Installing a large limestone monolith, any advice?

[TylerDurdenk]

I am just about to take delivery of a large piece of limestone, it has been cut to provide a completely flat base. It's going to be within falling distance of a window so I need to make sure it's a stable as possible. Have a look at the photos, the stones dimensions are; Height - 3ft 4” , Width - 2ft, Depth - 12”.



I have laid 2 level paving slabs under the weed membrane. Should I just sit it on those, or should I have another bed of mortar?

Thanks in advance

 

[bernardgreen]

No matter how firm the base is my concern would be the risk of it toppling over either by accidental push or wind eddies round that corner. The 40 inch height and 12 inch foot print means it doesn't have to lean far before the centre of gravity is outside the footprint at which point toppling is inevitable

A solid base and some form of anchoring. A 2 foot long one inch diameter steel pin fitted into a hole drilled one foot up into the slab and one foot down into the base would ( should ) cater for all but the strongest push.

 

[TylerDurdenk]

Thanks Bernard. Do you really think this stone could be blown over!?
The stone is bottom heavy as it starts wide and comes to a point at the top, I would be amazed if even the strongest wind was able to move it even the smallest amount, let alone bring it to the tipping point.

 

[bernardgreen]

Do you really think this stone could be blown over!?

Unlikely to be blown over but recent winds did take out a dry stone garden lamp pedestal that had stood for decades.

 

[LeadFarmer]

Another alternative it to chock it against the wall with a piece of timber during the winter. But that would rely upon having no wind during the summer, and you remembering chock it in the winter.

When its delivered stand it upright and try and push it over. If its rock solid then you should be ok. For peace of mind then the method suggested by bernard would be best.

 

[r896neo]

Items like this are nearly always dowelled into a concrete footing. Its dangerous not to. Never mind the wind its more a child climbing on it is the main danger. A length of rebar or stainless rod embeded into a concrete base and then the corresponding hole in the stone filled with a cement slurry just before placing it. The problem is you need to lift it into place.

If you really don't want to go down this route then bond it to the flags as strongly as possible. Tile cement usually gives the best grip, prime both surfaces with sbr.

 

[Doggit]

Although it's bottom heavy, at 12" wide, a wind wouldn't topple it, but the ground could tilt under it. I would put a bed of mortar under the 2 paving slab (possibly wider than the two slabs at their narowest point), and then a quick dab of cement under the stone when you put it in place.

 

[TylerDurdenk]

The slabs are fully bedded on mortar, with extra mortar around them.
I've had the stone delivered and placed it on tile adhesive so it should be bonded well to the slabs.
If it falls over I'll eat my hat.

 

[bernardgreen]

Bit late now but this explains how to make it very safe

http://www.stonesafe.co.uk/stability-system-installing-lawn-memorials/

 

[Doggit]

Um, would that be waterproof tile adhesive by any chance; if not, get the condiments ready.

 

[endecotp]

You'll "eat your hat" ?!

Is that a child in your avatar picture?

http://www.bbc.co.uk/news/uk-scotland-glasgow-west-37895437

Maybe a bit of cement will hold it for the time being, but will it still be secure when your grandson climbs on it in 25 years time?

 

[Doggit]

On reflection, I'd have gone with resin to bed it in.

 

[JohnD]

I don't know how this one on Hayling was done. It's on a sand and shingle beach, on a mound.