Stone shed - slipforming sort of

[jrckelley]

Hi everybody,
I finally have a question that cant be answered by the search button so I had to sign up.
I am thinking of building a stone shed for my lathe - mill and some woodworking tools. I was thinking about laying rough sand stone in 1 meter high sections and then forming up behind it leaving a gap of 150mm. I would then fill this gap with concrete. I know it is an overkill but i like to build things 10x stonger than they have to be (harder for someone to make me pull them down).
So my question is, when laying the stone (say average 500x300x200 lxHxD) would you use a mortar (lime) or a cement mix. I have got some books on the subject but they all say cement, however in the australian sun I would be worried about exspansion rates and the cement would just crack (or worse the sandstone would). any thoughts?
Thanks

[seriph1]

Hi and welcome to the forum!

I am no expert on these things but every one of the dozens of period restoration program I have watched, always states that lime mortar has properties that enable the stone to breathe and move slightly without cracking ... in addition, its adhesion properties are lower than cement therefore it will fail before the stone fractures, enabling repointing when necessary without damaging the stonework.

Are you building this bunker because of the noise produced by your milling? If so, I reckon you may not get the result you're hoping for because those machines produce a lot of very low frequency sound, which travels through solids. Aerated block (Hebel) works far better according to my mate who had a run-in with council because neighbours complained about the noise....

When I was researching building a stone home, my mason recommended building a shed as it would help me develop all the skills required to build a home. Unfortunately the project didn't fly but it would've been grand. Nothing beats stone for me.

[jrckelley]

thanks for the advise, thats what i was thinking.
The reason for the "bunker" is that i live in the midle of the bush (outside sydney) and lots of fires + it is under a dozen or so real big iron bark trees so i would like it to be able to take a direct hit (I like the shade from the trees to much to cut them down
I think thermal exspansion would be the big issue. from this site
http://www.fhwa.dot.gov/pavement/pccp/thermal.cfm
you can see that sandstone is similar to concete so it should be ok.
However a good mortar mix can only be a good thing so I will probably us a 6/1/1 mix (sharp sand/cement/mortar) as per another post on this site.
When I costed up the shed in stone - it wasn't that much more than a colorbond or timber (did some one say fire) shed, just alot more work.
Thanks again
(i'll post some inpiring pictures in a couple of monthss)

BTW - MY cousin built a bluestone cottage just out of ballart (he got most of the stone for free from farms) and it looks awsome. you guys have nice stone in Vic.

[Dirty Doogie]

The 150mm deep slipforming is going to be hard work and will require correct reinforcing so it doesnt pull the stone wall over. If the sandstone is an iregular shape I would tend to use cement base mortar. I have seen and worked on a few sandstone structures that used cement mortar and they have had no problems with cracking provided the stonework sits on concrete foundation.

The lime mortar would be preferred however if the sand stone was put down on a stone / rubble foundation (which many period structures used).

[Brickie]

I have got some books on the subject but they all say cement, however in the australian sun I would be worried about exspansion rates and the cement would just crack (or worse the sandstone would). any thoughts?
Thanks

Use expansion/control joints to minimise cracks, although, the old buildings dont us expansion joints and they are still standing.

The main reason for masonry failure is poor foundations.

[jrckelley]

Thanks for the advise, I think I'll go concrete morter with big footings ( 600mm wide 300 deep) with 16mm reo. Its on bedrock so it should be ok. and I will probably use waffle pods in the centre (don't feel like digging into hard stone for trenches. I will also use gal starter bars into the bedrock to provide a key joining the two together. It's going to be a long process (i did a drystack wall last weekend and that took ages).

thanks again