Building Black Limestone Wall - advice on mortar (or not)

[Rsian]

Hi all,

I wonder if someone can please advise?

I have built a pizza oven which sits on breeze blocks, and am now at a stage where I need to tidy things up a bit and wrap a wall around it which will allow me to place a ledge around the oven too.

I am looking to buy some black limestone walling (pictured), and having spoken to someone in the suppliers office, and they believe that it should not be cemented down.

Can someone advise exactly how I should go about laying this type of brick as I'm not quite sure now where to go with this (all pictures below of my oven, current lock wall, and example of how the black limestone walling has been laid in the advert)?

Surely if it is not mortared, it is at risk of falling quite easily?

Thanks in advance!

 

[theprinceofdarkness]

You must not use cement anywhere around this ere' thing. Due to the fact that the oven will be running at 200*C, the blocks will expand and if cemented might explosively crack. Use a very weak lime mix, this will allow movement at the joints rather then cracking. And again because of the high temperature it has to be kept dry, if any of the blocks soak up water , this could turn into steam and cause cracking, this is pointed at where your shelf is as sitting water can make its way into the centre of the construction.
Those limestone blocks look as though they have smooth top and bottom faces where they have been cut with a bandsaw. I would put in some indentations with a masonry drill to provide a small "key" for your lime. I would also arrange for the cavity to be vented, so allowing the outer skin to run at a lower temperature and help with drying out.
Frank

 

[jeds]

I would avoid mortar for two reasons; water WILL get behind and mortar will just hold it in and also it just wouldn't look right. It would look much better in dry stone style - like the small garden wall in your picture. I'd lay them like that with maybe small mortar dabs at the rear to hold them as necessary - but none near the face. They are only cosmetic really - not part of the oven - so you can't go far wrong structurally.

 

[Rsian]

Hi both,

Thanks for the replies.

Before your I saw your responses I just spoke to another supplier of these bricks and explained the scenario.
He has suggested to dry stack the wall, and back fill the entire cavity with a mortar mix (didn't say what the mix should be).

Could this work also?

*Note - the entire oven is fully insulated from the hearth and stand, so there will be no oven heat anywhere near this brick work (if this helps with different build options).

 

[jeds]

The stones are cut to be laid dry - as shown in the pictures. I'm not sure what backfilling will add? I'd just lay them dry and use small dabs of mortar on the inner side if the top courses need stabilising.

 

[Rsian]

Hi jeds,

The concern I raised with the guy I spoke to was that as there is space for a cavity, could the wall easily be 'pushed in', or if someone fell into it, it could just collapse if it is not motared anywhere?

It is essentially a four'ish foot high wall, with no support front or back (because of the cavity), and I'm just a bit concerned about it's stability?