supporting large rock steps

TimSullivan · Jul 30, 2002

My wife and I are working on our new home and her wish is to use the large flat rocks for walkways and for steps to our porch. We have pulled several stones out of our ravine and are now trying to decide how to support them so they do not settle. Our main concern is the stone that we want to use for the step from our porch. We only need one step and want to use a 6’ by 5’ stone that is 5” thick. The good side is nice and flat and the down side is somewhat irregular but does not vary more that an inch or so from level.

We have used smaller stones to make walkways before and have been happy with the use of #1 stone and a little finer stone to fill between the rocks but need to raise the large stone by the porch about seven inches above the grade at the porch. The freeze in our Upstate New York winters is a concern too. I have thought of using pressure treated 6x6’s to support the step.

Our son lived in Vermont for several years and we always liked the use of the large stones at the entrances of homes. How are these stones supported?

ELMO67 · Jul 30, 2002

Tim, my father and I have done similar projects to this for many of my 40 years, at first with me watching, of course, but eventually helping. We live in an area of Ct. where the subsoil is an excellent draining gravel. This is probably the place to start. If your subsoil isn't very good, ie: clay type mix, maybe a foot or so of good, coarse, well draining gravel that has been compacted should work out ok. On top of that you could use more compacted gravel or some larger stone to get to the elevation you need. The main key to making it last is using a well draining, compacted base. Of course some settling may occur, but with floating steps it is easy enough to readjust to level as neccesary( although in our case, it generally takes quite a few years before that is needed). Good luck- have fun with it!

MJones · Jul 30, 2002

Tim,

I would build up to the desired height with stones to set the large stepping stone. You have two options to keep it from settling. Which one you choose will depend on whether you want to used dry-stacked stone (no mortar) or mortared stone. Personally, I have had better luck with mortared stone when doing steps. Step one would be to dig footers to below freeze line (in my area it is 18 to 20 inches, but I'm sure it is deeper in upstate NY). If you choose to use dry-stack stone, fill the footers to just below grade with crushed stone (I usually use #57) to allow the water to drain below the freeze line. This will prevent any frost-heave of your steps. If you choose mortared stone, pour rebar reinforced concrete in your dug footers to just below grade. Then, you can lay your stone to desired height and set your stepping-stone on top. I would recommend laying your stepping-stone on a ever-so slight slope to allow water run-off.
Mike

TimSullivan · Jul 30, 2002

Elmo, thank you for the info.

I built a set of steps out of field stone in mortar at a past house and was pleased with the way they turned out. I dug four foot deep for footers and used concrete with rebar. That was twenty years ago and the steps are still in good condition.

The subsoil drains well down to about eight feet then there is clay. So this time around we wanted a simpler look and too we only have the one step. What I am thinking of doing is digging two foot deep by two foot wide trenches and fill with gravel over stabilizing fabric. That will bring me to grade. I took a walk in the ravine today and found three flat stones that with some trimming will raise the step stone to the right height. I need five or six more so I will go father down the stream tomorrow. I want to use the longest stones I can find to minimize the number in order to make it more stable. That is also the reason I was thinking of using the 6x6 pressure treated. I thought it would be more stable on the gravel. The boss is not sure how the 6x6 would look. I have to admit that I would prefer the stone support too. It is just that it takes a lot of work to get the stones out of the ravine. It is deep and the sides are very steep.

To give you an example, it took Jane and I five hours to pull the big stone up the seventy-five foot wall of the ravine. That is with a 4300, a 3/4T heavy duty FWD truck, seventy-five feet of half inch cable, three 3/8 log chains, two sets of heavy tractor tire chains to hold the rock, two come a longs and a three pulley block and tackle with a 100’ of one inch rope. Each of the pulley blocks weighs about eighty pounds. The rock has to be pulled up through a maze of trees and its course constantly adjusted.

The smaller three foot by three foot rocks that are four inches thick take about 30 minutes to pull up. Gee, I only need about fifteen of them for the walkway.

Back to the step, once the support stones are in place, I would fill the cavity with more gravel and set the big stone. Am I missing anything?