1m High Retaining Wall

[jcoopergs]

Hi all,

Firstly, excellent forum and it's giving me the inspiration to build my own dry stone wall.

The plan is to build a 1 (m) high x 22 (m) length wall with a slight curve in the middle. Ideally dry-stone. However, the rock is not all that flat. I've pasted a link with an example of a previously built wall using this type of rock (below).

http://www.fitzgeraldquarries.com.au/pr ... xpressway/

I've spoken with the builder of this wall and it is also 1 (m) high, he stated that he mortared the back as the rock was not ideal for dry stacking up to 1(m).

Just a few questions for the construction;
- In your opinion is this type of rock usable for fully dry stone up to 1 (m) height?
- Have people used the mortar backing technique and is this applied to the back of the wall after it's laid?
- Would a gravel base footing suffice (rather than concrete base) and what depth and width would you recommend for the footing?
- How wide would you recommend the base of the wall and tapered width to the top?

Many thanks - James

[bloop]

Hello James,

The answers to your questions are - yes your stone is suitable for building a wall up to and beyond 1 metre high. However from the photos you supplied the majority of the stones appeared to be traced ie they have been laid with their long axes along the line of the wall and in some cases laid at 90 degrees to their bedding planes - not recommended. Your wall is in effect a veneer and has little inherent strength to retain anything. For strength, stones should be laid with their long axes into the wall.
Secondly, use of the back mortaring technique is in reality cladding as above and I only use it when a true drystone wall cannot be built but the customer wants the drystone appearance. An example would be cladding onto a concrete block face which has ties inserted. Remember that water will build up behind a mortared wall of any form that does not have weep holes to allow drainage - this situation does not occur behind a drystone retaining wall which allows water to percolate through it. I am sure it rains in Oz sometimes!
Lastly never use gravel as a footing or as hearting (back fill) as it has no inherent strength. Your footing should use the largest stones laid as described above and a simple rule of thumb is depth of a retaining wall should at least exceed half the envisaged finished height.

Hope this helps

[Nigel]

Thats good advice from Bloop.

I have to repair a 'retaining wall' this coming summer, the problem is that its just a face, one sided, a retaining wall is just that, a wall. Anything less is just cladding a bank and asking for trouble.

good luck.

Nigel.

[GregLee]

Hi, I'm also in Australia, I'm just an amateur using stone I dig out of the hill on my farm. Your stone looks good for proper drystone walling. As Bloop says, just remember to place the stones long end into the wall, and fill all the hearting with properly placed stones, don't just drop gravel in to fill it up. Builders in Australia don't usually know much about drystone walling,they are addicted to cement. I like to build freestanding walls about 1.15m high, about 700mm wide at the base tapering to about 500mm on top. You don't need foundations, just a shallow trench to get rid of organic matter. Drystone walls can settle, but you need the biggest stones at the bottom for the foundation. Save the flattest stones for the top.
I work on the basis of 1 cubic metre to a linear metre of wall, you get some wastage and it takes up a lot less space stacked in a wall. I have built a couple of 30m walls, the stone I use is similar to yours, it makes a great wall. Take your time and expect to get better as you go along, experience is the best teacher. The main thing you need to learn quickly is keeping your fingers out of the way.
There are some great resources on the dswa website, check out all their downloads and read as much as you can about the basic techniques, they aren't that difficult.