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View Full Version : Landscape timber steps - rebar vs pipe?



Victor Robinson
05-31-2016, 1:52 AM
I'll be constructing some garden steps out of 4x6 or 6x6 PT lumber for our sloped backyard later this summer. My plan was to tie them to one another and into the ground with rebar. I've seen it done with large screws as well but the rebar seems to accomplish the two functions with one fastener (joining steps to one another as well as anchoring in the ground).

However, while we were strolling through the local botanical gardens, I noticed some of their timber steps constructed in a slightly different manner - instead of rebar they had used pipe - around 1" diameter. I suppose this would provide a little bit of drainage (?), but other than that I couldn't really figure out why it would be preferable over rebar. Seems it would also eventually fill with dirt and debris.

Can anyone enlighten me?

Rich Engelhardt
05-31-2016, 5:09 AM
Rebar is really soft steel. It bends real easy. You can't count on it to hold something enough to prevent it from moving.
For steps - or for something like a retaining wall - you want something more rigid than rebar.

Oops - I forgot to add - the goop in the treated will probably eat up the rebar in short order also.

Rich Riddle
05-31-2016, 8:09 AM
Rich Engelhardt hit the nail on the head. I routinely bend rebar with my hand and a board. It's soft and easy to bend. You can use pipe if you want or attempt to find some solid stock somewhere. Pipe would prove an easier and less costly product to use.

Bob Grier
05-31-2016, 10:03 AM
The house I purchased 2 years ago was built in 1989 and has garden steps constructed of pressure treated timbers as well as shallow flower beds and other landscape features such as short terraces constructed with pressure treated timbers defining the perimeters. The timbers are 4x4, 4x8, 6x8. Most are drilled and held in place with #4 rebar. I do not know how long any of them have been in the ground here in the Pacific Northwest but all the wood is in poor condition. Note that the second step in the picture is spongy and collapses when stepped on. The other steps are fairly solid. You can see the rebar spiked through the steps into the ground is holding them in place, even the rotten one although it may have contributed to the rot.

I have removed approximately 80 feet of the rotted timbers to make room for shed and patio. The timbers are all rotten and come apart in pieces. The portion of the rebar in the ground is in poor condition but definitely holding what is left of the timbers in place. One 15' timber was used as a wheel stop for cars turning around in the driveway. It was still in the original installed position.

My suggestion is to consider constructing steps with flat rocks, pavers or other mineral material and not use organic material. That is what I am gradually doing. I expect San Francisco is more forgiving than Seattle in regards to wood rot but Phoenix would probably be the type climate best suited for wood longevity.

338376

Ole Anderson
05-31-2016, 10:12 AM
Rebar or pipe will keep a step or base of a retaining wall from sliding, but don't count on it to keep a wall from tipping over due to the weight of soil behind it. For that you need to tie it into the soil behind with a tieback, or step it back substantially. I would use #5 rebar in the bottom course to keep it from sliding and treated landscape timber screws to hold successive layers together. And always use timbers treated and rated for ground contact,they use much more chemical than those rated for above ground use.

Victor Robinson
05-31-2016, 2:42 PM
Thanks Rich and Rich. If one steps up to pipe instead of rebar, is an equivalent diameter of pipe stronger? What kind of pipe would be best for ACQ contact? One advantage of rebar is I could drive them pretty deep fairly easily with a SDS-max hammer and ground rod driver. Larger diameter would require the sledge...boo.

Thank you Bob. Your point about organic vs mineral is well-taken. My wife and I keep going back and forth about this for the backyard. We have retaining walls to do as well, which also factor into the wood vs concrete debate. We will probably be leaving the home in a year or two and at that point it will become a rental property, so there is obviously an attraction to "set it and forget it." At the same time, the cost (especially hiring out) of concrete or stone is astronomical, especially in this area. For a small yard in what will eventually become a rental property, it is difficult to justify and afford the cost. At the same time, my impression is one can realistically expect only 10-15 good years out of timber-constructed steps/walls, and maybe another 5-10 years with repairs or "tolerable" rot.

At the moment I'm leaning towards timber steps and concrete walls, but sort of go back and forth.

Thank you Ole. Your point is well-taken about rebar keeping walls from tipping. For short (3 ft) walls on footers, it should suffice, no? As for steps, is there any advantage to having rebar into the ground (say, 4 ft deep?) at each step, or only on the bottom step?

Erik Loza
05-31-2016, 2:46 PM
What about using railroad ties instead of PT lumber? My mother in law's place in East TX had some steps made of those that must have been 30+ years old.

Erik

Victor Robinson
05-31-2016, 3:20 PM
What about using railroad ties instead of PT lumber? My mother in law's place in East TX had some steps made of those that must have been 30+ years old.

Erik

I seem to remember something about these being "illegal" in residential use or something like that due to the creosote/carcinogenicity? Not that PT lumber is any less toxic, lol. I haven't tried sourcing them locally...may be an option though undoubtedly frowned upon in our locale...

Malcolm McLeod
05-31-2016, 3:24 PM
What about using railroad ties instead of PT lumber? My mother in law's place in East TX had some steps made of those that must have been 30+ years old.

Erik

+1 on the RR ties for rot resistance, especially if in direct contact with the soil. (Or buy all the Bois D'arc timbers on the planet.:))

But like everything, your specific conditions make much of the advice you get here subject to question. How much water runoff? Freeze/thaw cycles? Soil type? Seismic/code requirements? Wall height? Soil load behind the wall or step? Slope? Space limitations? Rise/Run of your steps? All of these impact cost, design, and longevity. If you're keeping the property, I'd be tempted t say longevity may be most important of the 3...? If so, there are lots of precast concrete options you might consider.

Only thing I'd add is look very carefully at some type of deadman (tie-back) - - even on steps - - if you have loose or clay soil.

Tom M King
05-31-2016, 4:04 PM
Our Dressage arena is rimmed with railroad ties held in place with rebar. I built it in the early '90s. Except for a piece I hit with the tractor drag, all of it is still where it was placed. The sand inside is 4 or 5 inches higher than on the outside of the railroad ties. I think either rebar or pipe will outlast the wood, but since no height of assembly was given, rebar may or may not be strong enough.

Jerome Stanek
05-31-2016, 5:51 PM
Rebar is really soft steel. It bends real easy. You can't count on it to hold something enough to prevent it from moving.
For steps - or for something like a retaining wall - you want something more rigid than rebar.

Oops - I forgot to add - the goop in the treated will probably eat up the rebar in short order also.

I have used number 5 and 6 rebar I would like to see you bend the number 6 rebar that is 3/4 inch thick

Victor Robinson
05-31-2016, 5:52 PM
Some construction details:

20 steps, ascending approx 10' over a run of 15'. 4' wide steps. The bottom step ends over a pre-existing concrete slab, so there may be a better way to anchor the bottom? Was going to build them as "U"s, then fill in with gravel/sand or pavers or concrete depending on wife's preferences. No major freeze/thaw issues here. Soil is fairly sandy so washes down a fair bit in the rainy season without adequate plantings or walls. We're about 40 blocks from the ocean.

Von Bickley
05-31-2016, 11:35 PM
I have used rail-road ties, landscape timbers, treated lumber, and had problems with all of them. In this part of the country, we have a heavy population of "fire ants' and they love any type of wood that you put on the ground. Just me talking, but I can't use any type of wood on the ground.

Ole Anderson
05-31-2016, 11:58 PM
Railroad ties are typically well used and there is a reason they are removed from service.

Rich Engelhardt
06-01-2016, 8:53 AM
I would like to see you bend the number 6 rebar that is 3/4 inch thickI don't know about that - - but - - the rebar I used for my little raised garden didn't hold up well at all.

John K Jordan
06-01-2016, 9:19 AM
I personally don't like to use pipe since it deforms easily when hammered. I've used rebar to hold both PT and railroad ties. As long as you are not building a retaining wall, either type of wood should stay in place. Unlike PT corrosion of tightly driven screws and nails, I would not be the least bit concerned with 3/4" rebar driven through a loose hole in a 6x6. I would put down a tamped layer of big gravel first to minimize settling and to allow good drainage. Some concrete support would be ideal but that's a lot more work.


I have also used long Timberlock screws to tie overlapping steps together. Had to drill holes to sink the heads a bit in thick timbers. I cut white oak on my sawmill for front steps to my house, 8"x12" I think. They have held up nicely for over 10 years now. I occasionally slosh some BLO on them.


JKJ

Todd Mason-Darnell
06-01-2016, 10:40 AM
OP might already know this, but he needs to make sure that the PT he gets is rated for ground contact if he is going to use it for steps. Since the change in chemical formulation of the preservative a few years ago, most PT is not rated for ground contact and will rot if left in a damp area.

In terms of rebar, how deep are you driving your pins? I ask because I have had very good luck using long galvanized lag bolts (12") as pins in this type of application.

Bob Grier
06-01-2016, 11:57 AM
Victor, if you are in sandy soil, the natural angle of repose for dry sand is a little over 34 degrees and your steps are planned to be the same, 15 horizontal to 10 vertical. Steps should be stable and you can keep sand from moving down slope when it rains by placing filter fabric behind and under the steps to let the soil drain but not allow sand particles to migrate. You can cover the filter fabric with aggregate like a thin layer of small crushed stone for bedding the steps. Round bedding stone on a slope would tend to migrate down slope more than crushed stone. Need to match the filter fabric to the soil.

My feeling abut wood contact with soil is that it only lasts so long and then becomes a liability if someone slips or trips on it due to slime or rot. Rough concrete lasts a long time. Something needs to be used to keep the steps from sliding and that could be rebar, pipe, or recessing (notching) their bottom into the soil.