[site]

Around here lots of folks want granite steps built into their walkways as necessary. We install about 100 steps (10 sets of 10)per year, and have always set them on a well compacted 1' of road base gravel. We have had some issues with settling though, and I am wondering how to conquer this problem once and for all. If I were to set them on concrete footings would I have to dig below the frost line? (3.5') or could I pour an oversized slab six inches below finished grade and set them on gravel on top of that?

[Lanelle]

I went out to a jobsite today where a friend in the industry was working. They had installed stepper size fieldstone boulders up a slope. They were just laid on compacted 'dirt' which appeared to be a clay/loam subsoil. I wondered about stability and if the stones were so large and heavy that they would stay in place without aid. What's your experience?

[Rex Mann]

The problem I usually find with building all steps is poor
compaction. Does not matter if I an using sandstone,
granite, pisa or versa-lok. Poor compaction will get you
settling, which leads to call backs. Rent or buy a jumping
jack AKA a rammer. That will allow you to get your 95%
compaction.

Peace,

[diginahole]

I would stick with the compacted granular base. 12" may be overkill but if it is installed in 3 or 4 lifts should give you a very solid base. If you are getting settling I see no other reason than insufficient compaction.

[Stonehenge]

How much care is taken to ensure that the stone directly behind a step (red arrow) is well compacted?

Often times that compaction leads to movement of the step in front of it (green).

[Stonehenge]

At least that's one of the things I struggle with...If that area is somewhat uncompacted, stone from further behind that step will settle in there, which means the back end of that step will sink a bit. Once that happens and there's any kind of backwards lean or batter, then water flows that way exacerbating that problem.

Don't know that I have a solution, just venting my thoughts....

[site]

We compact carefully and in small lifts all around the stones. Our average steps look just like stonehenges drawing. We are also careful to pitch all steps about 1/8 bubble forward to avoid puddles. The problem seems to be that the frost pushes the steps downhill about 1/2 inch, then the pavers which meet the top of the tread settle and need repair.

[Rex Mann]

Gravity is a great thing when its working with and not against you. If you are confident you are achieving maximum compaction then you can rule out that. What we have done is use portland cement integrated into the base. This will "stiffen" it up and help stabilize the base material. Also, are you using a geo-textile under your base. This prevents the base from migrating into the soil. You could also put a concrete toe behind each step. Similar to a concrete toe for pavers. This toe will help keep the next step in place over time. Good luck.

Peace,

[Stonehenge]

Rex, would the toe you mention sit on the tread of the lower step to retain the next higher step, or would it be underneath the higher step? I'm not sure I understand.

Jeff

[Paul]

I would guess alot depends on the type of soil that you are dealing with. We have always used a 3/4-" gravel then adjusted it with limestone screenings with port land added. With limestone steps we also drill and add a couple of rebar to the front edge then grouted it to hide them, granite you would have to hide them by drilling the hole under the edge, more of a blind hole.

Rex's hint about the fabric is great, just make sure it wider than the footing.

The rebar should stop the steps from moving forward as long as the toe of the first step can't move.

[Stonehenge]

Paul, what type of grout do you use?

[Rex Mann]

Jeff,

The toe would go behind the first riser about half way up. The riser of the 2nd step overlaps or sits on the riser below. IE: with Pisa. With stone steps most use only one piece. The platform and the riser are the same unit. Same idea.

Peace,

[Stonehenge]

Rex, you mean like what's pictured below? (Pisa on left, stone on right)

[ianc]

I try to get a normal step riser therefore I place flagstone pieces in behind and above the front step, this way I can get a shadow line detail and maintain a uniform riser. have used epoxy and morter to hold in place - never had a problem with stones creeping forward

I found out from my insurance broker that if any part of the landscaping install fails due to workmanship - my liability policy will kick in
-----------BUT-------
if the installation failed because it was bad by design - that I am not covered,

therefore is someone falls on steps that were designed and specified by you with a different riser - you may be exposed.

[diginahole]

Nice work Ian. Good to see you here.