Retrofit fireproof to safe

[danoid]

Hello,

So I’ve been given an old safe which is just metal.

I’d like to make this somewhat a fireproof safe and for something to waste my evenings on.

If I was to use hardiebacker on the inside, how would I attach it to the internal sides and roof of the safe? Normally you’d screw in hardiebacker but obviously I can’t do that.

I know it’ll never truly be fireproof but better to have some somewhat important documents in that rather than a normal A4 binder like I have now.

If hardiebacker isn’t the best for what I want, what is and how would I stick it to the internal sides and roof?

Thanks

 

[JohnD]

plasterboard is very suitable. As well as being fire-resistant, it actually absorbs heat, which causes the water of construction to break down and boil off as steam, which absorbs heat.

You can make a plasterboard box to surround the safe. plasterboard is quite easy to score and snap to size. You can screw it to a frame of wooden battens on the inside, and seal all joints with mixed-up gypsum plaster (not filler) which is fire resisting in the same way.

it is better to put the casing on the outside

professional safes are made in much the same way, but they have an inner and an outer steel cabinet, with the fireproof layer between them. In fire safes the steel cabinets are very thin and not burglar resitant.

if you are fond of woodwork you could buy one of more fire-proof doors, cut them into pieces, and use them to build a fire-proof cabinet around your safe. you can get fire resisting caulk and expanding foam (pink) to seal all joints and openings to prevent smoke or hot air getting inside. I suppose you could also use the pink foam to glue the cabinet to the steel safe.

 

[danoid]

Unfortunately I can’t case the outside to where it’ll go is nearly bang on the size of the safe.

I thought plasterboard is considered combustible?

The whole safe is pretty small so if I was to put wooden battens then plasterboard I’ve lost a lot of space.

I do have some odd bits of hardiebacker already but not sure what adhesive to use

 

[Exedon]

If you want to go for fireproof have a look at ceraboard refractor material used in boilers good up to 1200 C.

 

[Deleted member 174758]

I thought plasterboard is considered combustible?

Not at all. It is fairly common for architects to spec steels with timber battening and one or two layers of PB for fire control - normally the pink FR version around steels, but fire cell walls are often specced at something like 2 x skins of 12.5 or 15mm PB, depending on requirement. 2 x 12.5mm grey (standard) on a stud wall/ceiling gives you an estimated 1 hour fire rating, whilst 2 x 12.5mm pink (FR) gives you 2 hours rating

 

[danoid]

Not at all. It is fairly common for architects to spec steels with timber battening and one or two layers of PB for fire control - normally the pink FR version around steels, but fire cell walls are often specced at something like 2 x skins of 12.5 or 15mm PB, depending on requirement. 2 x 12.5mm grey (standard) on a stud wall/ceiling gives you an estimated 1 hour fire rating, whilst 2 x 12.5mm pink (FR) gives you 2 hours rating

Oh I see now.

As I’ve already got hardiebacker can you recommend any adhesives? I’m think “stick like sh*t” as it says concrete and metal

 

[^woody^]

Shouldn't such a safe be heat proof and not just fireproof? I'm not sure hardybacker is some magic insulator to keep internal temperature down

 

[lostinthelight]

Unfortunately I can’t case the outside to where it’ll go is nearly bang on the size of the safe.

I thought plasterboard is considered combustible?

The whole safe is pretty small so if I was to put wooden battens then plasterboard I’ve lost a lot of space.

I do have some odd bits of hardiebacker already but not sure what adhesive to use

If you cut the back and sides the height of the inside minus the thickness of sheet, cut the top piece to full size , push top piece up to roof and when you position the side pieces , it should pretty much self lock in position ..then drop the floor in,...if it doesn't stay together you'll have to leave your wedge in there to keep it up.

 

[conny]

And don't forget a layer on the inside surface of the door.

 

[Deleted member 174758]

I’m think “stick like sh*t” as it says concrete and metal

Something like that - the stuff I've used to bond cement fibre board to steel was very rubbery (can't remember the name, though).

Install the top and bottom, fitted tight and then the back and sides and the sides/back can be made to carry the weight if the top

Just seen LitLs response....

 

[JohnD]

Shouldn't such a safe be heat proof and not just fireproof? I'm not sure hardybacker is some magic insulator to keep internal temperature down

I know that gypsum is endothermic in a fire, due to the water content breaking down and blowing out as steam.

AFAIK cement board, and most other materials, are not.

 

[Deleted member 174758]

Shouldn't such a safe be heat proof and not just fireproof? I'm not sure hardybacker is some magic insulator to keep internal temperature down

Cement fireboard is a heat insulator, but for domestic floors above public stairwells I've used Promat Supalux fireboard (@ £90+/sheet) in conjunction with Promatect 250 (both sides of the floor) to get a 2 hour underside + 2 hour top side rating. Calcium silicate is the compound often used for the highest fire/temperature resistance

Promat are a British firm based in Heywood Greater Manchester and theircsite contains full technical data specs

 

[freddiemercurystwin]

Not at all. It is fairly common for architects to spec steels with timber battening and one or two layers of PB for fire control

It's not good practice to protect a steel beam with timber battens and board, if protecting a steel beam then steel angles should be used rather than timber battens. Or the fireboards can be screwed together around the beam.

In the event of a fire when a beam is protected by board on timber battens, the timber battens will expand and twist/deform at different rates to the steel beam as the whole thing heats up, potentially causing the boards to be forced off, the threads on the fixing screws holding the boards on can char the timber and loosen and pop out too.

 

[JohnD]

Calcium silicate is the compound often used for the highest fire/temperature resistance

Like sandlime bricks

 

[conny]

Are we all over thinking this?
The OP says the only thing he has in there at the moment is a folder about A4 size. This suggests it's a small wall mountable safe so will not contain a great deal of items when full. The priority is to protect the items from catching fire through self combustion I presume. Therefore a layer of incombustible material should suffice surely? If the temperature rises so high to damage the contents then, clearly, no one is going to be able to remove the safe without wearing a full heat resistant suit.