I have a pillbox a bit like the one below, but it is intact. I need to cut a hole in the roof, 2m x 1m rectangle. The pic below shows quite a lot of steel in a RC slab ~350mm thick. I know a man with an explosives licence (no really. He used to work in tin mines and kept his ticket). Or would you go for a big petrol saw and lots of dust?
Cheers!

You would need a seriously large amount of explosives to blow a hole through the roof of that.

they were pretty much designed to be proof against exactly the sort of thing that you’re proposing I would have thought?

McMoonter’s your man though.

With the size of the rebar and thickness of the slab, forget it and call a couple of Diamond Drilling Companies.

That is NOT a job for a Stihl saw.

Really? I had imagined drilling a load of holes in the shape of the cut, putting the c4 (or whatever) in said holes, and when they blow they all link together and out drops the block. Simple, non?!

McMoonter’s your man though.

Chuck Norris I is not! 😯

hammer and bolster + elbow grease

daisy for the metal work.. 😀

What Lowey said ^

That is NOT a job for a Stihl saw.

Maybe if it’s your Stihl.

It’s what tool hire companies are for. 😉

Can’t you just turn it upside down?

Our local tool hire place has stone cutting chainsaws with diamond+carbide teeth. You bolt a guide track down and go for it. Sure rebar is no problem. I bet they are quite a handful though, water when cutting to reduce dust and cool chain. You pay so much per mm tooth wear.

are you just doing this to let more light in or for access?

If it’s to let light in I’d be tempted to attack the walls – you can just cut the bricks out to enlarge the existing holes?

More importantly how can I get myself a bunker, need a new shed!

Our local tool hire place has stone cutting chainsaws with diamond+carbide teeth. You bolt a guide track down and go for it. Sure rebar is no problem. I bet they are quite a handful though, water when cutting to reduce dust and cool chain. You pay so much per mm tooth wear.

We purchased one of these when we saw a demo of them working. We were going to use them to cut holes in prestressed floor slabs. They are horrific things to use form a vibration standpoint, rebar above 10mm rips the blade to pieces and the chains cost a fortune.

We sent it back. Get a specialist in. Wont cost you much and they will do the job safely and quickly, be it stitch drilling or saw cutting.

are you just doing this to let more light in or for access?

to mount a gun on. 8)

Aren’t these things all listed these days? Are you allowed to go around hacking them?

The roof will have been cast as a monolithic slab. When you cut through all trhe rebar, there’s a chance the remaining roof will collapse, or at least form cracks. You may need to provide some extra support around the opening, which is quite large in proportionn to the slab area.

I say ‘chance’ and ‘may’ as these things are quite substantial. However, don’t forget to post the video of you standing on the roof cutting your hole, just the bit where you disappear downwards in a cloud of dust will do.

Just as a quick pointer be very **** careful during the last cut because as it drops it’ll snagg like ****. Oh and also consider its weight once it’s dropped thro. Probably around 1.5 tonne so you’re not gonna just roll it out as one 😉

Explosives would be very inefficient for this.

The plastic explosive would be used to “strip” the concrete from the rebar. From a military engineers pov when blowing a bridge or similar, the structure would then collapse as the rebar could not support it on its own.
Also you would need a LOT of explosive to have any effect on it.

As mention above a specialist diamond cutting would be the answer. Still wouldn’t be cheap mind!
If your in the NE I can recommend these A19 drilling

As RobH says check it’s not listed.

ACROs under the off-cut to stop the blade nipping as you finish off the cutting. Should be fun breaking the off-cut up to get it out too!

I recon the best bet is to not bother.

We need pictures 🙂

Its not next to a pool house is it?

😉

Also you would need a LOT of explosive to have any effect on it.

DEFINITELY video it then.

Please tell us why you want this done? 🙂

EDIT: why not just remove the entire roof with a crane and start again?

You don’t need a lot of explosive. You just need shaped charges:

Seems a shame to destroy a bit of history.

However what you could do is try an internal explosion to lift the roof off a few inches and then have it drop down on the walls causing the hole thing to collapse.

Failing that a linear shaped charged might do it. You can find the various equations kicking around on the net, but it’s not really a home made job!

Edit: as pointed out, just piling explosive next to it will do very little (but it will look cool!).

Thought this might be fun 🙂

Need a hole so we can put a large box full of clever electronics, which drive some machinery nearby. The other option is to build a purpose built house/shed, but seeing as we have this thing and it’s sat doing nowt it’ll be nice to use it.

May well end up going through a wall rather than roof, but was trying to avoid too much change to the external appearance. I guess we can use the original bricks again to block up the hole.

Will get some pics once it’s finished, about March time hopefully.

?

Chuck Norris I is not!

I dunno…..

The roof will have been cast as a monolithic slab.

❓ 😯

?

That’s a surface to air missile. You want one of these – fires a shaped charge and then flies a bomb through the resulting hole. Clever.

[video]http://www.youtube.com/watch?v=7s74pmpHlvA[/video]

That’s a surface to air missile.

I was implying that this was the electronics he’d be mounting on the thing post roof top excavations.

dont know of any hire shops that have anything capable of cutting through 350mm stihl saws are only 100mm road saws are 150/200mm would agree that either specialist required or hire core drill and drill series of holes linking them all together start now and you should be finished by christmas

So in summary then, your best bet is about 15-20 sacks of C4. Job done.

I spent two weeks on Orkney, back in the eighties blowing these things up! Not once did the explosives damage the roof, other than relocating it 50 feet or so to one side. We pretty much blew the walls apart and then had a half day or so attacking each ‘lid’ with pneumatic drills wherever it landed – one buried itself 4/5ths deep in a peat bog which was fun.

I don’t think your explosives pal is going to be much use!

diamond drilling would be an answer but and it a big one.. the re bar will murder the bit so thats out, i think that pneumatic hammer is your way forward and cut the bar with a torch when you can get to em.. i ‘d make the hole larger than required so you can reface it to size assuming it will be non load bearing

If you’ve got the access….

JCB with a concrete pecker?

What’s JCB hire? 8 hour minimum for £150? plus pecker? lot cheaper than diamond drilling crew and having to pay for all the bit wear….

Don’t think you’ll end up with a very neat hole whatever you do.

You could pour sulphate on it and wait a wee while for the concrete to be attacked by the aggressivity….

Are pill boxes listed structures by English Heritage,no matter who owns them.

Could you not use a thermal lance to cut it?

Make yourself some thermite, pour a nice big thick ring, light with magnesium and stand well back.