Stacked Rock Retaining Wall

[Flyboy]

G'day,
Moving on to plan G for the retaining wall ....

The latest (and hopefully final) design is for a stacked rock retaining wall, which I've attached. I'll be using random rubble blocks sized up to whatever 1 bloke can lift. Does anyone have any tips/advice for building one of these?

A couple of questions :
Whats the best way to cut bushrock (up to around 200mm thick), angle grinder or bolster and hammer?
Would the best way to build the wall be course by course, or build the ends first then fill in the middle?
Will no doubt think of more later;)

Cheers

[Eddie Jones]

My old mate Hadrian could have used you. The only thing I can see wrong is a max of 1500mm high wouldn't keep out pygmies, let alone marauding Scots.

[Dan_574]

You can build these without using any mortar do a google search on dry stone wall building, heres a few but there are heaps,

http://www.easy2diy.com/cm/easy/diy_ht_index.asp?page_id=35720755
http://www.vincistone.com/how_to_center/how_to_build_stone_walls.htm
http://www.bobvila.com/HowTo_Library/Building_a_Dry_Stone_Retaining_Wall-Walls_and_Fences-A1533.html

There is even a weekend course run at Mt Annan botanical garden,

http://www.rbgsyd.nsw.gov.au/mount_annan_botanic_garden/events_activities/mount_annan_botanic_garden_calendar/event_view?SQ_CALENDAR_VIEW=event&SQ_CALENDAR_EVENT_ID=7291314

There is no need to cut the rocks unless they are too big too move, its just a big jigsaw puzzle. there are walls that have been up for hundreds of years that havent used mortar. What stone would you use? The squarer the stone the easier to lay I would imagine. one day I will have about 300m of dry stone wall, I reckon it looks fantastic.

[Flyboy]

Thanks for the links, Dan. I would have preferred a dry stone wall, but the engineer wouldn't sign off on it without having large stones (1 - 1.5 tonnes) as the base stones. Access is a problem and everything has to be hand carried down to the site.

The stone I'm using is just random rubble, varying in size from around 200-500mm long and 100-300mm thick. Hopefully won't have to do too much cutting, but will probably have to cut the odd infill piece here and there.

Cheers

[elphingirl]

A couple of questions :
Whats the best way to cut bushrock (up to around 200mm thick), angle grinder or bolster and hammer?
Would the best way to build the wall be course by course, or build the ends first then fill in the middle?

Hi Flyboy

My partner and I built one of the walls of our house together - a 5m long and 3.5m high double faced stone wall - so I feel qualified to make a couple of comments here:
Firstly, there are no details of the footing on your drawing, for 1.5m high wall you should absolutely be in the hands of an engineer.
Secondly, we got a couple of lessons from a stonemason. This was invaluable - we could not have done the job without these.
The best tool to split up bush rock is a special stone chisel (tungsten-carbide tipped - around $180) and mallet. We bought an angle grinder in anticipation and rarely used it.
It will be easier to start with the ends of the wall, then you can stringline from one end to the other to get a line for the centre. I've also seen wooden profiles built in the shape of the batter.
Also, be extremely careful about the drainage behind your retaining wall. You are probably right - the stones will hold through gravity alone without grout, but if there is any heaving of water-loaded soil behind the all it will overturn it. Line the whole back of the wall with screenings, provide weepholes through the wall at intervals, as well as the aggy pipe.

Good luck, it is very slow, cold and messy work (it took us two years of a day a week to complete our wall).

Cheers, Justine

[Flyboy]

G'day Justine, sounds like a fairly hefty wall you've built:eek: I should have mentioned in my first post that the drawing for the wall is only a generic design that you can use for walls up to 1500 high. Our wall is 7m long and 800 high.
There is no actual footing as such, the wall sits 300 deep in the sand and the base is about 800 wide.
As you suggested, I'm leaning towards building the ends first, then running stringlines for the middle. My main worry is that using random rubble could introduce inaccuracies in the placing of the line. Did you find that this happened in your case?
Good point about the drainage, I'm still waiting to hear back from the engineer about that. Seeing as though he's only specified 30% grout the whole wall will be fairly porous, so I was wondering if the agline/gravel would be necessary.

Cheers

[Dan_574]

Flyboy have you considered using gabion baskets,

www.geofabrics.com.au

the ones down here cost $66 for a 2x1x1, another great product if you have enough rocks. Ive seen the wall you mention being built near me in a new estate, its over 2m tall in sections and they didnt use a footing, they laid a thin layer of concrete about 100mm thick then placed the stones on top. They just shovelled mortar on the stones to bind them and take up any areas where the rocks didnt meet. they then came through later with a trowel and added more mortar to tidy up the face. If yours is out of site you dont need to.
Wheres the retaining wall, is it near your house. The australian standards say you only need an engineer for anything over 800mm so you could get away with a dry stone wall if you needed to.

[elphingirl]

Hi Flyboy

Glad to hear it's only 800mm! Sand is nice surface to build on - won't expand or contract, but if there is any water flow through, it will remove, and potentially some of your lower stones will move. Again, I'd probably get some advice from a stonemason, most around Central Victoria where we are do build on constructed footings (pity you can't bring in the big stones for the base course - they would be great!)
Cheers
Elphingirl

[Flyboy]

Dan, pity I didn't start this post a few months ago, gabion baskets would have been ideal. Unfortunately the stacked rock wall is the last in a long list of options offered by the engineer, and I'm afraid if I change my mind again I won't get the thing finished in the months holidays I've got coming up. Interesting what you say about the AS only requiring an engineer over 800mm. I've tried to get out of using an engineer but our council want one over 600mm:rolleyes:

Elphingirl, I hear what you're saying about water. The wall is on a tidal river and water movement around and through the wall has been one of the biggest issues with the engineer. It's been a fine line between having the wall set deep enough in the sand so that it's not affected by water movement and having it too deep and it becomes impossible to excavate. Hopefully he's got his numbers right:)

[elphingirl]

Sounds like your engineer is earning his money! Our council actually over rode the specification our engineer set for our house footings. Needless to say he was not impressed - would have fought it on principle had we not wanted to get started ASAP.
Can you post a picture when you are done?
Cheers Justine

[Flyboy]

No worries, might be a couple of months though:)

BTW, what did you top your wall with? Had heard that a lot of the strength off the wall comes from how heavy/solidly built the top is.
Also do you remember exactly what your stone chisel was called? And how thick were the blocks you were cutting with it? Had a look at Bunnings but they only showed me a choice of 4 or 5 cold chisels.

Thanks

[elphingirl]

Flyboy

Our wall was ties through extensively with strong metal ties, so really that's where much of the strength comes form. I traditional times they would have tied with large stones from face to face, but they would wick moisture and cold from one site to the other. This way we were able to incorporate insulation between the two sides. So the top of our wall didn't actually have to be that strong.

In fact we built the wall up to existing Oregon rafters (the wall itself slotted in between the barge board (outside) and exposed rafter (inside), so the reality was that the top of the side we finished on is rather flimsy - placing the final couple of stones was pretty challenging.

Can't remember the name of the chisel - will check on the weekend when we are back at the house. We didn't get it from Bunnings though - from a specialised importer. We also go back to the quarry where we bought all the stone, where they sharpen up the t-c edge for us. It's NOT an ordinary chisel - no matter Bunnings say. We did use ordinary cold chisels and bolsters (killed a couple of those) too though. With that tool we split pieces of sandstone that were up to 80cm x 30cm thick.

My partner did all that though - I am pretty weak - I just got to lay the stones. As you can imagine there is a lot of percussion that goes through your arms - he couldn't do a whole day of it. On the plus side for me - he definitely developed some great upper body muscles!

Cheers, Justine - if I can get the name of the supplier I'll let you know.

Cheers

[masterblaster]

Hey Flyboy.
Youknow that sounds almost the same as one l built on my last house. NSW to then and was told l could go 1 mtr high with no engineers or whatever .
Ours was about 7 mtrs long then curved round 2 more mtrs so 9ish all up .
Mate l made a dry wall to start with bush rocks , what a pain . Because mine had a dirt hill behind it so even though l put a layer of stones on the inside the dirt all grew grass and weeds through the rock none stop .
ln the end we got fed up with all the weeds and look of it so l did the unthinkable and ripped it all down then re-did the lot with morter and little flow pipes for drainage .
Never saw another blade of grass or dirt coming through again after that it was definately the most hassle free way for us .
l also didn't have to worry about rocks fitting too prettally with morter .
Cheers
MB

[Tonyz]

We built a dry stone wall over 10 years ago 12m long 80-1200 high with side walls either end one of these up the driveway the other up the fence boundry. We have limestony/heavy clay soil. The back of it has age pipe at base then gravel between rocks and soil. There was no mortar used its had a truck crash into it over 40 Kph and still stands strong. Yes weeds get inbto it but then also into the rose garden Tonto