Securing gun safe to waffle pod slab

[Obie73]

Hi there, I have a gun safe that I want to bolt to the concrete floor of the house. The slab was made with waffle pod construction, which is a lot of thick polystyrene foam blocks, laid out in a grid pattern, which the concrete is poured over. Apparently the concrete is quite thin just under the surface of the floor, above the foam blocks, unless you happen to put the bolt down through one of the intervening bits of deep concrete between the blocks of foam. With the safe came four bolts for securing it to the floor. Not being a home handyman or tradie type I went online to find out what they're called and they look like they are what's called a sleeve anchor type bolt. They are 9mm dia and about 110mm long.

Can anyone advise if they are going to suit a waffle pod type slab? Or should I get something a bit shorter? Thanks.

[Larry]

Do you have many options on where you want to place the safe. I assume it is going against a wall. so that will restrict the placement of the bolts somewhat. How thick is the concrete at its thinnest? If the safe is large enough you may be able to position the bolts so they intercept the thick part if you can determine where that is. You only need two anchor points to the floor. GPR could identify the thickness of the concrete below but that would be costly and perhaps not have the resolution the other option is to drill test holes to find the thin points then move away from them. Honestly I wouldnt worry about whether it was thick or thin just choose your fastener of choice and put two it the floor and two into the wall on a stud. It will pass any cop push test they dont want to do any damage as long as it doesn't rock you will be sweet. I would put money that you could just put down some contact adhesive along with the bolts and it will never move.

[Oldbloke]

Do you have many options on where you want to place the safe. I assume it is going against a wall. so that will restrict the placement of the bolts somewhat. How thick is the concrete at its thinnest? If the safe is large enough you may be able to position the bolts so they intercept the thick part if you can determine where that is. You only need two anchor points to the floor. GPR could identify the thickness of the concrete below but that would be costly and perhaps not have the resolution the other option is to drill test holes to find the thin points then move away from them. Honestly I wouldnt worry about whether it was thick or thin just choose your fastener of choice and put two it the floor and two into the wall on a stud. It will pass any cop push test they dont want to do any damage as long as it doesn't rock you will be sweet. I would put money that you could just put down some contact adhesive along with the bolts and it will never move.

This. Two in the stud will make a huge difference. One up high, the other about halfway.

[Oldbloke]

You could buy something like these for the wall studs. But get ones about 6 or 8mm x 75 if available.

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[Obie73]

The other thing I forgot to mention is that it's a steel frame house. So I can't attach the top of the safe to wooden studs behind the plaster. The contact adhesive idea might work, if I first glue a strip of wood to the plaster wall, because there's a kicker board at the base of the wall and therefor the safe is out from the wall about 10mm. Then glue the top of the safe to the wooden strip. What sort of glue is used? 'Liquid nails' or something like that? The other (expensive) alternative I don't really want to do is get someone to install wooden studs between the metal frame uprights inside the wall and then reinstall the plaster board.

I have a suspicion the concrete might only be about 40 cm thick over the top of the foam blocks. I'd say at a guess it would be difficult even with a special gadget to find where the thickest part of the concrete is (but I could be wrong on that). Yes it's going up against a wall, in a corner. Thanks for your advice!

[Pendous]

Ob, You will find your house slab to be thicker than you imagine.
On top of the pods will be rebar chairs or some other support 40mm or so in height. Your house slab should 80mm plus thick.
Stay away from the sleeve type anchors. They can sometimes be difficult to install and more difficult to remove.
Instead source 'Masonry anchor screws/masonry screws'. Easy to install and remove.

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You will need to confirm the anchor size requirements for your state.
Here is idea of what you might be looking for
https://www.bunnings.com.au/ramset-10-x-60mm-galvanised-ankascrew-masonry-anchor_p2260276
These will work even if you manage to drill the entire slab depth. They also work in brickwork or hollow masonry.

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[Obie73]

Thanks Pendous! So the slab will be at least 80mm -- that sounds much better than 40mm (I made a typo in my previous post, writing "cm" instead of mm). I will go with your recommendation and get the masonry anchor screws. Just need to check the diameter of the pre-drilled holes in the base of the safe. I think in Queensland it just has to be bolted down either to the floor or the wall studs, but not necessarily both. As long as it passes the wobble test I don't think I will need to use liquid nails to secure the top part of it. Doing that will be messy, and problematic if I need to move the safe for any reason.

[No1Mk3]

I drove concrete agitators for several years and delivered to hundreds of pod slabs, the average floor varies from 85 to 110mm. The bolts Pendous showed work fine, i would use 10x100. You can screw into a steel house frame, use self drilling, self tapping screws of 6 to 10mm if the frame lines up with the safe.

[Larry]

Best to remove that skirting board as well as you want the back of the safe up against the wall. One of those vibrating tools you see on TV work really well for that. I did mine that way to cut a piece out.

Te cops dont want someone to get a crow bar behind the safe up against a wall to pry it away.

[Obie73]

Excellent advice No1Mk3 and Larry. Will most likely do as you suggest. Glad I came here to ask for advice, it's been very helpful.

[Blr243]

Penetration of the slab compromises the protection from termites Steel framed homes still have a stack of untreated timber . I’d be useing 75 mm ankascrews ( screw bolts )

[No1_49er]

Penetration of the slab compromises the protection from termites Steel framed homes still have a stack of untreated timber . I’d be useing 75 mm ankascrews ( screw bolts )

"Penetration of the slab compromises the protection from termites" - If the hole is abandoned (not filled with a fastener) then it is conceivable that termites might use the hole as a highway. But, even if vacant, how would they then navigate their way though the (non-existant) void between the floor and the base of the security container?
Thinking absolute worst-case scenario, and the belt and braces principal, why not fill the hole with some sort of sealant prior to inserting the dynabolt/ankascrew/whatever?

[bigrich]

The other thing I forgot to mention is that it's a steel frame house. So I can't attach the top of the safe to wooden studs behind the plaster. The contact adhesive idea might work, if I first glue a strip of wood to the plaster wall, because there's a kicker board at the base of the wall and therefor the safe is out from the wall about 10mm. Then glue the top of the safe to the wooden strip. What sort of glue is used? 'Liquid nails' or something like that? The other (expensive) alternative I don't really want to do is get someone to install wooden studs between the metal frame uprights inside the wall and then reinstall the plaster board.

I have a suspicion the concrete might only be about 40 cm thick over the top of the foam blocks. I'd say at a guess it would be difficult even with a special gadget to find where the thickest part of the concrete is (but I could be wrong on that). Yes it's going up against a wall, in a corner. Thanks for your advice!

I drilled mine, waffled slab as well I went down 100mm and didn’t go through the concrete. I believe they’re a bit thicker than 40mm . Otherwise they’re be a lot of busted up houses. Do a small diameter test hole and see if you can get down 100mm

[Blr243]

I’d b very surprised if it was 40 mm 100 is such a standard thing I expect it would be 100. Even though it would be a small crawl space I don’t trust termites. I have seen them get into just about anywhere . I once saw 17 of them riding on the back of a chital stag They are extremely determined and motivated by hunger . There is termite proof silicone you could squirt into the hole prior to useing ankabolt screws if u accidentally penetrate the slab.

[bigrich]

The big joke is termites eat wood for the cellulose. Guess what those big coolite blocks in the waffle slabs are made out of ? I’ve got a mate in pest control and he’s seen surf and boogie boards under houses that are just a shell. Completely eaten out. Termidor is the best pesticide for them. Is there a minimum bolt size for bolting down a safe? I’ve got a mate who used 8x75 I think. It’s solid.

[yoshie]

Police aren't going to make you remove a bolt to confirm its length or diameter, they will lean on it to confirm it won't wobble tho. The cheap safes (not really safes) are very thin and have a bit of flex in them. You might find a fixing in the wall will be necessary.