demolishing concrete roof

I will be demolishing an outhouse/kitchen that is joined to the neighbour's by a party wall. The roof is a concrete slab (not connected to the house) and may run across mine and the neighbours. The neighbour is worried that the demolition may damage her side. I guess the roof may have rebar in. Build around 1920s. Obviously a heavy roof falling at an angle could take it's 9" support wall with it. I guess I need to slice it with a diamond cutter. It needs to be as flush as possible to the 9" wall it rests on. I will be attaching the inner skin of a cavity wall to the old wall. What is the best/safest way to take this roof off ? Cheers, Simon.

Reply to
sm_jamieson
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I had exactly the same quandary a few years ago while building my extension, I thought about a diamond disc cutter but thought I'd have a go first with a lump hammer. As the concrete was pretty old and not that strong a mix, I managed to nibble away bit by bit - being more careful the closer I got to their part of the roof and all went well. I must admit that I was a bit worried that it would all come tumbling down in a cloud of dust (me included) but I got quite a good edge in the end. My extension ended up a couple of inches shy of their section so I used some flashing to bridge the gap. While it went ok for me - if I was to do it again I would not try to save pennies on hiring the proper tool and use the disc cutter to at least give me a line to break to - a bit more peace of mind. Good luck. Franko.

Reply to
Franko

IANADemolitionEngineer

I would suggest propping up the roof from below, then cutting from above parallel to but some distance away from the party wall, to separate the main weight of the roof from the neighbour's structure. The roof may also need propping/buttressing from the non-shared side to prevent everything going diagonal. It's probably not much fun being on top of several tonnes of collapsing concrete parallelogram. Then the separated roof can be brought down by appropriate means, and the remaining overhang from the party wall worked on with more precision.

Owain

Reply to
Owain

Is this some sort of add-on to the back of your houses?

Sounds likely.

How will you prevent water ingress to her side when you've done yours?

Piecemeal, not damaging her side.

Pictures?

Reply to
Chris Bacon

Yes, there is a sticking-out bit of the kitchen (no slab over), with a door to a wash-house and finally an outside toilet. The wash-house and outside loo have the slab over - it supported a water tank originally.

Initially with tarpaulin etc. I am building an extension that will join to the exposed party wall with an inner leaf of cavity wall.

I will be posting pictures of this whole job soon. I seem to have been harping on about it for ages !

I think it may be a good idea to first remove the bulk of the roof by taking out a square from the middle with a diamond cutter, supporting the chunk from beneath and then lowering it. This would keep the weight balanced. Cheers, Simon.

Reply to
sm_jamieson

Check your insurance to see if they'll pay up should it all go horribly wrong... :-)

Seriously, thinking about it, it's worth checking. If it collapsed some time later on then there could be huge liabilities.

G.

Reply to
G.W. Walker

Yep. Which raises some questions about DIY / insurance etc. I will start another thread about it. Simon.

Reply to
sm_jamieson

I'd try it like this:

2 1

-------+--------------------------------+--------------- | | |

-----------------------+-------------------------------- ===== 3 ===== | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |

Support the slab with Acrojacks and boards. Make the cuts in the order shown - when cutting 3 you may want to prop it with bits of timber as you go, and pull the props away with rope once you're out of range. Then whack it from above, standing on the party wall so you don't go down with the rubble. Finally remove manageable chunks to tidy up the remaining edge. Don't blame me if you get squashed - I'm not known for the safety of my exploits.

Reply to
Rob Morley

Disc cutter is definately the way to go. The saw-cut will not onl seperate the two slabs, but will help minimise the noise and vibratio transfered throught to your neighbours property. However, if you ar cutting flush with the 9 inch wall it spans on to prior to breaking ou the roof, you will need to place a forrest of acrow props underneath t temporarily support it while you demolish it.

Otherwise, demolsih up to a foot away from the support and then saw cu the last bit. Be careful which way you demolish it though! Check whic way it spans and break the slab in strips parallel.

Hope this helps

-- Cordless Crazy

Reply to
Cordless Crazy

doing that would cause the roof to expand sideways with great force, I'd avoid that. I also wouldnt be too happy cutting no 3 while standing under it!

Dynamite would ensure the pieces coming down were small enough not to bring any wall down. But.... :)

I'm unclear about the exact layout of all this, so dont take anything I say as gospel here. But obviously you need to ensure the old roof gets adequate support at its new boundary end.

After cutting on the boundary to isolate the neighbour's roof, I'd prop yours with timber then cut panels of roof out, then when the last bits come down there's no chance of it knocking an end wall out. Timber could be screwed to the crete roof to keep it there, or made into a frame with some extra bits. Acros are more money and probably no easier or quicker in this case, plus to support a sloping roof you'd still need to attach them to something so they cant move.

NT

Reply to
meow2222

I was anticipating that the outer (non-party) wall would allow sufficient movement (and possibly come down at the same time!) - maybe I should have been clearer on that. But you're probably right that it's a bad idea.

As I said, timber props might be a good idea :-)

Reply to
Rob Morley

As an extra piece of information WRT cutting versus hammering, my advice is to not put a hammer anywhere near it until you have cut completely through the thickness of the concrete (I'm guessing it's 4 inch?) - for this you will need a diamond disk and preferably a petrol driven sthilsaw. Any hammering, chiseling etc will leave hairline cracks all over the entire slab, soon noticable when it rains in.

Reply to
Phil L

Just bash the bliddy thing off in bits, and cut off when close to finish. It sure ain't worth all the pain.

Reply to
Chris Bacon

50/50 which end gives.

Thinking a bit more here, you'll only need one prop in total. Each crete panel thats cut out is cut top and bottom first, then side, so no prop needed. Only the last panel needs a prop since its not supported by crete on one side.

NT

Reply to
meow2222

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