If for some reason you are unable to achieve that, have the bolt ( especially wedge anchor). Installed in the original slab, that will help keep your new pad from braking.

FWIW

 

[hafejd30]

Make sure you control the humidity if it’s a damp environment. I put my safes in my basement this past year. I was surprised to see it as humid as it was 70-80%. My basement is dry with zero water issues whatsoever.

I now have canisters in my safes and a bigger dehumidifier along with another dehumidifier in the gun area itself.

My humidity is constantly monitored and stays 40-50% in the room and 35-40% in the safes

 

[hafejd30]

I had a smaller dehumidifier which I thought was doing the job. It was in the other half of the basement by the drain. I immediately moved it next to my gun safes and in the 24 hours emptied a 3 gallon pail several times. Dropped from 76% to 50% overnight

With my bigger dehumidifier running where this one used to be I’ve only dumped maybe 2 gallons in the last few months from the one in the gun room.

Just food for thought before you make the move

 

[Maggot]

I had a smaller dehumidifier which I thought was doing the job. It was in the other half of the basement by the drain. I immediately moved it next to my gun safes and in the 24 hours emptied a 3 gallon pail several times. Dropped from 76% to 50% overnight

With my bigger dehumidifier running where this one used to be I’ve only dumped maybe 3 gallons in the last few months from the one in the gun room.

Just food for thought before you make the move

Right about the moisture. Basements are notorious for that. Water makes mold.

 

[hafejd30]

Right about the moisture. Basements are notorious for that. Water makes mold.

Right. Mines dry. I never would have guessed it be that high. Some basements you walk into and it hits you. They must be 90+ %. My monitor system and kestrel showed the same results

 

[redneckbmxer24]

Damprids work as well if not better than a dehumidifier rod or canister for putting inside a safe and they have zero potential to start a fire inside of a safe where you don’t want a fire.

 

[hafejd30]

Damprids work as well if not better than a dehumidifier rod or canister for putting inside a safe and they have zero potential to start a fire inside of a safe where you don’t want a fire.

I’ve been running those 750g silica gel canisters. One in each safe. Both safes are under 40%. Plus the dehumidifiers for the room overall. Which holds usually 40-50% depending on the weather

Im in the UP of Michigan. In Winter the humidity is very low in the basement. Spring when the snow melts it be the highest

It was eye opening at first but it maintains without any issues easily now

I have everything down there. Guns, reloading room with primers/powders etc

 

[redneckbmxer24]

I’ve been running those 750g silica gel canisters. One in each safe. Both safes are under 40%. Plus the dehumidifiers for the room overall. Which holds usually 40-50% depending on the weather

Im in the UP of Michigan. In Winter the humidity is very low in the basement. Spring when the snow melts it be the highest

It was eye opening at first but it maintains without any issues easily now

They work, I just got tired of recharging them all the time. The damprids seem to pull way more moisture but last way longer than a recharge, and when it’s full I just throw it in the trash and hang up a new one. You can also empty the water and refill the pack but I just chuck them because I buy in bulk so they’re cheap. I also found that after a while the silica canisters didn’t work as well as they once did and need replacing.

 

[ClangClang]

Luckily my basement is very dry. Averages around 45% RH in the summer, around 35% RH in the winter.

I keep one of the rechargeable EvaDry units in my safe and in the 18+ months I've been in this house, I've never had to recharge it once. Its not showing any absorbed moisture whatsoever. Back when I lived in VA I had to recharge it every 3-4 weeks.

I just want to pour this pad in the highly unlikely scenario I get some water in the basement, burst pipe, etc. Also, my insurance requires 6" stillage for anything below grade for coverage against flood/water damage. This is my forever home (I hope) so might as well do it right.

 

[hafejd30]

Luckily my basement is very dry. Averages around 45% RH in the summer, around 35% RH in the winter.

I keep one of the rechargeable EvaDry units in my safe and in the 18+ months I've been in this house, I've never had to recharge it once. Its not showing any absorbed moisture whatsoever. Back when I lived in VA I had to recharge it every 3-4 weeks.

I just want to pour this pad in the highly unlikely scenario I get some water in the basement, burst pipe, etc. Also, my insurance requires 6" stillage for anything below grade for coverage against flood/water damage. This is my forever home (I hope) so might as well do it right.

Ah ok that makes more sense. I thought you had issues with it being damp from the initial post

Safes are better in basements anyways for fire protection. If the house torches it’s likely ending up down there anyways

The 4ft of water after a major fire won’t do it any justice but you can open it up and get stuff drying asap

 

[sirhrmechanic]

Just wondering if you really need the concrete slab on your slab? If you are looking to reinforce the existing slab, you could grab a 36 x 48 piece of steel… 3/8” or 1/2” and anchor that to the floor. If you really want to spread the load, put it on a layer of grout or even tile adhesive. then put the safe on that. It would be easier than pouring and a lot less work. And certainly give you a solid pad for your safe.

Just a thought.

Cheers! Sirhr

 

[ClangClang]

@sirhrmechanic I want to pour a raised pad for protection from water. Not because the existing slab needs reinforcement. Just in case I ever have a burst pipe or something stupid. Additionally, my insurance specifically requires any items stored in the basement that I wish to be covered under the policy must be raised 6" off the ground level.

 

[John?]

Just wondering if you really need the concrete slab on your slab? If you are looking to reinforce the existing slab, you could grab a 36 x 48 piece of steel… 3/8” or 1/2” and anchor that to the floor. If you really want to spread the load, put it on a layer of grout or even tile adhesive. then put the safe on that. It would be easier than pouring and a lot less work. And certainly give you a solid pad for your safe.

Just a thought.

Cheers! Sirhr

The OP also wants to correct a sloped floor before setting the safe.

Otherwise, yours is a great suggestion.

 

[sirhrmechanic]

The OP also wants to correct a sloped floor before setting the safe.

Otherwise, yours is a great suggestion.

I missed that…

 

[Aftermath]

I would not pour a single cc of concrete for this situation. Seriously.

Have any of you ever moved a safe that sat on even a 20 year old (well cured) slab for any period of time?

OP, make a frame of treated 2x6. Place joists 6" on center. Stagger 2x6 bracing inside of those joists 6" on center. Use a polyurethane construction adhesive and good decking screws to assemble this base. Glue and screw 3/4" treated plywood to the frame. Place screws 3" from the corners and 6" on center everywhere you can touch wood under the plywood. You can use a primer and then paint it camouflage.

I have similar and made my base so that there is a toe kick under the front edge.

If you think you need to secure that safe to the concrete under, you still can, but if that is really a concern you need a bigger safe full of stuff and/or a good dog and a mean woman.

 

[hollowoutadime]

Good move to get the safe up off the floor. Regular quickrete is fine, no PSI to worry about with for a gun safe. Use a mixer and carry it down in 1/2 filled 5 gallon buckets. I use a concrete vibrator to get rid of the voids. I think you can rent one of about $100.

You can tapcon the form.

You could skip the concrete and do a 2X12" (taller) wood box tapconned to the slab from the inside. Taller is better, brother in law go 10" of water a month ago, contents of safe probably damaged.

 

[Bullfrog08]

Good move to get the safe up off the floor. Regular quickrete is fine, no PSI to worry about with for a gun safe. Use a mixer and carry it down in 1/2 filled 5 gallon buckets. I use a concrete vibrator to get rid of the voids. I think you can rent one of about $100.

You can tapcon the form.

You could skip the concrete and do a 2X12" (taller) wood box tapconned to the slab from the inside. Taller is better, brother in law go 10" of water a month ago, contents of safe probably damaged.

He's not placing cc of concrete....hes placing cubic feet, because AMERICA!!!!

 

[hafejd30]

Honestly I leave the metal skids the safe comes on (Winchester) to make it easier to move. I live in the country and I’m not really worried about someone stealing the safe. After moving it around I think it be easier and quicker to just rip it open with some tools than to try and move it. I half ass thought about mounting some big casters to the bottom to move it around if I want in the future

I know what it takes to get that probably 700 lbs box (including contents) up those stairs. Nobody in there right mind would take it as a whole in my opinion. But maybe your insurance requires it be bolted down. But I’m here to tell you that won’t matter either

 

[Aftermath]

He's not placing cc of concrete....hes placing cubic feet, because AMERICA!!!!

Because AMERICA isn't replying to the comment he thought he was....
Carry on.

 

[doubloon]

I missed that…

That's OK. I missed the part where making the bottom of a bucket thicker helps prevent it from flooding. But I don't know a lot about concrete and even less about basements.

 

[Aftermath]

Honestly I leave the metal skids the safe comes on (Winchester) to make it easier to move. I live in the country and I’m not really worried about someone stealing the safe. After moving it around I think it be easier and quicker to just rip it open with some tools than to try and move it. I half ass thought about mounting some big casters to the bottom to move it around if I want in the future

I almost agree with the casters.

Even in, maybe especially in, the most populated places.

I mean, I live way out in the country on 112 acres. If I was gone, someone stealing my stuff would not be noticed by anyone. At least if I had neighbors close by someone might notice.

There is absolutely nobody moving my safe, even empty, without time and equipment. They would be far better off just cutting it open.

The reason I say almost to casters is supporting the inner portion of the base. An angle iron base designed to support 1000 lbs or more and then the casters is one damned good idea.

 

[Aftermath]

That's OK. I missed the part where making the bottom of a bucket thicker helps prevent it from flooding. But I don't know a lot about concrete and even less about basements.

EVERY basement I have ever built or seen, and I have built a bunch and seen more, have floor drains. The idea here is to raise the thing off the floor high enough to prevent the inside getting wet while the drain tries to catch up.

I agree, though, without a drain or sump pump, any such effort is sort of futile....except, in this case, it also allows compliance to the insurance requirements.

 

[hafejd30]

I almost agree with the casters.

Even in, maybe especially in, the most populated places.

I mean, I live way out in the country on 112 acres. If I was gone, someone stealing my stuff would not be noticed by anyone. At least if I had neighbors close by someone might notice.

There is absolutely nobody moving my safe, even empty, without time and equipment. They would be far better off just cutting it open.

The reason I say almost to casters is supporting the inner portion of the base. An angle iron base designed to support 1000 lbs or more and then the casters is one damned good idea.

I wanted a big safe. Like those 70 gun or whatever they are. But after moving these (one is 400 the other is like 600lbs) several times I said F that.

Our fire department has opened several bigger safes and I watched someone I thought would struggle to open a beer can pop one similar to mine in less than 30 minutes with a crow bar.

I’ve come to the conclusion that it’s easier to just open them on site than to move them. Should I ever become a thief

 

[ironpony52]

I agree with the 2x12 framed base. Allowing for the slope will be easy. You won't have to bend over to reach the bottom. Steel sitting on concrete = no go for me.
Carpet will draw moisture on top of concrete.

 

[ironpony52]

I wanted a big safe. Like those 70 gun or whatever they are. But after moving these (one is 400 the other is like 600lbs) several times I said F that.

Our fire department has opened several bigger safes and I watched someone I thought would struggle to open a beer can pop one similar to mine in less than 30 minutes with a crow bar.

I’ve come to the conclusion that it’s easier to just open them on site than to move them. Should I ever become a thief

Stihl 2 stroke 14" cut off saw will cut it in half in a few minutes.

 

[Aftermath]

I wanted a big safe. Like those 70 gun or whatever they are. But after moving these (one is 400 the other is like 600lbs) several times I said F that.

Our fire department has opened several bigger safes and I watched someone I thought would struggle to open a beer can pop one similar to mine in less than 30 minutes with a crow bar.

I’ve come to the conclusion that it’s easier to just open them on site than to move them. Should I ever become a thief

Yes. My main safe is advertised as a 60 gun safe. I think 850 lbs empty. I use the rods that go down the barrel and velcro to the shelf above and have customized the shelving. My safe very easily holds 75 long guns, 50 handguns and some other valuables like spotting scope and other stuff. It's fire rated, too.

But, just like your experience and just like the OP, I know this isn't keeping someone with time, skills and gear from stealing it all and I also know that a real fire is likely to roast almost everything, but it is insurance company compliant and heavy enough that some asshole without time or tools is not taking it anywhere.

 

[doubloon]

EVERY basement I have ever built or seen, and I have built a bunch and seen more, have floor drains

I expect there to be drains and I admit I have no knowledge of it but putting more solid concrete on top of existing solid concrete without increasing the size/capacity of the drains it would only be adding a couple three cubic feet of catch up to the equation ... whatever adding up the cumulative diameter of all the drains is times the thickness of the concrete added?

Unless there's something like a spillover trap somewhere that's bigger that acts like a retention pool for water being drained off ?

I'll google me some basement drain designs to see if I can understand better. Just an idiot trying to understand how much time would be bought by adding another 6" of concrete without adding more drain capacity.

 

[hafejd30]

Yes. My main safe is advertised as a 60 gun safe. I think 850 lbs empty. I use the rods that go down the barrel and velcro to the shelf above and have customized the shelving. My safe very easily holds 75 long guns, 50 handguns and some other valuables like spotting scope and other stuff. It's fire rated, too.

But, just like your experience and just like the OP, I know this isn't keeping someone with time, skills and gear from stealing it all and I also know that a real fire is likely to roast almost everything, but it is insurance company compliant and heavy enough that some asshole without time or tools is not taking it anywhere.

In a real fire if it’s in the basement against a concrete wall it will likely be just fine. Letting your fire department know it’s there will allow them to concentrate efforts to protect it.

You will however have water to deal with. Likely several feet of it

We have fought fires where the safe isn’t even fire resistant and were able to protect it. Smoke and heat rise. If positioned correctly and protected you’ll have some smoke/moisture get in there but it could be minimal. Now if it’s around a fire load or the collapsed on it may be a different story.

Against a corner with concrete block or poured is excellent. Dead center of the basement is a bad idea. Even after the fire is over it will take a bunch more effort to get to it and get it open. To minimize moisture damage you want it open asap

 

[Aftermath]

I expect there to be drains and I admit I have no knowledge of it but putting more solid concrete on top of existing solid concrete without increasing the size/capacity of the drains it would only be adding a couple three cubic feet of catch up to the equation ... whatever adding up the cumulative diameter of all the drains is times the thickness of the concrete added?

Unless there's something like a spillover trap somewhere that's bigger that acts like a retention pool for water being drained off ?

I'll google me some basement drain designs to see if I can understand better. Just an idiot trying to understand how much time would be bought by adding another 6" of concrete without adding more drain capacity.

It depends....

Is the drain clogged?
How big is the drain diameter and how fast is the water entering? Can the water entering be drained away fast enough by this drain system?
If there is no drain, can the pump keep up and/or overcome? Some combo...same question.
Is it flooding with water or jello (viscosity)?

 

[ironpony52]

I expect there to be drains and I admit I have no knowledge of it but putting more solid concrete on top of existing solid concrete without increasing the size/capacity of the drains it would only be adding a couple three cubic feet of catch up to the equation ... whatever adding up the cumulative diameter of all the drains is times the thickness of the concrete added?

Unless there's something like a spillover trap somewhere that's bigger that acts like a retention pool for water being drained off ?

I'll google me some basement drain designs to see if I can understand better. Just an idiot trying to understand how much time would be bought by adding another 6" of concrete without adding more drain capacity.

IMO I believe the reasoning is most basement "floods" are going to be a water heater, dripping waterline, something that is not going to dump massive gallons at once even a broken line would be slow enough that hopefully you find it hear it etc.
If you are 6"s above the floor that is a fair amount of water before it damages something. Sitting on the floor 1/4" its wet.
Our water dept monitors the wireless meters and will contact us if it is running full bore. and ask hey what's up ? MIL had a leak and they called her, when I fill the pool that call.

 

[Aftermath]

In a real fire if it’s in the basement against a concrete wall it will likely be just fine. Letting your fire department know it’s there will allow them to concentrate efforts to protect it.

You will however have water to deal with. Likely several feet of it

We have fought fires where the safe isn’t even fire resistant and were able to protect it. Smoke and heat rise. If positioned correctly and protected you’ll have some smoke/moisture get in there but it could be minimal. Now if it’s around a fire load or the collapsed on it may be a different story.

Against a corner with concrete block or poured is excellent. Dead center of the basement is a bad idea. Even after the fire is over it will take a bunch more effort to get to it and get it open

By the time the volunteers get here, I hope they bring stuff for smores.

 

[doubloon]

It depends....

Is the drain clogged?

Si. And does the pump have electricity? I can follow all that. A 8" drain pipe will only move so much water as will a 40 GPM pump.

But a 8" drain in a 30' x 40' x 10' tall room is still a 8" drain in a 30' x 40' x 9'6" tall room. Same for a 40 GPM pump.

The floor is the floor either way and 2 foot of water in a room with a 10 foot ceiling is still 2 foot of water in a room with a 9 1/2 foot ceiling. I've been stumped by simpler problems before so it's definitely not your fault if I don't understand. Maybe tequila will help.

ETA: I see my error and it's a doozy. I read it as pouring a 30 foot by 40 foot slab, not a 30 inch by 40 inch slab.

He would be adding 6" by whatever volume is left by the basement floor not covered ... carry on.

I think it was the mention of the sunken area in the middle of the basement that messed me up.

I'm definitely in favor some kind of welded construction safe stand at this point.

IMO I believe the reasoning is most basement "floods"

Yeah, difference between 30" and 30' is what screwed me up

 

[Aftermath]

Did I mention that I have 3 good dogs AND 1 mean woman. Pity the fool...

 

[Aftermath]

Si. And does the pump have electricity? I can follow all that. A 8" drain pipe will only move so much water as will a 40 GPM pump.

But a 8" drain in a 30' x 40' x 10' tall room is still a 8" drain in a 30' x 40' x 9'6" tall room. Same for a 40 GPM pump.

The floor is the floor either way and 2 foot of water in a room with a 10 foot ceiling is still 2 foot of water in a room with a 9 1/2 foot ceiling. I've been stumped by simpler problems before so it's definitely not your fault if I don't understand. Maybe tequila will help.

He's only wanting to increase the floor height by 6" under the safe. He wants to buy those 6" of capacity (minus, if you want to get particular, the capacity now absorbed by that 6")

 

[hafejd30]

By the time the volunteers get here, I hope they bring stuff for smores.

Right. If your home when the fire starts you can usually do a few things to hold it back for a bit. Closing doors/window help a lot. Fire extinguishers

They make those fire extinguisher reactive balls. Basically a red ball that blows up when fire gets to it. Hang one of those babies up near the safe.

The biggest thing is not keeping a fire load around the safe. If it’s not there it can’t burn. The fire will vent itself by that time and the heat will take that route out

I know this is off topic of the OP question. But still something to consider when placing a safe in your basement overall. Especially if you’re pouring a permanent slab for it

 

[Baron23]

Make sure you control the humidity if it’s a damp environment. I put my safes in my basement this past year. I was surprised to see it as humid as it was 70-80%. My basement is dry with zero water issues whatsoever.

I now have canisters in my safes and a bigger dehumidifier along with another dehumidifier in the gun area itself.

My humidity is constantly monitored and stays 40-50% in the room and 35-40% in the safes

A Golden Rod is your friend

Gun Safe Golden Rod Dehumidifier Rod

The Golden Rod Dehumidifier from Lockdown eliminates humidity, mildew and condensation from gun safes, boats, campers or other small areas that harbor moisture

www.lockdown.com

 

[ClangClang]

@Aftermath I thought about the moisture issue and just framing out a base, that but I want this safe secured. I'm not concerned about anyone dragging this safe back up the stairs, but an unsecured safe can be tipped over and pushed onto its back in 60 seconds and then it's very vulnerable to a simple prying attack. (And of course I''ll be putting in motion sensors, a wifi camera, and a water sensor - all on battery backup). And roger on the dogs and the mean woman too

@hollowoutadime I would love to go taller like you're suggesting (12" was my first idea), but the safe moving company uses a hydraulic stair climber that can lift a maximum of 8" so I'm somewhat limited.

@redneckbmxer24 @ironpony52 good call on the carpet just being a sponge to hold moisture against the safe. You're right. I'm deleting that from my plan. It will just be the concrete pad plus a 1/4" sheet of solid HDPE on top as a moisture barrier.

@everyone - yes the room does have an 8" floor drain. I'm going to look into installing a sump pump as well, although that will be a future project. But the prior owner said he had never had water in the basement in the 33 years he lived here and I believe him, the carpets and drywall are all original and there isn't a single water stain anywhere.

 

[doubloon]

He's only wanting to increase the floor height by 6" under the safe. He wants to buy those 6" of capacity (minus, if you want to get particular, the capacity now absorbed by that 6")

Yeah, I read it wrong. I edited my earlier post to highlight my stupidity.

I still lean toward a safe stand that could be moved if necessary.