veneer a block wall w/ river rock

[Nicky]

Hi, I'm in California and I have an exterior 4 foot retaining wall made of block. I have piles of river rock I want to put in front of this wall. I plan on digging a footing and inst. a wire mesh to the wall? I want the footing to be kinda wide, like 10" or so, so that I can inst larger and smaller stones and still keep them pretty flush. How deep should my footing be? Can I use a pre mixed basic mortar? Do I just put misc. rocks on top for the cap or is there a better way? Any tips would be appreciated, I plan on being here forever and like to do things right. Thanks

[Rich]

If you go 10" wide you would be more than safe with 8" depth. Pre-mixed mortar will get more expensive than renting a mixer and buying bags of cement.
For the cap you could look around for flat, square cut stone.. then you won't have to worry much about (not sure where in CA you live) freeze/thaw cycles as it will shed water to the sides.

[roger g]

I,ve seen it done a couple of ways. One way is where you split the stones in half. That way you double yoour stones and you have a flat back that sticks to your block wall. Apparently they are easy to split once you see the grain. I never could see or find the grain. T he other way is just stack the stones. They use lots of mortar on the back and just a llittle inbetween. They do about one row at a time and wedge llittle pebbles between the stones to keep distances otherwise the mortar would just squeeze out. Later ther come with a cake decorating type bag and squeeze in mortar where they want it. They also use a reall sticky type of mortar that sticks to smooth stones. I don't know what they do about the expansion and contraction of stone and mortar.

roger

[Rich]

It would be pretty difficult to split round river rock.. unless it's different than river rock we have around here. You would have to cut (wet saw) every one of them.

[roger g]

No, I,ve seen them crack the rock with one smack but they obviously knew what they were doing. Many times I've watched stone masons take granite field stones the size of footballs or even basket balls, turn them around looking for the grain that i could never find, then smack it and break it in half. Sometimes with a chisel. If you ever look at a granite wall or fireplace you will see that they are basically flat faced. R ough but flat. They ccan even break them into thinner pieces if the grain is right. Once they break the boulder in half the eddges of the cut are quite sharp, so they wack around the edges of the cut to chamfer the edges to give it a raised face look. I used to love watching these guys with stone chips flying all over the place. A lot of things were done long before diamond saws were built.

roger

[Nicky]

I won't be cutting every stone, I don't need to anyways because I have a lot of them. I dont think these stones will split anyway. I'm just concerned about the mortar and application to wall. I will come back and mortar the joints after but to stack and adhere to wall do I stay with a mortar or use a thinset or add anything to mix? Thanks for your input.

[Rich]

I would stick with mortar just due to the weight of the stone. Shanley may be around to give a better answer.

[Shanley]

I'd use type s mortar and also I'd form and pour a solid concrete cap as opposed to a stone cap...the mortar joints in the stone cap will shrink and crack due to a decrease in volume as the mortar hydrates. This will allow water infiltration that shortens the life span of the wall